T H E T H E O R E T I C A L D E V E L O P M E N T, V A L I D A T I O N A N D P R A C T I C A L I M P L E M E N T A T I O N O F A N X – R A Y V I E W I N G T O O L F O R T H E A S S E S S M E N T F O R A R T H R O P L A S T Y I N T E R M I N A L K N E E O S T E O A R T H R I T I S by Dr Christiaan Rudolf Oosthuizen (Student number: 1830796) A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Supervisor: Professor Sebastian Magobotha, BSc (Hon), MBChB, FCS (Ortho) SA, Adjunct Professor (Wits) Co-supervisor: Professor Faith Bischof, BSc (Physiotherapy), MSc (Physiotherapy), PhD (Wits), Adjunct Professor (Wits) Johannesburg, November 2022 ii DECLARATION I, Christiaan Rudolf Oosthuizen, declare that this thesis is my own, unaided work. It is being submitted for the Degree of Doctor of Philosophy in the branch of Orthopaedic Surgery at the University of the Witwatersrand, Johannesburg. It has not been submitted before for any degree or examination at any other University. ………………………… (Signature of candidate) 7th day of November 2022 at Johannesburg iii STUDENT AND CO-AUTHORS DECLARATION Declaration: Student’s contribution to articles and agreement of co-authors I, Christiaan Rudolf Oosthuizen, student number 1830796, declare that this Thesis is my own work and that I contributed adequately towards research findings published in the articles stated below which are included in my Thesis. Signature of Student ……………………………………… Date: 7 November 2022 Name of Primary Supervisor: Prof Sebastian Magobotha Signature of Primary Supervisor Date: 7 November 2022 Agreement by co-authors: By signing this declaration, the co-authors listed below agree to the use of the articles by the student as part of his Thesis. In cases where the student is not the 1st author of a published article, the primary supervisor must explain (under comments) why the student is entitled to use the paper for his/her degree purposes. Article 1: Title: The Knee Osteoarthritis Grading System for Arthroplasty. The Journal of Arthroplasty, 2019, 34 (3), 450-455. Authors Name Signature Date 1st author Christiaan R. Oosthuizen 18/08/2018 iv 2nd author Tsuneari Takahashi 29/08/2018 3rd author Mack Rogan 18/08/2018 4th author Christian H. Snyckers 16/08/2018 5th author Duwayne P. Vermaak 16/08/2018 6th author Gareth G. Jones 18/08/2018 7th author Andrew Porteous 08/09/2018 8th author Innocent Maposa 30/09/2018 9th author Hemant Pandit 23/08/2018 Comments by primary supervisor: It is clearly illustrated in this article that the authors found the knee osteoarthritis grading system a useful tool in assessing the type of arthroplasty implant to use in osteoarthritis of the knee. Article 2: Title: The patient results and satisfaction of knee arthroplasty in a validated grading system. International Orthopaedics, 2019, 43 (12), 2747-2755. Authors Name Signature Date 1st author Christiaan Rudolf Oosthuizen 30/04/2019 2nd author Catherine Van Der Straeten 30/04/2019 3rd author Innocent Maposa 30/04/2019 4th author Christian Hugo Snyckers 13/05/2019 5th author Duwayne Peter Vermaak 30/04/2019 6th author Sebastian Magobotha 30/04/2019 Comments by primary supervisor: This article illustrates that when KOGS is used as a Tool for UKA, the patients Oxford Knee Scores were higher because it was the right implant for the condition of the knee deterioration. Article 3: Title: Impact of correctable mediolateral tibiofemoral subluxation on unicompartmental knee v arthroplasty implant survival in patients with anteromedial osteoarthritis. South African Orthopaedic Journal, 2021, 20 (4), 196-201. Authors Name Signature Date 1st author Christiaan R. Oosthuizen 08/01/2021 2nd author Innocent Maposa 08/01/2021 3rd author Sebastian Magobotha 27/01/2021 4th author Hemant Pandit 08/01/2021 Comments by primary supervisor: This article demonstrates that KOGS can differentiate clearly between different grades of Osteoarthritis with clear and predictable outcomes in implant survival and revision surgery. vi ABSTRACT Purpose of the thesis: The essence of this submission is to present a validated tool to improve the identification of the suitable recipient for unicompartmental knee arthroplasty (UKA) and thereby facilitate the improvement of the clinical assessment and use of the UKA. The study completed a peer-reviewed validation of the new X-ray based “Knee Osteoarthritis Grading System” (KOGS) to facilitate the accuracy/appropriateness of the arthroplasty implant required in knee surgery whether it is total knee arthroplasty (TKA) or UKA. Three studies evaluated different aspects of the system and this forms part of new empirical data that should help to facilitate the use of less invasive procedures for Kellgren and Lawrence grade 4 osteoarthritis (OA) in the tri-compartmental knee joint. The first publication validated the KOGS as suitable to distinguish the different degenerative stages in need of a UKA (72% was selected from the cohort of KOGS Grades 1 and 2 knees) or a TKA (22.5% was selected from the cohort of KOGS Grades 3 and 4 knees). The second publication selected the arthroplasty required and treatment implemented according to KOGS, and obtained at least the same, if not better results for the specific implants published in the literature with the distribution of TKA at 26%, medial-UKA at 59%, lateral- UKA at 13% and patellofemoral arthroplasty at 2%. The revision of TKA and UKA was no worse than the distribution in the literature with ipsilateral degeneration the most common failure mode in the UKA. The third publication verified the authenticity of KOGS Grade 2 as a more severe degeneration with a relative ‘instability’ in the knee, with poorer results recorded for a unicompartmental knee implant in relation to the KOGS Grade 1, deemed to be more ‘stable’. In this study, the short prospective study (P) followed a similar pattern to the retrospective larger study (R). Further advantages of this empirical study are: 1. Recognising the different stages of pathology according to the KOGS classification, allowing empirical data accumulation. vii 2. The implant identification of the pathological stage is now possible e.g., UKA versus Bi-UKA, bicompartmental or TKA from the different stages of degeneration (different implants are used for a specific stage). Further subsets of degeneration are identifiable, relative to known results in UKA and TKA e.g., isolated single compartment OA in KOGS Grade 1 with an intact Anterior Cruciate Ligament (ACL) compared with isolated single compartment OA with ACL reconstructed knees (KOGS Grade 3A). 3. Various methods of clinical assessment and patient-reported outcome scores (PROMS) of the deteriorating KOGS Grades can be compared with different implants and as such, identify the optimal implant for a specific grade of degeneration (e.g., KOGS Grade 1 UKA versus Grade 1 TKA or Grade 4A Bi-UKA versus TKA). viii DEDICATION ix To the Oosthuizen family! x PRESENTATIONS ARISING FROM THE THESIS 1. Global Oxford Masters Symposium, 24–25 September 2012; Oxford, England: a) An X-ray score system to evaluate/qualify the knee for the suitability of a Partial Knee Replacement (PKR) or a Total Knee Replacement (TKR). 2. Amplitude International Hip and Knee Symposium, 13 April 2015; Cape Town, South Africa: a) Treatment options for early osteoarthritis of the knee. 3. The Partial Knee Meeting 2016, 17–18 March 2016; Knokke, Belgium: a) Comparison of Cemented and Uncemented Partial Knee Arthroplasty (PKA) results. b) Comparison between published X-Ray Knee Instability and Degenerative Score (X- KIDS) and new Knee Arthroplasty Grading System (KAGS). c) Constitutional Knee Wear Patterns and Incidence for Partial Knee Replacement. 4. 13th Meeting of the Combined Orthopaedic Associations 2016 (COMOC), 11–15 April 2016; Cape Town, South Africa: a) The results of the Cementless Partial Knee Arthroplasty (PKA) and ACL reconstructions. b) Comparison between the published “X-Ray Knee Instability and Degenerative Score (X-KIDS)” and the new “Knee Arthroplasty Grading System (KAGS)”. c) Comparison of Cemented with Uncemented Partial Knee Arthroplasty (PKA) results. d) Constitutional Knee Wear patterns and incidence for Partial Knee replacement. 5. i-Decide 2016 Symposium (Stryker), 21–23 July 2016; Pretoria, South Africa: a) Assessment as to suitability for a UNI. 6. Amplitude International Knee Symposium, 22–24 September 2016; Lyon, France: a) Assessment of focal knee osteoarthritis for arthroplasty. 7. Oxford Partial Knee 40 Year Symposium, 26–27 September 2016; Oxfordshire, United Kingdom: a) The Knee Osteoarthritis Grading System. 8. Knee (Sports Medicine and Arthroplasty) and Hip Symposium, 27–29 October 2016; Cape Town, South Africa: a) The Knee OA Grading system (KOGS) as a Guide to Arthroplasty. 9. 18th EFORT Congress 2017 (European Federation of National Associations of Orthopaedics and Traumatology), 31 May – 2 June 2017; Vienna, Austria: xi a) The Knee Osteoarthritis Grading System (KOGS). 10. The Partial Knee Meeting 2018, 25–26 January 2018; Bruges, Belgium: a) Comparison of cemented and cementless Unicompartmental Knee Arthroplasty. 11. Life Healthcare Central Region CPD, 19 May 2018; Johannesburg, South Africa: a) The Knee Osteoarthritis Grading System (KOGS) for arthroplasty. 12. 64th SAOA Congress 2018 (South African Orthopaedic Association), 3–6 September 2018; Pretoria, South Africa: a) Wear Patterns of Medial and Lateral Compartments in the Knee. b) The Results of Anterior Cruciate Ligament (ACL) Reconstruction and Unicompartmental Knee Arthroplasty (UKA). c) Validation of KOGS (Knee Osteoarthritis Grading System). 13. Recon Instructional Course & Recon Interactions Meeting (Zimmer Biomet), 31 October – 2 November 2018; Cape Town, South Africa: a) Interactive X-ray case discussion. b) Avoiding early complications (and when to revise a PKA). 14. EKS Arthroplasty Conference 2019 (European Knee Society), 2–3 May 2019; Valencia, Spain: a) Validation of KOGS (Knee Osteoarthritis Grading System). b) The Results of Anterior Cruciate Ligament (ACL) Reconstruction and Unicompartmental Knee Arthroplasty (UKA). c) Wear Patterns of Medial and Lateral Compartments in the Knee. 15. Annual conference of Tissue Repair and Regeneration, 29–30 November 2019; Zhejiang Chinese Medical University, Hangzhou, China: a) Moving From Total to Unicompartmental Knee Arthroplasty: A Precursor to Tissue Repair & Regeneration of Arthritic Conditions of the Knee. 16. 66th Congress of the SAOA (South African Orthopaedic Association), 20–22 November 2020; Cape Town, South Africa: a) Impact of correctable mediolateral femorotibial subluxation on implant survival in patients with anteromedial Osteoarthritis. xii PUBLICATIONS AND BOOK ARISING FROM THE THESIS 1. Oosthuizen CR, Burger S, Vermaak DP, Goldschmidt P, Spangenberg R. The X-Ray Knee Instability and Degenerative Score (X-KIDS) to determine the preference for a partial or a total knee arthroplasty (PKA/TKA). SA Orthopaedic Journal. 2015;14(3):61-69. 2. Hamilton TW, Pandit HG, Lombardi AV, Adams JB, Oosthuizen CR, Clavé A, Dodd CA, Berend KR, Murray DW. Radiological Decision Aid to determine suitability for medial unicompartmental knee arthroplasty: development and preliminary validation. Bone Joint J. 2016 Oct;98-B(10 Supple B):3-10. 3. Campi S, Pandit HG, Oosthuizen CR. The Oxford Medial Unicompartmental Knee Arthroplasty: The South African Experience. J Arthroplasty. 2018 Jun;33(6):1727- 1731. 4. Oosthuizen CR, Takahashi T, Rogan M, Snyckers CH, Vermaak DP, Jones GG, Porteous A, Maposa I, Pandit HG. The Knee Osteoarthritis Grading System for Arthroplasty. Journal of Arthroplasty 2019 Mar;34(3):450-455. 5. Oosthuizen CR, Van Der Straeten C, Maposa I, Snyckers CH, Vermaak DP, Magobotha S. The patient results and satisfaction of knee arthroplasty in a validated grading system. Int Orthop. 2019 Dec;43(12):2747-2755. 6. Oosthuizen CR, Maposa I, Magobotha S, Pandit H. Impact of correctable mediolateral tibiofemoral subluxation on unicompartmental knee arthroplasty implant survival in patients with anteromedial osteoarthritis. SA Orthop J. 2021;20(4):196-201. 7. Oosthuizen CR. The UKA (Knee Osteoarthritis Grading System). Textbook South Africa: Reach Publishers, 2020. ISBN 978-0-620-85273-9. xiii ACKNOWLEDGEMENTS Thank you to all who contributed to the goal of developing a rudimentary tool for arthroplasty of the knee. ● Professor Sebastian Magobotha ● Professor Faith Bischof ● Professor Hemant Pandit ● Margaret Houman ● Andricha Viljoen ● Enie Mabokela ● Dr Maxwell Jingo and Brenda Milner ● The authors who contributed to the publications (Drs T. Takahashi, C.H. Snyckers, D.P. Vermaak, G.G. Jones, A. Porteous, I. Maposa, C. Van Der Straeten) ● The Oosthuizen family xiv TABLE OF CONTENTS DECLARATION ....................................................................................................................... ii STUDENT AND CO-AUTHORS DECLARATION ............................................................. iii ABSTRACT .............................................................................................................................. vi DEDICATION ....................................................................................................................... viii PRESENTATIONS ARISING FROM THE THESIS ............................................................... x PUBLICATIONS AND BOOK ARISING FROM THE THESIS .......................................... xii ACKNOWLEDGEMENTS ................................................................................................... xiii TABLE OF CONTENTS ........................................................................................................ xiv LIST OF FIGURES ............................................................................................................. xviii NOMENCLATURE ............................................................................................................... xix CHAPTER 1: INTRODUCTION AND LITERATURE REVIEW .......................................... 1 1 INTRODUCTION ......................................................................................................... 1 1.1 Epidemiology of Degenerative Knee Osteoarthritis .............................................. 3 1.2 The TKA ................................................................................................................ 3 1.2.1 Indications ........................................................................................................ 4 1.2.2 Results .............................................................................................................. 5 1.2.3 Surgical Technique Innovations ....................................................................... 6 1.2.4 TKA Design ..................................................................................................... 9 1.3 The UKA ................................................................................................................ 9 1.3.1 Indications ...................................................................................................... 10 1.3.2 Results ............................................................................................................ 12 1.3.3 Discussion about age ...................................................................................... 13 1.3.4 Developments ................................................................................................. 13 1.3.5 Barriers ........................................................................................................... 16 xv 1.3.6 Outcomes ........................................................................................................ 17 1.3.7 Function .......................................................................................................... 18 1.3.8 Complications and “revision” ........................................................................ 19 2 RESEARCH AIM ....................................................................................................... 21 3 GRADING SYSTEM DEVELOPMENT AND LITERATURE REVIEW ................ 22 3.1 The New Study: The Knee Osteoarthritis Grading System (KOGS) for Arthroplasty ..................................................................................................................... 22 3.1.1 The Constitutional TFJ wear pathology ......................................................... 23 3.1.2 The X-ray Method of KOGS .......................................................................... 24 3.2 Existing Grading Systems .................................................................................... 27 3.2.1 Kellgren and Lawrence System (K&L) 1957 ................................................ 27 3.2.2 Ahlbäck Classification System 1968.............................................................. 27 3.2.3 The X-Ray Knee Instability and Degenerative Score (X-KIDS) 2015 .......... 27 3.2.4 Radiological Decision Aid to determine the suitability for medial compartmental knee arthroplasty 2016 ........................................................................ 28 CHAPTER 2: RESEARCH METHODS ................................................................................. 29 1 METHODS .................................................................................................................. 29 1.1 Development and validation of the Knee Osteoarthritis Grading System (KOGS) – Publication 1 (see Chapter 3) ........................................................................................ 30 1.2 Implementation of the KOGS – Publication 2 (see Chapter 4) ........................... 32 1.3 Evaluation of the KOGS – Publication 3 (see Chapter 5) ................................... 33 2 SELECTION CRITERIA ............................................................................................ 34 2.1 Inclusion criteria .................................................................................................. 34 2.2 Exclusion criteria ................................................................................................. 34 CHAPTER 3: PUBLICATION 1 – THE KNEE OSTEOARTHRITIS GRADING SYSTEM FOR ARTHROPLASTY ......................................................................................................... 35 CHAPTER 4: PUBLICATION 2 – THE PATIENT RESULTS AND SATISFACTION OF KNEE ARTHROPLASTY IN A VALIDATED GRADING SYSTEM ................................. 43 xvi CHAPTER 5: PUBLICATION 3 – IMPACT OF CORRECTABLE MEDIOLATERAL TIBIOFEMORAL SUBLUXATION ON UNICOMPARTMENTAL KNEE ARTHROPLASTY IMPLANT SURVIVAL IN PATIENTS WITH ANTEROMEDIAL OSTEOARTHRITIS ................................................................................................................ 54 CHAPTER 6: DISCUSSION ................................................................................................... 61 CHAPTER 7: CONCLUSION ................................................................................................ 65 REFERENCES ........................................................................................................................ 67 APPENDIX A .......................................................................................................... 79 ETHICS CLEARANCE CERTIFICATE NO. M1704112 .................................. 79 APPENDIX B .......................................................................................................... 80 ETHICS CLEARANCE CERTIFICATE NO. M1704111 .................................. 80 APPENDIX C .......................................................................................................... 81 ETHICS CLEARANCE CERTIFICATE NO. M1704114 .................................. 81 APPENDIX D .......................................................................................................... 82 DATA COLLECTION SHEET FOR ETHICS CLEARANCE RECEIVED ..... 82 APPENDIX E .......................................................................................................... 83 INFORMATION SHEET PRESENTED TO PATIENT / INVITATION TO PARTICIPATE .................................................................................................... 83 APPENDIX F........................................................................................................... 85 PARTICIPANT CONSENT SHEET ................................................................... 85 APPENDIX G .......................................................................................................... 86 THE OXFORD KNEE SCORE (OKS) QUESTIONNAIRE .............................. 86 APPENDIX H .......................................................................................................... 88 PUBLICATION 1 – “COHORT A” ASSESSMENT SHEET FOR EVALUATORS ................................................................................................... 88 APPENDIX I ........................................................................................................... 89 PUBLICATION 1 – “COHORT B” ASSESSMENT SHEET FOR EVALUATORS ................................................................................................... 89 xvii APPENDIX J ........................................................................................................... 90 SPECIFIC INSTRUCTIONS TO EVALUATORS FOR “COHORT B” ASSESSMENT .................................................................................................... 90 APPENDIX K .......................................................................................................... 92 THE KNEE OSTEOARTHRITIS GRADING SYSTEM (KOGS) – TREATMENT GUIDE (ATLAS) ....................................................................... 92 APPENDIX L .......................................................................................................... 93 THE KNEE OSTEOARTHRITIS GRADING SYSTEM (KOGS) – LEGEND . 93 APPENDIX M ......................................................................................................... 96 STUDENT’S CONTRIBUTION TO THE RESEARCH AND WRITING OF THE PUBLISHED PAPERS ............................................................................... 96 APPENDIX N .......................................................................................................... 97 COPYRIGHTS FROM THE PUBLISHER – PUBLICATION 1 ....................... 97 APPENDIX O .......................................................................................................... 98 COPYRIGHTS FROM THE PUBLISHER – PUBLICATION 2 ....................... 98 APPENDIX P........................................................................................................... 99 COPYRIGHTS FROM THE PUBLISHER – PUBLICATION 3 ....................... 99 APPENDIX Q ........................................................................................................ 101 PLAGIARISM DECLARATION ...................................................................... 101 xviii LIST OF FIGURES CHAPTER 1 Figure 1.1: Anteromedial Osteoarthritis in the knee (a) treated with unicompartmental knee arthroplasty (b) and total knee arthroplasty (c) in the radiographs. ........................................... 2 Figure 1.2: Postoperative Anteroposterior and Lateral X-ray views of the knee. .................... 4 Figure 1.3: Anteroposterior long length alignment view. ......................................................... 8 Figure 1.4: Unicompartmental knee arthroplasty with the Mobile Bearing implant. ............. 10 Figure 1.5: Unicompartmental knee arthroplasty with the Fixed Bearing implant. ............... 10 Figure 1.6: Hip-knee-ankle view. ........................................................................................... 15 Figure 1.7: X-rays of varus coronal plane alignment in unicompartmental knee arthroplasty. .................................................................................................................................................. 15 Figure 1.8: The X-ray sequence views for the Knee Osteoarthritis Grading System. ............ 25 xix NOMENCLATURE AC1 First-order Agreement ACL Anterior Cruciate Ligament AMOA Anteromedial Osteoarthritis AP Anteroposterior AVN Avascular Necrosis CPAK Coronal Plane Alignment of the Knee CT Computed Tomography FB Fixed Bearing FDA Food and Drug Administration FFD Fixed Flexion Deformity FJS Forgotten Joint Score HKA Hip-knee-ankle IQR Interquartile Range JLCA Joint Line Conversion Angle JSN Joint Space Narrowing K&L Kellgren and Lawrence KA Kinematic Alignment KOGS Knee Osteoarthritis Grading System MB Mobile Bearing MCL Medial Collateral Ligament xx MRI Magnetic Resonance Imaging NJR National Joint Registry NZJR New Zealand Joint Registry OA Osteoarthritis OKS Oxford Knee Score PA Posteroanterior PCL Posterior Cruciate Ligament PFA Patellofemoral Joint Arthroplasty PFJ Patellofemoral Joint PKA Partial Knee Arthroplasty PROMS Patient-reported Outcome Scores RA Rheumatoid Arthritis ROM Range of Motion TFJ Tibiofemoral Joint TKA Total Knee Arthroplasty UK United Kingdom UKA Unicompartmental Knee Arthroplasty USA United States of America WOMAC Western Ontario and McMaster Universities Arthritis Index X-KIDS X-Ray Knee Instability and Degenerative Score 1 CHAPTER 1: INTRODUCTION AND LITERATURE REVIEW 1 INTRODUCTION The degenerative knee presents to the clinician at a symptomatic stage with patient variance depending on symptomatology, deformity, and functional impairment. In the National review of adult elective orthopaedic services in England (2015) [1], a revealing statement is made about the real value of orthopaedic procedures: “It is clear that one of the reasons for the rising demand for orthopaedic procedures is the significant life enhancing impact of the procedures. It is the swift return for patients to good or enhanced function and to work and normal family life, which makes orthopaedics such a high demand service. It is this financial benefit to the economy, of re-enabling people, that should be remembered when considering the cost and scale of the provision”. The research by Mohammad [2] of over 8,000 medial Oxford unicompartmental knee arthroplasty (UKA) procedures interpreted that: “Very good outcomes were achieved by both designer and non-designer surgeons. The patient-reported outcome scores (PROMS), medical complication rate, and non-revision re-operation rate were better than those found in meta- analyses and publications for total knee arthroplasty (TKA), but the revision rate was higher [3]. However, if failure is considered to be all re-operations and not just revisions, then the failure rate of UKA was less than that of TKA”. The registries reflect hard data with survival as the endpoint, not distinguishing the misguided use of the UKA for unsuitable indications. This was researched by Kennedy et al. [4] and their assessment was quite revealing on data from 2006 – 2010, determining that only 20% of those revised had initial correct indications for UKA, with one-third presenting with unsuitable osteoarthritis (OA) for arthroplasty i.e., not “Kellgren and Lawrence” (K&L) grade 4 [5]. Furthermore, two-thirds were revised inappropriately for undiagnosed causes of pain. The authors evaluating the New Zealand Joint Registry (NZJR) published “The lifetime revision risk” [6] and came to the conclusion that the risk of failure was higher in the younger UKA-group (46 – 50 years; 40.4%) and decreased sequentially to the oldest (86 – 90 years; 3.7%) with aseptic loosening the primary cause (and in females twice as prevalent as males) [6]. The incidence of sepsis was only 4% of all UKA revisions and 27% of the TKA with males 2 dominating this category according to Tay et al. [6]. This study from 1999 to 2019 with 13,481 cases [6], follows a previous assessment from Tay et al. coming to the same conclusion of the UKA revision tendency [7]. Goodfellow [8] with his NZJR data analysis of the initial report [9] found that, despite more excellent clinical outcomes and results, the UKA was revised more often than similar presenting TKA’s. Kazarian et al. [10] in a Markov study concluded that surgical treatment using the UKA is more beneficial and cost-effective than non-surgical treatment of the affected knee suitable for an arthroplasty. Figure 1.1: Anteromedial Osteoarthritis in the knee (a) treated with Unicompartmental Knee Arthroplasty (b) and Total Knee Arthroplasty (c) in the radiographs. The indications for a UKA and a TKA differ markedly, although they can overlap. The decision to use a specific prosthesis should be clinically evaluated. One of the major shortcomings in the use of the UKA is a specific tool to determine the most suitable and specific implant required. This can be achieved by grading accessible and cost- effective specialised knee X-rays with a validated grading system supporting the selection of the most suitable implant for the degenerative knee pathology. The essence of this thesis is to present a validated tool that can facilitate the improvement of (a) (b) (c) 3 the clinical assessment and advance the use of the UKA. The methodology of the “Knee Osteoarthritis Grading System” (KOGS) was based on the specified X-rays, observation of in-situ wear patterns, development of the “X-ray Knee Instability and Degenerative Score” (X-KIDS) [11] and the “Radiological Decision Aid” [12]. 1.1 Epidemiology of Degenerative Knee Osteoarthritis Degenerative knee OA is a dominant health driver with a major increase in expenditure in health sectors with the lifetime cost expenditure being $140,300 and eventual TKA in 54% of all OA knees [13]. This will increase to 70% of all OA knees having a TKA with the indications of arthroplasty increasing from a K&L [5] grade 3 or 4 to a symptomatic joint grade 2 with less structural damage (The increase of knee arthroplasty is estimated to be more than 650% in the next 15 years). Globally it is estimated that the UKA usage is about 10% [14]. In a macro study from the literature of 88 studies with 10,081,952 participants, “The Global Disease Study”, the prevalence of knee OA is 22% (over 40 years of age) and the “incidence of knee OA was 203 per 10,000 person-years” [15]. The UKA is effectively being under-utilised in the treatment of degenerative OA despite the prevalence of suitable recipients requiring a knee arthroplasty in the National Health Service in 47,6% of patients [16]. 1.2 The TKA The total knee replacement has been accepted for the last 40 years as the remedy for single compartment as well as tri-compartmental degeneration with minimal restriction in selection criteria. 4 Figure 1.2: Postoperative Anteroposterior and Lateral X-ray views of the knee. Total knee replacement in constitutional alignment. 1.2.1 Indications The knee presenting with OA can be suitable for a TKA without boundaries in application as the indications can be justified for any knee condition with degenerative changes as seen on the X-rays. This is a major concern as K&L [5] grades 2 and 3 become acceptable for such invasive surgery, as there is no system that can evaluate the X-rays to discern the options that are probably appropriate. The lack of defined indications and the use of the TKA as the appropriate implant is being questioned by various authors in recent times due to the poor functional outcomes achieved with current implants. Escobar et al. [17] developed a TKA appropriateness algorithm based on: • Pain • Function • Physical examination • Radiographic signs of OA • History of prior knee surgeries This algorithm selects at least 20% of TKA procedures investigated to be inappropriate [17]. Dan Riddle [18] adapted the algorithm for TKA in the United States of America (USA) and assessed 34% of the TKA procedures to be inappropriate. The improvement after surgery of the Western Ontario and McMaster Universities Arthritis Index (WOMAC) in the inappropriate group was only 2.3 points versus 19.8 in the rest of the 5 cohort in a follow-up study [19]. This is partly due to the ill-defined indications for a TKA without a reliable grading system of degeneration as a complimentary guide to the indications for arthroplasty. The TKA implant evolved using different surgical techniques to facilitate results that are acceptable in functionality and alignment with resection of at least the anterior cruciate ligament (ACL) with measured resection, ligament balancing and ‘kinematic alignment’ (KA) procedures. The TKA requires removal of the distal femoral cartilage with chamfer cuts as well as a tibia chondral and meniscal cartilage removal at an accepted neutral cut of 90° on the long axis of the tibial surface. This changes the majority of the patients’ native kinematics to facilitate an ‘acceptable and functional’ implant position. The development of condition-specific patient-prompted studies (PROMS) indicate poor acceptance and functional results of the TKA in more than 20% – 30% of recipients [20] concurring with the contention from Bellemans [21]. 1.2.2 Results The results of TKA obtained with the ‘condition-specific’ PROMS illuminated the difference between the functional ability the patient experiences and the survival rate that has been the prominent foundation feature for promoting the TKA ahead of the UKA. The awareness of individuality, associated with normal function for the individual patient, is becoming more relevant as the patient demands better function from arthroplasty. This dissatisfaction is being addressed by improving surgical techniques to better placement and alignment, according to criteria pre-determined by the surgeon and assisted by robotic science. Survival results for TKA is acceptable at 93% over 20 years and is higher than the UKA but with a higher permanent pain factor, with two times increase of venous thromboembolism, myocardial infarct, and deep infection. There is at least a three times higher incidence of a stroke, a four times higher risk of death in the first 30 days (and 15% higher for 8 years thereafter) and a functional deficit not assessed by the survival rate assessment criteria of the TKA [22]. The UKA revision rate to a TKA is higher than a TKA/TKA revision rate but the latter revision is exponentially more severe and complex, with poor results and a higher death rate according to Liddle [23-24]. 6 The ‘Hinge’ TKA has a mortality rate of 10% after 2 years and is still regarded not to be a failure, but changing a bearing due to impingement, or a dislocation, is regarded as a failure with the UKA. The prevalence of chronic pain (pain persisting longer than 3 to 6 months) in TKA is more than 20% of all procedures associated with utilitarian limitations, associated pain-related distress, depression, and social confinement according to a review study by Wylde [25]. This incidence is more than 10% in the study of Beswick et al. [26] with no author achieving less than 6% with permanent knee pain. The UKA produces better outcomes according to the meta-analysis and review study by Santoso et al. [27] and has a 0.7% incidence of permanent pain. Acceptance of the ipsilateral UKA/patellofemoral joint arthroplasty (PFA) option as an acceptable treatment rather than a TKA can contribute to reduce the high morbidity of the TKA revision [28]. 1.2.3 Surgical Technique Innovations In general, the TKA interventionists use John Insall’s description [29] of mechanical axis, so- called neutral alignment, as the ‘gold standard’; the alignment created does not fit all patients. Anatomical alignment for TKA was originally described by Hungerford and Krackow [30] to recreate the anatomic joint line where the overall joint line is set at 3° varus to the mechanical tibial axis. The reconstruction with these two-dimensional methods in knee arthroplasty is not always the reconstruction of the constitutional alignment, but the surgeon’s decision on alignment. Howell [31] patented and published the “Kinematic Alignment” (KA) technique in 2005 to restore normal alignment by using three kinematic axes; the transverse axis of the femur (the tibia flexes and extends around this axis); the transverse axis on the femur (the patella flexes and extends around this axis); and the longitudinal axis of the tibia (perpendicular to the joint line) for internal and external tibia rotation. The axes are either parallel to the joint line or rotate perpendicular to the joint line and is endeavoured to be maintained during the surgical procedure [32] with results published in 2013 showing a low re-operation rate of 1.4%. No catastrophic failures were found [32]. Bellemans [21], in this quest to restore constitutional alignment in the TKA milieu refined the assessment with their Coronal Plane Alignment of the Knee (CPAK) to define the various phenotypes that they assessed and classified with a new matrix on joint line orientation as 7 valgus and varus or neutral mechanical axes [33]. Their pursuit is not to restore ‘neutral’ alignment as defined by a neutral tibial cut in TKA but to circumvent the joint line conversion angle (JLCA) due to the pathological process, and assess pre-disease ‘native’ anatomy and alignment comfortable for the specific patient [21,33-35]. The surgical procedure will then implement the pre-disease position for the implant. The correct implementation of the CPAK method of evaluation and subsequent surgery requires long-term studies to confirm the efficacy. The concept is important and a quantum leap improvement in the TKA technique to individualise the anatomy for better placement. The problem that is not being addressed adequately is the implant that sacrifices the anatomy including ligaments. The open review study from Lording et al. [36] for EFORT in 2017 is concerned that the Bellemans-suggested system [21] does not fully consider the sagittal knee alignment and rotational alignment with soft tissue balance. The ‘correct placement’ of the TKA implant is driven by ‘robotic’ alignment techniques, creating a new industry with debateable benefit as seen in the current literature with a very large cohort of 2392 mechanical axis TKA and 2392 robotic TKA from Tompkins with a 5- year follow-up [37]. The study from Y. Kim [38] with a suitably large cohort of 975 robotic-assisted knees and 990 conventional TKA’s seems to confirm that after 10 years, the robotic implant insertion does not improve survival or functional score results and does not warrant the extra cost incurred for this treatment. The problems associated with robotic surgery is the cost and effective time in theatre [20], as the length of the procedure after 120 minutes determines the increase of infection [39] and therefore the higher probability of incurring additional revision costs. Figure 1.3 shows the native varus alignment on the right suitable for a UKA (KOGS Grade 1). The left knee has been treated with a primary TKA and, after failure, altered to a TKA hinge. The preferred treatment could have been a medial UKA for isolated medial compartment wear on the left knee, as is found in the right knee, to restore the constitutional alignment [40]. 8 Figure 1.3: Anteroposterior long length alignment view. The figure shows the native varus alignment on the right suitable for a UKA (KOGS Grade 1). The left knee has been treated with a primary TKA and, after failure, altered to a TKA hinge. The preferred treatment could have been a medial UKA for isolated medial compartment wear on the left knee, as is found in the right knee, to restore the constitutional alignment. The TKA is a solution of last resort and “UKA resurfacing techniques” should be considered if the indications are met as a substantive share of CPAK or kinematic “TKA repairs” could be treated with UKA implants that would be constitutionally aligned without the need for specific alignment technology. 9 1.2.4 TKA Design The new alignment techniques do not address the loss of the cruciate ligaments in a quest for normal kinematics in the TKA design, as the medial and lateral compartments must be individualised with variable thicknesses of bearing and retention of all stabilising structures e.g., the ligaments. The development of cruciate-retaining TKA implants improves the ‘TKA concept’ without addressing the restoration of the native anatomy and is a measured resection of the femur and then ‘implant fixed angulations’ and not the natural anatomy of the native knee. The advantage of this concept is the retention of the ACL and posterior cruciate ligament (PCL) function with a 3° intra-articular varus tibia cut and plastic bearing replacement as is required in the medial and lateral compartments. The knee that is suitable for this procedure is limited and classified as KOGS Grade 3B. This is where the patella is symptomatic and arthritic with a single tibiofemoral joint (TFJ) focal lesion and KOGS Grade 4A where both TFJ’s are present with OA in an intact ACL knee. The practical prevalence of this requirement is in the vicinity of 4% of all knee arthroplasty. The only ‘total’ arthroplasty that can attain near normal function is the use of a Bi-UKA rather than a TKA, as the resurfacing can be individualised in each compartment with the retention of the ligaments in isometric restoration, e.g., where the inherent KA is retained. The call is for improved non-operative treatment modalities to lower the cost, but the focus should be to improve the diagnosis and the development of a less-morbid procedure than TKA with stricter qualifications for this ‘end-stage’ treatment modality. 1.3 The UKA The major reason for the enduring acceptance of the TKA as the ‘gold standard’ is the controversies and results surrounding the different philosophies of the partial knee development, with the UKA driven by the success of the Oxford mobile bearing (MB) implant. The fixed bearing (FB) implant was recently improved with new available materials together with improved surgical technique in association with ‘robotic’ developments. 10 Figure 1.4: Unicompartmental knee arthroplasty with the Mobile Bearing implant. Postoperative Anteroposterior and Lateral views of the knee. Figure 1.5: Unicompartmental knee arthroplasty with the Fixed Bearing implant. Postoperative Anteroposterior and Lateral X-ray views of the knee. 1.3.1 Indications A significant consensus was reached at the European Knee Society in 2019 (Valencia) as it 11 declared the UKA the ‘gold standard’ for isolated knee pathology as the 10-year survival results of 96% for TKA and 94% for UKA is not significantly different and major benefits are derived for the patient with the minimal approach. Multiple publications contradicted the findings of Kozinn and Scott [41] in their 1989 publication postulating that the UKA could be used in 2% of all patients and is thus not practical to be used. The thresholds proposed by Kozinn and Scott [41] using weight, age, activity, the state of the patellofemoral joint (PFJ) and chondrocalsinosis should not be considered as contraindications for the use of the Oxford UKA. In the Pandit study of 1,000 prospective cases, the unnecessary contraindicated patients, in fact, did better than the “normal” indicated knees for UKA [42]. These were expanded to include isolated avascular necrosis (AVN) lesions and can be adjusted for FBs to include deficient ACLs [14,35-35]. The contraindications for the Oxford mobile option are deficient ligaments, infection and lateral facet OA or severe grooving of the patella with medial tibiofemoral disease [43]. The UKA as a treatment option had various influencing factors, including: • An initial poor result from the publication of the Oxford Group by Goodfellow from his first 103 Oxford’s in 1988 [44]. • Poor results achieved with poorly designed products and the inexperience of the surgeon was highlighted by Price [45] and Liddle [23] with great improvements over time. • Ratification of the indications and factors influencing the implementation of the UKA, such as age, sex, young males with higher failure risk, previous pathology, expectations of the patient and the expertise of the clinician are factors to consider according to Böhler et al. [46]. • The reproducibility of the surgical technique and the cost (the overall costs are almost always lower due to early discharge, less need for rehabilitation and less risk of major complications) [45-49]. • The different registry results [50] and the limitation of each variant (mobile and fixed) elevated the surgical barrier for frequent implementation of the device. • The inexperienced process of postoperative assessment; the progress of healing and understanding the long-term ‘pathological’ X-ray appearance (e.g., misinterpretation of ‘physiological’ radiolucency) [50]. • The ease of revising the UKA lowers the threshold for revision with even less pain than a similar TKA [8]. 12 • The TKA is the accepted treatment solution for complications, although the ipsilateral OA progression can be salvaged with a better functioning UKA (discussion by Justin Cobb at Bruges 2018 Partial Knee Meeting, ‘Resisting Register’s pressure’) [51]. • Complications associated with the UKA, e.g., dislocation, loosening and/or wear of the FB- design and promoting the FB as a short-term solution due to erosive wear [52]. • The UKA is in a much better position to deal with ethnic idiosyncrasies, e.g., smaller implants and hyperflexion requirements in normal life where a chair is a luxury or not needed, e.g., in the central Asian areas. 1.3.2 Results The National Joint Registry (NJR) for the United Kingdom (UK) reports a higher revision rate for UKA at 3.2 times that of TKA [53-55]. Even with PROMS, there is no advantage to doing the UKA according to the registries [53-55]. This is further complicated by the high-volume UKA surgeons, with an increased revision rate being classified as outliers in the UUK and were cautioned to improve their arthroplasty results despite instituting the more conservative and functional arthroplasty available (personal communication with Justin Cobb). The data from the NZJR indicates that UKAs have fewer poor results than TKAs and more excellent clinical outcomes but get revised more often as concluded by Goodfellow in his critique of this data analysis [8]. The NZJR results indicate that UKA revisions are higher and predominantly due to loosening, whereas the TKA dominates at 27% due to sepsis versus 4% in the UKA-group [6]. “The most striking difference in revision rates occurs in patients who have a worse score postoperatively than preoperatively” – an Oxford Knee Score (OKS) less than 20 [8]. Patients in these categories have a 10% chance of being revised if they had a TKA and a much greater chance of being revised (60%) if they had a UKA [24]. Therefore, the revision rate of the UKA in registries is three times higher than TKA with a low revision barrier in UKA, as TKA with similar OKS (see Appendix G) is revised in 10% of cases where it is virtually 100% in the UKA. The TKA/TKA revision is exponentially more severe and complex than UKA to TKA, with poor results and a higher death rate according to Liddle [23-24]. The indication is that factors that are independent of outcome, increases the revision rate by five times, and with increased utilisation and education, the revision rate could be minimised [4,24]. 13 1.3.3 Discussion about age The elderly are prime candidates for the less morbid UKA although there is the current tendency to administer the ‘final solution’, a TKA, to prevent further procedures [56]. The exponential rise of utilisation in the younger age group of 50-59 years is disconcerting, as the disproportionate increase cannot be attributed to an increase of population or obesity, but more likely to extended indications. Moreover, many studies have demonstrated that 25% of patients with a TKA are not satisfied with the condition specific result [57-58]. Long-term results recently published in 2018 by Kim et al. [59], concluded the UKA as a useful procedure for patients under 60 years of age despite the complications (dislocation (7.5%), loosening (2.5%) and of lateral progression (0.8%) usually associated with increased activity. The projection for primary and revision knee surgery as shown by Kurtz [60] confirms a large quantitative increase of arthroplasty from 2005 to 2030 with dire cost consequences, especially as the NZJR indicates that 27% of the TKA revisions are due to sepsis [6]. 1.3.4 Developments The long-standing conflict between the two different UKA philosophy proponents, MB, and FB, has been set aside to focus on the need to convince the orthopaedic surgeon and the public of the major improvements attained in recent years. Substantially, the UKA is a resurfacing technique with two different solutions developed: the FB implant as a polyradial metal femoral prosthesis and a flat polyethylene tibia e.g., the St Georg Sled (1969) and the Marmor (1972); and secondly the spherical MB design by Goodfellow and O’Connor in 1978. The hybrid development of a fixed and mobile bearing option on one tibia plateau is near completion and could solve the dislocation issue of the MB and the wear problem of the FB with a re-tread solution. The resurfacing with the Oxford MB philosophy is more precise in tolerance but without the femoral anatomy replication. The implant simulates the femoral rotation of the distal condyle achieving a kinematic centre of rotation with a mobile congruent bearing on a flat surface of the tibia. Due to the spherical nature and precise isometric placement, the MB accumulates less volumetric wear from the bearing surfaces and is more forgiving to surgical error with longer survival terms [34-35]. 14 The tibia in FB is a near-flat surface with eventual erosion of the bearing at the kinematic rotation point on the joint-line articulation surface. The FB developments are concentrated on replicating the femoral condyle anatomy as best possible with newer patient-specific computed tomography-based (CT) implants to prevent edge-loading with robotic technology being beneficial. The principle of both philosophies is to maintain the ligaments at anatomical length to facilitate isometric balance in flexion and extension as a replication of function and alignment, therefore the restoration of normal kinematics. The ultimate position that the TKA kinematic alignment [21,31-32] is trying to replicate is inherent in the MB design and to a lesser degree in the FB, as it is more difficult to attain. Genetic ‘abnormal kinematics’ can be the cause of the enhanced varus or valgus wear. On average this pathological cause of malfunction took 66 years in males and 65 years in females to become suitable for surgery and can hardly be improved by surgeon ‘rationality’ in knee arthroplasty. The CPAK-TKA concept is the closest replication of constitutional KA of the various phenotypes as described by MacDessi [33,61] and most likely a technical improvement on Howell [31-32]. The data indicates that there are 9 specific groups of knees with varus alignment contributing 31%, neutral alignment 54% and valgus aligned knees 13%. 15 Figure 1.6: Hip-knee-ankle view. Varus deformity confirmed with reduction in constitutional alignment as seen below. Figure 1.7: X-rays of varus coronal plane alignment in unicompartmental knee 16 arthroplasty. The measured difference of the varus seen in the left knee was reduced within 1° of the constitutional alignment as measured. It is likely that the CPAK matrix classification can benefit the identification of the ‘outlier UKA’ with a higher incidence of failure. These knees could be identified by the classification and can require adaptation of surgery in FB as seen by the results of Plancher [62] who did a study to see the benefit of ‘correct’ placement of the implant. It is unwise in the UKA to adapt the kinematics with bony cuts or ligament releases to facilitate ‘normal’ kinematics perceived by the surgeon. This is rarely necessary unless abnormal anatomy is identified and being corrected. The MB surgical technique was simplified with the ‘Microplasty’ insertion technique, developed by the Oxford-group. The dislocation of the bearing was a frequent complication prior to this technique and is now less than 1%. The insertion technique of the FB concept leans itself to the ‘robotic’ developments, as the femoral component requires precise insertion to prevent edge loading on a 90° neutral tibial implant. Currently the FB is taught to be inserted ‘loose’ as the precise tolerance of the MB technique cannot be replicated with normal instrumentation. 1.3.5 Barriers There are multiple barriers to the use of the UKA with peer group pressure, inadequate training, fear of ipsilateral progression, fear of a dislocating bearing and a daunting learning curve. The ‘influence’ of the PFJ OA is a common excuse to do a TKA rather than a UKA [63] with a real impact far beyond what the pathology deserves. This was evaluated by Hamilton in his research with no contraindication in most knees with degeneration unless lateral facet OA of the PFJ is present in a medial UKA or severe grooving of the PFJ [63]. Further problems are associated with the overload of TKA procedures required in teaching hospitals where the indications for a TKA is less restrictive and could be implemented and necessary in K&L grade 2 – 3 [5], resulting in trainees being less exposed to UKA. This assessment from Kennedy [4] exposed the high incidence of failure due to the lack of adherence to the indications proposed by the Oxford-group [34-35] of having bone-on-bone 17 contact (K&L grade 4 [5]). The cornerstone of the KOGS in the assessment for arthroplasty is bone-on-bone degeneration i.e., full thickness wear in at least one compartment considered to be a K&L grade 4 [5] to obtain the optimal recipient and prevent the use of UKA without the correct indication. 1.3.6 Outcomes The major advantage of the UKA is minimal invasion, retention of ligaments and maintenance of the native constitutional alignment and kinematics without any ligament balancing or ‘neutralising’ of the tibial cut. The confluence of the UKA technology, correct indications and surgical improvement has led to the “forgotten joint score” (FJS) evaluation by Zuiderbaan in 2017 [64] and corroborated by Gill in 2021 [65] comparing the TKA versus UKA, with the UKA significantly better in performance than the TKA. From a biomechanical point of view, the main characteristics of the medial and lateral compartments are different. The medial compartment is subject to high loads, with limited translation of the articular surface point of contact in the horizontal plane, whereas these displacements are more important with much smaller loads in the lateral compartment [66]. In his 2006 study, Weidow [67] demonstrated that a focal compartmental lesion accelerated wear in the ipsilateral compartment, and it is common sense to prevent further damage with the restoration of balance and stability with a minimal invasive solution like a UKA. The spherical mobile design accommodates unique anatomical features to individual patients e.g., recurvatum and excessive varus knees in CPAK 1 phenotype [33,61]. The results of the UKA have improved with less blood loss, less risk of transfusion, improved gait restoration function as well as fewer re-admissions after surgery [68]. The UK NJR of 2016 indicated better OKS for UKA but 2.1 times the revision rate of the TKA [69]. Current literature comparing the UKA to the TKA indicates similar effectiveness with similar outcomes over 5 years with higher patient approval and cost-effectiveness in the UKA group than in the TKA [22]. Multiple studies indicate the benefit of minimal invasive surgery with less morbidity with the UKA and better functional outcomes [70-72], as did a systematic review and meta-analysis by Wilson in 2019 [73] confirming the superior results for the UKA but with higher revision rates. 18 1.3.7 Function The UKA improves functional restoration with a reliable long-term outcome to complement the physiological age and the patients’ preference. UKA is the least destructive restoration of the anatomy, thereby restoring the constitutional kinematic pattern and proprioception at an earlier focal stage of degeneration (K&L grade 4 [5]) before secondary damage occurs. In a study by Ischii [74], he indicated that in any kind of TKA there is significant reduction of the quadriceps function compared to aged-matched controls and it deteriorates over time unless specifically maintained. This is the primary reason to retain function with anatomy-sparing procedures that maintain normal proprioception of the realigned knee. Jones and Cobb [75] from the UK and Seeger and Clarius [76] from Germany are proponents of the partial knee philosophy and especially interested in gait analysis after arthroplasty and the damage done with the removal of the ACL. They confirm in their studies the deficit caused by changing the TFJ offset in the accepted TKA practice. This creates an objective functional deficit in the TKA, with the UKA gait proven to be more physiological with a better cadence and higher top walking speed. This is further seen in the quicker return to sporting activities as well as better postoperative knee scores as evaluated by different authors such as Dr JC Ho [77]. In the Naal cohort [78], the rate of return to sporting activities achieved after 18 months was 95%. Most of their patients stated that the UKA surgery had maintained or improved their ability to participate in sports or recreational activities and they scored higher in the OKS – SF36, than normal age-related scores. Pietschmann [79] also reported that many of their patients (80.1%) returned to their sporting level of activity after UKA surgery. Isaac [80] demonstrated that the UKA resulted in better dynamic proprioception than TKA. In a prospective study in Edinburgh by Scott [81] of 289 TKA patients, of whom 261 (90%) worked before the procedure in active employment at the time of undergoing TKA, only 105 (40%) went back to work and, of these, 34% returned to their same jobs after a mean of 13.5 weeks. The conclusion is that the under 50-year-old patients invariably go back to work and between 50- and 60-year-old patients, only half returned to work. In this regard, the under 60- year-old patients with UKA perform much better, according to the literature, in activity levels after the surgery, according to Walker et al. studies in Heidelberg [82-83]. Further evidence from Waldstein [84] indicated the ‘activity return rate’ to be between 87% and 98% of patients in 2972 UKAs. Witjes in Sports Medicine 2016 [85] compared UKA with the TKA in returning to sporting activity following UKA and TKA, with the conclusion that UKA 19 attains the better result. In the younger age group, the dissatisfaction rate of a TKA is 25% according to the study from Edinburgh (Scott et al.) [57], with K&L grades 1 and 2 OA [5], poor preoperative OKS, complications and multiple operations contributing to the high dissatisfaction rate. The dissatisfaction rate improved to 14% for patients over the age of 80 when the functional requirement is less [57]. When the knee joint complies with the indications for a UKA intervention, there is no convincing evidence in the literature to substantiate delaying the procedure. With timeous interventions like the UKA to restore balance and alignment in the knee, the ipsilateral progression of OA can be reduced as assessed by Kang [86] in his study on patient-specific implants that reduced the contact stresses in the lateral compartment. Furthermore, the ipsilateral osteophytes in the healthy compartment are not predictors of reduced cartilage volume or wear, even with the most severe degree of osteophytes [87]. The increased motion in the ipsilateral compartment with focal pathology will also be reduced with the restoration of the constitutional kinematic pattern as evaluated by Weidow [67]. 1.3.8 Complications and “revision” The results of the UKA are blemished by the acceptance of a bearing dislocation by the arthroplasty community as an event of revision despite the remedy of replacing this with a thicker or same bearing when the cause of the dislocation was remedied without disturbing the bone implant interface. This creates an advantage for the TKA in survival results, not considering the qualitative, where the salvage TKA procedure becomes the ‘gold standard’ as a matter of course. A prospective study of 1,000 knees published in 2011 by Pandit [42] indicated a survival of the Oxford implant of 96% after 10 years with survival even greater, at 99.8% when the implant was not removed and preferably treated with an ipsilateral implant. This highlighted the problem of “revision” in UKA and the deemed poor results in the acceptance of ipsilateral progression as a failure despite the option of not removing the implant and treating the ipsilateral lesion with a UKA. The development of the classification of partial knee combinations to record and facilitate a staged approach to the OA knee treatment by Garner [88] will contribute to a positive view of ipsilateral OA treatment with UKA and complements the vision of a less invasive and staged tri-compartmental approach [89]. 20 There are three distinct problems associated with the UKA as a viable alternative to the TKA and our study aim is to address one of the major obstacles; the identification of the correct knee pathology for UKA and TKA as evaluated on X-ray. Problem 1: Radiological Identification of the suitable knee for a UKA or a TKA: A common theme of resistance to the less invasive UKA is that the suitable knee is seldom seen and therefore does not warrant the education or application to identify the selection despite the classifications of K&L [5] and Ahlbäck [90]. Keyes et al. [91] examined 200 knees and reflected that the Ahlbäck classification [90] represented the anatomical nature of medial gonarthrosis as seen on X-ray. The general view that the knee OA progression is certain to develop in the ipsilateral side despite a balanced insertion of a UKA was not supported in a 10-year survival study by Weale et al. [92], as the mechanical properties of the knee elements are restored. With the normal ligaments retained, isolated medial wear is a focal disease and does not progress to the other compartments if anatomically restored [16]. A major obstacle of this accepted treatment approach is the unreliable identification of the variety of degenerative stages of the tri-compartmental degenerative knee [93]. Problem 2: Learning curve and Surgical volume: Despite the majority clinician attitude, the UKA replicates the native constitutional alignment with the obvious advantages already relayed. The learning curve is steep as the use in the beginners’ hand is complicated due to negative peer group pressure, higher failure rate, treatment seen as temporary and the inability to select the correct knee with an empirical tool. The problematic lack of education and relative infrequent use of the implants is leading to high failure rates especially in teaching institutions where more terminal degenerative knees can be found. This is further amplified by the work from Kennedy [4] indicating poor selection of recipients for a UKA and subsequent failures. The NZJR 2010 [94] found a surgeon performing fewer than 12 UKA’s per annum has a higher revision rate than those performing more than 12. Liddle et al. [95] found that surgeons performing at least 20% UKA’s in their knee arthroplasty practices have the same revision rate as that of their TKA group. The reliability and reproducibility of the surgical techniques of insertion have been widely criticised in that it 21 compromised the survival results. The major negative influence of osteophytes in the ipsilateral compartment and PFJ is a common excuse for the TKA default usage. Problem 3: Development of new prosthetic innovations: There has been resistance from the ‘old school’ who prefers and are adept to implant TKA as well as the orthopaedic corporations driving new TKA enhancing technology with new window-dressing concepts. The lack of investment to enhance the UKA concept is largely due to the reluctance from the orthopaedic community to sanction the UKA technology. 2 RESEARCH AIM To introduce a novel Knee OA Grading System that enables an Orthopaedic Surgeon to identify the severity of the degeneration in the knee and reach an informed decision on whether a TKA or UKA would be most suitable for each patient. This study addresses the problem of selection with an X-ray based OA grading system as a tool for improved identification of the ‘stage of degeneration’ to assist the surgeon in implementing the preferred arthroplasty procedure for the degeneration diagnosed. The assessment guides the surgical decision when arthroplasty is considered and distinguishes between the need for a UKA or TKA. Using a grading system allows comparative research to evaluate the results of similarly graded degenerative knees being treated with different types of implants. The system supplements a good clinical examination, adherence to previous indications and contraindications as proposed by the Oxford school of thought [34-35]. The ultimate philosophy is to reconstitute native knee function using the normal anatomy as the reference and recovering constitutional alignment and therefore good clinical outcomes [34- 35,95-96]. The objectives to reach this aim: 22 a) Publication 1 (see Chapter 3): To develop and validate the novel deteriorative degenerative knee OA grading system. b) Publication 2 (see Chapter 4): To implement the validated grading system at multi-centre orthopaedic practices and compare the clinical results of KOGS graded knee deterioration with patient satisfaction data and implant survivorship with the completion of a PROMS questionnaire; the OKS (see Appendix G). c) Publication 3 (see Chapter 5): To evaluate the difference in outcomes of the classification categories/groups from the grading system. 3 GRADING SYSTEM DEVELOPMENT AND LITERATURE REVIEW 3.1 The New Study: The Knee Osteoarthritis Grading System (KOGS) for Arthroplasty There is no grading system classifying the knee degeneration for arthroplasty that includes the PFJ. The KOGS was developed from the X-KIDS [11] to be more intuitive, with the advantage of recognising the PFJ as part of the arthroplasty cascade. The current grading systems used to evaluate knee degeneration was proposed by K&L [5] in 1957 and Ahlbäck [90] in 1968 and reviewed by Keyes et al. [91] in 1992, confirming the medial compartment degenerative progression as illustrated by Ahlbäck [90]. These studies have been accepted since their publications as the basis for developing visual correlated treatment regimens for knee OA from conservative to arthroplasty. These classifications are currently used to determine the appropriateness for specific treatment options. Altman et al. [97] indicated that the best method to assess OA of the knee is with an anteroposterior (AP) weight-bearing radiograph, which assesses narrowing, osteophytes and sclerosis in the medial and lateral compartments and delivers the greatest sensitivity. He further classified the knee degeneration according to the cause in Idiopathic, Primary and Secondary groups covering all joints without a focus on the knee joint [98]. This was further improved by the posteroanterior (PA) Rosenberg/Lyon Schuss view assessment of the TFJ degeneration [99]. 23 3.1.1 The Constitutional TFJ wear pathology • Background: Knee degeneration is progressive if not treated at the right stage of development and it shows a repetitive and progressive pattern in the constitutionally aligned knee. The pathology can be mapped by evaluating the wear pattern on the tibia plateau surface and correlating wear to the X-ray appearance. This pattern has a natural progression due to repetitive constitutional knee kinematics e.g., in the medial compartment. • Progression of Constitutional Medial Wear: Medial UKA is suitable for degeneration of a stable knee (intact ligaments) or with the reconstruction of ligamentous stability. The medial TFJ wears predominantly central-medially, comprising isolated anterior and medial wear or, in advanced cases, as an indeterminate ‘deep dish’ encroaching on the posterior third of the surface as the ACL weakens [34-35,100-101]. The medial compartment process of degeneration without ligamentous insufficiency was evaluated by dividing the harvested plateau in UKA into three zones: anterior, middle, and posterior, as did the first authors who identified the anteromedial wear pattern suitable for UKA [102]. This is the natural deterioration progression found by the author over years of observation and is not applicable to every knee, but a projected process to understand the mechanical effect of the deteriorating evolvement [40]: a) Isolated wear on medial or anteromedial area. b) Early varus without subluxation depending on loss of cartilage thickness. c) Progressive varus with larger defect and secondary osteophyte formation in the medial, lateral, and patellofemoral compartments. d) Subluxation without ligamentous instability due to progressive wear defects. e) Lateral tibia spinous process impingement onto the lateral femoral condyle. f) Loss of extension due to anterior, posterior, and intercondylar osteophytes. The osteophytes anterior to the ACL and in the intercondylar notch will cause extension loss/fixed flexion deformity (FFD). g) Large medial wear defects will cause ‘pseudo-laxity’ with osteophytes contributing to the eventual ACL function loss and subsequent posterior wear on the tibial plateau with eventual tri-compartmental degeneration. 24 h) With increasing subluxation, the ACL signs of disruption are seen on the X-rays with rounding of the spiky spinous processes due to the instability. i) The PFJ and the lateral compartment deteriorates with further impingement of the tibial spine onto the femoral condyle [40,100]. j) With severe degeneration the knee ‘stabilises’ due to large defects with restriction of motion and massive osteophyte formation. • Progression of Constitutional Lateral Wear: The lateral degeneration process seems to cause the ACL rupture at a later stage, as there is less ‘instability; with subluxation (medial TFJ is less lax with less rollback) and only with severe and increasing valgus, medial collateral ligament (MCL) instability develops with rigidity of the lateral ligamentous structures. Range of Motion (ROM) is initially maintained and progressive wear with loss of extension is relatively mild. This is the also the natural deterioration progression found by the author [40]: a) Isolated wear causes increasing valgus. b) Progressive wear causes more external rotation of tibia. c) Medial compartment is maintained for longer with the degeneration progression. d) The ACL fails less often with progression in severe deformity. Lateral compartment degeneration is similar to the medial compartment but in reverse, where the wear is predominantly central and posterior on the tibial plateau. 3.1.2 The X-ray Method of KOGS • Sequences: 1. Standing AP [97,103] and Lateral [91,104] with patella skyline [105-107]. 2. Rosenberg view/Lyon Schuss 15° (medial TFJ) [99], 45° (lateral TFJ) [108-110]. 3. Stress views in 20° of flexion [34-35,111-112] confirm the stress views as the best for evaluating the contralateral compartment for wear and confirming the correctable varus wear with intact MCL. 25 Figure 1.8: The X-ray sequence views for the “Knee Osteoarthritis Grading System”. (a) Standing Anteroposterior view; (b) Lateral view; (c) Patella skyline; (d) Rosenberg view 15°; (e) & (f) Stress views. Standard X-rays are cost-effective and suitable for OA of the knee [113-115]. The standard X-ray is still the most accessible, user-friendly, and reliable system for general use, and is Food and Drug Administration (FDA) approved in arthroplasty [113-115]. This is accepted by the Oxford Group as the ‘gold standard’ for arthroplasty assessment as similarly published by the American Academy of Orthopaedic Surgeons comparing standard X-rays with the findings of Magnetic Resonance Imaging (MRI) [114]. The MRI is a too sensitive and more detailed evaluation of cartilage degeneration, but less pragmatic compared to standard radiography [115]. A plain radiograph (or even MRI scan) with typical bone-on-bone changes in an isolated compartment and presence of osteophytes in the other compartments, without evidence of joint space narrowing (JSN), is often diagnosed by (a) (b) (c) (d) (e) (f) 26 radiologists (or rheumatologists) as ‘tri-compartmental OA’, but evidence suggests that, despite the possible early OA defects, it does not convert to early UKA failure (OA progression) [116]. Adelani [114] concludes in his research publication that MRI is not the most suitable examination as a therapeutic gauge when the joint space is less than 50% of normal (the category that progressively becomes suitable for arthroplasty). For the surgeon it is economically unfeasible to incorporate MRI, with limited funds available in the treatment algorithm of knee OA. This is further compromised by the diverse interpretation from radiologists with little or no clinical experience. The development of an accurate Artificial Intelligence Application for routine evaluation of X-ray parameters can further enhance the value of simple X-rays and compensate for the MRI cost and sensitivity problem. There is room for the MRI when severe pain without the requisite bone contact between the femur and tibia need further assessment as to the possible cause of this pain, as part of the work-up before an arthroplasty is offered. The differential diagnosis must be completed, e.g., severe pain and inability to walk due to posterior root injury to the meniscus, bone contusion or infection, etc. Finally, despite the abnormal findings on an MRI, it does not always correlate with the outcome achieved when implementing a UKA [117]. This indeed makes life difficult for the treating orthopaedic surgeon, as patient and General Practitioner might be convinced that the only treatment option is a TKA, which is not necessarily the case. As it is apparent, this is, in part, due to the limitations of existing classification systems and partly due to the historical inherent bias against the UKA. Early intervention in OA without bone-on-bone wear does have poorer results [118-119]. The limitation of the MRI is its sensitivity with a megaphone effect on decision making and not practical for accessible use. The use of long-standing views – hip-knee-ankle (HKA), is not included in the series of required X-rays due to the extra cost not adding to the decision for a UKA or TKA. This is undoubtedly required when performing a constitutional kinematic reproducing procedure like that prescribed by Bellemans [21] and MacDessi [33,61]. The goal of the CPAK philosophy is for the replication of the constitutional alignment by classifying the nine different phenotypes of presentations and then to surgically replicate the 27 alignment. In the event of deciding against a UKA, the specific X-ray views e.g., long-standing views, should be considered, depending on the philosophy and surgical technique that is going to be implemented. 3.2 Existing Grading Systems 3.2.1 Kellgren and Lawrence System (K&L) 1957 The K&L system [5] is a method on a routine AP view of classifying the severity of knee OA using five grades, 0 ‒ 4: • Grade 0: no radiographic features of OA are present • Grade 1: doubtful JSN and possible osteophytic lipping • Grade 2: definite osteophytes and possible JSN on AP weight-bearing radiograph • Grade 3: multiple osteophytes, definite JSN, sclerosis, possible bony deformity • Grade 4: large osteophytes, marked JSN, severe sclerosis and definite bony deformity. 3.2.2 Ahlbäck Classification System 1968 The Ahlbäck classification system [90] estimates the severity of OA of the knee joint in patients with chronic knee pain using five grades, 1 ‒ 5: • Grade 1: joint space narrowing (less than 3 mm) • Grade 2: joint space obliteration • Grade 3: minor bone attrition (0 ‒ 5 mm) • Grade 4: moderate bone attrition (5 ‒ 10 mm) • Grade 5: severe bone attrition (more than 10 mm). The above-mentioned classifications [5,90] evaluate the severity of TFJ degeneration by X-ray. They do differ in grading as the latter is graded with a painful joint that progresses from K&L grade 3 [5]. The limitation of the system in knee surgery is that it is applicable to all joints without indicating a possible treatment in the knee. 3.2.3 The X-Ray Knee Instability and Degenerative Score (X-KIDS) 2015 The X-KIDS system (Oosthuizen et al.) [11] was developed incorporating K&L grade 4 [5] as a 28 starting point as well as researching a scoring method defining the extent of degeneration with ‘weighted points’ attributed to features commonly found with OA in the knee. This system identifies features (narrowing, osteophytes and subluxation) to improve the evaluation of factors that indicate degeneration and influence the surgeon when he decides on a specific prosthesis. An important shortcoming of the Score [11] is that it does not recognise the PFJ degeneration. The experience and publication of the X-KIDS was the catalyst for the eventual KOGS, as the system was laborious to learn and complicated without including the patella. This was addressed and validated with a much improved and simple grading system indicating the severity of the degeneration by grade progression. 3.2.4 Radiological Decision Aid to determine the suitability for medial compartmental knee arthroplasty 2016 The publication of the “Radiological Decision Aid” in The Bone and Joint Journal [12] was inspired by the proposal and publication of the X-KIDS [11] to improve the identification of the medial compartment degeneration that was suitable for a UKA. This is only medial compartment specific and did not include the lateral compartment or the PFJ. The existing systems indicate wear but unfortunately, they do not confirm the tri-compartmental status with important shortcomings such as the X-KIDS [11], nor does it recognise the PFJ degeneration. The limitation is that it does not evaluate the lateral compartment or severe isolated PFJ degeneration without TFJ involvement. The noted current X-ray systems cannot grade the tri-compartmental degeneration of the knee and therefore cannot give a holistic view – at a glance, on all three compartments to facilitate a decision for implant selection. The system is still subject to intra-articular findings not seen on the routine X-rays due to inadequate views or developing pathology like infection or AVN. 29 CHAPTER 2: RESEARCH METHODS 1 METHODS To achieve each of the objectives, different methods were required. The implementation of these methods formulated around the publication of three peer-reviewed research papers. The theoretical development of the KOGS was primarily due to the inability to find a system whereby, at a glance, an indication of the possible implant requirement could be made. The wear pattern of every patient was noted, photographed and the corresponding X-rays evaluated. This was then correlated with the Oxford indications for surgery as well as the literature from K&L [5], Ahlbäck [90], Keyes [91] and other salient publications like Rosenberg [99] and Goodfellow et al. [34-35]. The first system developed was a scoring system published in 2015, the X-KIDS [11] and this was followed by the further publication of “The Radiological Decision Aid” in 2016 [12]. This evolvement of KOGS is from existing grading systems, the evaluation of the anatomical pathology and the variety of implants currently available. These associations led to the eventual idea of a tri-compartmental system with progressive deteriorating evidence in the knee to represent arthroplasty surgery and complement new implant technologies. The nature of the grading is in a progressive degeneration with more intricate arthroplasty solutions that could be possible as the grading deteriorates. The results of the KOGS can be compared for different implants e.g., UKA versus TKA for KOGS Grade 1 knees. The “KOGS” grading system, if applied correctly, will allow an increased use of the UKA as the primary treatment with the TKA as a salvage procedure: • KOGS Grade 1: stable degenerative changes in one compartment. Treatment options: UKA medial or lateral (MB or FB) or PFA. • KOGS Grade 2: deteriorating condition due to progressive wear and weakening of the ACL, compared to KOGS Grade 1, with relatively unstable subluxation that is reducible. Treatment options: UKA medial or lateral (MB or FB). 30 • KOGS Grade 3A: degenerative changes in one compartment and with ACL not functional, ruptured or already replaced, there is a higher risk for further deterioration (there are two elements of knee stability affected). Treatment options: UKA medial or lateral (MB or FB) with ACL reconstruction. • KOGS Grade 3B: one TFJ and PFJ degeneration, two compartments involved with deteriorating knee (two elements affected). Treatment options: UKA medial or lateral + PFA. • KOGS Grade 4A: Both TFJs are involved with intact ligaments. Treatment options: suitable for Bi-UKA or cruciate retaining TKA. • KOGS Grade 4B: Terminal bi-compartmental OA knee with ACL or other ligament injury. Treatment option: suitable for TKA. 1.1 Development and validation of the Knee Osteoarthritis Grading System (KOGS) – Publication 1 (see Chapter 3) The development and validation of the KOGS was a retrospective study of patients’ records and X-rays. A cohort of 330 consecutive patients that received either UKA or TKA from the private orthopaedic surgery practice during January 2016 to October 2017 were included according to the selection criteria indicated below at Section 2 (Selection Criteria). The cohort was derived from patients presenting with terminal degenerative changes, deemed suitable for knee arthroplasty. There was no attempt to obtain a specific trait in this assessment but only to obtain professional opinions from knee surgeons familiar with UKA and TKA treatment options on a large cohort (330) of X-ray sequences. Their preference and skill were compared to the KOGS decision that they subsequently evaluated in a scrambled fashion of the same cohort. • X-ray: The prescribed sequence of X-rays was adequate to investigate the different tibial plateau wear patterns and the PFJ as assessed in the literature and concluded in the first publication as well as with the tibial wear pattern assessments. The sets of preoperative knee X-ray sequences from the cohort of the 330 consecutive patients (anonymised) were provided to seven experienced orthopaedic surgeons as “Assessment A” (see Appendix H) to assess and evaluate. All seven experts performed UKA and TKA surgeries 31 as part of their arthroplasty experience, with a spread of at least 20% UKA as the basis for participation. The assessment by the experts of the 330 cases was based on their experience as users of UKA and TKA and their interpretation of their individual preference. The experienced knee surgeon (individual evaluator) indicated whether a given patient is suitable for the implementation of a UKA or a TKA according to their normal routine based on the X-ray assessment of cohort “A”. For “Assessment B” (see Appendix I), the same sets of X-rays were scrambled and provided to the same evaluators as cohort “B” with the specific instructions, the KOGS (see Appendix J), to grade the degeneration in the knee accordingly. To establish inter-rater reliability, the results of “Assessment A” (cohort A) would then be compared to the results of “Assessment B” (cohort B) for each evaluator, to assess the level of concordance between their recommended type of knee arthroplasty and the KOGS. Construct validity of these results were compared with the surgical choice made by the surgeon (based on intraoperative findings) to establish the type of knee arthroplasty a patient was offered. • Data Analysis: As there are no similar studies in literature, expert statistical help and opinion was used with the assistance of Dr Innocent Maposa from the Faculty of Health Sciences, Health Sciences Research Office at the University of the Witwatersrand. The sample sizes, data and statistical analysis were different for each objective. The study did not target any trait or require any specific sample size, although it was suggested to be more than a 100, as the validation was based on the professional evaluation of the presented cohort of X-ray appearances. Statistical analysis was performed using STATA version 14 [120]. Assessments from the evaluators were analysed for compliance based on the assessment method used. Concordance and agreement methods were used in this study to assess the level of concordance of the seven evaluators between the A and B Cohorts for each evaluator and against the actual arthroplasty implemented. Concordance analysis is needed to establish the validity of a new diagnostic measuring or rating technique or to demonstrate the near equivalence of multiple measuring or rating techniques [121]. The generalised Cohen’s kappa coefficient for nominal measurements was used as well as Gwet’s first-order agreement (AC1) coefficient [122]. Strength of agreement between the assessors was rated as per the value of kappa coefficient (poor: <0.00, slight: 0.00- 0.2, fair: 0.21-0.4, moderate: 0.41-0.6, substantial: 0.61-0.8, and almost perfect: 0.81-100) [123]. 32 However, Cohen’s kappa has some weaknesses, that is, it is susceptible to trait prevalence and to balance these, Gwet’s AC1 coefficient was implemented. The latter is usually very stable in the presence of trait prevalence [124]. The agreement, kappa and Gwet’s AC1 coefficient results were interpreted according to benchmarks developed by Landis and Koch [125] and recommended by Viera and Garrett [123] and Wongpakaran et al. [124]. The outcome measures were: • To assess whether the recognition of isolated compartmental pathology is achievable with the implementation of the KOGS • To validate the novel KOGS classification as a suitable, reliable, and accurate tool when assessing an individual patient to undergo UKA or TKA. 1.2 Implementation of the KOGS – Publication 2 (see Chapter 4) The implementation of the validated grading system was a retrospective study of patient records, clinical results, and X-rays. A total of 1177 consecutive knees were gathered from three different multi-orthopaedic surgery practices, surgically treated with the recommended knee arthroplasty (UKA, PFA or TKA) from a good clinical examination by the respective orthopaedic surgeon and categorised by KOGS. The results of the data were evaluated according to each type of surgery performed, the incidence of major complications, the functional OKS, and the KOGS category. • Data Analysis: Patients categorised by KOGS and treated with the favoured implant (UKA, PFA or TKA) from different institutions were gathered to compare the clinical results with patient satisfaction data and implant survivorship. Survival analysis methods (such as the Kaplan-Meier survival curves and log-rank test) were utilised to assess the KOGS grading selection, the effect of time on major complications and implant survival probabilities by surgery option (based on the KOGS grading criteria) between patients’ characteristics. The outcome measure was: 33 • To evaluate the results of the supportive diagnostic tool (KOGS), thereby confirming that there are no significant differences in the survivorship prospect of patients that receive UKA and those that receive TKA based on the criteria. 1.3 Evaluation of the KOGS – Publication 3 (see Chapter 5) The evaluation of the difference in the outcomes of two categories/groups from KOGS was a retrospective and prospective comparative study of patient records and X-rays. The retrospective study consisted of 436 consecutive patients that received UKA from May 2012 to October 2017. The prospective study consisted of 272 cases of patients diagnosed with anteromedial osteoarthritis (AMOA) that received UKA from November 2017 to May 2020. The patients were assessed with KOGS and grouped accordingly: • Group 1 (KOGS Grade 1): patients diagnosed with AMOA without mediolateral subluxation or • Group 2 (KOGS Grade 2): patients diagnosed with AMOA with mediolateral subluxation. The results, implant survival and patient satisfaction were compared between the two groups. • Data Analysis: 436 knees were used for the retrospective study, and for the prospective study, 272 knees were used to compare KOGS Grades 1 and 2. Survival analysis methods (Kaplan-Meier and log- rank test) were utilised to compare implant survival between the KOGS Grades (1 and 2) and the cohorts (R and P). Associations between categorical variables were evaluated using Chi- square (χ2) or Fisher’s exact tests, as appropriate. Continuous variables were summarised and presented as mean and range, or as median and interquartile range (IQR). A student’s T-test for normally distributed data or the Mann-Whitney U-test for non-normally distributed data was used to compare group differences in continuous variables. The multivariable Cox proportional hazards model was used to determine risk factors for time to revision. The outcome measure was: • To compare and evaluate the outcomes of UKA between the two groups/grades as categorised by KOGS. 34 2 SELECTION CRITERIA For Publication 1 (see Chapter 3) as well as Publication 3 (see Chapter 5), all the evaluated patients were sourced from consecutive treated patients for arthroplasty in the private practice of Dr CR Oosthuizen. Publication 2 (see Chapter 4), the evaluated patients were sourced from all the authors in their private practices as indicated in the publication. The selection criteria are applicable to the full cohort of all three publications. 2.1 Inclusion criteria • Patients attending the Orthopaedic outpatients with knee pathology. • Patients older than 18 years. • A full complement of X-ray views must be available (i.e., Standing AP and Lateral with patella skyline; Rosenberg view/Lyon Schuss [99] 15° medial TFJ, 45° lateral TFJ and Stress views in 20° of flexion). • At least one of the three compartmental joints in the knee should have bone-on-bone contact (K&L grade 4 [5]). • The ‘unaffected’ (healthy) weight-bearing TFJ compartment must be more than 5mm in width and parallel (congruent) to the opposing joint surfaces on the stress view. 2.2 Exclusion criteria • Patients with incomplete records and X-rays. • Patient-specific considerations or preferences. • Patients with excessive deformities. • Patients with clinical findings such as AVN or Rheumatoid Arthritis (RA). • Clinically assessed disruption of ligaments. • Contraindications as proposed by the Oxford school of thought [34-35]. 35 CHAPTER 3: PUBLICATION 1 – THE KNEE OSTEOARTHRITIS GRADING SYSTEM FOR ARTHROPLASTY Oosthuizen C.R., Takahashi T., Rogan M., Snyckers C.H., Vermaak D.P., Jones G.G., Porteous A., Maposa I., Pandit H.G. Published: Journal of Arthroplasty. 2019 Mar;34(3):450-455. Impact factor: 4.757. Statement of Contributions of Joint Authorship Oosthuizen C.R.: 55% (Candidate) Conceptualisation of original idea, conducted the research, writing and compilation of the manuscript Takahashi T.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript Rogan M.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript Snyckers C.H.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript Vermaak D.P.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript Jones G.G.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript Porteous A.: 5% (Research Colleague) Participated in the research as the cohort investigator and co-author of manuscript 36 Maposa I.: 5% (Research Colleague) Assisted with data analysis, preparation of tables and figures and co-author of manuscript Pandit H.G.: 10% (Research Colleague) Assisted with data analysis, interpretation of results, reviewing the manuscript and co-author of manuscript Chapter 3 is an exact copy of Publication 1 referred to above. https://pubmed.ncbi.nlm.nih.gov/30528787/ The Journal of Arthroplasty 34 (2019) 450e455 Contents lists available at ScienceDirect The Journal of Arthroplasty journal homepage: www.arthroplastyjournal .org Primary Arthroplasty The Knee Osteoarthritis Grading System for Arthroplasty Christiaan R. Oosthuizen, MBChB, MMed (Orth) a, b, *, Tsuneari Takahashi, MD, PhD c, d, Mack Rogan, MBBCh, FRCS (Orth), FCS (Orth) e, Christian H. Snyckers, MBChB, MMed (UP), FCSA (Ortho) f, Duwayne P. Vermaak, MBChB, MSc (Sports Med), MMed (Orth) g, Gareth G. Jones, MBBS, PhD, FRCS (Orth) h, Andrew Porteous, MBChB, FRCS (Ed), FRCS (Tr & Orth) i, Innocent Maposa, MSc (Statistics), PhD (Statistics) j, Hemant Pandit, FRCS (Orth), DPhil (Oxon) d a Private Orthopaedic Practice, Johannesburg, South Africa b Division of Orthopaedic Surgery, University of the Witwatersrand, Johannesburg, South Africa c Department of Orthopaedic Surgery, Jichi Medical University, Shimotsuke, Tochigi, Japan d Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, Leeds, United Kingdom e Johannesburg, South Africa f Department of Orthopaedic Surgery, University of Pretoria, Pretoria, South Africa g Private Orthopaedic Practice, Pretoria, South Africa h MSk Lab, Imperial College, London, United Kingdom i Avon Orthopaedic Centre, North Bristol NHS Trust, Bristol, United Kingdom j Division of Epidemiology and Biostatistics, Faculty of Health Sciences, Wits School of Public Health, University of the Witwatersrand, Johannesburg, South Africa a r t i c l e i n f o Article history: Received 17 September 2018 Received in revised form 22 October 2018 Accepted 8 November 2018 Available online 15 November 2018 Keywords: X-ray osteoarthritis grading knee arthroplasty One or more of the authors of this paper have dis conflicts of interest, which may include receipt of paym institutional support, or association with an entity in may be perceived to have potential conflict of inte disclosure statements refer to https://doi.org/10.1016/ * Reprint requests: Christiaan Rudolf Oosthuizen, M 3158, Honeydew, Johannesburg 2040, South Africa.. https://doi.org/10.1016/j.arth.2018.11.011 0883-5403/© 2018 The Author(s). Published by Elsevie a b s t r a c t Background: The aim of this study is to validate the Knee Osteoarthritis Grading System (KOGS) of progressive osteoarthritic degeneration for the tri-compartmental knee. This system defines the site and severity of osteoarthritis to determine a specific knee arthroplasty. Methods: The radiographic sequence for KOGS includes standing coronal (anteroposterior), lateral, 30� skyline patella, 15� and 45� Rosenberg and stress views in 20� of flexion. Cohen’s kappa and related agreement statistical methods were used to assess the level of concordance of the 7 evaluators between A and B cohorts for each evaluator and also against the actual arthroplasty used. Sensitivity and speci- ficity was also assessed for the KOGS in identifying true partial knee arthroplasties (PKAs) and total knee arthroplasties (TKAs) as decided from the cohort A evaluations. Results: From a cohort of 330 patients who were included in the study, 71 (22.5%) underwent a TKA pro- cedure, 258 (78.2%) a PKA, and 1 (0.3%) was neither a TKA nor PKA. KOGS was able to identify true PKAs (sensitivity) in the range of 92.2%-98.5% across all the different evaluators. The KOGS method was able to identifya PKAor a TKAwith anaccuracy ranging from92% to 98.8% across all differe