POC US for Shoulder Dislocation

April 27, 2021

By Bri Hartman MD

Reviewed by Jonathan Kaplan MD

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 Apr;37(4):757-761. doi: 10.1016/j.ajem.2019.02.024. Epub 2019 Feb 19. PMID: 30797607.

Introduction and background information

  • Shoulder dislocations are a very common injury in the Emergency Department, affecting approximately 2% of the population and leading to 200,000 visits annually
  • X-rays are traditionally obtained for the diagnosis of shoulder dislocations, and then obtained for confirmation of reduction of the dislocation
  • X-rays are an imperfect imaging modality in that they require a radiation dose, may take a significant amount of time to obtain depending on the resources available in a department, and posterior dislocations are difficult to evaluate radiographically and are often missed
  • POCUS is a readily available imaging modality that can be performed at bedside without the need for radiation

What was the primary objective of this study?

  • The primary objective of this study was to determine the diagnostic accuracy of POCUS for identifying shoulder dislocation and reduction when compared to the gold standard of x-rays
  • The secondary objective was to evaluate the diagnostic accuracy of POCUS for identifying fractures associated with dislocations

Methods and study design

  • The study was a systematic review using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses – Diagnostic Test Accuracy (PRISMA-DTA) – Identified 900 articles through database searching, narrowed to 475 – articles included all prospective or randomized control trials assessing the accuracy of POCUS for shoulder dislocations with no language, date, or age restrictions
  • All studies had confirmatory imaging such as X-ray or CT performed. Cadaver reports, case reports, and retrospective studies were excluded
  • Data from each study was extracted that included: study location (ED/ICU), study inclusion criteria, study exclusion criteria, mean age of study patients, percentage of shoulder dislocations, percentage of dislocation types (anterior, posterior, inferior), ultrasound transducer, ultrasound technique, sonographer trainer, operator specialty, operator experience (attending/non-attending), and true positives, false positives, true negatives, and false negative for both identifying dislocations and identifying fractures
  • The quality of each study was then assessed using the QUADAS-2 tool
  • Data analysis was performed by calculating sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio using a bivariate random effects model and then all data were calculated with a 95% confidence interval
  • Heterogeneity was assessed using chi-square and I-square statistics with a p-value <0.1 or an I-square >50% considered significant for heterogeneity
  • I² statistic describes the percentage of variation across studies that is due to heterogeneity rather than chance, it does not inherently depend upon the number of studies considered
  • Receiver-operating characteristic curves were then constructed with observed study data and a 95% CI confidence region and a linear regression test of funnel plot asymmetry with a p-value of <0.1 for the slope coefficient was considered significant for asymmetry

Results

  • 7 studies were selected for the final data analysis after the 900-> 475 original studies were analyzed and excluded for various reasons
  • Of the seven studies selected, 739 “assessments” (does not mention if these are 739 patients or simply 739 ultrasounds) were performed – these studies were prospective, observational trials that took place in Iran, the US, or Turkey. 6/7 took place in the ED, the majority were performed by Emergency Medicine providers (resident, attending, or student), and five studies used a linear transducer, one study used a curvilinear probe, and the other allowed use of either linear or curvilinear
  • Mean age was 35.1 years with 82.3% of patients being male. Overall dislocation rate was 41.4%, and only 2 posterior dislocations were seen and no inferior dislocations
  • POCUS overall had a 99.1% sensitivity and a 99.9% specificity for the diagnosis of shoulder dislocation with a positive likelihood ratio of 796.2 and negative likelihood ratio of 0.01
  • There are many techniques with which to performed ultrasound of the shoulder – the anterior + lateral and the posterior technique were seen in the studies evaluated
  • Posterior technique was seen to have a 99.0% sensitivity and 99.7% specificity for the diagnosis of shoulder dislocation with a LR+ of 338.7 and LR- of 0.01
  • Anterior + lateral technique showed a sensitivity of 92.9% and specificity of 100% for shoulder dislocation with LR+ of 308.5 and LR- of 0.08
  • Secondary outcome measure assessment of the presence of associated fracture showed a 97.9% sensitivity and a 99.8% specificity with a LR+ of 399.2 and LR- of 0.02 with I-square of 80%
  • Six studies were at unclear risk of bias for patient selection due to use of a convenience sample and three studies were at unclear risk of bias for the reference standard due to inadequate description of the blinding technique. One study did have some questions regarding applicability of study given that the study excluded patients with BMI >35 and excluded posterior shoulder dislocations entirely

Discussion

  • POCUS is highly sensitive and specific for identifying shoulder dislocations and reductions
  • Could potentially reduce delays in treatment time – one study found that pre-reduction radiographs delayed time to treatment by 30 minutes
  • POCUS may decrease overall healthcare costs by reducing total number of radiographs performed
  • POCUS was also sensitive and specific for identifying associated fractures, but CI was wide and further studies are needed to better determine the diagnostic accuracy and clinical utility of POCUS for this modality
  • This review expanded the search to included more studies and also performed a meta-analysis while previous reviews on similar topics failed to perform meta-analysis of the data
  • Operator variability may be the biggest limitation to the utility of this tool – training protocol shoulder be developed to determine how best to image the shoulder

Were there limitations?

  • No randomized control trials were identified or evaluated in this review
  • Providers are not blinded to the physical exam findings which may have influenced their decision on patient inclusion in each study
  • Very limited data available for posterior dislocations given only 2 were seen in this study set
  • There was significant statistical heterogeneity which may have been due to variations in the training and experiences level of the sonographers

Take-home points

  • Of 739 assessments performed with various sonographic techniques utilized, POCUS overall had a 99.1% sensitivity and a 99.9% specificity for the diagnosis of shoulder dislocation
  • Posterior technique was seen to have a 99.0% sensitivity and 99.7% specificity for the diagnosis of shoulder dislocation
  • Anterior + lateral technique showed a sensitivity of 92.9% and specificity of 100% for shoulder dislocation
  • Ultrasound of associated fracture showed a 97.9% sensitivity and a 99.8% specificity
  • Need additional studies to evaluate ultrasonography for identification of posterior shoulder dislocations

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