The John Thomas sign

The John Thomas (JT) sign is also known as Throckmorton sign. The sign can only be found in men – a patient has a positive JT sign if his penis points towards the side of pathology on a radiograph of the pelvis.

The sign tends to be commented on by middle-aged male radiologists and orthopedists suffering from Peter Pan syndrome. Some may even suspect an occult fracture purely based on the observed radiographic penile orientation. While this can clearly be very amusing (in the same way that some people can’t help but laugh when they hear the word “Uranus”) the question remains – is the sign actually of any use?

Throckmorton sign John Thomas sign
Throckmorton sign: Penis Points to Pathology

A few studies have tried to answer this question.

The first was published by a few of my countrymen in the Medical Journal of Australia back in 1998. They found that the the sensitivity (70%; 95%CI 62-78%) and specificity (67%; 95%CI 60-75%) for the JT sign were low. A more recent study from the UK found that JT sign had sensitivity of 30.0% (95% CI 21.2-40.0%) and specificity of 86.0% (95%CI 77.6 – 92.1%). Clearly there are significant disparities in the findings of these studies, and a larger study is urgently needed. A future study must control for confounders such as patient handedness, whether boxers or briefs are worn, and which way things usually like to hang.

At this stage, although JT sign compares reasonably well with Homans‘ sign (a useless test some misguided souls might still use to diagnose deep vein thrombosis), I think the astute emergency physicians among us will wisely elect to actually look for pathology on the radiograph rather than rely solely on the JT sign.

Conclusion: more studies needed.


References


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the names behind the name

Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also the Innovation Lead for the Australian Centre for Health Innovation at Alfred Health and Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.

After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.

He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE.  He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.

His one great achievement is being the father of two amazing children.

On Twitter, he is @precordialthump.

| INTENSIVE | RAGE | Resuscitology | SMACC

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