Imaging Review of Subscapularis Tendon and Rotator Interval Pathology

As the largest rotator cuff muscle, the subscapularis plays a major role in stabilizing the glenohumeral joint, in conjunction with surrounding rotator cuff structures. Injury to the subscapularis tendon can be isolated, but more commonly is seen in conjunction with supraspinatus tendon pathology. Injury can be associated with biceps pulley instability, superior labral anterior-posterior (SLAP) tears, humeral head subluxation, and anterosuperior and coracoid impingements. The involvement of the rotator interval can lead to what is called “the hidden lesion,” due to its difficulty to diagnose during arthroscopy. Understanding the anatomical relations of the subscapularis tendon with the rest of the rotator cuff and rotator interval, as well as common patterns of injury that involve the subscapularis tendon, can aid in proper diagnosis of these injuries leading to prompt surgical repair. This review describes the anatomy of the subscapularis muscle and tendon, and the magnetic resonance imaging (MRI) patterns of subscapularis tendon injury.

Structural and Functional Results of Subscapularis and Conjoint Tendon After Latarjet Procedure at 8-Year Average Follow-up

Background: The Latarjet procedure involves initial dissection through a longitudinal split of the subscapularis tendon with only a final partial closure to accommodate the transferred coracoid bone. Furthermore, by transferring the coracoid bone block to the anterior glenoid, the surgeon completely alters the resting and dynamic route of the attached conjoint tendon. The eventual structural and functional integrity of the subscapularis and conjoint tendons is currently unknown. Purpose: To examine the structural and functional integrity of the subscapularis and the conjoint tendon after the Latarjet procedure at an 8-year average follow-up. Study design: Case series; Level of evidence, 4. Methods: Twenty patients with anterior shoulder instability at a mean age of 30 years (range, 19-50 years) underwent the open Latarjet procedure. Clinical examination at the final follow-up included quantitative isometric measurement of abduction and internal rotation strength compared with the nonoperative side. Patients were assessed via radiograph examination and preoperative computed tomography. Final position and healing of the transferred coracoid bone block were evaluated using standard radiographs. At follow-up, the subscapularis and conjoint tendon were evaluated via magnetic resonance imaging (MRI) with metal artifact reduction techniques and via ultrasound. Results: Nineteen of the 20 shoulders remained stable at the final follow-up; there was 1 redislocation (5%) after 14 months. The mean Rowe score was 83 points (SD, 17.9 points), the mean Constant score was 85 points (SD, 8.1 points), and the Subjective Shoulder Value was 80% (SD, 18%). The mean abduction strength of the operative shoulder was 7.41 ± 2.06 kg compared with 8.33 ± 2.53 kg for the nonoperative side ( P = .02). The mean internal rotation strength at 0° for the operative shoulder was 8.82 ± 3.47 kg compared with 9.06 ± 3.01 kg for the nonoperative side ( P = .36). The mean internal rotation strength in the belly-press position for the operative shoulder was 8.12 ± 2.89 kg compared with 8.50 ± 3.03 kg ( P = .13). Four of 20 shoulders showed mild tendinopathic changes of the subscapularis tendon but no partial or complete tear. One patient exhibited fatty degeneration Goutallier stage 1. Conjoint tendon was in continuity in all 20 shoulders on MRI scans. Conclusion: Abduction, but not internal rotation strength, was slightly reduced after the Latarjet procedure at a mean of 8 years of follow-up. The subscapularis tendon was intact based on ultrasound examination, and the conjoint tendon was intact based on MRI scans. Subscapularis muscle girth relative to the supraspinatus muscle remained intact from preoperative measurements based on MRI scans.

Identifying Key Factors Associated with Subscapularis Tendon Tears and Developing a Risk Prediction Model to Assist Diagnosis

Background: Subscapularis (SSC) tendon tears can cause pain and restricted motion of the shoulder, but accurate diagnosis of this lesion on magnetic resonance imaging (MRI) is challenging, especially in small and partial tears. There are no studies that have established a method to reliably assess the risk of subscapularis tendon tears.Methods: Data on 460 patients who received shoulder arthroscopic surgery with preoperative shoulder MRI were collected retrospectively. Of these, patients with SSC tendon tears were defined as the SSC tear group, and patients with intact subscapularis tendon were enrolled in the non-SSC tear group. Logistic regression analysis was used to identify the risk factors of SSC tendon tears which were then incorporated into the nomogram. Results: Among 22 candidate factors, five independent factors including coracohumeral distance CHD (oblique sagittal) (OR, 0.75; 95%CI, [0.67-0.84]), fluid accumulation (Y-face) (OR, 2.29; 95%CI, [1.20-4.38]), long head of biceps tendon (LHB) dislocation/subluxation (OR, 3.62; 95%CI, [1.96-6.68]), number of posterosuperior (PS) rotator cuff tears (OR, 5.36; 95%CI, [3.12-9.22]), and MRI diagnosis (OR, 1.88; 95%CI, [1.06-3.32]) were identified as key predictors associated with subscapularis tendon tears. Incorporating these predictors, the nomogram achieved a good C index with a good agreement on the risk estimation of calibration plots. Higher total points of the nomogram were associated with a greater risk of subscapularis tendon tears. Conclusion: The diagnostic accuracy of conventional 3.0-T MRI for SSC tendon tears was insufficient. Our study revealed critical predictors associated with subscapularis tendon tears. When evaluating the severity of subscapularis tendon injury, more attention should be paid to these tear-related factors. We developed and validated s satisfactory prediction model to improve the diagnostic performance of MRI which was convenient for clinicians to reach a consensus on risk assessment and identify the SSC tendon tears.