Does the Extent of Tear Influence Pseudoparesis in Patients With Isolated Subscapularis Tears?

Background: Surgeons tend to associate pseudoparesis with massive rotator cuff tears. However, little is known about the degree to which isolated subscapularis tears might be associated with pseudoparesis of the shoulder.

Question/purpose: Is the extent of subscapularis tears associated with pseudoparesis?

Methods: A retrospective analysis identified all patients with subscapularis tears from 2010 to 2021 in the longitudinally maintained shoulder arthroscopy archive of one university hospital's shoulder section of the orthopaedic department. After exclusion, 106 of 152 patients with isolated subscapularis tears who underwent arthroscopic surgery were included in the study. Sixty percent of the patients were women, and the mean ± SD age was 52 ± 11 years. Patients who were scheduled for arthroscopic surgery were divided into two groups according to the presence or absence of pseudoparesis preoperatively. Pseudoparesis was considered to be active forward elevation > 45º but < 90º, which is a simple and reproducible measurement that can be taken using a goniometer, and demonstrated complete passive forward elevation. Pseudoparesis was present in 41% (43 of 106) of patients with an isolated subscapularis tear. Data on tear severity (according to Lafosse type, noted during arthroscopy), integrity of the subscapularis tendon (noted during arthroscopy), fatty degeneration (using the Goutallier grading system on MRI), arthroscopic findings of biceps disorder, superior labrum anterior to posterior (SLAP) lesions, and pain severity (measured by VAS score) were recorded. We used logistic regression analysis to examine the relationship between pseudoparesis and disruption of the tendinous part of the subscapularis.

Results: After accounting for potentially confounding factors such as biceps disorders and muscle atrophy, we found that pseudoparesis was associated with decreased tear severity according to the Lafosse classification (adjusted OR 0.2 [95% CI 0.1 to 0.7]; p = 0.01) and with disruption of the tendinous portion of the subscapularis (adjusted OR 21 [4 to 128]; p = 0.001). Patients with less severe tears (Lafosse type I) have lower odds of experiencing pseudoparesis compared with those with more severe tears (Lafosse types II, III, and IV), and patients with disruption of the tendinous portion of the subscapularis have substantially higher odds of pseudoparesis compared with those with an intact tendinous portion. No association was found between pseudoparesis and subscapularis fatty degeneration, biceps disorder, or SLAP lesions.

Conclusion: This study provides initial evidence suggesting that isolated subscapularis tears are associated with pseudoparesis. The main finding of this study is that isolated subscapularis tears that involve the tendon extending to the inferior part of the subscapularis have higher odds of being found with pseudoparesis. These findings highlight the importance of maintaining the integrity of the superior tendinous part of the subscapularis for active forward elevation > 90°.

Level of evidence: Level III, therapeutic study.