Anatomic and reverse total shoulder arthroplasty (aTSA, rTSA) are well-established treatments for patients with primary osteoarthritis and an intact cuff. However, it is unclear whether aTSA or rTSA provide superior outcomes in patients with preoperative external rotation (ER) weakness.
A retrospective review of a prospectively collected shoulder arthroplasty database was performed between 2007-2020. Patients were excluded for preoperative diagnoses of nerve injury, infection, tumor, or fracture. Analysis included 333 aTSAs and 155 rTSAs performed for primary cuff-intact osteoarthritis with 2-year minimum follow-up. Defining preoperative ER weakness as strength ≤7.2 pounds, 3 cohorts were created and matched: 1) weak aTSAs (n = 74) vs normal aTSAs (n = 74), 2) weak rTSAs (n = 38) vs normal rTSAs (n = 38), and 3) weak rTSAs (n = 60) vs weak aTSAs (n = 60). We compared ROM, outcome scores, strength, complications, and revision rates at latest follow-up.
Despite weak aTSAs having poorer preoperative strength in FE and ER (P<.001), neither of these deficits persisted postoperatively compared to the normal cohort. Likewise, weak rTSAs had poorer preoperative strength in FE and ER, overhead motion, and Constant, SPADI, and UCLA scores (P<.029). However, no statistically significant differences were found between preoperatively weak and normal rTSAs. When comparing weak aTSA versus weak rTSA, no differences were found in preoperative and postoperative outcomes, proportion of patients achieving the MCID and SCB, and complication and rate of revision surgery.
In preoperatively weak patients with cuff-intact primary osteoarthritis, aTSA leads to similar postoperative strength, ROM, and outcome scores compared to patients with normal preoperative strength, indicating preoperative weakness does not preclude aTSA use. Furthermore, patients who were preoperatively weak in ER demonstrated improved postoperative rotational motion after undergoing aTSA and rTSA, with both groups achieving the MCID and SCB at similar rates.

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