Successful osteosynthesis of an unstable mesoacromion in 6 shoulders: a new technique.

Six patients with impingement syndrome associated with an unstable mesoacromion underwent successful acromial fusion performed with a new technique. Preoperative symptoms included pain from a combination of 3 sources: movement at the mesoacromial cleft, junction of the medial cleft with the distal clavicle, and dynamic impingement of the unstable anterior acromion on the underlying rotator cuff. Two patients reported the onset of pain after a blow to the top of the acromion that supposedly rendered the mesoacromion unstable. Three patients had a tear of the supraspinatus tendon. The operative technique utilized 4.5-mm cannulated Herbert screws for fixation, a dorsal wedge osteotomy of the nonunion site, a dorsal bone graft fashioned from an anterior acromion cut, a figure-of-eight suture, and a postoperative abduction brace. Tilting the anterior acromial fragment up and fusing it together worked to relieve impingement. An acromioplasty was not performed. The 3 rotator cuff tears were repaired. After 3 to 6 years of follow-up, all 6 shoulders were rated as excellent according to criteria similar to that of the American Shoulder and Elbow Surgeons.

Magnetic resonance imaging for evaluation of failed repairs of the rotator cuff. Relationship to operative findings.

We used magnetic resonance imaging to evaluate thirty shoulders in twenty-nine patients who had unacceptable pain and loss of function after at least one operative procedure for a lesion of the rotator cuff. A preoperative history was recorded and physical and radiographic examinations were performed before magnetic resonance imaging. All patients had a reoperation two to 156 months (average, thirty-two months) after the operation. The results of the magnetic resonance imaging and the findings at the most recent operation were then compared with regard to the integrity of the rotator cuff, the deltoid muscle, and the long head of the biceps tendon. The sensitivity and specificity of magnetic resonance imaging for the diagnosis of full-thickness tears, partial-thickness tears, and intact rotator cuffs were 84 and 91 per cent, 83 and 83 per cent, and 80 and 100 per cent, respectively. The positive and negative predictive values were 94 and 77 per cent, 56 and 95 per cent, and 100 and 96 per cent, respectively. Three shoulders had a clinically detached and retracted origin of the deltoid muscle that was identified correctly on magnetic resonance imaging, and this finding was confirmed operatively. A rupture of the long head of the biceps tendon was identified correctly in four of six shoulders. In one of the two remaining shoulders, the rupture was obscured on magnetic resonance imaging because of a so-called balloon artefact from a nearby metal suture anchor. Magnetic resonance imaging detected two unexpected lesions: a denudation of the articular cartilage in one shoulder and a ganglion cyst in the supraspinatus muscle in another.

The anatomy and potential effects of contracture of the coracohumeral ligament.

In 63 anatomic specimens of the shoulder, the coracohumeral ligament was found to be a clear, well-developed structure in 59 and absent or vestigial in four. The origin of the coracohumeral ligament was consistently found at the base of the coracoid process. The insertion was more variable, between the rotator interval, supraspinatus, and subscapularis. In fresh specimens, the coracohumeral ligament was tight with maximal external rotation, which increased an average of 32 degrees on sectioning this ligament only. The coracohumeral ligament has been found to be shortened in various pathologic states. Its release may be required to restore restricted external motion when doing arthroplasties or to allow adequate mobilization of the tendons when repairing retracted tears of the rotator cuff.

Experimental evaluation of seven different spinal fracture internal fixation devices using nonfailure stability testing. The load-sharing and unstable-mechanism concepts.

Fracture site immobilization capabilities of seven internal spine fixation systems were experimentally evaluated: Harrington double distraction (plain, supplemented with Edwards sleeves, supplemented with sublaminar wires), Luque rectangle, Kaneda device, transfixed Kaneda device, and Steffee plates. Stability evaluation involved comparing the three-dimensional motion that occurred across an experimentally created L1 slice fracture, and the load resistance of the implants when subjected to axial, flexion, extension, lateral bending, and torsional loads. Each implant was tested on 15 different vertebral segments from 200-250-lb calves. All implants load-shared with the fractured vertebral column to varying degrees. All except the Steffee plate system showed an obvious biomechanical weakness in one or more load modes. The unstable 4R-4bar mechanism configuration of bilevel spinal implants was identified. Mechanism configurations allow free movement with little or no resistance to the applied load until load sharing by the spinal column stops the collapse and resists the applied load.