Review Question - QID 219490

The patient presents with pain and decreased function after an anatomic total shoulder arthroplasty (TSA) with an identifiable injury event in the acute postoperative period. The associated imaging demonstrates a failure of the lesser tuberosity osteotomy (LTO) repair, which would clinically manifest with subscapularis insufficiency identified with bear hug or abdominal compression testing.

Subscapularis failure after TSA is a recognized cause of postoperative morbidity with multiple potential etiologies. There are several strategies for subscapularis takedown during the surgical approach, including a peel, tenotomy, or LTO. No single strategy has produced a significant difference in outcomes within the literature, and all require meticulous repair after TSA. As demonstrated in Figure A and Illustration A, an LTO was performed in this patient, and they suffered a traumatic failure of the repair after a forced external rotation movement in the acute postoperative period. In addition to the radiographic evidence of repair failure, the patient would likely manifest signs of subscapularis insufficiency on clinical examination. These could include weakness with the abdominal compression (or belly press) test, an internal rotation lag sign, excessive passive external rotation compared to the contralateral side, and/or a positive bear hug test. The bear hug test is performed by having the patient place the ipsilateral palm on the contralateral deltoid and resist the examiner pulling the arm away anteriorly, with a positive test being at least 20% weaker than the unaffected side.

Jackson et al. performed a study to determine the rates of subscapularis healing in 15 patients who underwent TSA with a subscapularis tenotomy performed during surgical exposure. They assessed healing with the use of ultrasound and found that seven of the 15 patients had a complete tear of the repaired tendon after a minimum of six months of follow-up. They noted a correlation between bear hug testing with dynamometry and tendon integrity but ultimately concluded that subscapularis tear after TSA is a common finding that cannot be reliably diagnosed with physical examination alone.

Entezari et al. performed a retrospective study evaluating the treatment of clinically significant subscapularis failure after TSA, primarily comparing direct repair with conversion to reverse TSA. They found that patients undergoing direct repair were more likely to be younger, exhibit a better comorbidity profile, and have a more acute presentation than patients treated with reverse TSA. They concluded that treatment of clinically significant subscapularis failure after TSA is multifactorial and should include the patient’s age, level of activity, comorbidities, timing and mechanism of failure, and functional expectations.

Figure A is an AP x-ray of the left shoulder demonstrating a TSA in an appropriate position with medial displacement of the lesser tuberosity. Illustration A is an axillary view of the same patient showing the displaced lesser tuberosity fragment off the anterior surface of the proximal humerus.

Incorrect Answers:
Answer 1: An external rotation lag sign would indicate infraspinatus weakness, which is less likely in this patient with radiographic evidence of a failed LTO.
Answer 3: The patient would likely have increased external rotation compared to the contralateral side. Though this could potentially be difficult to accurately assess in the acute postoperative period due to the traumatic LTO failure and expected stiffness, complete loss of passive external rotation would be more consistent with a locked posterior dislocation.
Answer 4: A positive drop sign would indicate supraspinatus weakness, which is less likely in this patient with radiographic evidence of a failed LTO.
Answer 5: Acromial stress fractures are a recognized complication after reverse TSA, with an incidence of 4%. This would be less likely in this patient after TSA with radiographic evidence of a failed LTO.