SPORTS RADIOLOGY SHOULDER DISLOCATION AMONG ATHLETES AN OVERVIEW OF COMMON INJURIES AND IMAGING FINDINGS – Written by Nima Hafezi–Nejad, Shadpour Demehri and John A Carrino, USA The Glenohumeral (GH) joint has a mobility is often termed hyperlaxity, a during sports activities. Second, SD may arise large range of motion that leaves it prone common feature among many athletes. as a result of chronic injuries, mostly in the to shoulder instability, ranging from Hyperlaxity may help athletes by enhancing form of recurrent microtrauma and overuse. subluxation to frank shoulder dislocation their range of motion. However, this may Secondary forms of impingement and (SD). Due to the shallow depth of the glenoid’s become a problem when it is accompanied injury to the dynamic soft tissue stabilisers osseous structure, shoulder stability is by a functional deficit and pathological may arise from recurrent microtrauma as achieved through a number of additional symptoms. Typical symptoms include well2. soft tissue stabilisers (including the glenoid pain and a subjective feeling of instability labrum). Rotator cuff muscles are the most or apprehension. While instability and ADVANCED IMAGING FINDINGS – AN important dynamic stabilisers of the GH hyperlaxity are two distinct phenomena, OVERVIEW joint. Other muscles that cross the GH joint, they frequently occur together in athletes Radiography remains the primary such as pectoralis major and latissimus dorsi, suffering from SD1. modality of choice when SD is suspected may potentially act as stabilisers as well. SD While purely atraumatic causes may (Figure 1). However, advanced imaging may arise from abnormal function of either account for a number of SDs among athletes, modalities including computed tomo- osseous (glenoid fossa and coracoacromial there are two main etiologies, behind athlete graphy (CT) and magnetic resonance arch) or soft tissue (glenoid labrum, articular SD. First, acute SD may arise as a result of imaging (MRI) are frequently needed cartilage, rotator cuff, long head of biceps being exposed to a considerable load or during the course of clinical decision- and deltoid muscles) structures1. bearing a sudden force during a traumatic making for athletes with SD. For advanced Laxity is characterised by mobility of the event. These injuries may also worsen with radiologic assessment, conventional MRI is humeral head on the glenoid fossa. Excessive repetition of similar traumatic episodes the most utilised modality. Intra-articular 354 1 2a 2b Figure 1: Anteroposterior radiograph demonstrating inferior shoulder dislocation 3a 3b (luxatio erecta) and displaced fracture fragment of the inferior glenoid (red arrow). Figure 2: Coronal (left) proton density-weighted image and axial (right) fat saturated proton density-weighted image of a young patient with anterior shoulder dislocation and Hill Sachs lesion (red arrow). Figure 3: Anterior shoulder dislocation, large haemarthrosis and osteo-cartilagenous Bankart lesion. contrast and MR arthrography may provide drawback of indirect MR arthrography is general, CT provides a powerful tool for the additional benefits. In athletes with MRI a lack of joint space distension. Indeed, assessment of osseous injuries and small contraindications, CT and CT arthrography direct arthrography achieves joint space fractures. Nevertheless, it has an inferior provide an acceptable alternative. distension by introducing the contrast performance when compared with MR Nevertheless, multi-detector CT scans are agent into the GH joint space. In the setting imaging in terms of contrast resolution for used for optimal characterisation of osseous of acute trauma, haemarthrosis can result soft tissue visualisation. While CT exposes injuries associated with SD3. in similar joint space distension leading the patient to a considerable amount to better visualisation of the articular of radiation exposure, the conversion MR IMAGING AND ARTHROGRAPHY surfaces, glenoid labrum, and ligamentous factor and thus the effective radiation MRI provides excellent visualisation of structures. In general, MRI and MR is much lower. CT has the advantage soft tissue and osseous abnormalities that arthrography provide excellent sensitivity of providing a rapid image acquisition, can occur in association with SD. With high- and specificity for detecting glenoid labrum with better compliance in claustrophobic resolution 3D acquisition, MRI is the most and ligamentous abnormalities (Figures 2 patients. Finally, in subjects with metallic important imaging tool for pre-operational and 3)3. artefact (frequently during post-operative evaluations. While direct MR arthrography assessments) CT provides fewer artefacts provides clear diagnostic benefits, it is an CT IMAGING AND ARTHROGRAPHY while the use of MRI may not be applicable invasive procedure. Recent research has CT imaging and arthrography provide in such patients (Figures 4 and 5)3. proposed indirect MR arthrography as a acceptable alternatives when MR imaging non-invasive alternative method with a and arthrography are contraindicated or ADVANCED IMAGING FINDINGS IN comparable diagnostic yield to direct MR unavailable. In fact, studies have declared ANTERIOR SHOULDER DISLOCATION arthrography. Indirect MR arthrography an almost identical accuracy when Anterior SD is the most common type of includes enhancement with intravenous arthrography is performed in the course SD among professional athletes. In anterior gadolinium-based contrasts. The major of shoulder CT, in comparison with MRI. In SD, the introductory force may involve an 355 SPORTS RADIOLOGY anterior-inferior movement of the humeral Perthes lesion is a distinct phenomenon rim and the glenoid labrum when athletes head (in relation to the glenoid fossa). After which is closely related to the Bankart fall on an outstretched hand with their dislocation, the inferior glenohumeral lesion. In some instances, during dislocation arms abducted. The compression may result ligament (IGHL) frequently pulls on the and while the IGHL is dragging the in glenoid articular disruption and may margin of the osseous glenoid fossa, and glenoid labrum, the scapular periosteal impose a superficial injury to the cartilage subsequently an avulsion fracture can occur. sleeve remains intact. This preserves the lining of the antero-inferior portion of the This avulsion fracture is also known as a anatomical position of the avulsed site and glenoid fossa. Cortical depressions may Bankart lesion. Depending on the presence results in what is known as a Perthes lesion. or may not occur. Sometimes a flap tear is (or absence) of osseous tissue in the avulsed Perthes lesions would be more likely to heal visible after the introduction of the contrast IGHL, Bankart lesions are classified as fibrous spontaneously. Diagnosis can be established agent (either in CT or MRI arthrography). or osseous lesions. In fibrous Bankart lesions, by visualising the distinct line of signal Osseous avulsion may occur at the humeral labral tears and disruption of the scapular contrast that lays between glenoid’s osseous attachment site of the IGHL (in contrast to periosteum occur. In either case, when structure and the glenoid labrum. In some the osseous Bankart lesion that avulses the displaced fragment is distant from its cases, the scapular periosteal sleeve may be from the glenoid rim) during SD. Unlike original position, the chance of spontaneous stripped medially, but remains intact. This Bankart lesions, humeral avulsion of the healing will be minimal. With antero- results in another phenomenon, known glenohumeral ligament (HAGL) is not a inferior labrum detachment, administration as anterior labral posterior sleeve avulsion common pathology, given the anatomical of a contrast agent into the joint space (ALPSA). The medially displaced scapular position and biomechanical function of the and visualising its extension beyond the periosteal sleeve may be partially healed. IGHL. A HAGL lesion changes the shape of detachment helps establish the suspected Visualising a glenoid rim that is devoid of the axillary recess from the normal 'U-shape' diagnosis. In cases with associated avulsed labral tissue is indicative of this diagnosis. to a 'J-shape', which can be visualised in an osseous components in the avulsed IGHL, CT Diagnosis can be confirmed by visualising arthrogram. has an excellent accuracy in detecting the the medially displaced and deformed fragment. In fact, even simplified diameter complex of the labrum and the adjacent ADVANCED IMAGING FINDINGS IN measurement derived from the CT scan ligamentous structures. POSTERIOR SHOULDER DISLOCATION can be used to provide clinically decisive The humeral head may also be injured Posterior SD is not as common as information (Figure 5; the b/a ratio may during SD in athletes. The humeral head the anterior SD. It usually requires an indicate the need for surgical management). may impose a compression on the glenoid overwhelming posteriorly directed force to 4 5 Figure 4: Coronal CT image demonstrating Hill Sachs deformity of the posterolateral humeral head (red arrow) and Bankart lesion in the anterior/inferior glenoid (black arrow). Figure 5: Sagittal CT image demonstrating Bankart lesion (b/a ratio is less than 0.20 to 0.25) therefore, bony Bankart repair (e.g. Latarjet procedure) may not be necessary. CT=computed tomography. 356 rupture the joint capsule and/or associated may require surgical intervention. In Overhead athletes: tennis serve and baseball periosteum. Similar to