Superior Labrum Anterior and Posterior Lesions and Microinstability

Superior labrum anterior to posterior lesions: Part 2 - Classification with arthroscopic correlation

The glenoid labrum deepens the glenoid fossa and allows for the attachment of the long head of the biceps tendon and glenohumeral ligaments, contributing to the stability of the glenohumeral joint. The superior labrum is a common site of labral injury. The acronym SLAP (superior labrum anterior to posterior or anteroposterior) lesion was introduced by Snyder and colleagues in 1990 to describe superior labral tears based on arthroscopic evaluation. This original classification has since been expanded, and there are currently 10 types of SLAP lesions. The article will describe and illustrate the 10 types of SLAP lesions by means of colour illustrations, MRI images and correlative arthroscopy images. A practical approach to the assessment of SLAP lesions will be recommended.

Contribution

The illustrated review functions as a crucial radiological guide for both radiologists and orthopaedic surgeons. The combination of illustrations, MR and correlative arthroscopic images enhances the comprehensive understanding of labral pathology. The value of the review lies in the presentation of imaging findings and classification, coupled with findings on arthroscopy. This understanding is vital in guiding orthopaedic management for patients, ensuring appropriate treatment strategies.

Superior labrum anterior to posterior lesions: Part 1 - Imaging and anatomy with arthroscopic classification

The glenoid labrum deepens the glenoid fossa and allows for the attachment of the long head of the biceps tendon and the glenohumeral ligaments, contributing to the stability of the glenohumeral joint. The superior labrum is a common site of labral injury, especially in athletic activities involving overhead activity. The acronym SLAP (superior labrum anterior to posterior or anteroposterior) lesion was introduced by Snyder and colleagues in 1990 to describe superior labral tears. The article will review the optimal technique to image the glenoid labrum, covering normal labral anatomy with special emphasis on the anatomic variants of the labrum that can be mistaken for SLAP tears by means of colour illustrations, magnetic resonance imaging and correlative arthroscopy images.

Contribution

The illustrated review functions as a crucial radiological guide for both radiologists and orthopaedic surgeons. The combination of illustrations, MR and correlative arthroscopic images enhances the comprehension of normal labral anatomy and its variants. The review underscores the significance of understanding anatomic variations that may be misinterpreted as pathology. This understanding is vital in guiding orthopaedic management for patients, ensuring appropriate treatment strategies.

Anatomical, functional and biomechanical review of the glenoid labrum

The glenohumeral joint is the most mobile joint in the human skeleton, supported by both active and passive stabilisers. As one of the passive stabilisers, the glenoid labrum has increasingly been recognised to play an important role in stability of the glenohumeral joint, acting to maintain intraarticular pressure, centralise the humeral head and contribute to concavity-compression stability. Several studies have investigated the macro- and micro-anatomical features of the labrum as well as its biomechanical function. However, in order to better understand the role of the labrum and its mechanics, a comprehensive anatomical, functional and biomechanical review of these studies is needed. Therefore, this article reviews the current literature detailing anatomical descriptions of the glenoid labrum, with an emphasis on its function(s) and biomechanics, as well as its interaction with neighbouring structures. The intimate relationship between the labrum and the surrounding structures was found to be important in glenohumeral stability, which owes further investigation into the microanatomy of labrum to better understand this relationship.

An assessment of SLAP type 5 lesions using proton density oblique sagittal imaging in magnetic resonance arthrography

BACKGROUND

Bankart lesions accompany superior labrum anteroposterior (SLAP) lesions; these are called SLAP type 5.

PURPOSE

To compare SLAP type 5 lesions using routine magnetic resonance arthrography (MRA) and thin-slice oblique sagittal proton density (PDW) sequences and correlation operation results.

MATERIAL AND METHODS

In total, 181 patients were admitted with shoulder instability. The study was completed with 44 patients. The presence or absence of isolated Bankart and SLAP type 5 lesions in routine MRA and PDW oblique sagittal images were evaluated separately. Absence of rupture scored 0 points, suspected ruptures scored 1 point, and apparent ruptures scored 2 points. The two scores were compared with the shoulder arthroscopy findings.

RESULTS

According to the findings in the shoulder arthroscopy, 40 patients had Bankart lesions and 17 patients had accompanying SLAP type 5 lesions. To detect a Bankart lesion, there was no significant difference between routine MRA sequences and PDW oblique sagittal images (P = 0.061). Routine MRA sensitivity was 95%, specificity 25%, positive predictive value (PPV) 92%, negative predictive value (NPV) 33%, while for PDW oblique sagittal images, sensitivity was 75%, specificity 100%, PPV 100%, and NPV 28.5%. In 8/17 type 5 SLAP lesions, routine MRA detected sensitivity 47%, specificity 92.6%, PPV 80%, and NPV 73.5%; in 14/17 SLAP type 5 lesions, PDW oblique sagittal images detected sensitivity 82%, specificity 100%, PPV 100%, and NPV 90% (P = 0.015).

CONCLUSION

The PDW oblique sagittal images may play a significant role in assessing the anterior and superior extent of the tears.

Magnetic resonance imaging of the shoulder

The aim of this article is to review the use of magnetic resonance imaging (MRI) for the evaluation of shoulder pain, which is a common clinical complaint of the musculoskeletal system. MRI is an essential auxiliary tool to evaluate these patients because of its high resolution and high sensitivity in depicting the soft tissues. This article will review the imaging technique, normal imaging anatomy, and most common imaging findings of disorders of tendons, labrum, and ligaments of the shoulder. It will also discuss common systemic diseases that manifest in the shoulder as well as disorders of the acromioclavicular joint and bursae. New advances and research in MRI have provided additional potential uses for evaluating shoulder derangements.

Imaging the Glenoid Labrum and Labral Tears

The shoulder joint is the most unstable articulation in the entire human body. While this certainly introduces vulnerability to injury, it also confers the advantage of broad range of motion. There are many elements that work in combination to offset the inherent instability of the glenohumeral joint, but the glenoid labrum is perhaps related most often. Broadly, clinical unidirectional instability can be subdivided into anterior and posterior instability, which usually raise concern for anteroinferior and posteroinferior labral lesions, respectively. In the special case of superior labral damage, potential dislocation is blocked by structures that include the acromion; hence, while damage elsewhere commonly manifests as clinical instability, damage to the superior labrum is often described by the term microinstability. In this particular case, one of the radiologist's main concerns should be classic superior labral anteroposterior lesions. The glenoid labrum is also subject to a wide range of normal variants that can mimic labral tears. Knowledge of these variants is central to interpreting an imaging study of the labrum because misdiagnosis of labral variants as tears can lead to superfluous surgical procedures and decreased shoulder mobility. This article reviews labral anatomy and normal labral variants, describes their imaging features, and discusses how to discriminate normal variants from labral tears. Specific labral pathologic lesions are described per labral quadrant (anteroinferior, posteroinferior, and superior), and imaging features are described in detail. Online supplemental material is available for this article. ^©RSNA, 2016.

Beyond the Cuff: MR Imaging of Labroligamentous Injuries in the Athletic Shoulder

Shoulder disease is common in the athletic population and may arise as a consequence of a single traumatic episode or multiple repeated events. Associated labroligamentous injuries can result in substantial disability. Specific athletic and occupational activities result in predictable injury patterns. Imaging in general and magnetic resonance (MR) imaging, in particular, are vital in establishing the correct diagnosis and excluding common mimicking conditions, to ensure timely and appropriate management. In this review, the utility of MR imaging and MR arthrography will be explored in evaluation of shoulder disease, taking into account normal variants of the labroligamentous complex. Subsequently, broad categories of labral lesions and instability, external and internal impingement, as well as nerve entrapment syndromes, will be discussed, while emphasizing their imaging findings in the clinical context and illustrating key features. More recent concepts of internal impingement and secondary subacromial impingement will also be clarified.

High-Resolution Qualitative and Quantitative Magnetic Resonance Evaluation of the Glenoid Labrum

OBJECTIVE

This study aimed to implement qualitative and quantitative magnetic resonance sequences for the evaluation of labral pathology.

METHODS

Six glenoid labra were dissected, and the anterior and posterior portions were divided into normal, mildly degenerated, or severely degenerated groups using gross and magnetic resonance findings. Qualitative evaluation was performed using T1-weighted, proton density-weighted, spoiled gradient echo and ultrashort echo time (UTE) sequences. Quantitative evaluation included T2 and T1rho measurements as well as T1, T2*, and T1rho measurements acquired with UTE techniques.

RESULTS

Spoiled gradient echo and UTE sequences best demonstrated labral fiber structure. Degenerated labra had a tendency toward decreased T1 values, increased T2/T2* values, and increased T1rho values. T2* values obtained with the UTE sequence allowed for delineation among normal, mildly degenerated, and severely degenerated groups (P < 0.001).

CONCLUSIONS

Quantitative T2* measurements acquired with the UTE technique are useful for distinguishing among normal, mildly degenerated, and severely degenerated labra.

Glenoid Rim Anatomy: Risk for Glenoid Vault Perforation During Labral Repair

Background:

Injuries to the glenoid labrum frequently require repair with anchors. Placing anchor devices arthroscopically can be challenging, and anchor malpositioning can complicate surgical outcomes.

Purpose:

To determine the safe insertion range and optimal insertion angle of glenoid labral anchors at various positions on the glenoid rim and to establish surgical guidelines that minimize risk of anchor perforation.

Study Design:

Descriptive laboratory study.

Methods:

Three-dimensional computed tomography scans of 30 normal cadaveric specimens were obtained. A virtual model of a generic labral anchor was inserted into the rim of the glenoid at the clockface positions represented by 12:00, 1:30, 3:00, 4:30, 6:00, 7:30, 9:00, and 10:30. At each position, the safe insertion range was the maximal range measured, and the optimal insertion angle was identified as the angle between the bisector of the safe insertion range and the glenoid face.

Results:

Progressing in the clockwise direction, beginning at the 12:00 position, the safe insertion ranges (mean ± SD ) were 55.9° ± 10.6°, 63.6° ± 17.6°, 47.7° ± 9.1°, 46.1° ± 8°, 73.9° ± 9.7°, 40.9° ± 6.5°, 40.4° ± 7.4°, and 39.9° ± 7.1°, respectively. The optimal insertion angles were 47.9° ± 7.6°, 53.1° ± 10.9°, 35.0° ± 4.4°, 42.4° ± 4.9°, 60.9° ± 8.4°, 36.6° ± 5.9°, 31.2° ± 4.9°, 34.8° ± 4.6°, respectively.

Conclusion:

Optimal insertion angles and safe insertion ranges varied significantly with respect to the position on the glenoid face. The safe insertion range and optimal insertion angle were found to be wider at the anterior glenoid as compared with the posterior glenoid. A posterolateral insertion angle was safer than an anterior insertion angle at the 10:30 position.

Clinical Relevance:

Proper arthroscopic technique resulting in anchor insertion at the correct angle, depth, and location will prevent anchor-related glenohumeral complications such as glenoid perforation, cartilage damage, persistent pain, decreased range of motion, and failure of the reconstruction.

Ultrasonography of the shoulder with arthroscopic correlation

Ultrasonography is a well-established and widely accepted modality for the evaluation of rotator cuff tears and injury to the biceps brachii tendon. Ultrasonography and magnetic resonance imaging have comparable sensitivity and specificity for diagnosing both full-thickness and partial-thickness rotator cuff tears. This article addresses the ultrasonographic diagnosis of abnormalities of the rotator cuff, rotator interval, and biceps brachii, with magnetic resonance imaging and arthroscopic correlation. Characteristic ultrasonographic findings as well as imaging pitfalls are reviewed.