Does improved external rotation following reverse shoulder arthroplasty impact clinical outcomes in patients with rotator cuff pathology and external rotation less than 0°?

Abstract

Background: The purpose of this study was to (1) evaluate whether improved external rotation (ER) in patients with preoperative ER <0° impacts their clinical outcomes following reverse shoulder arthroplasty (RSA) for rotator cuff (RC) pathology and (2) describe the differences in preoperative factors and postoperative outcomes in this patient population. Our hypothesis was that clinical outcomes would not be affected by improvement in ER using a lateralized glenosphere design.

Methods: We retrospectively reviewed 55 patients with preoperative ER <0° who underwent primary RSA for RC pathology with lateralized glenosphere. Pre- and postoperative physician-reported ER was blindly measured using a videographic review of patients externally rotating their arm at the side. Patients were evaluated using 5 different patient-reported outcome score thresholds, measured at 12 months postoperatively: (1) minimal clinically important difference (MCID) for American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES) scores (ie, ≥20-point increase); (2) MCID for Simple Shoulder Test (SST) scores (≥2.4-point increase); (3) visual analog scale (VAS) for pain score >0; (4) mean ASES score (≥75); and (5) mean SST score (≥6.8), each of which was used to stratify the patients into 2 groups-greater than or equal to vs. less than the threshold. This resulted in 5 different evaluations comparing the 2 groups for any difference in postoperative ER or preoperative factors, including Hamada and Goutallier scores.

Results: Regardless of the measured outcome, there was no difference in either postoperative physician- or patient-reported ER between patients who achieved scores higher or lower than the thresholds. Both Hamada and Goutallier score distributions were not different between groups across all the evaluated outcomes. Patients who achieved the MCID for ASES had worse preoperative VAS pain (7 vs. 4, P = .011) and SST (1 vs. 3, P = .020) scores. Across all outcome thresholds, except MCID for SST, pain reduction (ΔVAS) was significantly more pronounced in patients exceeding the thresholds. Improved forward flexion rather than ER was observed in those who achieved the ASES (160° vs. 80°, P = .020) and SST MCIDs (150° vs. 90°, P = .037). Finally, patients who exceeded the thresholds experienced higher satisfaction rates.

Conclusion: Improvement in ER does not appear to impact patient-reported outcome measures, including ASES and SST in patients with preoperative ER <0° undergoing RSA with a lateralized glenosphere. Patients with more severe pain and worse function at baseline experience less postoperative pain and clinically significant improvement in their reported outcomes.

Keywords: ER <0; External rotation; outcomes; pain; reverse shoulder arthroplasty.