Risk factors for progression of supraspinatus tear size and fatty infiltration in nonsurgically treated rotator cuff tears

<h2>Abstract</h2><h3>Background</h3> There is no clear information on structural changes of rotator cuff tears during nonsurgical management. In particular, the risk factors for the progression of tear size and fatty infiltration still remain poorly understood. Identifying such factors is essential for optimizing treatment strategies and follow-up planning. <h3>Methods</h3> We retrospectively examined 80 shoulders (43 men, 37 women; mean age, 68.4 years) with partial and full-thickness rotator cuff tears treated nonsurgically. All patients underwent initial and follow-up MRI examinations at ≥12 months with a mean follow-up of 22.2 ± 12.6 months. Progression of supraspinatus (SSP) tear size was defined as a mediolateral increase of ≥10 mm or ≥5 mm/year, and progression of SSP fatty infiltration was defined as an increase in the modified Goutallier classification. Univariate analyses were conducted to determine potential risk factors, including age, sex, initial tear size, subscapularis (SSC) tear, infraspinatus (ISP) tear, initial fatty infiltration of SSC, SSP, and ISP, critical shoulder angle (CSA), and the presence of persistent pain at follow-up. Factors with significant associations were entered into multivariate logistic regression for determining independent predictors. <h3>Results</h3> On follow-up MRI, both SSP tear size and fatty infiltration demonstrated significant progression. Univariate analyses revealed a significant association between tear size progression and initial tear size (P < 0.001), SSC fatty infiltration (P = 0.004), and larger CSA (P = 0.013). SSP fatty infiltration progression was significantly associated with older age (P = 0.04), initial tear size (P = 0.01), SSC tear (P = 0.03), SSC fatty infiltration (P < 0.001), and larger CSA (P = 0.04). Multivariate logistic regression identified medium-sized tears (OR 17.1, 95% CI 4.3–68.3, P < 0.001) and SSC fatty infiltration grade ≥2 (OR 8.1, 95% CI 1.7–38.5, P=0.009) as independent risk factors for SSP tear size progression, whereas CSA was not significant (OR 1.1, P=0.2). For fatty infiltration progression, SSC fatty infiltration grade ≥2 was an independent risk factor (OR 10.4, 95% CI 1.7–64.1, P=0.01), whereas age (OR 1.2, P=0.05), medium-sized tears (OR 3.3, P=0.13), SSC complete tear (OR 1.9, P=0.5), and CSA (OR 1.1, P=0.41) were not significant. <h3>Conclusions</h3> Progression of SSP tear size and fatty infiltration during nonsurgical treatment is closely associated with SSC fatty infiltration. Monitoring of SSC involvement may help identify patients at higher risk for progression of SSP tear size and fatty infiltration and support decisions.