Fatty infiltration predicts retear and functional impairment following rotator cuff repair: systematic review and meta-analysis

INTRODUCTION: Fatty infiltration (FI) in rotator cuff (RC) is detected in many patients with complete RC tears. But there remains controversy on the prognostic effects of FI in RC tears, especially for patients with moderate and severe FI. This study aims to systematically review the relationship between the severity of preoperative FI and risk of retear, and the association between preoperative FI and functional outcomes. MATERIALS AND METHODS: We searched PubMed, Embase and Web of Science for studies on association between preoperative FI and retear or functional outcomes following complete RC repair. FI was assessed using Goutallier classification and global fatty degeneration index (GFDI). Meta-analysis was performed to determine odds ratios (ORs) for retear among patients with mild (grade 0-1), moderate (grade 2) and severe (grade 3-4) FI in RC tears. We delivered qualitative synthesis on association between FI and functional outcomes. RESULTS: Eighteen studies with 1997 patients were included in the systematic review and ten studies were included in the meta-analysis. Patients with GFDI ≤ 1 had lower retear odds (OR = 0.08, 95%CI 0.02-0.29, p < 0.01). Moderate FI in supraspinatus muscle (SSP) was associated with higher retear odds compared with mild FI (OR = 1.95, 95%CI 1.09-3.48, p = 0.02) and severe FI was associated with more retear compared with moderate FI (OR = 3.37, 95%CI 1.08-10.53, p = 0.04). Similar effects were observed in FI in infraspinatus muscle (ISP) (moderate vs. mild: OR = 2.22, 95%CI 1.07-4.62, p = 0.03; severe vs. moderate: OR = 2.06, 95%CI 1.02-4.16, p = 0.04). The severity of FI in subscapularis muscle and teres minor muscle was not observed to be associated with the retear rates. In functional outcomes, lower grade of FI in GFDI was associated with better prognosis. FI in single muscles failed to present prognostic effects on functional outcomes. CONCLUSIONS: The severity of FI in SSP and ISP showed effects on retear following complete RC repair. The GFDI was a compatible predictor for risk of anatomic and functional impairment.