JSES - 2026-08-24 - Journal Article
Predictors of External Rotation Recovery following Reverse Shoulder Arthroplasty in Patients with Preoperative Lag Signs.
Boubekri AM, Zmistowski B, Devana SK, Keener JD
Topics
Key Takeaway
In rTSA patients with preoperative ER lag signs, preoperative active ER1 >25°, ER2 >40°, and ER2 lag <25° predicted functional ER recovery with AUC 0.74–0.76, while implant lateralization/distalization angles showed no independent correlation with ER outcomes.
Summary Depth
Choose how much analysis to show on this article page.
Summary
This study asked whether preoperative motion parameters or implant geometry (LSA/DSA) predict functional ER recovery after rTSA in patients with preoperative ER lag signs. Fifty-five patients underwent retrospective analysis with ROC-derived thresholds for functional ER (ER1 ≥30°, ER2 ≥60°). rTSA improved active ER1 from 20° to 44° and ER2 from 53° to 69°; preoperative motion thresholds predicted functional recovery (AUC 0.74–0.76), whereas LSA/DSA did not independently correlate with ER function, and failure to achieve functional ER negatively impacted ASES scores (p=0.03–0.045).
Key Limitation
The absence of data on concomitant or staged tendon transfer procedures (latissimus dorsi, lower trapezius) prevents determination of whether patients below the predictive thresholds would benefit from augmentation at the time of rTSA.
Original Abstract
BACKGROUND
Reverse shoulder arthroplasty (rTSA) restores forward elevation reliably but produces variable gains in external rotation (ER), particularly in patients with posterior rotator cuff deficiency. The relative contributions of external rotation in adduction (ER1) and abduction-plane (ER2) motions, and their impact on functional recovery, remain poorly defined. This study sought to identify predictors of ER recovery following rTSA in a group of patients with preoperative ER lag signs.
METHODS
A retrospective cohort of 55 primary rTSA patients (mean age = 69 years; 56% male) with ≥2-year follow-up was analyzed. Active and passive ER1 and ER2 were recorded with ER lag defined as passive minus active ER. Radiographs measured the lateralization and distalization shoulder angle (LSA/DSA) and pre-operative Hamada grading. Functional ER was defined as ER1 ≥30° and ER2 ≥60°. ROC analysis identified preoperative motion thresholds predictive of functional recovery.
RESULTS
rTSA significantly improved forward elevation (112° to 142°) and active ER1 (20° to 44°), ER2 (53° to 69°) (p< 0.001). Mean ER lag decreased from 23° to 8° (ER1) and 31° to 15° (ER2). Functional ER1 increased from 38% to 81% and functional ER2 from 60% to 86% of subjects. Failure to achieve both functional ER1 (p=0.03) or ER2 (p=0.045) negatively affected ASES scores. Preoperative active ER1 >25°, ER2 > 40°, and ER2 lag < 25° predicted functional recovery (AUC 0.74 to 0.76). No independent correlation was found between LSA/DSA and ER function.
CONCLUSION
rTSA reliably improves ER function in patients with preexisting ER signs, but recovery depends primarily on preoperative motion and lag magnitude rather than radiographic measurements of implant geometry. Patients with active ER1 > 25°, ER2 > 40° and ER2 lag <25° can expect functional ER following rTSA alone. Patients with ER lag signs >50% of passive ER are less likely to achieve functional ER following rTSA alone.
LEVEL OF EVIDENCE
Level IV; Case series; Treatment study.