Imaging of Glenoid Labrum Lesions

Biomechanics and Pathoanatomy of Posterior Shoulder Instability

Posterior glenohumeral instability represents a wide spectrum of pathoanatomic processes. A key consideration is the interplay between the posterior capsulolabral complex and the osseous anatomy of the glenoid and humeral head. Stability is dependent upon both the presence of soft tissue pathology (eg, tears to the posteroinferior labrum or posterior band of the inferior glenohumeral ligament, glenoid bone loss, reverse Hill Sachs lesions, and pathologic glenoid retroversion or dysplasia) and dynamic stabilizing forces. This review highlights unique pathoanatomic features of posterior shoulder instability and associated biomechanics that may exist in patients with posterior glenohumeral instability.

3-Tesla T2 Mapping Magnetic Resonance Imaging for Evaluation of SLAP Lesions in Patients with Shoulder Pain: An Arthroscopy-Controlled Study

This study investigated the ability of T2 mapping to assess the glenoid labrum and to differentiate between healthy labral substances and superior labral anterior posterior (SLAP) lesions using arthroscopy as the gold standard. Eighteen patients (mean age: 52.4 ± 14.72 years, 12 men) with shoulder pain were examined using 3-Tesla T2 mapping. All the patients underwent shoulder arthroscopy. Using morphological sequences for correlation, regions of interest covering the entire labral substance were placed in the corresponding T2 maps. The diagnostic cutoff values, sensitivities, and specificities, as well as the inter-reader correlation coefficients (ICCs) determined by two independent radiologists, were calculated. The mean T2 value was 20.8 ± 2.4 ms for the healthy labral substances and 37.7 ± 10.63 ms in the patients with SLAP lesions. The maximum T2 value in normal labrum (21.2 ms) was lower than the minimum T2 value in the patients with SLAP lesions (27.8 ms), leading to sensitivities, specificities, and positive and negative predictive values of 100% (95% CI 54.1-100.0) for all the cutoff values between 21.2 and 27.8 ms. The ICCs ranged from 0.91 to 0.99. In summary, the data suggest that evaluation and quantification of the labral (ultra)structural integrity using T2 mapping may allow discrimination between arthroscopically confirmed SLAP lesions and a healthy glenoid labrum. T2 mapping may therefore be helpful in diagnosing patients with suspected labral damage.

Imaging of Anatomical Variants of the Long Head Biceps Tendon

Anatomical variants of the long head of biceps (LHB) tendon are widely discussed in the literature. As one of the few intra-articular tendons, magnetic resonance arthroscopy can quickly evaluate the proximal part of LHB morphology. It provides good assessment of both intra-articular and extra-articular portions of the tendons. In-depth knowledge about imaging of the anatomical LHB variants discussed in this article is useful preoperatively for orthopaedists and also helps avoid potential diagnostic misinterpretations.

Imaging Posterior Instability of the Shoulder

Posterior instability of the shoulder is much less common than anterior instability with a clinical presentation that is often less obvious, making the diagnosis more challenging and more easily missed. We describe the imaging findings of posterior instability so the radiologist can make the diagnosis and provide a detailed description, enabling the surgeon to make more informed decisions regarding management and surgery.

SLAP Injury and the Superior Labrum

Injuries around the superior labrum are a common cause of shoulder dysfunction and pain. The injuries sustained result mainly from repetitive microtrauma but can also occur following a fall on outstretched hand. Both athletic and general populations can be affected. Injuries to the superior labrum are called superior labrum anterior and posterior (SLAP) tears. Based on cross-sectional imaging findings, the literature defines four main SLAP tears (I–IV) and six extended types (V–X). An accurate description of imaging findings of the SLAP tear type, along with concomitant findings, aids clinicians in treatment planning. We also briefly discuss management options, postoperative appearance of superior labral repair, and the diagnosis of a retear.

Capsular Injury and Inflammation

The capsular and ligamentous structures of the glenohumeral joint are important for stability of the shoulder. These structures are best evaluated by MR imaging. Familiarity with normal and abnormal appearance of the capsular structures of the shoulder is important to ensure that important pathology is not overlooked. Injury to the capsular structures can occur in the setting of trauma and most commonly involves the inferior glenohumeral ligament and axillary pouch. Adhesive capsulitis is a common inflammatory condition with characteristic imaging features that should be considered in the absence of alternative diagnoses.

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.

Glenoid labrum pathology

The glenoid labrum is the fibrocartilage of the shoulder joint, anchoring the joint capsule and shoulder ligaments. Morphology varies regionally, especially in the superior and anterior region; these variants can sometimes be confused with pathological aspects. The labrum is often involved in shoulder pathology, by single trauma or, more often, repeated microtrauma. It seems logical to classify and to describe tears according to two criteria: the sector involved, and associated pain or instability. In the superior labrum, SLAP lesions are the most frequent. These combine labral lesion and lesion of the proximal insertion of the long head of the biceps brachii tendon. The most frequent form is SLAP II. They may be associated with instability or not. In the antero-inferior and postero-inferior labrum, lesions are mainly due to instability, particularly Bankart lesions (capsulolabral avulsion) anteriorly and Kim's lesion posteriorly. Circumferential labral lesions may be found in unstable shoulder. Finally, postero-superior lesions involve Walch's internal impingement: repeated contact between the deep surface of the cuff and the labrum, which takes on a degenerative aspect, with a kissing lesion of the cuff. There is no general rule for management: some labral lesions are resected and others fixed. The cause (which is usually shoulder instability), however, needs to be assessed and treated.