A total of 30 dislocations were identified for an overall incidence of 2.3% (30 of 1293) in the practice of a high volume reverse total shoulder surgeon. 21 patients met the inclusion criteria and were included in the analysis. 14 patients sustained completely atraumatic dislocations; 7 patients sustained dislocations during lifting or range of motion activities. 9 patients were excluded as they did not have a closed reduction performed. Eight patients underwent immediate revision secondary to known infection, and 1 patient was unable to be reduced by closed means, either in the clinic or in the operating room, and underwent immediate revision to a larger glenosphere and humeral socket.
These authors then reviewed the 21 patients with acute dislocations after reverse total shoulder arthroplasty that were reduced in the office and the immobilized for 6 weeks in 30 degrees of external rotation.
10 of these had had prior surgery and 8 had had prior arthroplasties. 13 dislocations occurred within the first 90 days after the reverse total shoulder; the average time to first dislocation was 200 days.
13 remained stable after closed reduction and temporary immobilization, 6 required revision surgery and 2 remained unstable.
Comment: Instability after a reverse total shoulder can occur at any point in the postoperative period. These results encourage an attempt at closed reduction in early or late dislocations of the shoulder, reserving reduction under anesthesia and surgical revision for irreducible or recurrent cases.
The authors point to three mechanisms for dislocation after reverse total shoulders: (1) bone or soft tissue impingement or asymmetric soft tissue tension, (2) excessive laxity in the shoulder from undersizing of the implant, (3) newly induced laxity secondary to acromial fracture. In this series, women more commonly had impingement or asymmetric soft tissue tension whereas male patients without prior surgery more often had excessive laxity of the shoulder.
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