The operative treatment of fractures of the proximal humerus can be complicated by poor bone quality. Our aim was to evaluate a new method which allows prediction of the bone quality of the proximal humerus from radiographs. Anteroposterior radiographs were taken of 19 human cadaver humeri. The cortical thickness was measured at two levels of the proximal humeral diaphysis. The bone mineral density (BMD) was determined for the humeral head (HH), the surgical neck (SN), the greater tuberosity (GT) and lesser tuberosity (LT) using dual-energy x-ray absorptiometry. The mean cortical thickness was 4.4 +/- 1.0 mm. Specimens aged 70 years or less had a significantly higher cortical thickness than those aged over 70 years. A significant positive correlation was found between cortical thickness and the BMD for each region of interest. The cortical thickness of the proximal diaphysis is a reliable predictor of the bone quality of the proximal humerus.

Suture anchors should be placed in the proximal-anterior and -middle parts of the greater tuberosity. In the distal parts, biodegradable hook-like anchors should be used with caution.

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The rotator cuff muscles maintain glenohumeral stability by compressing the hunieral head into the glenoid. Disruption of the rotator cuff compromises concavity compression and can directly affect the loads on the glenohumeral joint. The purpose of this study was to quantify tlie effect of rotator cuff tears on the magnitude and direction of glenohumeral joint reaction forces during active shoulder abduction in the scapular plane using nine cadaveric upper extremities. Motion of the full upper extremity was simulated using a dynamic shoulder testing apparatus. Glenohumeral joint reaction forces were measured by a universal forcemoment sensor. Five conditions of rotator cuff tears were tested: Intcict, bicoiiiplete Suprcispiiiutus Teur, Coiiiplete SLil)rcis~)iiicitus Teur, Supru.~~~inutuslInfi.u.~piizatirs Tear, and Global Tear. Reaction forces a t the glenohumeral joint were found to steadily increase throughout abduction and peaked at maximum abduction for all conditions tested. There were no significant differences in reaction force magnitude for the intact condition (337 f 88 N) or those involving an isolated incomplete tear (296 f 83 N ) or complete tear (300 f 85 N) of the supraspinatus tendon. Extension of tears beyond the supraspinatus tendon into the anterior and posterior aspect of the rotator cuff led to a significant decrease in the magnitude of joint reaction force (126 f 31 N). Similarly, such tears resulted in a significant change in the direction of the reaction force at the glenohumeral joint. These results suggest that joint reaction forces are significantly affected by the integrity of the rotator cuff, specifically, by tlie transverse force couple formed by the anterior and posterior aspects of the cuff. The quantitative data obtained in this study on the effect of rotator cuff tears on magnitude and direction of the reaction force a t the glenohumeral joint helps clarify the relationship between joint motion, joint compression and stability.

Medialization and anteromedialization are equivalent in their ability to correct abnormal patellar mechanics and kinematics.

Tears of the rotator cuff are accompanied by muscle atrophy, which has direct implications on patient outcome after rotator cuff surgery. However, no reliable method exists to determine muscle volumes in situ. The current authors evaluated the reliability of magnetic resonance imaging in assessing rotator cuff muscle volumes. Muscle volumes were determined in 10 shoulders from cadavers using two methods: (1). oblique sagittal shoulder scans were obtained, the contours of the supraspinatus, infraspinatus and teres minor, and subscapularis muscles were traced, and muscle volumes were calculated using image analysis software; and (2). rotator cuff muscles were dissected and muscle volumes were measured by water displacement. The average magnetic resonance imaging volume of the supraspinatus, infraspinatus and teres minor, and subscapularis muscles were 36 +/- 12, 96 +/- 41, and 99 +/- 33 mL, respectively. There was a significant correlation between magnetic resonance imaging and water displacement measurements. The intraobserver and interobserver variabilities were less than 4%. The results indicate the magnetic resonance imaging is a reliable method to determine rotator cuff muscle volumes with good intraobserver and interobserver variability. This method may prove valuable preoperative assessment of rotator cuff muscles and prediction of outcome after rotator cuff repair.

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