Does the Fatty Infiltration Influence the Re-tear Rate and Functional Outcome After Rotator Cuff Repair? A Systematic Review and Meta-analysis

Purpose Fatty infiltration (FI) of the rotator cuff muscles occurs after rotator cuff tears (RCTs), which may affect the outcome of the repair procedure. This study aimed to determine the relationship between preoperative FI and the rate of re-tear and functional outcomes after rotator cuff repair. Methods Computerized databases, including PubMed, EMBASE, Web of Science, and Cochrane Library database were searched for studies published from the inception date to January 2022. Two reviewers independently screened the titles and abstracts using prespecified criteria. Articles were included if they clearly stated the effect of varying degrees of FI on the outcome after shoulder cuff repair. Comparison was performed by different degrees of FI analysis: no FI is grade 0–1, FI is grade 2 and above. Statistical analysis was performed using Review Manager 5.4.1 software. Results A total of 16 articles involving 1383 patients from 8 countries were included. The follow-up period ranged from 8 to 121 months. In terms of re-tear rate: patients with preoperative FI had significantly higher rates of re-tear compared with patients without FI (OR 4.60, 95% CI 2.22–9.54, p < 0.0001), supraspinatus FI VS no FI (OR 2.06, 95% CI 1.00–4.24, p = 0.05), infraspinatus FI VS no FI (OR 2.42, 95% CI 1.19–4.91, p = 0.01). In terms of functional scoring: patients without FI had higher postoperative Constant–Murley (Constant) scores than those with FI (MD − 5.06, 95% CI − 9.40 to − 0.72, p = 0.02), there was no clear evidence that preoperative FI was related to postoperative American Society of shoulder and elbow physicians scores and the University of California at Los Angeles scores and range of motion. Conclusion FI after RCTs significantly increases the risk of postoperative re-tear and leads to worse functional scores, especially FI of the infraspinatus muscle. However, FI does not seem to reduce postoperative range of motion.