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The 'John Thomas' sign and pelvic fractures-Fact or humorous myth?: A systematic review and meta-analysis
Louis Gerber1, Abdullah E Laher1, Callistus O A Enyuma1,2
1Department of Emergency Medicine, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, South Africa.
Objectives:
An incidental and sometimes humorous finding on an Antero-Posterior (AP) pelvis X-ray view is that of the John Thomas Sign (JTS), which is defined as positive, when the penile shadow points towards the side of a hip or pelvic fracture in male patients. Despite previous research reports and studies performed on the JTS sign, uncertainty with regards to its clinical relevance still remains. The objective of this review was to assess the clinical validity and accuracy of this sign by performing a systematic review and meta-analysis.
Methods:
In accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search was performed (May 2017), using the following databases: BMJ best practice, Cochrane Database of Systematic Reviews, EMBASE, PubMed and Scopus. Studies comparing the predictability of the JTS were critically appraised. The summary effect (and 95% CI) was estimated using a random effect model and the Restricted Maximum Likelihood Method. The pooled sensitivity as well as the summary effect log odds ratio was determined. Selected studies were further ranked for quality and relevance using the Critical Appraisal Skills Program (CASP) (Oxford 2013) tool.
Results:
In total, nine articles were isolated and assessed. A total of 1942 participants were included. The mean sample size amongst these included studies was 243 participants with a median of 198 participants. Since the necessary data needed for the Meta-analysis was only present in the 6/9 studies assessed, these 6 were analyzed further. The JTS was positive in 1089 out of 1439 patients with a pooled sensitivity of 75.7% (95%CI, 73.4%-77.9%). There was a large variation in the sensitivity and specificity amongst studies, accounting for a non-significant summary Odds Ratio effect of -0.03.
Conclusions:
Based on this review, there is insufficient statistical evidence to support the reliability of the JTS to predict the laterality in the case of a hip fracture on the standard AP pelvis x-ray.