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 impacted 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 Clinical Difference (MCID) for ASES (i.e. ≥ 20 point increase); 2) MCID SST (≥ 2.4 increase); 3) VAS pain > 0; 4) mean ASES (≥ 75); and 5) mean SST (≥ 6.8), each of which was used to stratify the patients into two groups 1) greater than or equal (≥) vs. less than (< ) the threshold. This resulted in 5 different evaluations comparing the group ≥ to the one < the threshold 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 distribution 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 = 0.011) and SST (1 vs 3, p = 0.020) 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=0.020) and SST MCID (150° vs 90°, p=0.037). 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.





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