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American Journal of Emergency Medicine (2013) 31, 449.e3–449.e5

Case Report

Fig. 1 Probe positioning with indicator marker towards thepatient's left.

Point-of-care ultrasound diagnosis and treatment ofposterior shoulder dislocation

Abstract

Acute traumatic posterior shoulder dislocations are rare.The diagnosis is often missed or delayed, as radiologicabnormalities can be subtle. We report a case of a 37-year-oldman who presented to the emergency department with severeright shoulder pain and inability to move his arm after a motorvehicle collision. Based on examination, he was initiallythought to have an anterior dislocation; however, point-of-care (POC) ultrasound clearly demonstrated a posteriorshoulder dislocation. Real-time ultrasound-guided intra-articular local anesthetic injection facilitated closed reductionin the emergency department without procedural sedation,and POC ultrasound confirmed successful reduction at thebedside after the procedure. This case demonstrates that POCultrasound can be a useful diagnostic tool in the rapidassessment and treatment for patients with suspected poster-ior shoulder dislocation.

A 37-year-old man presented to the emergency depart-ment with right shoulder pain after a motor vehicle collision.He was the restrained driver of a vehicle that was struck by atractor-trailer. At the moment of impact, his right shoulderstruck the steering wheel. The patient reported a poppingsensation accompanied by severe pain in the shoulder. Uponphysical examination, the patient's arm was adducted andinternally rotated. He was unable to actively externally rotatethe arm and complained of severe pain with attempts topassively abduct the shoulder. Inspection revealed promi-nence of the coracoid anteriorly. A firm prominence,subsequently recognized as the humeral head, was palpatedposteriorly. We did not initially recognize that these findingswere suggestive of a posterior dislocation.

Given initial concern for possible anterior shoulderdislocation, a point-of-care (POC) ultrasound examinationwas performed by the treating emergency physicians using a5- to 2-MHz curved array transducer (SonoSite M-Turbo,Bothell, WA). The transducer was placed on the patient'sposterior shoulder parallel to the scapular spine and held overthe lateral edge of the scapula so the glenoid and the humeralhead could be visualized (Fig. 1). Note that in contrast tostandard emergency ultrasound convention, the indicator

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marker is towards the patient's left as the provider is scanningfrom behind the patient. In a normal shoulder, the humeralhead is seen articulating within the glenoid.With external andinternal rotation of the arm, articulation of the humeral headwithin the joint can be appreciated. In anterior dislocations,the humeral head is displaced anterior to the glenoid and isseen in the far field of the ultrasound image. In contrast, theultrasound image in this patient (Fig. 2) demonstrates thehumeral head displaced posterior to the glenoid. Based onultrasound findings, we made the diagnosis of posteriorshoulder dislocation. Anterior-posterior and scapular Y-viewradiographs of the shoulder were subsequently performed(Fig. 3). Widening of the glenohumeral joint was suggestiveof dislocation; however, films were subsequently read byradiology as inadequate to make a definitive diagnosis.

After obtaining informed consent, we performed ultra-sound-guided intra-articular injection of local anestheticunder sterile conditions. In contrast to the posterior approachused to make the diagnosis, the transducer was placedanteriorly on the patient's shoulder with the probe markernow towards the patient's right and the beam parallel to thecoracoid process and humeral head. Morphine was admin-istered for pain relief before the procedure. A 22-gaugespinal needle was inserted lateral to the probe and advancedinto the joint anterior to the humeral head. Twenty millilitersof 1% lidocaine was injected and visualized sonographically

Fig. 2 Pre-reduction ultrasound.

449.e4 Case Report

as anechoic fluid deposited within the joint space (Fig. 4).The patient reported decreased pain after the injection, andreduction was performed with traction on the internallyrotated and adducted arm followed by slow external rotationand abduction. Simultaneously, a second provider appliedposterior pressure on the humeral head. After completion ofthe procedure, the patient was able to fully range theshoulder, and POC ultrasound (Fig. 5) confirmed reductionof the joint.

The shoulder is the most commonly dislocated joint inthe body, but acute posterior dislocations are rare,representing less than 3% of all shoulder dislocations [1].Posterior shoulder dislocations are classically described inthe setting of intense muscle contractions from seizures or

Fig. 3 Anterior-posterior and

electrocution, but most commonly occur as a result oftrauma, such as after a direct blow to the shoulder, a fallon an outstretched arm, or a motor vehicle collision [2-4].The diagnosis of posterior shoulder dislocation is oftendifficult to make and has been reported as missed in morethan 50% of initial presentations [5]. The clinical picturemay appear similar to more common diagnoses, such as ashoulder contusion or rotator cuff tear, and associatedfractures can distract clinicians from making the diagnosis[6]. Anterior-posterior films can appear grossly normal,and the classic appearance of the “light bulb sign” isabsent in most cases [7]. Other radiographic signs ofposterior shoulder dislocation have been described, butthey are subtle and not uniformly present [8,9]. Computedtomography can be used to confirm the diagnosis in certaincases but is resource and time intensive and exposes thepatient to radiation. Early diagnosis is critical, however, asa delay in reduction can lead to chronic degenerativechanges or avascular necrosis of the humeral head.

Several case series have demonstrated the use of POCultrasound for the identification of acute anterior shoulderdislocations and confirmation of reduction [10,11]. Simi-larly, there are studies demonstrating the use of POCultrasound-guided intra-articular joint injection for analge-sia in the reduction of anterior shoulder dislocations [12].These same techniques can be applied to patients withposterior dislocations [13]. To our knowledge, the use ofultrasound to guide intra-articular joint injection foranalgesia in posterior shoulder dislocations has not beenpreviously described. This case demonstrates that, forpatients presenting with suspected posterior shoulderdislocation, POC ultrasound can be used to rapidly confirmthe diagnosis, facilitate successful intra-articular anestheticinjection, and confirm successful reduction.

scapular Y-view x-rays.

Fig. 5 Postreduction ultrasound.

Fig. 4 The needle (asterisks) is visualized entering the joint space anterior to the humeral head (h). Local anesthetic deposition is seen as ananechoic fluid deposition (arrow) within the joint.

449.e5Case Report

Sierra Beck MDMikaela Chilstrom MD, RDMS

Department of Emergency MedicineEmory University School of Medicine, Atlanta

GA 30303, USAE-mail address: sierra.c.beck@emory.edu

http://dx.doi.org/10.1016/j.ajem.2012.06.017

References

[1] McLaughlin H. Posterior dislocation of the shoulder. J Bone Joint SurgAm 1952;24(3):584-90.

[2] Robinson CM, Seah M, Akhtar MA. The epidemiology, risk ofrecurrence, and functional outcome after an acute traumatic posteriordislocation of the shoulder. J Bone Joint Surg Am 2011;93:1605-13.

[3] Hashmi FR, Pugh M, Bryan S. Simultaneous bilateral posteriordislocation of shoulder. Am J Emerg Med 2002;20(2):127-8.

[4] Tan AH. Missed posterior fracture-dislocation of the humeral headfollowing an electrocution injury to the arm. Singapore Med J 2005;46(4):189-92.

[5] Kowalsky MS. Traumatic posterior glenohumeral dislocation: classi-fication pathoanatomy, diagnosis, and treatment. Orthop Clin NorthAm 2008;39(4):519-33.

[6] Robinson CM, Aderinto J. Posterior shoulder dislocations andfracture-dislocations. J Bone Joint Surg Am 2005;87(3):639-50.

[7] Mouzopoulos G. The “Mouzopoulos” sign: a radiographic sign ofposterior shoulder dislocation. Emerg Radiol 2010;17:317-20.

[8] Gor DM. The trough line sign. Radiology 2002;224(2):485-6.[9] Arndt JH, Sear AD. Posterior dislocation of the shoulder. Am J

Roentgenol Radium Ther Nucl Med 1965;94:639-45.[10] Halberg MJ, Sweeney TW, Owens WB. Bedside ultrasound for

verification of shoulder reduction.AmJEmergMed 2009;27(1):134.e5-6.[11] Blakeley CJ, Spencer O, Newman-Saunders T, et al. A novel use of

portable ultrasound in the management of shoulder dislocation. EmergMed J 2009;26:662-3.

[12] Stone MB, Sutijono D. Intraarticular injection and closed glenohum-eral reduction with emergency ultrasound. Acad Emerg Med 2009;16(12):1384-5.

[13] Yuen CK, Chung TS, Mok KL, et al. Dynamic ultrasonographic signfor posterior shoulder dislocation. Emerg Radiol 2011;18:47-51.