Radiographic study of the anatomic relationships of the greater tuberosity.

Accurate reproduction of the anatomic relationship is important in nonconstrained prosthetic arthroplasty. However, the geometry of the glenohumeral joint for prosthetic components has not been established. In this study, we evaluated the relationship between the position of the greater tuberosity and various geometric measurements in the glenohumeral joint. Radiographs of 519 shoulders without osseous lesions were reviewed. There were 296 male and 223 female patients, with a mean age of 49.7 years. Four parameters were measured on true anteroposterior radiographs, including the distance between the humeral head-greater tuberosity junctional point and the top of the humeral head, as well as the neck shaft angle. There were significant differences in all parameters between males and females. The distance between the humeral head-greater tuberosity junctional point and the top of the humeral head significantly correlated with the neck shaft angle in both males (P <.01, r = 0.468) and females (P <.01, r = 0.639). If the neck shaft angle of the replacement is smaller than the anatomic neck shaft angle of the patient, the placement of the humeral head component with the same distance between the humeral head-greater tuberosity junctional point and the top of the humeral head as that before surgery might not reproduce the anatomic glenohumeral joint. We conclude that determining the distance between the humeral head-greater tuberosity junctional point and the top of the humeral head and its relationship to the neck shaft angle is important for the prevention of postoperative subacromial impingement.