An anthropometric evaluation of the glenohumeral joint in a South African population.
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The glenohumeral joint (GHJ), the most mobile yet unstable joint in the body, is comprised of a large humeral head which fits into the relatively smaller socket formed by the glenoid fossa. While this articulation allows for a wide range of motion, it predisposes the shoulder to injury. There is a paucity of literature on the biomechanics of the GHJ in the South African population. The aim of the study was to evaluate the anthropometric parameters of the GHJ, with emphasis on the coracoid process, glenoid fossa, bicipital groove (BG), long head of the biceps brachii tendon (LHBBT) and the transverse humeral ligament (THL). This study comprised of two subsets (n = 404), viz. (i) anthropometric evaluation of the scapula and proximal humerus [n=324: Scapula – Right (R): 80, Left (L): 84; Male (M): 68, Female (F): 96; Humerii – (R): 80, (L): 80; (M): 68, (F): 96] and (ii) cadaveric dissection of the LHBBT and THL [n=80: (R): 40, (L): 40; (M): 44, (F): 36], both of which focused on morphological and morphometric parameters. Results (i) (a) Shape of glenoid fossa = Type 1 (inverted comma): (R): 16.47%, (L): 10.98%; (M): 20.12%, (F): 7.32%; Type 2 (pear): (R): 14.02%, (L): 15.24%; (M): 18.29%, (F): 10.98%; Type 3 (oval) : (R): 18.29%, (L): 25.00%; (M): 27.44%, (F): 15.85%. (b) Notch type of glenoid fossa: Type 1 (without a notch): (R): 1.83%, (L): 7.32%; (M): 6.71%, (F): 2.44%; Type 2 (with one notch): (R): 46.95%, (L): 43.90%; (M): 59.15%, (F): 31.70%. (c) Mean parameters of coracoid process (mm): Length (CL): (R): 41.74±4.74, (L): 41.50±4.87; (M): 42.07±4.73, (F): 40.74±4.84; Width (CW): (R): 13.27±1.89, (L): 14.18±11.90; (M): 13.05±1.90, (F): 15.07±14.49. (d) Mean parameters of glenoid fossa (mm): Horizontal diameter 1 (HD1): (R): 18.40±3.27, (L): 17.51±2.87; (M): 18.23±3.29, (F): 17.38±2.60; Horizontal diameter 2 (HD2): (R): 24.45±2.88, (L): 23.64±2.63; (M): 24.22±2.74, (F): 23.68±2.83; Vertical diameter (VD): (R): 35.23±3.10, (L): 34.88±3.03; (M): 35.26±3.18, (F): 34.64±2.79. (e) Mean coracoglenoid distance (CGD) (mm): (R): 27.40±8.34, (L): 28.15±3.53; (M): 28.19±7.41, (F): 27.00±3.38 .(f) Mean dimensions of BG (mm): Length: (R): 66.64±9.06, (L): 68.31±11.52; (M): 67.44±9.12, (F): 67.53±12.25; Width: (R): 8.98±1.49, (L): 9.27±1.30; (M): 9.18±1.45, (F): 9.05±1.31; Depth: (R): 7.73±1.31, (L): 7.20±1.18; (M): 7.43±1.29, (F): 7.53±1.24. (ii) (a) Mean parameters of the LHBBT (mm): Length: (R): 81.99±21.28, (L): 79.73±17.27; (M): 79.82±19.66, (F): 82.14±19.03; Width: (R): 4.28±1.31, (L): 4.67±1.43; (M): 4.35±1.17, (F): 4.63±1.60. (b) Mean parameters of the THL (mm): Length: (R): 20.91±5.24, (L): 21.19±6.36; (M): 21.52±5.71, (F): 20.48±5.92; Width: (R): 16.65±6.92, (L): 16.63±7.49; (M): 16.83±6.65, (F): 16.40±7.84. In this study, Type 3 (oval) was observed to be most prevalent shape of the glenoid fossa, which corroborated the findings of previous studies. Type 2 (with one notch) was found to be the predominant notch type, differing from the literature reviewed. The mean VD, HD1, HD2, CL and CGD were larger in male individuals, while female individuals presented with larger means of CW. Both BG length and depth were increased on the right side; with the latter yielding a statistically significant difference thus suggesting that an increased depth is a common finding in the right side of individuals. Although the BG length and depth were noted to be greater in female individuals, male individuals presented with larger widths. The mean length and width of the THL were markedly smaller than those reported in previous studies. Any variation from the normal musculoskeletal composition of the GHJ is fundamental to understand rotator cuff disease, tendinitis and shoulder dislocation. This study may provide clinicians and biomechanical engineers with reliable anthropometric reference parameters of the GHJ for the design of prosthesis and may also act as diagnostic tools of degenerative pathology.