US Case of the Month - Sonography of Shoulders
/Case 1:
A young female presented to the Emergency Department with right shoulder pain. She was in the back of a police vehicle, handcuffed with her hands behind her back, and slid as the vehicle rounded a corner. She attempted to catch herself and experienced immediate onset of pain in her right shoulder. She denied additional complaints. She had no prior history of injury or surgery to the affected shoulder. On exam, she had visible deformity of her right shoulder but was neurovascularly intact.
Figure 1 - (left) Right Anterior Sohulder dislocation Pre reduction. Note the humeral head deep to the glenoid fossa on ultrasound. (Right) Left Shoulder in normal alignment for comparison
Figure 2 - Right Anterior Shoulder Dislocation Pre (left) and Post (Right) reduction.
Point-of-care ultrasound and x-rays both demonstrated an anterior shoulder dislocation (Figure 1), which was reduced following sedation with IV ketamine. Successful reduction was demonstrated in real-time with ultrasound (Figure 2) and confirmed radiographically. Patient remained neurovascularly intact, and was discharged in a sling and swath.
Case 2:
A middle-aged male presented to the Emergency Department with left shoulder pain after an MVC in which he was a restrained driver. The pain was sharp, constant, and began immediately after the accident. He denied additional complaints. On exam, he had a left shoulder deformity with the humeral head palpable posteriorly. He had no neurovascular compromise.
Figure 3 - Left Posterior Shoulder Dislocation, Note the humeral head superficial to the glenoid fossa.
Figure 4 - Right Shoulder, normal, for comparison
Ultrasound showed a posterior shoulder dislocation (Figure 3), and x-rays suggested an associated reverse Hill-Sachs deformity. Patient underwent closed reduction following injection of intra-articular lidocaine, and remained neurovascularly intact post-reduction. He was placed in a sling and swath, and eloped prior to confirmatory post-reduction imaging
Ultrasound evaluation of the shoulder
Shoulder dislocation is a common orthopedic complaint seen in the Emergency Department, occurring with an incidence of 23.9 per 100,000 person-years and resulting in approximately 70,000 ED visits annually in the United States (1). Anterior dislocations account for the overwhelming majority of injuries (~95%), with posterior dislocations occurring in 2-5% of cases and inferior dislocations in <1%.
Radiographs have long been the gold standard for the diagnosis of dislocation, evaluation for associated fractures, and confirmation of successful reduction. Obtaining pre-reduction films increases the time to reduction (2) and cost to patients, however, while minimally affecting clinical management (3). Point-of-care ultrasound has emerged as an alternative diagnostic modality that is less expensive than radiography, is faster (4), and has no associated radiation exposure yet is both highly sensitive and specific for shoulder dislocation. In a 2019 systematic review and meta-analysis incorporating data from 7 studies, Gottleib et al. reported a pooled sensitivity of 99.1% and specificity of 99.9% for point-of-care ultrasound in the diagnosis of shoulder dislocation, with LR+ of 796.2 and LR- of 0.01 (5). Moreover, Lahham, et al. demonstrated that ultrasound could be used to reliably diagnose shoulder dislocations even when employed by novice sonographers with no medical background (6). Limited data suggests ultrasound may also have utility in detecting fractures associated with shoulder dislocations, with reported sensitivity and specificity both approaching 100%, however further studies are needed (5). Accordingly, ultrasound may be best used as a diagnostic alternative to radiographs in patients who are at low risk for associated fracture, such as those suffering a recurrent, atraumatic dislocation or who are ≤ 35 years of age without a dangerous mechanism of injury (e.g. MVC, assault, fall >10 feet, sports-related injury) (7). Ultrasound may also be a useful adjunct to x-rays in cases of posterior shoulder dislocation, which may have subtle or occult radiographic findings (8).
Post-reduction films are typically obtained to confirm successful shoulder reduction. In the case of reductions performed under sedation, the delay required for acquisition and interpretation of post-reduction films may result in the need for re-sedation in the case of a failed procedure. In contrast, ultrasound offers a means for real-time confirmation (9) with excellent specificity for reduction, though its relatively low sensitivity suggests follow-up radiographs should still still be obtained (10). Ultrasound can also be used to guide intra-articular injection of lidocaine to facilitate reduction, eliminating the need for procedural sedation entirely (11).
Image Acquisition
Depending on the patient’s habitus, either a linear or curvilinear probe can be used to evaluate for shoulder dislocation. Standing behind the patient’s injured shoulder, orient the transducer parallel to and just below the scapular spine, then slide the transducer laterally until both the glenoid fossa and humeral head are visible. In the case of an anterior dislocation, the humeral head will be farther from the transducer than the glenoid fossa, and will appear deep to the gIenoid on the screen. The opposite is true for a posterior dislocation; the humeral head will appear superficial to the glenoid as it is closer to the transducer. If the shoulder is not dislocated, the patient should be able to internally and externally rotate the arm with the shoulder in adduction, and the articulation of the humeral head with the glenoid should be readily visible on screen.
Post by Kate Connelly, MD
Dr. Connelly is a PGY-3 in Emergency Medicine at the University of Cincinnati
Editing by Patrick Minges, MD
Dr. Minges is an Ultrasound-trained and Clinical Faculty in Emergency Medicine at the University of Cincinnati.
References
Zacchillli MA and Owens BD. Epidemiology of shoulder dislocations presenting to emergency departments in the United States. J Bone Joint Surg Am. 2010;92:542-549.
Schuster M, Abu-Laban RB, and Boyd J. Prereduction radiographs in clinically evident anterior shoulder dislocation. Am J Emerg Med. 1999;17:653-658.
Perron AD, Ingerski MS, Brady WJ, et al. Acute complications associated with shoulder dislocation at an academic emergency department. J Emerg Med. 2003;24(2):141-145.
Secko MA, Reardon L, Gottlieb M, et al. Musculoskeletal ultrasonography to diagnose dislocated shoulders: A prospective cohort. Ann Emerg Med. 2020;76(2):119-128.
Gottlieb M, Holladay D, and Peska GD. Point-of-care ultrasound for the diagnosis of shoulder dislocation: A systematic review and meta-analysis. Am J Emerg Med. 2019;37:757-761.
Lahham S, Becker B, Chiem A, et al. Pilot study to determine accuracy of posterior approach ultrasound for shoulder dislocation by novice sonographers. West J Emerg Med. 2016;17(3):377–382.
Emond M, Gariepy C, Boucher V, et al. Selective pre-reduction radiography in anterior shoulder dislocation: The Fresno-Quebec rule. J Emerg Med. 2018;55(2):218-225.
Beck S, Chilstrom M. Point-of-care ultrasound diagnosis and treatment of posterior shoulder dislocation. Am J Emerg Med. 2013;31:449 e3-5.
Halberg MJ, Sweeney TW, and Owens WB. Bedside ultrasound for verification of shoulder reduction. Am J Emerg Med. 2009;27:134 e5-6.
Ahmadi K, Hashemian AM, Sineh-Sepehr K, et al. Bedside ultrasonography for verification of shoulder reduction: A long way to go. Chin J Traumatol. 2016;19:45-48.
Penn M and Williams O. Can acute shoulder dislocations be reduced using intra-articular local anaesthetic infiltration as an alternative to intravenous analgesia with or without sedation? Emerg Med J. 2020;37(11):725-728.
