Written by Chris Thom
Spoon Feed
This multi-center study demonstrated high accuracy of POCUS for the identification of elbow fractures.
Elbow joints prefer the sound waves
This study enrolled 215 patients across 4 hospitals who presented with a suspected elbow fracture. The ED physicians who performed the POCUS exam had < 15 minutes in elbow ultrasound training. POCUS exams were performed prior to diagnostic x-ray and were considered positive for fracture when there was elevation of the posterior fat pad. Radiologist interpretation of the x-ray served as the gold standard and was considered positive if a fracture was seen or if a posterior fat pad was called on the x-ray. 143 out of 215 patients had a fracture identified on x-ray (67%), with 28 of these having only a positive fat pad sign on x-ray. POCUS sensitivity was 91% (95%CI 85-95) and specificity was 93% (95%CI 85-98). 13 patients had false negative POCUS exams, with 7 of those being treated conservatively and 6 having surgical repair. The authors note that 5 of 6 of these patients had readily detectable olecranon fractures on physical exam. Using POCUS first on these patients would have enabled a 34% reduction in x-ray utilization.
How will this change my practice?
The literature surrounding POCUS for fracture identification continues to grow. POCUS can readily pick up a joint effusion, which creates the elevated posterior fat pad as in the current study. We can use this in two ways: to detect fractures and avoid unnecessary x-ray, or to detect fractures that otherwise might be missed by x-ray. While the sensitivity was not perfect in the current study, it was high enough that one could likely employ the test in lower pretest probability cases to avoid x-ray utilization. Plain film is by no means perfect for elbow injuries, and POCUS may actually have the edge in detecting certain fracture types. If the x-ray is negative, but POCUS shows a large hemarthrosis with elevated fat pad, that likely indicates a radiographically occult fracture.
POCUS pro-tips and clips:
Identification of an elbow effusion and an elevated posterior fat pad is very easy to do with minimal training. Simply place the high frequency linear probe on the posterior surface of the distal humerus overlying the olecranon fossa. The bone will appear as a bright, echogenic “canyon”. If a joint effusion is present, this will appear as an anechoic or hypoechoic area directly adjacent to the bone, with a resultant “elevation” of the posterior fat pad. Hemarthrosis can be a bit more echogenic than simple joint fluid. This trick can be used for atraumatic cases, as inflammatory joint conditions causing effusion can also be seen in this view. It can also be used to easily facilitate ultrasound-guided arthrocentesis.
Source
Diagnostic accuracy of point-of-care ultrasound of the posterior fatpad in elbow fractures. Emerg Med J. 2025 Jan 22:emermed-2024-214448. doi: 10.1136/emermed-2024-214448. Epub ahead of print. PMID: 39848669
