[Reverse prosthesis and os acromiale or acromion stress fracture]

We reviewed cases of acromion stress fracture or os acromiale among a consecutive series of 240 reverse prostheses implanted between 1995 and 2003.

Ten patients presented os acromiale, ten fracture-fragmentation of the acromion, and one nonunion of the scapular spine. The reverse prosthesis was implanted via a deltopectoral approach with no specific procedure on the acromion. There were 17 women and four men, mean age 72 years. The dominant side was involved for 70%. The prosthesis was indicated for excentered glenoid deterioration (n=14), massive rotator cuff tears without osteoarthritis (n=5), and failure of a hemiarthroplasty (n=2). Seventeen patients were reviewed with more than two years follow-up.

87.5% of the acromial lesions became dislocated postoperatively due to the traction of the deltoid. There was no significant difference between os acromiale and acromion stress fracture. The acromial displacement did not compromise the objective outcome since the Constant score was comparable to that obtained in 179 cases with no acromial lesion reviewed with the same follow-up. Unlike these later shoulders, there were two cases of scapular spine fracture postoperatively, leading to poor function (pain and motion scores less than the global score).

Acquired or congenital acromial lesions are not a contraindication for reverse prosthesis. Postoperative fracture of the scapular spine is less well tolerated and may required revision for osteosynthesis.