[Surgical revision for instability following reverse shoulder arthroplasty]

In the case of unstable shoulder joint arthroplasty with recurrent dislocations, the aim of surgery is to restore increased soft tissue tension and, thus, joint stability.

Indications include recurrent dislocations of the shoulder arthroplasty or instability of the arthroplasty in the case of obvious biomechanical weaknesses.

In addition to general contraindications such as comorbidities that prevent surgery, surgery should initially be avoided in favor of infection remediation in the case of a critical soft tissue situation in the access area and an existing infection.

After positioning in the modified beach-chair position with the upper body elevated by 30° and the arm moving freely on a separate table, the deltoid-pectoral approach is performed. The arthroplasty is exposed and luxated using a Homann hook. Increased lateralization can now be achieved by changing the baseplate and/or the glenosphere (+2 or +4 mm in each case). The "jumping distance" can also be increased by selecting a larger glenosphere. If the glenohumeral inclination angle of the inserted arthroplasty is 155°, the epiphysis is changed to an angle of 135° (if necessary, with the addition of a spacer) so that additional humeral (bifocal) lateralization is achieved. If the tuberosities can no longer be refixed or are even missing, a tuberculoplasty is performed using a cement construct attached laterally to the arthroplasty epiphysis. After a final stability check and radiological control, a Redon drain is inserted and the wound is closed.

Immediately postoperatively, the patient is fitted with an abduction orthosis and the affected shoulder is immobilized for 2 weeks (formation of a neocapsule). This is followed by early functional active and passive therapy without weight-bearing on the arm for a total of 6 weeks.

For unstable arthroplasty, the surgical treatment described above can achieve a significant improvement in the stability of the arthroplasty with a low redislocation rate. Nevertheless, attention should be paid to biomechanically correct arthroplasty implantation with refixation of the tuberosity during the initial treatment.