Have you ever wondered if ultrasound could help you diagnose a distal forearm fracture? Well I’m here to answer that for you today! The short answer is “yes, it absolutely can”!

Now, I can hear your voices right now: where is the evidence? Well, come on down!

Evidence – Study #1

In pediatric forearm fractures, Douma-den Hamer performed a meta analysis demonstrating a sensitivity of 97% , specificity 95% , positive likelihood ratio (LR) 20.0 and negative LR 0.03. With the 6-view method showing higher specificity and positive LR compared to the 4-view method.

A 6-view method which you can perform with copious gel or in a water bath in the attached image.

Limitations:

• Although ultrasonographers were blinded for the x-ray results, they were obviously aware of clinical exams and history.

• There is a need for universal definition of a threshold value for fracture as obtained by ultrasound. Up till now some studies used only cortical disruption (e.g. steps, brakes, gap, interruptions), while others also included (subperiostal) hematomas and soft tissue changes. These different definitions in threshold likely affects the results for fracture detection in Salter Harris 1 fractures in children and other subtle fractures.

• In general there should be an uniform technique for visualization and fracture definition in ultrasound for distal forearm fractures.

• The measured difference in sensitivity and specificity in this study between ulna and radius is partly explained by the fact that accompanying ulna fractures (especially near the joint) were missed, and the prevalence of ulna fractures, accompanied or isolated are lower than radial fractures.

• Conventional x-ray was used as reference standard comparator, which is not the golden standard to detect fractures. Occult fractures occur in convention x-ray in about 2–36% due to overlapping structures, under-mineralized ossification centres and non-perpendicular x-ray beam to the fracture line. Because the included studies compared ultrasound to conventional x-ray, true fractures seen on ultrasound, but missed by conventional x-ray were labelled as false positive. Actual sensitivity could even increase further if these fractures were labelled rightly or a more sensitive imaging modality was used.

• Finally the majority of the studies were in the pediatric population but this may be a strength as an open physis could be a false positive

Evidence – Study #2

Most recently, a systematic review of blinded studies investigating its effectiveness in the identification of upper and lower limb fractures has been performed. In this study, Champagne et al demonstrated highest diagnostic accuracy in fractures of the foot and ankle. The pooled sensitivity and specificity of US was 93% and 92% for upper limb fractures , and 83% and 93% for lower limb fractures.

Limitations:

1. Trials which used ultrasonography to image multiple anatomical sites or which recruited smaller participant populations reported lower diagnostic accuracies. The former is a finding that has been previously reported in the literature and suggests that focussed sonographer training on specific anatomical regions may result in greater accuracy due to the learning curve associated with imaging different bones.

2. Several of the included studies had small sample sizes. The influence of sample size on diagnostic accuracy highlights the imprecision of small studies and supports the authors’ recommendations that future research be conducted in larger groups with a more focussed anatomical region of interest.

3. Ultrasonography is a user-dependent imaging modality, and few studies measured the effect of sonographer experience and training on the reliability of their imaging. Intra- and interrater reliability were infrequently reported, with only three of the 26 included studies noting values for these

Where can I learn more?

Now that you see the evidence is pretty good, here is a video on how to perform it.

Here are some hot takes from a pretty good blog on the US technique and highlights the fact that you can also perform a sweet hematoma block while you’re looking at it under the sonographic microscope.

References: