JAAOS - 2026-05-15 - Journal Article
Outcomes of Reverse Total Shoulder Arthroplasty With Lateralized Implant in a Patient With High Grade of Fatty Infiltration of Infraspinatus and Teres Minor Muscle.
Kim HG, Baek E, Kim SC, Kim JS, Suh DH, Yoo JC
Topics
Key Takeaway
Lateralized RTSA achieved equivalent ROM and Constant score improvements regardless of infraspinatus fatty infiltration grade, though high-FI patients had significantly lower absolute ER strength at final follow-up (p=0.007).
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Summary
This study compared clinical outcomes of lateralized RTSA in patients with high-grade (n=88) versus low-grade (n=51) infraspinatus fatty infiltration (Goutallier classification) using preoperative MRI. ROM, Constant score, and magnitude of strength improvement did not differ significantly between groups, but absolute forward elevation (p=0.049) and ER strength (p=0.007) were lower in the high-FI cohort at final follow-up. Multivariate analysis identified BMD, tear size in the mediolateral dimension, ISP FI grade, and preoperative ER lag angle as independent predictors of poor postoperative ER strength.
Key Limitation
Retrospective design with no standardized postoperative rehabilitation protocol introduces confounding in strength outcome measurement across the study period.
Original Abstract
AIMS
This study aimed to evaluate the clinical outcomes and complication rates after reverse total shoulder arthroplasty (RTSA) with lateralized implant for patients with high-grade fatty infiltration (FI) of posterior rotator cuff including infraspinatus (ISP) and teres minor (TM).
METHODS
From January 2016 to June 2022, 139 patients who underwent primary RTSA with single lateralized implant with at least 2 years of follow-up were reviewed. According to FI of ISP from preoperative MRI, patients were divided into high ISP FI group (n = 88) and low ISP FI group (n = 51). Clinical outcomes and complications were compared between the two groups. A subgroup analysis was done with a high ISP FI group divided into low TM FI group (n = 77) and high TM FI group (n = 11).
RESULTS
At final follow-up, there was no significant difference in range of motion of forward elevation ( P = 0.282), external rotation (ER; P = 0.467), and Constant score ( P = 0.252) between the high ISP FI group and the low ISP FI group. At the final follow-up, patients in the high FI group demonstrated significantly reduced strength in both forward elevation ( P = 0.049) and ER ( P = 0.007) compared with those in the low FI group. However, the mean improvement in muscle strength from preoperative to postoperative evaluation in forward elevation and ER showed no significant difference between two groups ( P = 0.559, 0.675, respectively). Subgroup analysis comparing low TM FI group and high TM FI group in the high ISP FI group showed that there were no notable differences in clinical outcomes between two groups. Bone mineral density, tear size in mediolateral dimension, ISP FI, and ER lag angle were found to be markedly associated with poor ER strength at final follow-up in univariate and multivariate analyses.
CONCLUSION
Lateralized RTSA yielded marked improvements in shoulder motion, including forward elevation and ER, despite severe fatty changes in the ISP and TM.
LEVEL OF EVIDENCE
III, Retrospective case-control study.