Intern Ultrasound of the Month: Shoulder Dislocation/Reduction

The Case

A 25-year-old female with history of recurrent right shoulder dislocation presented to the emergency department for right shoulder pain. The patient was attempting to remove something from her hair when she felt a pop in the right shoulder and developed immediate pain with the inability to move her arm.

On arrival to the emergency department, she reported 10 out of 10 pain in her right shoulder. Her exam revealed a palpable step-off with diffuse tenderness and limited abduction of the arm secondary to pain. Grip strength, sensation, and radial pulses were intact.

There was high suspicion for shoulder dislocation given the patient’s presentation and history. A point of care ultrasound was performed to confirm the diagnosis and to establish a baseline prior to x-ray and reduction attempt.

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POCUS findings: Ultrasound of the posterior right shoulder demonstrates anterior displacement of the humeral head relative to the glenoid fossa, consistent with an anterior dislocation.

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Case continued: Xrays confirmed anterior dislocation. The patient underwent procedural sedation and reduction of the right shoulder. Unfortunately, the ultrasound machine was not available after the initial attempt and post-reduction films demonstrated persistence of dislocation. Therefore, the patient underwent a second procedural sedation and reduction.

After this attempt, POCUS was then used to evaluate for reduction. As shown below, the humeral head is now located within the glenoid fossa and glides smoothly with internal/external rotation (elbow fully adducted), thus confirming successful reduction.

 
POST REDUCTION ULTRASOUND W/ DYNAMIC EXAM

POST REDUCTION ULTRASOUND W/ DYNAMIC EXAM

 

Shoulder Dislocations: Brief Background

Epidemiology

  • Shoulder dislocations account for 50% of all major joint dislocations [1] 

  • Estimated incidence rate of 23.9 per 100,000 person-years [2]

  • Shoulder dislocations can be further subclassified into:

    • Anterior (95-97% of all cases)

    • Posterior (2-4%)

    • Inferior (up to 0.5%)

  • About 70% of all anterior dislocations occur in patients under the age of 30 [1]

Clinical signs [1]

  • Arms held to side

  • Prominent acromion, classic “squared off” appearance of shoulder

  • Absence of humeral head or loss of normal rounded contour of the shoulder

  • Fullness in the anterior shoulder

  • Limited range of motion of the arm, with significant pain with internal rotation and adduction (unable to use affected arm to touch opposite shoulder)

Concomitant fractures [1]

  • Occur in 20-25% of cases

  • Factors associated with increased risk: age over 40, first time dislocation, humeral ecchymosis, traumatic mechanism

 

POCUS Assessment for Shoulder Dislocation

Technique and findings

Posterior approach

  • Most common

  • Curvilinear or linear probe is placed in transverse orientation along the scapular spine with probe marker to the sonographer’s left

  • Slide probe laterally until the glenoid fossa and humeral head can be visualized

  • Normal: humeral head is in close alignment with the glenoid fossa

    • Optimal cutoff for normal (when anterior dislocation is suspected) is less than 0.46 cm in one study [3]

acep shoulder-2.png
 

Anterior dislocation: humeral head will appear deeper on the screen relative to the glenoid fossa (or not visualized at all depending on the depth of the probe, especially if linear probe, and extent of dislocation).

Posterior dislocation: humeral head will appear closer to the surface than the glenoid fossa

*Think about direction relative to the probe (which is posterior)

 
 
anterior dislocation1.png
posterior dislocation.png
 

Tip: Perform dynamic exam — with the arm adducted and elbow flexed at 90 degrees, have the patient internally and externally rotate the shoulder --> if you see clear rotational articulation of the humeral head and glenoid, the joint is intact.

*Note: this is the left shoulder so the humeral head is lateral to the glenoid (opposite the images from the case)

*Note: this is the left shoulder so the humeral head is lateral to the glenoid (opposite the images from the case)

Lateral approach [4]

  • Probe is placed in longitudinal orientation just below the lateral end of the acromion

  • Normal: humeral head is aligned just below the acromion

  • Anterior dislocation: increased distance between the acromion and humeral head: “widening of the subacromial space sign”

lateral approach.png

Anterior approach [4]

  • Probe is placed in transverse orientation below the lateral end of the clavicle at the coracoid process (identified via palpation)

  • Normal: humeral head is aligned lateral to the coracoid process

  • Anterior dislocation: humeral head is seated below the coracoid process & is not visible on ultrasound: “disappearance of humeral head sign”

Benefits

  • Adjunct to standard radiographs (AP and Scapular Y views)

  • Very high sensitivity and specificity (both approaching 100%) for the diagnosis of shoulder dislocation [5-9].

  • Allows for more rapid confirmation of diagnosis [3] and successful reduction [9], which is especially useful immediately after a reduction attempt before sending the patient off for xrays, as demonstrated in this case.

Limitations

  • Analysis for fracture is sonographer-dependent and highly variable among studies, with sensitivity ranging from 97.9% [5] to 52% [6], likely due to differences in training and technique

Take home points

  • Shoulder dislocation is the most common major joint dislocation, with nearly 70% of cases occurring in patients under the age of 30

  • POCUS is highly sensitive and specific for the diagnosis of shoulder dislocation

  • POCUS is a powerful tool for confirming dislocation or reduction and is especially useful immediately after a reduction attempt

  • X-rays may be more sensitive at identifying fractures and should be obtained in patients for whom a traumatic mechanism is known or suspected

POST BY: DR. BEJAN KANGA, PGY1

FACULTY EDITING BY: DR. LAUREN MCCAFFERTY

 

References

1. Simon RR, Sherman SC, Koenigsknecht SJ. Emergency Orthopedics: The Extremities, 5th ed, McGraw-Hill, New York, 2006.

2. Zacchilli MA, Owens BD. Epidemiology of shoulder dislocations presenting to emergency departments in the United States. J Bone Joint Surg Am. 2010; 92(3):542-9.

3. Secko MA, Reardon L, Gottlieb M, Morley EJ, Lohse MR, Thode HC, Singer AJ. Musculoskeletal Ultrasonography to Diagnose Dislocated Shoulders: A Prospective Cohort. Annals Emerg Med. 2020; 76(2): 119-128

4. Yuen CK, Mok KL, Kan PG, Wong YT. Ultrasound diagnosis of anterior shoulder dislocation. Hong Kong J Emerg Med. 2009; 16: 29-34.

5. Gottlieb M, Holladay D, Peksa GD. Point-of-care ultrasound for the diagnosis of shoulder dislocation: A systematic review and meta-analysis. Am J Emerg Med. 2019; 37(4):757-761

6. EJM Journal Watch: Summaries of and Commentary on Original Medical and Scientific Articles from Key Medical Journals. https://www.jwatch.org/na51038/2020/03/16/point-care-ultrasound-diagnosing-shoulder-dislocations.

7. Gottlieb M, Russell F. Accuracy of Ultrasound for Identifying Shoulder Dislocations and Reductions: A Systematic Review of the Literature. West JEM., 2017; 18(5):937-942

8. Akyol C, Gungor F, Akyol AJ, et al. Point-of-Care Ultrasonography for the Management of Shoulder Dislocation in ED. Am J Emerg Med. 2016; 34(5): 866–70

9. Boswell B, Farrow R, Rosselli M, et al. Emergency Medicine Resident–Driven Point of Care Ultrasound for Suspected Shoulder Dislocation. South Med J. 2019; 112(12):605-609

UltrasoundLauren McCaffertypocus, ultrasound, MSK Ultrasound, shoulder dislocation, ortho