POCUS: Shoulder Dislocation

Case:

An 18-year male with a history of a left shoulder dislocation presents with a chief complaint of “my shoulder is out of place.” Prior to arrival, the patient fell during a soccer game and felt his shoulder dislocate. He is neurovascularly intact.

Introduction:

The glenohumeral joint is the most commonly dislocated major joint in the body. The glenoid is shallow, with only a small portion of the humeral head articulating with it. While this allows for a wide range of motion, this makes the shoulder an unstable joint. Anterior dislocations account for 95 to 97% of all glenohumeral dislocations. Posterior dislocations account for most of the remainder, whereas inferior and superior dislocations are rare [i]. It is important that the dislocation is reduced as soon as safely possible since neurovascular complications increase with time.

A common practice is to obtain radiographs before reduction of a shoulder dislocation to confirm the diagnosis and exclude fractures. Recent literature has demonstrated the advantage of point-of-care-ultrasound (POCUS) in detecting both anterior and posterior shoulder dislocations. However, further investigation is necessary to assess the ability of ultrasonography in detecting fractures associated with dislocation [ii]. Factors associated with fractures include age over 40, first-time dislocation, and traumatic mechanism. When all three factors were absent, the negative predictive value for the presence of a fracture was 96.6 percent (95% CI 88.3-99.6) [iii]. If none of the aforementioned criteria are met and the clinician feels that this is an uncomplicated anterior shoulder dislocation, pre-reduction radiographs are unnecessary.  

X-rays are often taken following a reduction to confirm successful reduction and exclude any fracture caused by the procedure. Post reduction films are time consuming and need to occur after any sedating medications have worn off. Imagine discovering that the reduction was unsuccessful? This patient may need to undergo sedation again, the length of stay is dramatically increased, and your patient is probably not thrilled!

Don’t worry, there is another option! Ultrasound is a cost-effective, portable, safe, and real-time tool that can be used in this situation. POCUS allows for a dynamic evaluation of the glenohumeral joint, immediately informing you of a successful reduction or the need for additional shoulder manipulation. Additionally, ultrasound can also be used to guide intra-articular local anesthetic. As good as this sounds, there are some limitations to using POCUS. Ultrasound is highly operator-dependent, it is not sensitive for a labral or rotator cuff tears, and fractures can be difficult to assess.

Let’s Scan

Figure 1: Getting set up

Grab a high-frequency, linear-array probe or the curvilinear probe. Depending on patient habitus and personal preference, either probe is a fine choice. Position the probe in the transverse orientation, behind the shoulder and over the scapular spine. Move the probe laterally until you can visualize the glenoid. Continue to move laterally until you have a good view of the humeral head.

Normal Shoulder:

Figure 2: Normal Shoulder Anatomy on POCUS

Figure 3: Normal Shoulder Anatomy on POCUS. 
Photo Source: https://sonostuff.com/2016/08/23/msk-pocus-2nd-installment-muscles-tendons-and-bones-oh-my-foamed-foamus-meded-ultrasound/

Figure 4: Normal Shoulder Anatomy on POCUS
Photo Source: http://www.foamem.com/2014/06/05/shoulder-ultrasound-intra-articular-injection-and-reduction-2/

If the shoulder is in appropriate anatomical position, the shoulder joint should be immediately adjacent to the glenoid. If the shoulder is not dislocated, the patient should be able to internally and externally rotate the shoulder while adducted, and the rotational articulation between the humeral head and glenoid fossa will be seen clearly on the ultrasound screen.

Abnormal Shoulder:

With an anterior dislocation, the humeral head will be deep on the screen, while with a posterior dislocation, the humeral head will be more superficial on the screen (closer to the probe).  A hyperechoic hemarthrosis is often seen in the joint when shoulder is dislocated.

Figure 5: Anterior Shoulder Dislocation 

Figure 6: Posterior Dislocation [iv]

Figure 7: Comparing Anterior Dislocations to Posterior Dislocations. Photo Source: http://www.emdocs.net/wp-content/uploads/2014/06/shoulderDislocation.png

Pain Control:

Another advantage to ultrasound is that it can be used to guide an intra-articular lidocaine injection. Systematic review articles have found that complication rate, length of stay, and cost were significantly lower in patients who received intra-articular lidocaine when compared with those who received intravenous sedation [i],[ii],[iii]. Sterilize the skin over the shoulder and place local anesthetic with a small bore needle. Use the ultrasound transducer to locate the glenoid and humeral head. Using a long axis or in-plane technique guide a 20-gauge spinal needle into the joint and inject 20 mL of 1% lidocaine into the joint space [iv]. Give the medication 10-20 minutes to kick in and proceed with your reduction.

Figure 8: Representation of intra-articular lidocaine injection

Video source: Dr. Shirley Wu

Take Home Points:

• Position the probe in the transverse orientation, behind the shoulder and over the scapular spine. Move the probe laterally until you can visualize the glenoid and the humeral head.
• With an anterior dislocation, the humeral head will be deep on the screen, while with a posterior dislocation, the humeral head will be more superficial on the screen (closer to the probe). 
• Complication rate, length of stay, and costs were significantly less in the intra-articular lidocaine group when compared with the intravenous sedation group

If you want to see more, here is a helpful 6 min video by Mike Stone on ultrasound for dislocation and tips on intraarticular lidocaine injections using US guidance.

Resident Reviewer: Dr. TJ Ye

Faculty reviewers: Dr. Otto Liebmann

References:

[i] Marx, John A, Robert S. Hockberger, Ron M. Walls, Michelle H. Biros, Daniel F. Danzl, Marianne Gausche-Hill, Andy Jagoda, Louis Ling, Edward Newton, Brian J. Zink, and Peter Rosen. Rosen's Emergency Medicine: Concepts and Clinical Practice. , 2014. Chapter 53, 618-642.e2

[ii] Abbasi S, Molaie H, Hafezimoghadam P, Zare MA, Abbasi M, Rezai M, Farsi D. Diagnostic accuracy of ultrasonographic examination in the management of shoulder dislocation in the emergency department. Ann Emerg Med. 2013 Aug;62(2):170-5. doi:10.1016/j.annemergmed.2013.01.022. Epub 2013 Mar 13.

[iii] Emond M, Le Sage N, Lavoie A, Rochette L. Clinical factors predicting fractures associated with an anterior shoulder dislocation. Acad Emerg Med. 2004Aug;11(8):853-8.

[iv] Mackenzie DC, Liebmann O. Point-of-care ultrasound facilitates diagnosing a posterior shoulder dislocation. J Emerg Med. 2013 May;44(5):976-8. doi: 10.1016/j.jemermed.2012.11.080. Epub 2013 Mar 13.

[v] Waterbrook AL, Paul S. Intra-articular Lidocaine Injection for Shoulder Reductions: A Clinical Review. Sports Health. 2011;3(6):556-559. doi:10.1177/1941738111416777.

[vi] Hunter, B, Wilbur, L MD.  Can Intra-articular Lidocaine Supplant the Need for Procedural Sedation for Reduction of Acute Anterior Shoulder Dislocation?  Ann Emerg Med 59(6): 513-4; 2012.

[vii] Ng VK, Hames H, and Millard WM: Use of intra-articular lidocaine as analgesia in anterior shoulder dislocation: a review and meta-analysis of the literature. Can J Rural Med 2009; 14: pp. 145-149

[viii] Custalow, Catherine B, James R. Roberts, Todd W. Thomsen, and Jerris R. Hedges.Roberts and Hedges' Clinical Procedures in Emergency Medicine. Philadelphia, PA: Elsevier/Saunders, 2013. Internet resource.