The Invisible MGHL Test: Diagnostic Value and Benefits for the Repair of Retracted Subscapularis Tears

Role of middle glenohumeral ligament in external shoulder rotation

Background

The middle glenohumeral ligament (MGHL) is one of the three ligaments that stabilize the anterior capsule of the shoulder. Recent work suggests that it inserts distally into the deep layer of the subscapularis tendon. The role of the MGHL remains debated. The hypothesis of this study was that the MGHL plays a significant functional role in limiting external rotation of the shoulder while allowing a wide range of motion through its distal insertion into the subscapularis rather than directly onto the humerus.

Methods

In a cadaveric study performed on 20 shoulders (10 subjects), the MGHL and the other anterior structures of the shoulder were successively cut according to a standardized protocol. At each stage, the external rotation range of the shoulder was measured with the arm at the side (ER 1) and in 90° abduction (ER 2) using a goniometer. After dissection, the structure of the MGHL and its distal insertion were analyzed.

Results

Cutting the MGHL led to significant increases in ER 1 but not in ER 2. Shoulder range of motion in ER 1 increased on average by 15 ± 5° (P < .001) after cutting the MGHL and by 21 ± 11° (P < .001) after subscapularis peel. The range of motion in ER 2 increased by 3 ± 4° (P = .048) after cutting the MGHL, by 4 ± 6° (P = .02) after subscapularis peel and by 25 ± 8° (P < .001) after cutting the inferior glenohumeral ligament. The MGHL was present in all dissected shoulders. It was leaf-like in 12 cases, cord-like in 6 cases and had a vestigial appearance in 2 cases. The distal insertion was in all cases in the deep layer of the subscapularis in a thickening of the anterior capsule in the superior part of the muscle, except for two cases in which the tendinous part of the subscapularis was also involved.

Conclusion

The MGHL limited shoulder external rotation by a similar amount as the subscapularis muscle. Further studies are required to understand the clinical relevance of these findings, notably for the treatment of shoulder stiffness.

Association Between Medial Displacement of the Middle Glenohumeral Ligament and Subscapularis Tear Severity

Background:

The intraoperative invisible middle glenohumeral ligament (MGHL) test has been shown to be associated with a subscapularis tendon retraction. However, the preoperative location of the MGHL and its association with subscapularis tear severity has not been evaluated.

Purpose:

To determine (1) the interrater reliability for identification and position of the MGHL, (2) any association between the MGHL position and subscapularis tears, and (3) the cutoff point at which MGHL position can predict subscapularis tear severity.

Study Design:

Cohort study (diagnosis); Level of evidence, 2.

Methods:

The magnetic resonance imaging (MRI) scans and surgical records of 176 patients were retrospectively reviewed by 3 independent orthopaedists. MGHL's identification, level (its position on axial MRI), and medial retraction ratio (distance from the lesser tuberosity to the MGHL divided by the width of the glenoid) were documented, and the interobserver agreement of the 3 indices was assessed. We calculated the association between subscapularis tears and the MGHL level and medial retraction ratio. Receiver operating characteristic (ROC) curve analyses were conducted to establish the optimal threshold of the MGHL medial retraction ratio to predict subscapularis tear.

Results:

The MGHL was identified by at least 2 reviewers in 124 individuals (70.5%). The interobserver reliability was very good for MGHL identification (κ = 0.766), moderate for MGHL level (κ = 0.582), and excellent for MGHL medial retraction ratio (intraclass correlation coefficient = 0.848). A low, positive correlation between MGHL level and subscapularis tear severity was found (Somers d = 0.392, P < .001), as well as a significant association between the medial retraction ratio and Lafosse classification of subscapularis tear size ( P < .001). A medial retraction ratio of ≥1.25 had a sensitivity of 0.70, a specificity of 0.83, and a positive likelihood ratio of 4.20, with excellent accuracy (area under the ROC curve = 0.820) to predict severe subscapularis tear.

Conclusion:

The MGHL was identified in 70.5% of shoulder MRIs. The location of the MGHL on preoperative MRI, as described by its level and the medial retraction ratio, was significantly associated with subscapularis tear severity, and a medial retraction ratio of ≥1.25 was predictive of a severe subscapularis tear.

Ultrasonography Outperforms Magnetic Resonance Imaging in Diagnosing Partial-Thickness Subscapularis Tear

PURPOSE

To evaluate the diagnostic reliability of ultrasonography (US) and magnetic resonance imaging (MRI) for subscapularis (SSC) tears with shoulder arthroscopy as the gold standard and to investigate the diagnostic value of 2 MRI signs (lesser tuberosity cysts and subcoracoid cysts) for SSC tears.

METHODS

We consecutively enrolled 437 patients who were scheduled to undergo arthroscopic rotator cuff repair from January 2019 to December 2020. Patients with previous shoulder surgery or shoulder fracture, recurrent shoulder instability, and systemic inflammatory disease were excluded. Preoperative US and MRI of the shoulder were performed and interpreted with a standardized approach. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of US and MRI were calculated using arthroscopic findings as the gold standard.

RESULTS

Of the 437 patients, 157 had SSC tears confirmed at the time of arthroscopy, 126 of whom had partial-thickness tears. US correctly diagnosed 122 of 157 patients with SSC tears, with an overall sensitivity of 77.7% (confidence interval [CI] 70.6%-83.5%), which was significantly greater than that of MRI (49.7%, CI 42.0%-57.4%, P < .001). For partial-thickness SSC tears, US correctly diagnosed 93 of 126 positive patients and 276 of 311 negative patients. This resulted in a sensitivity of 73.8% (CI 65.5%-80.7%), specificity of 88.7% (CI 84.8%-91.8%), and accuracy of 84.4% (CI 80.7%-87.5%). As with MRI, the sensitivity, specificity, and accuracy were 38.1% (CI 29.7%-47.2%), 86.5% (CI 82.3%-89.9%), and 72.5% (CI 68.2%-76.5%), respectively. Lesser tuberosity cysts and subcoracoid cysts were 2 MRI signs with high specificity (98.2% and 94.6%); however, their sensitivities were relatively low (19.8% and 33.8%).

CONCLUSIONS

US is a reliable and accurate diagnostic method for SSC tears, especially in easily missed partial-thickness tears. Lesser tuberosity cyst and subcoracoid cyst are highly specific but insensitive MRI signs for SSC tear.

LEVEL OF EVIDENCE

Level I, diagnostic, testing of previously developed diagnostic criteria.

Subcapularis tendon tear: A structure-based arthroscopic description

INTRODUCTION

Subscapularis (SSC) tendons differ from supraspinatus tendons, although both have similar histologic structure comprising two layers with distinct collagen fiber organization.

HYPOTHESIS

The partial/full-thickness tear classification for the supraspinatus based on tendon structure can be applied to the subscapularis tendon on objective criteria.

MATERIAL AND METHODS

The present study used 100 films of arthroscopic rotator cuff repair involving SSC lesion. Lesions were reported on 3 objective criteria: horizontal superior tendon edge visibility, lesser tuberosity bone exposure, and lateral tendon edge visibility. Combining the three distinguishes deep, superficial or interstitial partial tear versus full-thickness tear. Degree of retraction was also noted.

RESULTS

Forty-six of the 73 partial lesions involved the deep articular layer, which was often retracted, but conserving the horizontal superior tendon edge and thus misleadingly suggesting SSC integrity; 23 were interstitial, without detachment from the lesser tuberosity; 4 involved only the superficial layer. Full-thickness tears were always retracted, with loss of horizontal superior tendon edge, visibility of the lateral tendon edge and presence of comma sign. Inter- and intra-observer reproducibility was satisfactory.

DISCUSSION - CONCLUSION

Like in superior cuff tear, a structure-based classification can be made of SSC lesions on objective criteria.

LEVEL OF EVIDENCE

IV.