Rotational changes in the throwing shoulder are due to bony as well as soft tissue adaptations.

Multiplanar spin-echo magnetic resonance imaging was performed on 54 patients with acute complete anterior cruciate ligament tears. Imaging was done within 45 days of index anterior cruciate ligament injury. Spin-echo T1- and T2-weighted images were used to determine the lesion morphology and location. Only the T2-weighted sagittal images were used for the incidence assessment; T2-weighted spin-echo imaging reflects free water shifts and best indicates the acute edema and inflammatory changes from injury. Eighty-three percent (45 of 54) of the knees had an osseous contusion directly over the lateral femoral condyle terminal sulcus. The lesion was highly variable in size and imaging intensity; however, the most intense signal was always contiguous with the subchondral plate. Posterolateral joint injury was seen in 96% (43 of 45) of the knees that had a terminal sulcus osseous lesion determined by magnetic resonance imaging. This posterolateral lesion involves a spectrum of injury, including both soft tissue (popliteus-arcuate capsuloligamentous complex) and hard tissue (posterolateral tibial plateau) injuries. The consistent location of the osseous and soft tissue injuries underscores a necessary similar mechanism of injury associated with these acute anterior cruciate ligament tears. Based on these characteristic findings, several proposed mechanisms of injury are discussed.

The electromyographic activity of eight muscles of the rotator cuff and shoulder girdle (supraspinatus, infraspinatus, subscapularis, pectoralis, latissimus dorsi, and the anterior, middle, and posterior deltoid) was measured from the nondominant shoulders of 11 subjects during a series of 29 isometric contractions. The contractions simulated different positions used for strength testing of the rotator cuff and involved elevation, external rotation, and internal rotation at three degrees of initial humeral rotation (-45 degrees of internal rotation, 0 degree, +45 degrees of external rotation) and scapular elevation (0 degree, 45 degrees, 90 degrees). Isolation of the supraspinatus muscle was best achieved with the test position of elevation at 90 degrees of scapular elevation and +45 degrees (external rotation) of humeral rotation. Isolation of the infraspinatus muscle was best achieved with external rotation at 0 degree of scapular elevation and -45 degrees (internal rotation) of humeral rotation. Isolation of the subscapularis muscle was best achieved with the Gerber push-off test. This study used four criteria for identifying the optimal manual muscle test for each rotator cuff muscle: 1) maximal activation of the cuff muscle, 2) minimal contribution from involved shoulder synergists, 3) minimal provocation of pain, and 4) good test-retest reliability. Based on the results of this study and known painful arcs of motion, an objective identification of the optimal tests for the manual muscle testing of the cuff was elucidated.

The objective of our study was to elucidate the characteristic pathoanatomy associated with patellar dislocation and report the preliminary results of early surgical repair. Twenty-three patients with documented patellar dislocation had standard radiographs and a magnetic resonance imaging scan. Intraarticular lesions were evaluated and treated arthroscopically followed by an open exploration of the medial aspect of the knee in 16 patients. Twelve patients were observed for a minimum of 2 years after surgical repair (average, 34 months). Eleven patients returned for a follow-up examination. Magnetic resonance imaging revealed effusion (100%), tears of the femoral insertion of the medial patellofemoral ligament (87%), increased signal in the vastus medialis muscle (78%), and lateral femoral condyle (87%) and medial patellar (30%) bone bruises. Arthroscopic examination revealed osteochondral lesions involving the patella and the lateral femoral condyle in 68% of cases. Open surgical exploration revealed tears of the medial patellofemoral ligament off the femur in 15 of 16 patients (94%). After medial patellofemoral ligament repair, none of the patients experienced recurrent dislocation. Overall 58% of the results were considered to be good or excellent and 42% were fair. Fifty-eight percent of the group returned to their previous sport with no or minor limitations.

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