Spectrum of lesions of the anterior capsular mechanism of the shoulder.

The anterior capsular mechanism appears to be the common denominator in a number of shoulder problems ranging from the recurrent dislocation ("too loose") to the frozen shoulder ("too tight"). The shoulder region and the anterior capsular mechanism can be carefully and accurately assessed by arthrography and cineradiography. Bicipital tenosynovitis has been held accountable for shoulder problems at each extreme of the spectrum. Bicipital tenosynovitis may exist in many shoulders; however, in corrective procedures for the unstable shoulder, the biceps becomes a dynamic reinforcement of the anterior capsule. In the frozen shoulder, the biceps tendon frequently is seen as normal at surgery and the anterior capsular mechanism is identified as the site of the essential lesion. Surgery may switch the patient's problem from one side of the spectrum to the other. Shoulder problems should be investigated thoroughly and evaluated in terms of the patient's requirements for shoulder motion as well as in terms of the orthopaedic surgeon's usual criteria for recommending corrective procedures.