Ultrasound G.E.L. – Ultrasound for Nail Bed Injury

Originally published on Ultrasound G.E.L. on 1/16/16 – Visit HERE to listen to accompanying PODCAST! Reposted with permission.

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The value of point-of-care ultrasound for detecting nail bed injury in [the] ED

American Journal of Emergency Medicine September 2016 – Pubmed Link

Take Home Points

1. Point of care ultrasound is accurate for nail bed injuries although some can be missed (sensitivity 93.9%)

2. Point of care ultrasound is very accurate for distal phalanx fracture.

3. Depending on your current practice pattern, finding these injuries on ultrasound may not change management.

Background

Nail bed injuries are common. The nail itself often times precludes comprehensive exam of the injured structures. Some have proposed lifting the nail to diagnose any underlying injury, but this can be uncomfortable to the patient and cause problems with healing. The idea here is to see if point of care ultrasound (POCUS) can be used to visualize injuries to the nail bed and to the underlying bone.

Questions

What is the diagnostic accuracy of POCUS for nail bed injury compared to direct visualization?

What is the diagnostic accuracy of POCUS for distal phalanx fractures compared to xray?

Population

Large tertiary care hospital, 200,000 annual census

ED patients, convenience sample enrolled when study physicians were working

Inclusion Criteria

• 18-65 yo
• blunt distal finger trauma
• subungal hematoma
• at least one of the following:

a) hematoma >50% nail bed

b) fracture of distal phalanx

c) disruption of periungal tissue or nail integrity

Excluded if did not consent

Who did the scans?

5 US certified attending physicians (one of whom taught the others)

1 hour theoretical lecture + 2 hour practical lecture on anatomy and injuries

Design

Prospective, cross-sectional pilot study over 7 months (11/13-5/14)

“Injury” defined as laceration or contusion of nail bed

Treating physicians blinded to POCUS

Intervention

1. Everyone first got an xray
2. Everyone got a point of care ultrasound (POCUS) of their finger tip
3. Each had nail bed inspection by lifting the nail

Scan

High frequency, linear transducer

Palmar and dorsal sides of distal phalanx with longitudinal and perpendicular planes

Fracture = disruption in cortical integrity

Injury = disruption of nail bed integrity

If couldn’t get good quality, used step off pad of 100 ml NS bag over nail

Video of how to do ultrasound of the finger using a water bath

Results

N = 45

Population was mean age 32, 77% male

66.7% were crush injuries, but others were “falling object” and “direct impact” which sounds like also crush injuries

Injuries:

-73.3% nail bed injury

-46.7% destruction of periungal tissue

-29% fracture on xray

-6.7% destruction of nail integrity

Primary Outcomes

Test characteristics of POCUS in Distal Finger Tip Trauma

For nail bed injury:

93.9% sens (CI 80-99), -LR – 0.06

100% spec (CI 74-100), +LR unable to calculate

For fracture:

100% sens (CI 79-100), -LR unable to calculate

98.4%* spec (CI 91-100), +LR 59

*US diagnosed 1 fracture that was not seen on xray, otherwise would be 100% specific – it may have just picked up a fracture that xray missed.

So lower sensitivity for nail bed injury but very specific. Good for inclusion or exclusion of fracture.

Confidence intervals are wider than you would like because of small population size.

Authors conclusions: you can use US instead of lifting up everyone’s nails and getting xrays for distal fingertip trauma.

Limitations

Small sample size (n=45)

Convenience population

Trained providers

Appears POCUS performers were not blinded to xray – could have biased the results (potentially inflating test characteristics for fracture).

Excluded other nail bed injuries not meeting initial criteria (another 30 patients in this case).

Wish they would have included times that it changed management – more patient centered outcome. Unclear if all the injuries diagnosed required repair or intervention.

Take Home Points

1. Point of care ultrasound is accurate for nail bed injuries although some can be missed (sensitivity 93.9%)

2. Point of care ultrasound is very accurate for distal phalanx fracture.

3. Depending on your current practice pattern, finding these injuries on ultrasound may not change management.

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