Analysis of rotator cuff muscles in adult human cadaveric specimens.

Management of irreparable massive rotator cuff tears remains a challenging and controversial problem. Defining glenohumeral force relations may allow for the development of treatment strategies based on biomechanical principles. Five fresh-frozen adult human cadaveric shoulder specimens were dissected to determine fiber length, mass, and lever arm of (a) the 3 bellies of the deltoid and (b) the rotator cuff muscles (supraspinatus, infraspinatus, teres minor, subscapularis). From these data, physiologic cross-sectional areas and moment relations were calculated. These relations provide evidence for a balanced axial force couple between the anterior and posterior rotator cuff. Demonstration of an axial force couple across the glenohumeral joint may have clinical significance for treatment of irreparable massive rotator cuff tears and may explain why many patients with full-thickness rotator cuff tears can regain acceptable shoulder function.

Anatomy, pathologic features, and treatment of acetabular labral tears.

There is an evolving body of knowledge regarding the acetabular labrum. Labral tears are most frequently anterior and often are associated with sudden twisting or pivoting motions. High clinical suspicion in association with positive physical findings are fundamental for the clinician to properly determine treatment for the suspected tear. Labral tears, especially those present for years, may contribute to the progression of hip osteoarthritis. Patients at risk include those with developmental dysplasia, those with tears greater than 5 years, and those with associated chondral full-thickness lesions. Chondral injuries may occur in association with a multitude of hip conditions including labral tears, loose bodies, osteonecrosis, slipped capital femoral epiphysis, dysplasia, and degenerative arthritis. Labral tears occurring at the watershed zone may destabilize the adjacent acetabular conditions. Arthroscopic observations support the concept that labral disruption, acetabular chondral lesions, or both frequently are part of a continuum of degenerative joint disease.