Structural Fate of Nonoperatively Treated High-Grade Partial-Thickness Rotator Cuff Tears: An Extended Investigation through Subsequent MRI Assessment.

Background: Managing high-grade partial-thickness rotator cuff tears (hPTRCTs) (>50% of thickness) of the supraspinatus tendon presents significant challenges; however, understanding long-term structural changes is limited. Purpose: To evaluate the long-term structural prognosis of nonoperative treatment for hPTRCTs of the supraspinatus tendon, focusing on survival rates and hazard ratios of risk factors for tear progression. Study Design: Case-control study; Level of evidence, 3. Methods: This retrospective review enrolled patients with magnetic resonance imaging (MRI)-proven symptomatic hPTRCTs of the supraspinatus tendon from November 2007 to December 2023. Patients underwent nonoperative treatment with follow-up MRIs. Clinical and imaging data were collected, and survival analysis was performed using the Kaplan-Meier estimation method. Risk factors were evaluated with univariate and multivariate logistic regression, followed by Cox proportional hazard model analysis. Results: Of the initial 1397 eligible patients, 268 (19.2%) were included in the final analysis after excluding those without follow-up MRI. Among them, 56 (20.9%) showed tear progression over a mean follow-up of 26 months, with a median survival time of 79.6 months. The 3-year, 5-year, and 8-year survival rates were 73.1%, 61.5%, and 42.1%, respectively. The overall annual hazard rate for tear progression was 10.1%, with a first-year hazard rate of 3.2% and a second-year hazard rate of 17.2%. Multivariate Cox proportional hazard analysis identified initial mediolateral (ML) tear size and tendinosis grade as significant predictors of progression. Patients with an ML tear size <62% had a hazard ratio (HR) of 1.78 (95% CI, 1.04-3.04), while those with tendinosis grade 2 had an HR of 3.51 (95% CI, 1.86-6.61), and tendinosis grade 3 had an HR of 2.23 (95% CI, 0.96-5.19), showing a trend toward significance. Conclusion: hPTRCTs exhibit a time-dependent pattern of structural progression, characterized by a relatively low risk in the first year, followed by a notable increase thereafter. Patients with intermediate-grade tendinosis or smaller mediolateral tear sizes appear to be at increased risk. Further research into the biological and biomechanical mechanisms underlying tear progression may improve treatment strategies and clinical outcomes.