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Twenty-five shoulders with recurrent instability and associated anterior glenoid rim lesions were reviewed to 1) develop a classification system of the lesions, 2) evaluate radiographic techniques in detecting the lesions, and 3) analyze the outcome of surgery. Lesions were classified into three types: Type I, a displaced avulsion fracture with attached capsule; Type II, a medially displaced fragment malunited to the glenoid rim; and Type III, erosion of the glenoid rim with less than 25% (Type IIIA) or greater than 25% (Type IIIB) deficiency. Lesions were detected by plain radiographs (19 shoulders) or supplemental CT-arthrograms (12 shoulders) or both. In 16 Type I fractures, both the bony fragment and capsule were reattached to the glenoid rim. In five Type II and three Type IIIA lesions, only the capsule was repaired to the remaining glenoid rim. In the one Type IIIB lesion, a coracoid transfer was performed. At an average followup of 30 months, 22 shoulders (88%) had satisfactory results without recurrent instability, whereas three shoulders (12%) had postoperative redislocations. The majority of recurrent anterior dislocations with associated glenoid rim lesions can be treated by suturing the fracture fragment or capsule or both to the glenoid rim and addressing associated capsular laxity.

We studied 148 professional baseball players with no history of shoulder problems to assess range of motion and laxity of their dominant and nondominant shoulders. There were 72 pitchers and 76 position players. Average external rotation with the arm in 90 degrees of abduction was statistically greater and average internal rotation was statistically less in the dominant shoulders than in the nondominant shoulders, both in pitchers and position players. There was no statistical difference in forward elevation of external rotation with the arm at the side of the body in either group. Both dominant and nondominant shoulders of pitchers had greater average range of motion in forward elevation and external rotation (both at the side and at 90 degrees of abduction) and less average internal rotation than those of position players. Regarding laxity testing, 61% of dominant shoulders in pitchers had a sulcus sign, as compared with 47% in position players. Also, this degree of inferior laxity was significantly greater in pitchers than in position players. Differences in range of motion and laxity exist in the throwing shoulder of athletes involved in overhead throwing motions and should be considered in rehabilitation protocols and surgical repair.

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Forty-four patients, ranging in age from 17 to 57 years (average, 32), were evaluated an average of 4 years (range, 2 to 9) after surgical reconstruction for Allman-Tossy Grade III acromioclavicular dislocations. Twenty-seven patients underwent repair for acute injuries (< 3 weeks after injury) and 17 patients underwent reconstructions for chronic injuries (> 3 weeks). Coracoclavicular fixation with heavy nonabsorbable sutures was used to correct superior displacement in all cases. In addition, transfer of the coracoacromial ligament to the distal clavicle was performed in 15 of the 27 early repairs and 17 of the 17 late reconstructions. Overall, 26 of 27 (96%) early repairs and 13 of 17 (77%) late reconstructions achieved satisfactory results. There was a trend for better results and return to sports or heavy labor with early repairs; however, this was not statistically significant (P = 0.065). When the results of early repairs were compared with those of late reconstructions performed more than 3 months after injury, the results of the shoulders undergoing early repair were significantly better (P < 0.01). Overall, 39 of 44 (89%) patients achieved a satisfactory result. Surgical reconstruction for acromioclavicular dislocation provides reliable results including use of the arm for sports or repetitive work.

Summary:The tensile properties of the inferior glenohumeral ligament have been determined in 16 freshly frozen cadaver shoulders. The inferior glenohumeral ligament was divided into three anatomical regions: a superior band, an anterior axillary pouch, and a posterior axillary pouch. This yielded 48 hone-ligament-bone specimens; which were tested to failure in uniaxial tension. The superior hand was consistently the thickest region, averaging 2.79 mm. The thickness of the inferior glenohumeral ligament decreased from antero-superiorly to postero-inferiorly. The resting length of all three anatomical regions was not statistically different. Total specimen strain to hilure for all bone-ligament-bone specimens averaged 27%. Variations occurred between the three regions, with the anterior pouch specimens failing at a higher strain (34%) thar, those from the superior band (24%) or the posterior pouch (23%). Strain to failure for the ligament midsubstance (11%) was found to be significantly less than that for the entire specimen (27%). Thus, larger strain must occur near the insertion sites of the inferior glenohumeral ligament. Stress at failure was found to be nearly identical for the three regions of the ligament, averaging 5.5 MPa. These values are lower than those reported for other soft tissues, such as the anterior cruciate ligament and patellar tendon. The anterior pouch was found to be less stiff than the other two regions, perhaps suggesting that it is composed of more highly crimped collagen fibers. Three failure sites were seen for the inferior glenohumeral ligament: the glenoid insertion (40%), the ligament substance (35%). and the humeral insertion (25%). In addition, significant capsular stretching occurred before failure, regardless of the failure mode. Key Words: Ligament-Biomechanics-Inferior glenohumeral ligament-Material testing-Instability-Shoulder.Recurrent anterior glenohumeral instability (dislocation or subluxation) is a common clinical problem that can often lead to significant disability. Maintaining glenohumeral stability is a complex phenomenon that depends on the interaction of dynamic muscular forces and static capsulo-ligamentous restraints. Many investigators have at-

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Nine fresh-frozen, human cadaveric shoulders were elevated in the scapular plane in two different humeral rotations by applying forces along action lines of rotator cuff and deltoid muscles. Stereophotogrammetry determined possible regions of subacromial contact using a proximity criterion; radiographs measured acromiohumeral interval and position of greater tuberosity. Contact starts at the anterolateral edge of the acromion at 0 degrees of elevation; it shifts medially with arm elevation. On the humeral surface, contact shifts from proximal to distal on the supraspinatus tendon with arm elevation. When external rotation is decreased, distal and posterior shift in contact is noted. Acromial undersurface and rotator cuff tendons are in closest proximity between 60 degrees and 120 degrees of elevation; contact was consistently more pronounced for Type III acromions. Mean acromiohumeral interval was 11.1 mm at 0 degrees of elevation and decreased to 5.7 mm at 90 degrees, when greater tuberosity was closest to the acromion. Radiographs show bone-to-bone relationship; stereophotogrammetry assesses contact on soft tissues of the subacromial space. Contact centers on the supraspinatus insertion, suggesting altered excursion of the greater tuberosity may initially damage this rotator cuff region. Conditions limiting external rotation or elevation may also increase rotator cuff compression. Marked increase in contact with Type III acromions supports the role of anterior acromioplasty when clinically indicated, usually in older patients with primary impingement.