Tuberculosis spine 'radiological spine at risk signs' in the adult population

Kanyemba, Stanley Ndakoro
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Introduction: Spine Tuberculosis is a common location of bone tuberculosis infection, often resulting in a kyphotic deformity with significant structural and neurological functional fall-out and mortality. 1, 3-6 Prevention of this kyphotic deformity is key in management of spinal Tb. Radiological studies done by Rajasekaran et al. is the only extensively published literature describing this kyphotic deformity with a predictable pattern of 4 radiographical features referred to as the ‘Spine at Risk Signs’.3-6, 8, 10 In describing these 4 Radiological signs, Rajasekaran et al. state that any 2 or more out of 4 imply a significant risk to the spine, thus providing a useful classification, treatment and prognostication tool. Importantly however, these 4 features where described only in the paediatric population and we ‘borrow’ this description to describe all TB-spine Xrays. Therefore, with this study we set-out to see if the same observations could be made in the adult population. Method: Cross sectional retrospective review based on patient records and radiographs kept by the Spine-Orthopaedics Unit at Charlotte Maxeke Johannesburg Academic Hospital. Data collected: Data was collected from a sample of 61 adults (adults as defined for the purposes of this study to be ≥16 years of age) patients with TB spine. Demographic data (Gender, Age) Radiological (X-rays were read by five examiners: the researcher, two specialists and two junior residents) - Level of Disease Involvement - Presence / absence of each of the four Spine At Risk Signs (SARS) as described by Rajasekaran: Diagram of the tuberculosis radiological signs for the ‘spine at risk’ according to Rajasekaran3, 11 o Fig. 1 a) – Separation of the facet joint. The facet joint dislocates at the level of the apex of the curve, causing instability and loss of alignment. b) – Posterior retropulsion. This is identified by drawing two lines along the posterior surface of the first upper and lower normal vertebrae. The diseased segments are found to be posterior to the intersection of the lines. c) – Lateral translation. This is confirmed when a vertical line drawn through the middle of the pedicle of the first lower normal vertebra does not touch the pedicle of the first upper normal vertebra. d) – Toppling sign. In the initial stages of collapse, a line drawn along the anterior surface of the first lower normal vertebra intersects the inferior surface of the first upper normal vertebra. ‘Tilt’ or ‘toppling’ occurs when the line intersects higher than the middle of the anterior surface of the first normal upper vertebra - Total SARS score o Scoring system is developed from each of the Rajasekaran signs, each sign representing a value of 1 o There for 4 signs, the maximum value is 4 meaning all signs are present and minimal score = 0, meaning no signs are present. Data file was assembled in consultation with a statistician. Results: Five researchers looked at Anteroposterior and lateral X-rays of the Thoracic, Thoracolumbar and lumbar spine affected by Tb to establish the presence of the four Tb Spine at Risk signs as described by Rajasekaran. A Sample size of 61 patients deemed statistically significant and representative of the prevalence of Tb spine in the population older than 15 years, ages ranging from 16 to 72 years. In keeping with major prevalence data, the mean age of our study group was 42 years with the highest incidence in the age group 36 to 49 years old, with a female preponderance of spine Tb at 54.1 %. The other 2 age groups are 17-35 at 32.8% and 50+ age group at 29, 5%. The lumbar spine 54.1% was the most affected, followed by the thoracic 29.5 % and thoracolumbar spine 16.4 %, we excluded the cervical spine for the purposes of this study. Tabulation of Spine at Risk observations, % who identified the SARS out of 61 SARS a) Separation SARS b) Retropulsion SARS c) Translation SARS d) Toppling Observer 1 57.4 52.5 21.3 31.2 Observer 2 18.0 9.8 13.1 4.9 Observer 3 24.6 4.9 4.9 6.6 Observer 4 32.8 34.4 27.9 49.2 Observer 5 3.3 21.3 16.4 18.0 Table. 1 Spine at Risk Observations The above observations show tabulated observations per percentage, with no agreement of what was seen by the different observers. The significance of this observations points to the poor reliability of this classification system to everyday use. Furthermore, using Cochran’s Q statistics there is significant interobserver variability showing inconsistency in the same observation about the presence of ‘Spine At Risk Signs’. Additionally, looking at Spine at risk Classification. % who identified the patient as being at risk Spines at risk Observer 1 49.2 Observer 2 0.0 Observer 3 8.2 Observer 4 44.3 Observer 5 21.3 Table. 2 Spine at Risk Classification The classification Fig. 1, such as the patients scored out of 4 show a similar trend as the Observation. There is also no agreement between the observers as to what was seen to be at Risk. Conclusion: Scoring and classification systems are an important tool in clinical practice, therefore our need to use them. The ‘Rajasekaran Spine At risk signs’ are such a valuable tool, but was only describe to be used in the population group 15 years and younger. Therefore, our need to extend its use in all adults affected by TB spine. However, in our study we see significant interobserver variability with the same X-rays presented to different observers. It is important to have agreement between observers before we can say that a given tool is acceptable for wide clinic use. Additionally, we could not accept the application of the scoring system within the ‘Spine at Risk Signs’. There is an overall paucity of literature on this subject; perhaps, a follow up study should be undertaken with prior training of observers, observers going through a few X-Rays together followed by clear instructions to review the X-Rays.
Original research submitted as partial fulfillment of the requirements for the Masters in Medicine degree in Orthopaedic Surgery at the Faculty of Health Sciences University of the Witwatersrand, Johannesburg. 24 November 2016