INSTABILITY OF THE SHOULDER AFTER ARTHROPLASTY

A replacement arthroplasty was performed in 236 shoulders at The Hospi tal for Special Surgery from 1984 through 1989. Ten patients (eight wo men and two men) from that group were identified as having instability of the shoulder at the time of follow-up, and the results for these p atients were reviewed retrospectively. The ages of the patients ranged from fifty-six to seventy-nine years. The instability was anterior in seven of the patients and posterior in three. The anterior instabilit y was caused by a rupture of the repaired subscapularis tendon. The op erative treatment of the anterior instability consisted of mobilizatio n and repair of the tendon, but three of the seven patients continued to have instability. A static stabilizer, consisting of an allograft o f Achilles tendon, was inserted in these three patients, and the resul t was a success. The etiology of the posterior instability (three pati ents) was multifactorial. Treatment consisted of correction of any sof t-tissue imbalance and revision of the prosthetic components as necess ary. All ten patients were followed clinically and radiographically fo r at least two years. All of the patients had some loss of motion of t he shoulder as compared with the motion before the dislocation. There were no neurovascular complications, problems related to the allograft s, or any other complications. We concluded that proper balancing of t he soft tissues and positioning of the prosthetic components are essen tial to a successful arthroplasty of the shoulder. The postoperative r ehabilitation should include a physical therapy program in which the r ange of motion of the arm that was achieved in the operating room is n ot exceeded. Early recognition and treatment of tendon disruption is i mportant when acute injuries are being treated. Instability after an a rthroplasty was treated successfully with reconstruction of the soft-t issue envelope or revision of the prosthetic components, or both, and sometimes with the use of an allograft to replace deficient soft tissu es.