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SPORTS RADIOLOGY DISLOCATION AMONG ATHLETES AN OVERVIEW OF COMMON AND IMAGING FINDINGS

– Written by Nima Hafezi–Nejad, Shadpour Demehri and John A Carrino, USA

The Glenohumeral (GH) 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. 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 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 ( 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

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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 (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

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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 abducted. The compression may result (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 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

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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 (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 Bankart lesions in general, experts agree that epidemiologic pitch anterior SD, ‘reverse’ Bankart lesions occur in surveillance systems should be improved to Overhead sports have higher rates of posterior SD when a posterior portion of the warrant the infrastructure that is needed to both common and uncommon injuries glenoid labrum is avulsed. ‘Reverse’ Bankart implement preventive measures4. associated with SD. Besides Bankart lesions can be diagnosed by visualising Regarding the mechanism of injury; lesions and other common injuries, contrast entry into the posterior glenoid throwing, a missed punch, falling and baseball pitchers may present with HAGL fossa, beyond the glenoid labrum. In some weight bearing (especially in an overhead and axillary pouch avulsions that are cases, the posterior scapular periosteal ) are of the most common etiologies. not common to other groups of athletes. structure may remain intact to some extent. However, a significant portion of athletes MRI evaluation of these patients may The partially avulsed posterior scapular may not specify a distinct etiology for also reveal glenoid labrum and rotator periosteal structure can be medially their SD. and instabilities are cuff tears. Careful evaluation of cartilage displaced; resulting in what is also known similar common pathologies that may or linings is necessary to diagnose associated as posterior labro-scapular sleeve avulsion. may not lead to SD5. cartilage defects6. A distinct line of intra-articular contrast between the medially displaced posterior scapular periosteal structure and the glenoid indicates the diagnosis. An incomplete, superficial tear in the posterior glenoid labrum can be easily missed. Known as a Kim lesion, it is associated with a loss in height of the glenoid labrum and an abnormal contour of the posterior labrum. Finally, similar to HAGL in anterior SD, posterior HAGL may occur during posterior SD. It is important to diagnose muscular injuries associated with posterior HAGL, including disruptions in the insertion of the teres minor.

INJURIES RELATED TO VARIOUS SPORTS SD happens during a variety of sports and among a variety of age groups. Associated sports include overhead sports, volleyball, baseball, contact sports, rugby, basketball and weightlifting. However, other sports including swimming, gymnastics, dancing and rowing are also associated with an increased risk of SD2. High school athletes may be at higher risk of SD. Previous reports have shown that athletic activities may be associated with up to four times higher risk of SD among high school athletes4. The rate ratio was highest for American football players, among high school students. Nevertheless, senior athletes in contact sports may bear an increased risk of SD. While SD corresponds to the more intense spectrum of injuries, other milder injuries such as strains and are much more common. These injuries are frequently associated with time loss from athletic activities. Boys are more likely to sustain / AFP Getty Images © ALAIN GROSCLAUDE significant injuries than girls. Importantly, a significant portion of associated injuries Image: Illustration of the tennis serve.

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Overhead sports have a higher rate of both common and uncommon injuries associated with shoulder dislocation

The overhead throwing motion is a Baseball batters lesser tuberosity fractures associated combination of a chain of sequential The distinctive pathology of the shoulder with direct trauma. Advanced evaluation (kinetic) positions and actions. Such in baseball batters has led to attempts to using MRI is usually performed to help motions are thoroughly studied for the define and describe the diagnosis of ‘batter’s the clinician in making the final decision two prototypic examples, namely the shoulder’. Batter’s shoulder is defined as for the choice of treatment in an athlete. tennis serve and the baseball pitch. When posterior instability of the shoulder as MRI may reveal cartilage defects and soft performed in the optimised fashion, they the result of common swinging motions tissue abnormalities that contribute to SD. result in maximised functionality and associated with missed balls. It contributes Finally, dynamic ultrasound can be useful in superior athletic performance. However, to injuries of the glenoid labrum. In an acute determining the joint laxity as well11. improper motion chains (including motions injury, radiography is the first modality from a defined ‘node’ to the next) may result of choice and can help exclude associated Ice hockey players in SD. Shoulder rotation, flexibility and fractures and dislocations. An axillary Ice hockey players may also be at high strength are some of the other determining view may be helpful in these cases. While risk of shoulder injuries. Previous reports factors7. In-depth biomechanical studies radiography provides the initial clue, suggested an injury rate of up to 20% in of these motions lead to the definition of advanced evaluation using MRI help reveal these athletes. Incidence appears to be disabled throwing shoulder (DTS). DTS has associated injuries, glenoid hypoplasia, increased among those playing at higher several determinants that may be under HAGL and other IGHL lesions. Careful levels. In a studied sample of National the influence of scapular and GH rotational evaluation of glenoid labrum, joint capsule Hockey League players, 75% of the athletes deficits. Superior labral and rotator cuff and chondral lesions are important for had Bankart lesions in their affected injuries may compromise GH joint function optimal treatment10. . IGHL tears, biceps subluxations, and contribute to DTS as well8. rotator cuff tears, GH chondral lesions and Contact athletes early osteoarthritis were some of the other Volleyball players The shoulder is the most common joint associated injuries12. Volleyball players share common injuries to be dislocated in contact athletes. SD with overhead athletes due to the nature of may occur in contact athletes following Rugby players shoulder’s movement; hyperabduction and acute trauma or as the result of cumulative Rugby players are also prone to a variety external rotation are common manoeuvres microtraumas. In the clinical evaluation of common and uncommon shoulder in these athletes. HAGL and axillary pouch of athletes in sports such as American injuries. Tackling other players may impose avulsions may also occur in this group football, wrestling, ice hockey and rugby, a great load on the anterior aspect of the of patients. Patients may bear capsular posterior instability should be a major shoulder. On the other hand, being tackled laxity and sub-clinical levels of instability. concern. Imaging evaluations starts with and landing in an improper position may Repetitive microtrauma contributes to the radiography. Axillary and supraspinatus accompany a risk of SD as well. In MRI development of HAGL and axillary pouch (apical oblique) views are particularly evaluations of these patients, anterior avulsion in these athletes. Other commonly- helpful in these cases. Radiography can glenoid labrum tears, antero-inferior associated injuries include labral tears, help diagnose associated glenoid rim translations and even superior labral lesions rotator cuff tears and cartilage injuries9. abnormalities, glenoid dysplasia and are commonly detected. Injury repair may

358 be challenging. Repeated injuries and 4. Robinson TW, Corlette J, Collins CL, 14. de Figueiredo EA, Belangero PS, Ejnisman recurrent tears are common detrimental Comstock RD. Shoulder injuries among B, Pochini Ade C. Complex shoulder factors in these athletes13. US high school athletes, 2005/2006- injuries in sports. BMJ Case Rep 2014; 2011/2012. Pediatrics 2014; 133:272-279. 2014. Other sports: basketball, wrestling, and 5. Owens BD, Duffey ML, Nelson BJ, 15. Shah AA, Selesnick FH. Traumatic weight lifting DeBerardino TM, Taylor DC, Mountcastle shoulder dislocation with combined Almost every professional athlete SB. The incidence and characteristics of bankart lesion and humeral avulsion (especially in sports with workloads on shoulder instability at the United States of the glenohumeral ligament in a the shoulders) may be at risk of SD. The Military Academy. Am J Sports Med 2007; professional basketball player: three- most commonly associated sports have 35:1168-1173. year follow-up of surgical stabilization. 2010; 26:1404-1408 been outlined above; nevertheless, current 6. Chang EY, Hoenecke HR Jr., Fronek J, literature is forming around establishing Huang BK, Chung CB. Humeral avulsions individualised types of shoulder injuries of the inferior glenohumeral ligament in athletes from different sports. Beside complex involving the axillary pouch in common injuries that are shared among all professional baseball players. Skeletal sports, uncommon shoulder injuries leading Radiol 2014; 43:35-41. to SD are of important diagnostic value in 7. Kibler WB, Wilkes T, Sciascia A. Mechanics the evaluation of professional athletes. Such and pathomechanics in the overhead uncommon injuries may include HAGL athlete. Clin Sports Med 2013; 32:637-651. and its associated nerve injuries among basketball athletes or SD in the setting 8. Kibler WB, Kuhn JE, Wilk K, Sciascia A, of pectoralis major injuries in Moore S, Laudner K et al. The disabled wrestlers14,15. In each case, advanced imaging throwing shoulder: spectrum of is an inseparable part of individualised pathology-10-year update. Arthroscopy patient care. 2013; 29:141-161. 9. Taljanovic MS, Nisbet JK, Hunter TB, Cohen RP, Rogers LF. Humeral avulsion of the inferior glenohumeral ligament in college female volleyball players caused Nima Hafezi–Nejad M.D. by repetitive microtrauma. Am J Sports Med 2011; 39:1067-1076. Post-Doctoral Research Fellow 10. Kang RW, Mahony GT, Harris TC, Dines JS. Posterior instability caused by batter's Shadpour Demehri M.D. shoulder. Clin Sports Med 2013; 32:797- Assistant Professor 802. Russell H. Morgan Department of References 11. Tannenbaum EP, Sekiya JK. Posterior Radiology and Radiological Sciences 1. Murray IR, Goudie EB, Petrigliano FA, shoulder instability in the contact School of Medicine, Johns Hopkins Robinson CM. Functional anatomy and athlete. Clin Sports Med 2013; 32:781-796. University biomechanics of shoulder stability in the 12. Dwyer T, Petrera M, Bleakney R, Baltimore, USA athlete. Clin Sports Med 2013; 32:607-624. Theodoropoulos JS. Shoulder instability 2. Doyscher R, Kraus K, Finke B, Scheibel in ice hockey players: incidence, John A Carrino M.P.H., M.D. mechanism, and MRI findings. Clin Sports M. [Acute and overuse injuries of the Vice-Chairman of Radiology, Attending Med 2013; 32:803-813. shoulder in sports]. Orthopade 2014; Radiologist 43:202-208. 13. Banerjee S, Weiser L, Connell D, Wallace Department of Radiology and Imaging 3. Bois AJ, Walker RE, Kodali P, Miniaci A. AL. Glenoid rim fracture in contact Hospital for Special Imaging instability in the athlete: the athletes with absorbable suture anchor right modality for the right diagnosis. reconstruction. Arthroscopy 2009; New York, USA Clin Sports Med 2013; 32:653-684. 25:560-562. Contact: [email protected]

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