Quantitative Anatomical Differences in the Shoulder

This study explored the radiographic and anatomical differences in normal shoulders between men and women, as well as factors such as race, height, weight, and age. A total of 205 patients with documented normal anatomical radiographs comprised the study population. Five fellowship-trained orthopedic surgeon reviewers measured head diameter, humeral head size, head to tuberosity distance, greater tuberosity width, neck-shaft angle, surface-arc angle, glenoid neck length, and distance from the lateral acromion process to the greater tuberosity on anteroposterior radiographs with the shoulder in external rotation. After the reviewers identified and marked defined anatomical landmarks, a comprehensive automated calculator was used to compute all parameters. Between men and women, head diameter (P<.001), humeral head size (P<.001), greater tuberosity width (P<.001), distance from the lateral acromion process to the greater tuberosity (P<.001), and glenoid neck length (P<.001) were significantly different, whereas race was not significantly different for any anatomical parameter. Using Spearman's rho, there was a strong correlation between head diameter/humeral head height and height (r_s=0.77/r_s=0.68), weight (r_s =0.62), and greater tuberosity width (r_s=0.66/r_s= 0.61); there also was a strong negative correlation between head to tuberosity distance and neck-shaft angle (r_s=-0.80). This study demonstrated precisely defined proximal humeral anatomical relationships and sizes using an advanced standardized imaging software program. With these data, orthopedic surgeons and implant designers can better understand the anatomy and glenohumeral relationships to re-create when performing total shoulder arthroplasty. [Orthopedics. 2017; 40(3):155-160.].