Abstract
Purpose: The purpose of our work was to report causes and results of treatment of anterior shoulder instability after implantation of a shoulder prosthesis.
Material and methods: This retrospective multicentric study included 51 patients with prosthetic anterior instability: 42 patients after first-intention shoulder prosthesis and nine after prosthesis revision. There were 39 women (79%) and 12 men, mean age 67 years, who underwent total shoulder arthroplasty (n=29, 57%) or hemiarthro-plasty (n=22, 43%). Thirty-eight patients (75%) had prosthetic dislocation and 13 (25%) subluxation associated with pain an loss of anterior elevation. The initial prosthesis was implanted for degenerative disease (n=29), rheumatoid arthritis (n=7), or fracture (n=15). Anterior prosthetic instability occurred early in 23 shoulders (first six weeks) and lat in 28 shoulders (7 after trauma, 21 without trauma). Conservative treatment by reduction-immobilisation was performed in 16 cases and prosthetic revision in 35. The patients were reviewed radiographically at mean 41 months follow-up (range 24–62).
Results: Subscapular tear or incompetence was the main cause of prosthetic anterior instability, observed in 87% of the cases. Technical errors concerning the prosthesis were also observed: oversized head, malrotation of the prosthesis. Associated complications were frequent: glenoid loosening (24%), polyethylene dissociation from the metal glenoid implant (10%), infection (10%), humeral fracture (4%). The final Constant score was 54 points and 55% of the patients were disappointed or dissatisfied. None of the shoulders were stable after consevative treatment. The prosthetic revision provided disappointing results with 51% recurrent anterior instability.
Discussion: Anterior instability of shoulder prostheses is a serious complication which responds poorly to treatment. Loosening of the subscapular suture is the main cause.
The abstracts were prepared by Docteur Jean Barthas. Correspondence should be addressed to him at Secrétariat de la Société S.O.F.C.O.T., 56 rue Boissonade, 75014 Paris.
