Preoperative IDEAL (Iterative Decomposition of Echoes of Asymmetrical Length) magnetic resonance imaging rotator cuff muscle fat fractions are associated with rotator cuff repair outcomes

Background and hypothesis: IDEAL (Iterative Decomposition of Echoes of Asymmetrical Length) imaging is a magnetic resonance imaging sequence that precisely measures rotator cuff muscle fatty infiltration. The influence of lower levels of fatty infiltration on outcomes after rotator cuff repair remains unclear. We hypothesized that increased preoperative fat fractions would be associated with inferior clinical outcomes after rotator cuff repair. Methods: We retrospectively identified patients who underwent arthroscopic rotator cuff repair with preoperative IDEAL imaging. Patients completed the Patient-Reported Outcomes Measurement Information System (PROMIS) Upper Extremity computer adaptive survey at a minimum of 2 years after repair. Muscle segmentation was performed on 4 consecutive slices. Correlations between intramuscular fat fractions and PROMIS scores were determined. Patients were grouped by PROMIS scores of 50 or greater and scores lower than 50 for comparison of fat fractions. Multivariate linear regression was performed to model PROMIS scores as a function of demographic characteristics, tear size, and fat fractions. Significance was defined as P < .05. Results: Eighty patients were included (mean follow-up, 42.5 +/- 10.7 months). Postoperative PROMIS scores were significantly inversely correlated with the infraspinatus (rho = 0.25. P = .02) and subscapularis (rho = -0.29, P = .009) fat fractions. The infraspinatus (7.2% +/- 4.9% vs. 5.2% +/- 3.0%. P = .046) and subscapularis (10.4% +/- 5.1% vs. 8.2% +/- 5.0%, P = .001) fat fractions were significantly higher for patients with low PROMIS scores vs. those with PROMIS scores of 50 or greater. In multivariate modeling, the infraspinatus fat fraction (beta = -0.68. P = .029) was the only significant independent predictor of postoperative PROMIS score. Conclusion: Intramuscular fat as determined by quantitative magnetic resonance imaging is an important factor in postoperative outcomes even in patients with lower levels of preoperative fatty infiltration. (C) 2019 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved.