This retrospective case series from a single high-volume shoulder service reviews 10 patients who developed instability after unconstrained total shoulder arthroplasty. It asks what causes anterior versus posterior instability and how successfully each can be treated. The paper addresses a complication that had been noted but rarely detailed in the literature.
When a shoulder replacement dislocates or subluxates anteriorly, assume the repaired subscapularis has ruptured and explore early. This paper shows the tendon becomes scarred and shortened over time, and delayed repair failed in nearly half of cases.
The underlying principle is that unconstrained implants have minimal bony stability, so the soft-tissue envelope is everything. Repair too tight and the subscapularis blows out when rehab pushes external rotation past what the repair allows. This is why postoperative motion must never exceed the range deemed safe in the OR.
For posterior instability, read the axillary radiograph for posterior glenoid erosion, which retroverts the glenoid component and directs the head backward. Correct version with bone grafting or component revision before blaming the soft tissues alone.
The practical framework: prevent instability with correct version and balance, recognize it early, and reserve Achilles allograft reconstruction for the unreconstructable subscapularis.
This retrospective case series from a single high-volume shoulder service reviews 10 patients who developed instability after unconstrained total shoulder arthroplasty. It asks what causes anterior versus posterior instability and how successfully each can be treated. The paper addresses a complication that had been noted but rarely detailed in the literature.
When a shoulder replacement dislocates or subluxates anteriorly, assume the repaired subscapularis has ruptured and explore early. This paper shows the tendon becomes scarred and shortened over time, and delayed repair failed in nearly half of cases.
The underlying principle is that unconstrained implants have minimal bony stability, so the soft-tissue envelope is everything. Repair too tight and the subscapularis blows out when rehab pushes external rotation past what the repair allows. This is why postoperative motion must never exceed the range deemed safe in the OR.
For posterior instability, read the axillary radiograph for posterior glenoid erosion, which retroverts the glenoid component and directs the head backward. Correct version with bone grafting or component revision before blaming the soft tissues alone.
The practical framework: prevent instability with correct version and balance, recognize it early, and reserve Achilles allograft reconstruction for the unreconstructable subscapularis.