Variation in human limb joint articular morphology |
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Authors: | Haley Horbaly Mark Hubbe Adam D. Sylvester Dawnie Wolfe Steadman Benjamin M. Auerbach |
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Affiliation: | 1. Department of Health and Human Performance, Congdon School of Health Sciences, High Point University, High Point, North Carolina, USA;2. Department of Anthropology, The Ohio State University, Columbus, Ohio, USA;3. Center for Functional Anatomy and Evolution, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA;4. Department of Anthropology, The University of Tennessee, Knoxville, Tennessee, USA Contribution: Conceptualization (supporting), Formal analysis (supporting), Writing - review & editing (equal);5. Department of Anthropology, The University of Tennessee, Knoxville, Tennessee, USA |
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Abstract: | Objectives Synovial joints in human limbs strike a balance between mobility, stability, and articular fit, yet little is known about how these conflicting demands pattern intraspecific variation in articular shape. In this study, we use geometric morphometrics to establish the apportionment and magnitude of morphological variance of the articular surfaces of the human shoulder, elbow, hip, and knee. We hypothesize that variances will be comparable between articulating surfaces within a joint and will be larger in joints with smaller ranges of motion, given their plurality of functional demands. Materials and Methods Three-dimensional landmarks were taken on the articular surfaces of the glenohumeral, humeroulnar, acetabulofemoral, and tibiofemoral joints from CT scans of 200 skeletons from the University of Tennessee Donated Skeletal Collection (84 females, 116 males). Root mean-squared distances between articulations calculated from Procrustes shape coordinates were used to determine variance distributions. Results We found no difference in variances for each articular surface between the sexes or between left and right articular surfaces. A high range of motion is associated with greater morphological variance; however, this pattern is largely driven by the concave articular surfaces of each joint, which consistently exhibit statistically greater variance than their convex counterparts. Discussion The striking pattern of differential variance between articulating morphologies points to potential disparities in development between them. Consistently higher variance in concave surfaces may relate to chondral modeling theory for the formation of joints. Establishing intraspecific morphological variance patterns is a first step in understanding coordinated evolution among articular features. |
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Keywords: | 3D geometric morphometrics articular surface functional morphology morphological variance synovial joints |
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