Geometric analysis of the humeral head and glenoid in the Indian population and its clinical significance

Abstract Background Total anatomic and reverse shoulder prostheses are designed to match the dimensions of the native bony anatomy. Chinese and Japanese bony dimensions of the shoulder have been found to be different from that of the Caucasian population. We hypothesized that the geometric dimensions of the humeral head and glenoid in the Indian population will also be different from that of the Caucasian population. Method Fifty patients underwent computerized tomographic scans of their normal shoulders. We calculated the Supero-Inferior (SI) diameter of the humeral head, Antero-Posterior (AP) diameter of the humeral head, radius of curvature of the humeral head, humeral head retroversion, humeral head thickness, inclination angle, critical shoulder angle (CSA), greater tuberosity angle (GTA), glenoid width, glenoid length, radius of curvature of the glenoid, glenoid inclination angle and glenoid version. Results The radius of curvature of the humeral head averaged 22.9 ± 1.7mm; the articular surface thickness, 17.1 ± 1.6mm; the SI diameter, 42.3 ± 3 mm. The SI diameter strongly correlated with the thickness (r = 0.617, p = 0.001). The AP/SI articular surface diameter ratio averaged 0.9 ± 0.9; articular surface thickness/ radius of curvature ratio, 0.7 ± 0.9; the inclination angle, 133.8 ± 6.4; and the retroversion angle averaged 33.5° ± 8.5°. The radius of curvature of the glenoid averaged 23.3 ± 3.4 mm; glenoid width, 24.0 ± 2 mm; SI length, 31.3 ± 2.2 mm; the glenoid inclination angle, 78.7°± 4.8° and the glenoid retroversion averaged 1.8° ± 3.8°. Discussion Compared with the Western population, our cohort had a smaller humeral radius of curvature (p=0.04), smaller articular surface diameter (p = 0.001), smaller inclination angle (p = 0.003), larger retroversion angle of the humeral head (p Conclusion Smaller sized options in humeral head diameter and thickness of the anatomic prosthesis and glenoid baseplate of the reverse shoulder prosthesis need to be made available to suit our population and avoid a mismatch.