Browsing by Author "Tommy, Kimberleigh Ashley"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    A comparative study of trabecular structure of the patellofemoral joint: Evolutionary and biomechanical perspectives
    (University of the Witwatersrand, Johannesburg, 2024) Tommy, Kimberleigh Ashley; Schepartz, Lynne
    The knee joint in primates is important in facilitating a variety of locomotor behaviours. The patellofemoral joint (PFJ), which encompasses the distal femur and patella, has been relatively understudied from an evolutionary and biomechanical standpoint. The lack of detailed information limits our understanding of joint loading and associated kinematics. Trabecular bone is an ideal material for study as it is highly responsive to mechanical loading associated with different postural and locomotor behaviours. This thesis sought to pursue the question, ‘How do different activities, different locomotor kinematics, and different taxa manifest variation in the internal structure of this joint?’. To do this, trabecular structures in the distal femur and patella were explored using an inter- and intra- specific perspective. Trabecular parameters quantified in this study were bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular spacing (Tb.Sp), connectivity density (Conn.D) and degree of anisotropy (DA). All analyses were conducted on high-resolution MicroCT scans where eight volumes of interest (VOI) of the distal femur and nine VOIs in the patella were quantified. Inter-specific analyses were conducted on extant primates (Homo, Pan and Papio) and Plio-Pleistocene hominins from South Africa (Australopithecus sediba, Australopithecus africanus, and Homo sp./Paranthropus robustus). To explore intra-specific variation within a single species, two human samples (Later Stone Age foragers and contemporary Post-Industrial South Africans) were analysed to determine the effects of activity levels and knee joint pathology (osteoarthritis) on trabecular bone structure. The findings of this study show that there were significant differences in trabecular structure among extant primates and Plio-Pleistocene hominins that indicate unique loading across the PFJ, likely as a result of kinematically different bipedalism and a broader locomotor repertoire than seen in living humans today. This study also showed that significant differences in trabecular structure occur among some extant primate species and that these are likely linked to differences in knee joint loading arising from species-specific knee structure and positional/locomotor behaviours. Within Homo specifically, results showed that trabecular structure in the distal femur and patella differed between groups that demonstrated different activity levels and varying degrees of pathological osteoarthritis. Together, these results show that trabecular structure in the PFJ reflects complex loading and that further interspecific and intraspecific studies are necessary to improve our understanding of structural integrity in the primate knee.
  • No Thumbnail Available
    Item
    A comparative study of trabecular architecture in the distal tibia of humans, hominoids and australopiths from South Africa
    (2018) Tommy, Kimberleigh Ashley
    Trabecular fabric in the distal tibia has been shown to be sensitive to subtle variation in ankle sagittal plane kinematics during locomotor-related loading in both mammals (Barak et al 2011) and birds (Pontzer et al 2006). Differences or similarities within hominoid trabecular structure can be insightful for interpreting gait kinematic experimentation in the hominin lineage leading to the evolution of obligate bipedalism. This study assessed trabecular structure in the distal tibia of extant hominoids, and an outgroup of baboons, to infer locomotor kinematics of the ankle joint in fossil hominin species. Four hypotheses were tested through analyses of trabecular properties in the distal tibia: 1. Trabecular architecture deep to the tibial plafond of primates is effective at distinguishing species characterized by divergent locomotor behaviours. 2. Trabecular structure deep to the tibial plafond in primates mirrors known kinematics of extant species and will therefore reflect loading conditions imposed by posture and locomotion. 3. Trabecular structure in the distal tibiae of Australopithecus africanus specimens from Sterkfontein Member 4 is more human-like than ape-like in structure, reflective of bipedality. 4. Trabecular structure of the medial malleolus in the primate ankle contains a locomotor signal. High resolution computed tomography (MicroCT) images (25μm -48μm voxels) were used to quantify trabecular bone structure deep to the tibial plafond and the medial malleolus in extant comparative species attributed to modern human hunter-gatherers (Homo sapiens), Pan troglodytes, Gorilla gorilla, Pongo pygmaeus and Papio hamadryas as well as four fossil hominins from Sterkfontein Cave (Member 4), South Africa attributed to A. africanus. Nine trabecular subregions were isolated beneath the articular surface of the tibial plafond and two subregions were isolated beneath the articular surface of the medial malleolus. Subregions were segmented into spherical trabecular volumes for quantification of localized structure. Descriptive statistics were used to visualize variation among and within species, followed by an analysis of variance (ANOVA) of trabecular parameters between species to test for statistical significance of observed group differences (p=0.05). A further stepwise discriminant function analysis (DFA) was conducted to assess the capability of trabecular structure to discriminate between species with divergent locomotor behaviours based on trabecular structural properties. The results of this study suggest that trabecular bone structure in the distal tibia of the primate species sampled is effective at distinguishing between species that are characterized by different locomotor behaviour repertoires. Differentiation in homologous regions is greater in presumed highly loaded regions (anterior) and less in regions of presumed low locomotor imposed loading. Trabecular structure in the distal tibia of extant comparative species sometimes matched predictions based on known kinematic data, indicating that these trabecular signals are functionally driven by posture and locomotion. Trabecular fabrics of the medial malleolus in extant non-human primates exhibited structural properties that reflected increased bone strength in their anterior region, suggesting a difference in loading exists across the anteroposterior axis of the medial malleolus (e.g., possibly differentiating relative amounts of climbing), although this difference could not be statistically tested due to small sample sizes. Trabecular structure of A. africanus distal tibiae was highly variable, with some properties exhibiting greater variation than observed in any single extant species. The extent of this intraspecific variability in trabecular structure suggests the presence of two potentially different morphs in Sterkfontein Member 4. One morph resembled a baboon-like structure, composed of numerous thin trabecular struts that were highly oriented (i.e., anisotropically distributed), while the other morph resembled overlapping human-like and ape-like traits observed in previous studies of trabecular architecture in A. africanus. Based on the findings of this study, it can be concluded that trabecular structure in the distal tibia is effective at distinguishing species based on locomotor behaviour repertoires, provided that homologous regions are sampled, and that trabecular bone structure and organization mirrors kinematic indicators of ankle loading regimes. When these criteria are met, trabecular fabrics may be a useful tool for reconstructing behaviour in fossil hominin specimens in order to corroborate external morphological studies.