Shoulder Dislocation Revisited - A Better Way to Diagnose?

By Michael Prats

Shoulder Dislocation Graphic

Musculoskeletal Ultrasonography to Diagnose Dislocated Shoulders: A Prospective Cohort

Annals of Emerg Med Feb 2020 - Pubmed Link


Take Home Points

1. A novel technique of posterior shoulder ultrasound showed perfect accuracy for diagnosing shoulder dislocation and reduction.

2. POCUS was 92% sensitive for non-Hills-Saks/Bankart fractures and less sensitive for Hills-Saks/Bankart fractures.

3. Although potential time savings with POCUS, unclear if clinically meaningful time difference based on this study.


Background

Ultrasound can be used to diagnose shoulder dislocations (as well as associated fractures!). In fact, these authors list about 10 publications including systematic reviews that show this has been done. We tackled this topic a few years ago, but it’s clear that its going to take a lot of evidence to shift people from the standard xray. In addition, there are multiple ways to perform this ultrasound and none seem perfect. In the current study, the authors introduce a novel scanning method and hope to provide more evidence of the diagnostic accuracy of point-of-care ultrasound for the diagnosis of shoulder dislocation. In addition, they evaluate more patient centered outcomes like time to diagnosis! Perhaps this study will be one step towards making this safe to adopt clinically.

Check out more on the prior evidence of POCUS for Shoulder Dislocation in the Evidence Atlas!


Questions

What is the sensitivity and specificity of point-of-care ultrasonography for the diagnosis of shoulder dislocation?

What is the optimal glenohumeral distance for discriminating dislocation from normal?

What is the accuracy for the presence or absence of a fracture?

What is the difference in time to diagnosis between POCUS and xray?


Population

Prospective, multi-center, observational study

Two academic EDs


Inclusion:

  • Adults with suspected shoulder dislocation WHEN investigator was present


Exclusion:

  • Multiple traumatic injuries

  • Decreased level of consciousness

  • Hemodynamically unstable

  • Did not consent


Design

After history and physical, blinded sonographer performed the prereduction scan (could be either before or after xray, but they could not see imaging)

If dislocated based on xray, treating physician reduced using any technique.

After reduction, sonographer repeated ultrasound (postreduction).

Postreduction xrays also obtained.


After each ultrasound, sonographer recorded:

  • Presence or absence of dislocation

  • Presence of a fracture

  • Time to perform ultrasound (assessed by independent observer, time from skin contact to diagnosis)

  • Sonographer confidence

  • Time at which exam was performed

  • Measured distance from glenoid rim to humerus


Primary Outcome: Sensitivity and Specificity of POCUS compared to radiography for diagnosis of shoulder dislocation


Secondary Outcomes:

  • Time required for POCUS image acquisition

  • Optimal glenohumeral distance for discriminating normal from dislocated

  • Accuracy for fracture

  • Sonographer confidence in diagnosis (verbal numeric scale 0-10)

  • Time to diagnosis: POCUS vs Xray


Power calculation assumed sensitivity of 95% → needed sample size 61


Who did the ultrasounds?

Ultrasound fellows or Fellowship-trained Emergency Physicians

Before enrollment, all providers underwent training on technique with short instructional video + practice on actual patients


The Scan

Curvilinear transducer

Curvi

Could use linear or curvilinear in their protocol (ultimately used curvilinear in 81% of cases)

This is the novel way to scan for shoulder dislocation described in this paper:

  1. Place the transducer over the spine of the scapula in transverse plane

  2. Slide laterally to find scapular notch (seems to be great scapular notch- aka spinoglenoid notch, not the suprascapular notch), then glenoid fossa and humeral head

  3. Look for dislocation → Increased glenohumeral distance

  4. Fan and look for fracture → Disruption in normal bone cortex

  5. If dislocation or fracture found, glenohumeral distance measured (really measures just the anterior-posterior distance)


Handy videos from the supplemental file:

Placement of Probe

Positioning of Patient

Probe Indicator Direction


Learn how to do Ultrasound for Shoulder Dislocation from 5 Minute Sono!

5minsono


Check out Shoulder Pathology on the POCUS Atlas!

thePOCUSAtlas


Results

N = 65

  • Median age 40 years

  • 58% male

  • 32% had hx of shoulder dislocation

  • 49% had shoulder dislocation

  • 29/32 (90.6%) dislocations were anterior

  • 38% had fractures on xray


Primary Outcome - Accuracy of POCUS Compared to Xray

Sensitivity: 100% (CI 87-100)

Specificity: 100% (CI 87-100)


Secondary Outcomes

Median Glenohumeral distance

Nondislocated: 0.22 cm (IQR 0.10 to 0.35)

Anterior: -1.83 cm (IQR -1.98 to -1.41)

Posterior: 3.30 cm (IQR 2.59-4 cm)

AUROC for GH distance for determining dislocation = 0.98 (CI .96-1)


Optimal Cutoff for GH distance for Anterior Dislocation = -0.46 cm

Unable to calculate posterior due to small sample size


Fractures

Ultrasound identified 52% (13/25) of fractures

Of the false negatives - 10 were Hill-Sachs, 1 was Bankart, 1 was surgical neck fracture

Non-Hill-Sachs/Bankart Fractures:

Sensitivity 92% (CI 60-99.6)

Specificity 100% (CI 92-100)


Median Time to Diagnosis

POCUS: 51 minutes (IQR 35-78 minutes)

Xray: 101 minutes (IQR 73-134 minutes)


Other Findings

All postreduction POCUS (performed in 27 of the 32 with dislocation) agreed with xray


POCUS Median Time to Performance: 43 minutes (IQR 23-60 minutes)

POCUS itself took 19 seconds (IRQ 10-36 seconds)


Sonographers’ confidence was 9.1/10 in nondislocated and 9.4/10 in dislocated


Interrater reliability

  • Kappa was 0.97 for dislocation

  • Kappa was 1 for non-Hill-Sachs/Bankart’s fractures


Strengths

Prospective, multicenter

Met power analysis for enrollment

Evaluated some patient centered outcomes (time to diagnosis)

Introduces a fast novel technique that makes sense, includes fracture identification

Quantified the abnormality unlike prior studies (glenohumeral distance cuff off)

Appropriate and complete statistics including Kappa, AUROC

Established the primary aim - that the diagnostic accuracy of US for shoulder dislocation is consistent with radiography. All 65 pts correctly diagnosed as dislocated or non dislocated compared with xray. Similar to other studies & this is the only finding that is conclusive (primary aim)


Limitations

Convenience population (only when investigators present). This ends up being an average of 3 patients/month, seems low especially for multicenter study. Although...60/65 patients were recruited at second institution - is it really a multicenter study?

Highly trained sonologists

Questionable blinding. Sonographer could be influenced by patient presentation - lack of joint motion, level of pain, clinical appearance of shoulder and what the patient says.

Not enough patients with posterior dislocations to draw conclusions.

Time savings - this was likely based on a radiologist’s read. Therefore this is not really a fair fight. We have encountered this problem many times when comparing the speed of ultrasound to other imaging modalities. Perhaps the most realistic comparison would be the time it takes for the emergency physician to interpret the xray compared to the time it takes the emergency physician to interpret the ultrasound. Likely these are similar times in most cases. The time savings in POCUS is that you can perform it immediately upon assessing the patient which most of the time could be before xray is performed. These authors do not faster to POCUS compared to time to xray, but they don’t seem to list specific times to compare.

Regarding fractures - first remember that this was a secondary outcome and this was not powered for this. The authors recognize that this study did not perform that well for all fractures - this could be a problem if you care about missing Hill-Saks or Bankart’s lesions. It was unclear whether or not it was decided a priori if the fractures would be separated into Hill-Sachs/Bankart and other fractures or if that was decided after the results.


Discussion

What to do now? Is it safe to skip the xray and just do an ultrasound? At this point, it seems that you could be justified in doing so; however, your practice will likely be influenced by current practice in your environment. This isn’t the first study to show that ultrasound is highly accurate. Given that the diagnosis is often clinically obvious, it would make sense that in a patient in which you have a high pre-test probability, you confirm your suspicion on ultrasound, that you could consider reducing it without initial xray. One in 12 fractures were missed in this study - that’s still quite a lot. You would have to accept that you might miss a fracture, although unlikely to be one of clinical significance. But what will happen when they follow up with orthopedics? “Where’s the xray?!” they might exclaim. It is best to make sure that your consultants are on board with this plan if you are going down this road.


Take Home Points

1. A novel technique of posterior shoulder ultrasound showed perfect accuracy for diagnosing shoulder dislocation and reduction.

2. POCUS was 92% sensitive for non-Hills-Saks/Bankart fractures and less sensitive for Hills-Saks/Bankart fractures.

3. Although potential time savings with POCUS, unclear if clinically meaningful time difference based on this study.


More Great FOAMed on this Topic

The Skeptics Guide to Emergency Medicine on this article

More Shoulder Ultrasound on The Ultrasound Podcast


Our score

4 Probes


Expert Reviewer for this Post

McDermott

Dr Cian McDermott FRCEM FACEM CCPU @cianmcdermott

Emergency Physician, Mater Misericordiae University Hospital, Dublin, Ireland


Reviewer's Comments

How I treat suspected shoulder dislocations (before COIVID19!)

  • Take history, focused exam and scan the shoulder roughly in that order

  • If US positive for dislocation then I aspirate for a potential hematoma and /or inject intra-articular local anaesthetic (US-guided)

  • Pre reduction, I often but not always send for a plain film to evaluate for fracture (non Hill-Sachs/ non Bankart lesion). Things that influence me on this are *proximal humeral bruising, *elderly patient, *non-typical external appearance of shoulder, *uncertainty on US especially when compared with other side. These are the difficult grey zone cases. I have not been looking for fractures by fanning up and down at the scapular notch but I will consider adding this to POCUS protocol - it makes lots of sense to me to do this

  • Sedate or use interscalene block to facilitate reduction

  • Repeat POCUS to confirm reduction when pain free or sedated

  • If X-ray not ordered pre-reduction, then I usually order it afterwards for the other downstream providers that expect it


My current scan protocol

  • Scan from behind patient with curvilinear probe lateral to spine of scapula at position 2 or 3

  • Look for negative or positive displacement from transducer surface and compare with unaffected side

  • Aspirate/ inject/ ISB as above then post reduction check w US


Suggested workflow on the basis of this paper

  • Use POCUS to determine if shoulder is dislocated or non-dislocated or if there is a significant fracture in a ‘typical’ patient (male, younger than 40 years, previous dislocation). Caution with elderly patients - you may consider pre-reduction XR if suspicious for fx

  • Consider US-guided aspiration or intra-articular injection. Attempt the reduction, confirm clinically and/or using POCUS. If successful, consider xray before clinic visit to look for Hills-Sachs or Bankart lesion. (This may not need to be done in ED)

  • If unsuccessful reduction, consider xray to look for non Hill-Sachs or Bankart fracture or subluxation that may have been missed by US (1 in 12)

  • Overall this paper gives me more confidence to attempt reduction w/out xray since it suggests a guide to GH distance that I should expect and also describes a technique for fracture evaluation. Practice changing paper which is always positive!!!


Cite this post as

Michael Prats. Shoulder Dislocation Revisited - A Better Way to Diagnose?. Ultrasound G.E.L. Podcast Blog. Published on August 03, 2020. Accessed on October 01, 2020. Available at https://www.ultrasoundgel.org/96.
Published on 08/03/20 05:00 AM
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