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Date: March 27th, 2020

Reference: Secko et al. Musculoskeletal Ultrasonography to Diagnose Dislocated Shoulders: A ProspectiveCohort. Ann Emerg Med Feb 2020

Guest Skeptic: Dr. Tony Zitek is an Emergency Medicine physician in Miami, Florida. He is an Assistant Professor of Emergency Medicine for Florida International University and Nova Southeastern University, and Tony is the Research Director for the Emergency Medicine residency program at Kendall Regional Medical Center.

DISCLAIMER: THIS IS NOT AN EPISODE ON COVID19

Here are five websites to get up-to-date information about COVID19:

Case: An 18-year-old, previously healthy male presents to the emergency department after sustaining an injury to his right shoulder after colliding with another player during a football game.  On examination, there is a loss of the normal rounded appearance of the shoulder.  You suspect the patient may have a shoulder dislocation.  He has no history of shoulder dislocations in the past.  Will you order an x-ray or perform a point-of-care ultrasound to confirm the diagnosis?

Background: Despite shoulder dislocations being a very common injury presenting to the ED, it has only been covered once on SGEM#121. This episode tried to answer whether it was better for the shoulder to be immobilized in an external or internal rotation post-reduction. We still don’t know if one position is superior to another.

Emergency physicians frequently perform pre- and post-reduction x-rays for patients with shoulder dislocations.  However, some prior studies suggest that the routine performance of these x-rays may not be necessary, especially in patients with recurrent dislocations who have not sustained any direct trauma [1-2].

Point-of-care ultrasound (POCUS) has previously been studied for the use of the diagnosis of shoulder dislocations with most prior data suggesting that POCUS is highly sensitive and specific for the diagnosis of shoulder dislocations [3-4].

As with other applications of POCUS, the use of ultrasound for shoulder dislocations has the potential to reduce the time to diagnosis, reduce radiation exposure, and lower cost.  However, prior studies about the use of POCUS for shoulder dislocations have used a variety of scanning techniques and some have utilized as few as 2 sonographers [4].  One study found only a 54% sensitivity for identifying persistent dislocation after a reduction attempt [5].

Clinical Question: What is the diagnostic accuracy of point-of-care ultrasound for the diagnosis of shoulder dislocations as compared with x-ray?

Reference: Secko et al. Musculoskeletal Ultrasonography to Diagnose Dislocated Shoulders: A Prospective Cohort. Ann Emerg Med Feb 2020

  • Population: Adult patients with suspected shoulder dislocations who presented to one of two EDs when a study investigator was present.
    • Exclusion: Patients with multiple traumatic injuries, decreased level of consciousness, or hemodynamic instability.
  • Intervention: Pre- and post-reduction POCUS utilizing a posterior approach in which they traced the scapular spine towards the glenohumeral joint. The POCUS technique they used is basically as follows — the sonographer palpates the spine of the scapula, and then places the ultrasound probe directly over the scapular spine. The study protocol allowed the sonographer to choose either a linear or curvilinear probe. The sonographer then follows the scapular spine laterally until the glenoid and humerus are identified. Using this technique, the glenoid and humeral head both look like hyperechoic semicircles. They should be very close to each other, and if not, that indicates a shoulder dislocation. After assessing for dislocation, the sonographer can assess for fracture by fanning the probe from a cephalic to caudal direction. A fracture appears as a disruption in the normal contour of the hyperechoic humerus. (shown below in Figure 1 from the manuscript).

Figure 1. A, Proper probe placement on the patient and the 3-step sequence to examine the shoulder from the posterior approach. The blue dot above the probe corresponds to the probe indicator. B, The corresponding ultrasonographic images to the probe placement in A at the level of the scapular spine (1), the glenohumeral joint (2), and the humerus (3).

  • Comparison: Pre- and post-reduction x-rays.
  • Outcomes:  
    • Primary Outcome: The diagnostic accuracy of POCUS for shoulder dislocations.
    • Secondary Outcomes: Presence or absence of fracture, time from triage to POCUS exam as compared to x-ray, time from POCUS exam initiation to diagnosis, determination of glenohumeral distance of non-dislocated and dislocated shoulders, and sonographer confidence in diagnosis (from 0-10).

Authors’ Conclusions: “A posterior approach point-of-care ultrasonographic study is a quick and accurate tool to diagnose dislocated shoulders. Ultrasonography was also able to accurately identify humeral fractures and significantly reduce the time to diagnosis from triage compared with standard radiography.”

Quality Checklist forObservational Study:

  1. Did the study address a clearly focused issue? Yes
  2. Did the authors use an appropriate method to answer their question? Yes
  3. Was the cohort recruited in an acceptable way? No
  4. Was the exposure accurately measured to minimize bias? N/A
  5. Was the outcome accurately measured to minimize bias? Yes/No
  6. Have the authors identified all-important confounding factors? Unsure
  7. Was the follow up of subjects complete enough? Yes
  8. How precise are the results? There were wide confidence intervals around the point estimate of sensitivity and specificity for dislocation identification and even wider for fracture identification.
  9. Do you believe the results? Yes
  10. Can the results be applied to the local population? Unsure
  11. Do the results of this study fit with other available evidence? Yes

Key Results: They enrolled 65 patients in the study. The median age was 40 years, 58% being male, 49% had a dislocation (29 anterior, 2 posterior and 1 inferior) and 32% had a history of dislocation.

POCUS had a 100% sensitivity, specificity, PPV and NPV for diagnosing shoulder dislocation.

  • Primary Outcome:
    • Sensitivity 100% (95% CI; 87-100)
    • Specificity 100% (95% CI; 87-100)
    • PPV 100% (95% CI; 87-100)
    • NPV 100% (95% CI; 87-100)
  • Secondary Outcomes:
  • 25/65 (38%) had fractures with 13 being Hill-Sachs/Bankart’s
  • Non-Hill-Sachs/Bankart’s Fracture:Sensitivity 92% (95% CI; 60-99.6), specificity 100% (95% CI; 92-100), PPV 100% (95% CI; 68-100) and NPV of 98% (95% CI; 89- 99.9).
  • POCUS was 43 minutes faster from exam to diagnosis compared to x-ray.
  • The median glenohumeral distance was –1.83 cm (IQR –1.98 to –1.41 cm) in anterior dislocations, 0.22 cm (IQR 0.10 to 0.35 cm) on non-dislocated shoulders, and 3.30 cm (IQR 2.59 to 4.00 cm) in posterior dislocations
  • Sonographers’ confidence in their POCUS diagnosis was 9.1 of 10 in non-dislocated cases and 9.4 of 10 in dislocated cases.

1) Accuracy of POCUS to Confirm Shoulder Dislocation: The data suggests that POCUS is highly sensitive and specific for the diagnosis of shoulder dislocation. However, this study utilized a convenience sample of patients that were all ultra sounded by one of six sonographers who were either ultrasound fellows or ultrasound fellowship-trained attendings.

That being said, there is some evidence that less-skilled sonographers can use this technique with high accuracy.  In fact, the authors cited a study by my friend Shadi Lahham from UC Irvine, in which novice sonographers had a 100% sensitivity and specificity using a posterior approach POCUS examination [6].  Overall, given the study at hand and the previous studies assessing POCUS for shoulder dislocations, we can say pretty confidently that POCUS, especially the posterior approach, has very high sensitivity and specificity for the diagnosis of shoulder dislocations.

The sonographers were very confident in their diagnoses (9.1/10). This was not surprising given the small group of skilled sonographers performed all the ultrasounds. It is unclear if POCUS would have the same diagnostic accuracy in the hands of a community emergency physician.

Additionally, while the study was technically “multicenter” in that two facilities were involved, one of the two sites enrolled only 5 patients.  Therefore, this was mostly a single center study. For these reasons, we question the external validity of the study, and I’m not sure that if the ultrasounds were performed by typical community emergency physicians that you would achieve such impressive results.

2) Accuracy of POCUS to Confirm Shoulder Reduction: In the study at hand, 27 of 32 subjects with dislocations had post-reduction POCUS exams performed to confirm adequate reduction.  Per the study protocol, all 32 were supposed to have had a post-reduction POCUS performed, but there were five cases where this did not happen. The manuscript says it was because the study sonographer was unavailable after the reduction for various reasons without further explanation. This could have introduced some bias and increases our skepticism of the results.

3) Accuracy of POCUS for Shoulder Fracture Diagnosis: Of the 65 patients, there were 25 (38%) with fractures.  POCUS identified only 52% of those fractures. However, all but one of the missed fractures was a Hill-Sach’s deformity or a Bankart lesion.  There were 12 non-Hill Sach’s/Bankart’s fractures in this study, and POCUS identified 11 of those 12. The one missed fracture was a surgical neck fracture.  Overall, POCUS was 92% sensitive (95% CI; 60% to 99.6%) and 100% specific (95% CI; 92% to 100%) for non–Hill-Sachs/Bankart’s fractures.

Hill-Sach’s and Bankart’s fractures are generally not relevant to the emergency management of patients with shoulder dislocations, so it’s probably okay to miss those fractures.

However, an 8% miss rate of non-Hill Sach’s/Bankart’s fractures is too high for American medicine.  Moreover, given the fact that the confidence interval on the sensitivity goes all the way down to 60% and that  the sonographers were all likely to be more skilled than average, an 8% miss rate may be lower than what would be expected if your standard community emergency docs started using POCUS for shoulder injuries.

4) Measuring the Glenohumeral Distance: The sonographers in this study calculated the “glenohumeral distance”. This isthe distance between the glenoid and the tip of the humeral head.  The median glenohumeral distance was –1.83 cm in anterior dislocations, 0.22 cm on nondislocated shoulders, and 3.30 cm in posterior dislocations. Negative numbers indicate the humeral head moved away from the ultrasound probe while positive numbers indicate the humeral head moved closer to the probe.

This is a bit difficult to understand without a picture, so we’ll put a figure in the blog to demonstrate what the authors were actually measuring. The authors found the optimal cutoff to distinguish an anterior dislocation from a nondislocated shoulder was -0.5 cm.

The point of measuring the glenohumeral distance is that when the shoulder is dislocated, the separation between the glenoid and humeral head should be pretty easy to see as the distance between the two is substantial:  usually about 2 cm for anterior dislocations and about 3 cm for posterior dislocations.

Figure 2:  The red arrows show the glenohumeral distance.

5) Time Saved with POCUS: The median time to POCUS from triage was 51 minutes (IQR: 36-77) as compared to 101 minutes (IQR: 73-134) for x-ray.  The amount of time saved in the real world (if any) is entirely dependent on the system in which the physician is working.

POCUS could save time in facilities that have long waits for x-rays.  However, in a facility with single-physician coverage, the x-ray tech may complete the x-ray before the physician has a chance to perform an ultrasound. Therefore, I don’t think we can say that POCUS would consistently result in a more rapid diagnosis in all facilities.

Comment on Authors’ Conclusion Compared to SGEM Conclusion: We generally agree with the authors’ conclusions.

SGEM Bottom Line: While POCUS has very good diagnostic accuracy, clinicians should keep using x-rays as their primary imaging study for patients with suspected shoulder dislocations.

Case Resolution: Given the direct trauma sustained by the patient in his football game and thus concern for possible fracture in addition to the concern for shoulder dislocation, an x-ray of the shoulder is performed.  The x-ray reveals a shoulder dislocation without an associated fracture. The shoulder is reduced, and reduction is confirmed with POCUS. The patient is discharged home with appropriate discharge instructions and follow-up advice.

Dr. Tony Zitek

Clinical Application: I don’t think ultrasound should take the place of x-ray at this time with regards to the evaluation of patients who have sustained a shoulder injury.  Primarily, this is because the accuracy of POCUS for the diagnosis of shoulder fractures has not been demonstrated yet.  There were only 12 non-Hill Sach’s/Bankart’s fractures in this study, so it’s hard to draw precise conclusions about POCUS for shoulder fractures. However, if there is really an 8% or more miss rate, POCUS should not be used for patients in whom shoulder fracture is on the differential diagnosis.  In their discussion, the authors argued that POCUS was accurate for the diagnosis of shoulder fractures, and as support for this statement they cited a prior meta-analysis that had reported that the sensitivity of POCUS for detecting fractures associated with shoulder dislocations was 97.9% [3]. However, when they mentioned that study, they neglected to report that that calculation was based on tiny numbers such that the 95% CI was 10.5 to 100%.

Remember, there is already evidence that you don’t need to get an x-ray to confirm the diagnosis of shoulder dislocation on every patient [1], especially those with prior dislocations and no direct shoulder trauma. The main reason to get an x-ray for many cases is, in fact, to make sure there is not a fracture as opposed to or along with the shoulder dislocation.  Therefore, in some cases of shoulder injury, no imaging (not even POCUS) is needed to accurately diagnose the shoulder dislocation.  In other cases, the x-ray is needed, not so much because you need to confirm the shoulder dislocation, but to exclude fractures. Pending further data to support the use of POCUS to accurately diagnose shoulder fractures, POCUS should not replace x-ray for shoulder injuries.

On the other hand, I like the idea the authors suggested of using POCUS to confirm the successful reduction of a shoulder dislocation.  Prior data has already found that, in some cases, it may not be necessary to perform any imaging after a shoulder reduction [2]. However, if you aren’t completely sure if you have reduced a dislocated shoulder and you don’t have any reason to believe that you caused a shoulder fracture with your reduction attempt (which is very rare), POCUS is likely sufficient to confirm the reduction as opposed to x-ray.  Additionally, if a patient was sedated for a shoulder reduction attempt, POCUS could be used to confirm the reduction while the patient is still sedated to avoid the messy situation of having to re-sedate the patient.

What Do I Tell the Patient? You have a shoulder injury.  Ultrasound is very accurate for the diagnosis of shoulder dislocations, but x-ray remains the first line imaging test to assess for both dislocation and fracture. I am concerned that you could have a fracture or a dislocation, so we are going to perform an x-ray.

Keener Kontest: Last weeks’ winner was Jonathan Godfrey a firefighter/Paramedic from Asheville, North Carolina. He provided five references for CXR and CT finding of #COVID19

  1. “peripheral ground-glass infiltrates and/or organizing pneumonia”on chest CT
    https://pubs.rsna.org/doi/10.1148/radiol.2020200988
  2. “The non-specific imaging findings are most commonly of atypical pneumonia, often with a bilateral, peripheral, and basal predominant distribution”
    https://radiopaedia.org/articles/covid-19-3?lang=us
  3. “Lung abnormalities during the early course of COVID-19 infection usually are peripheral focal or multifocal ground-glass opacities affecting both lungs in approximately 50%–75% of patient. As the disease progresses, crazy paving and consolidation become the dominant CT findings, peaking around 9–13 days followed by slow clearing at approximately 1 month and beyond.”
    https://pubs.rsna.org/doi/10.1148/radiol.2020200527
  4. “Unilateral Pneumonia, Bilateral Pneumonia, Ground-glass opacity” to chest x-ray https://www.sciencedirect.com/science/article/pii/S1477893920300910
  5. “Findings on chest imaging in COVID-19 have been similar to findings seen in previous years from the SARS-CoV and MERS-CoV outbreaks. A recent cohort analysis of 41 patients infected with COVID-19 found all but 1 with bilateral lung involvement.8 A study of computed tomography (CT) scans of 21 patients with COVID-19 infection showed 3 (21%) with normal CT scans; 12 (57%) with ground-glass opacity only; 6 (29%) with ground-glass opacity and consolidation at presentation; and interestingly, 3 (14%) with normal scans at diagnosis. Fifteen patients (71%) had 2 or more lobes involved, and 16 (76%) had bilateral disease.29 Of the 18 patients with positive findings on chest CT, all had the presence of ground glass opacities, with 12 of the 18 having concomitant lobar consolidations.29” https://www.iephysicians.com/wp-content/uploads/2020/03/EB-Medicine_COVID-19-Update.pdf

Listen to the SGEM podcast to hear this weeks’ question. Send your answer to TheSGEM@gmail.com with “keener” in the subject line. The first correct answer will receive a cool skeptical prize.

Remember to be skeptical of anything you learn, even if you heard it on the Skeptics’ Guide to Emergency Medicine.

References:

  1. Edmond M, Gariepy C, Boucher V, et al. Selective prereduction radiography in anterior shoulder dislocation: the Fresno-Quebec Rule. J Emerg Med 2018;55:218-225.
  2. Harvey RA, Trabulsy ME, Roe L. Are postreduction anteroposterior and scapular Y views useful in anterior shoulder dislocations? Am J Emerg Med 1992;10:149-151.
  3. Gottlieb M, Holladay D, Peksa GD. Point-of-care ultrasound for the diagnosis of shoulder dislocation: a systematic review and metaanalysis. Am J Emerg Med 2019;37:757-761.
  4. Abbasi S, Molaie H, Hafezimoghadam P, et al. Diagnostic accuracy of ultrasonographic examination in the management of shoulder dislocation in the emergency department. Ann Emerg Med 2013;62:170-175.
  5. 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.
  6. 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;17:377-382.