Averyl Shindruk, MD & Michael Schick, DO
Emergency Medicine Residency, University of California Davis Medical Center
A previously healthy 6-year-old girl presents with a chief complaint of right arm pain after a witnessed fall while running. She denies other injuries.
Physical exam
| Blood pressure | Pulse | Respiratory Rate | Pulse Oximetry | Temperature |
|---|---|---|---|---|
| 110/80 | 122 | 24 | 99% both hands | 36.9 |
General:
Well-appearing female, appropriately tearful.
Extremity:
Right distal upper arm with edema and tenderness to palpation. No TTP of right humeral head, right distal radius or ulna, carpals. Radial pulses strong and equal bilaterally.
Neurologic:
Sensation to light touch intact in median, ulnar, and radial nerve distributions. Motor function intact in median, radial, and ulnar distributions: Able to make 'A-OK' sign, extends wrist, MCP, thumb IP joints, with full PIP and DIP extension of all digits.
Skin:
No ecchymosis or dimpling in right antecubital fossa. Right hand warm and pink. Capillary refill < 2 seconds.
Clinical Differential Diagnosis
Ultrasound Imaging Findings
Non-injured distal arm for comparison. Ultrasound image of normal long axis of the distal arm with intact cortex (red arrow), adjacent overlying tendon (yellow arrow) without separation by fluid, fat pad (blue arrow) is flat and does not bulge above humeral line.
Non-injured distal arm imaged in long axis. Ultrasound video shows normal distal arm with intact cortex, adjacent overlying tendon without separation by fluid, fat pad is flat and does not bulge above humeral line.
Ultrasound image of the right elbow: Disruption of hyperechoic line representing supracondylar cortex (red arrow). Mixed hypoechoic and hyperechoic fluid superficial to cortex representing lipohemarthrosis (yellow arrow). Bulging posterior fat pad beyond humeral line (blue arrow).
Transverse view of the right posterior distal arm annotated demonstrating a lipohemarthrosis in a grade 1 supracondylar fracture.
Transverse view of the right posterior distal arm annotated demonstrating a lipohemarthrosis in a grade 1 supracondylar fracture.
Long axis view of the right posterior distal arm annotated demonstrating a lipohemarthrosis in a grade 1 supracondylar fracture.
Long axis view of the right posterior distal arm annotated demonstrating a lipohemarthrosis in a grade 1 supracondylar fracture.
Differential Diagnosis Based on Imaging
Occult supracondylar fracture with lipohemarthrosis.
Clinical Course and/or Management
The patient was splinted in the Emergency Department with a long-arm splint at 40 degrees of elbow flexion and scheduled for one week follow up with pediatric orthopedic surgery. Repeat radiographs showed a non-displaced supracondylar fracture, Gartland type 1. The patient remained in a long-arm cast for three weeks and recovered with full range of motion of the elbow at five weeks.
Diagnosis
Occult supracondylar fracture with lipohemarthrosis
Discussion
Supracondylar humerus fractures are one of the most common traumatic fractures and the most common type of elbow fracture in pediatric patients, seen most often in children ages 5-7 after a fall on an outstretched arm. Extension-type injuries occur in 95-98% of cases. The workup of suspected supracondylar fractures currently depends on radiographs. If there is no obvious fracture, an occult fracture can be diagnosed based on secondary radiographic signs including a posterior fat pad sign or 'sail sign,' (which can have low specificity), displacement of the anterior humeral line (which can be challenging in patients <5 years old), or alteration of Baumann's angle.
Occult supracondylar fractures (those with initially normal radiographs that are diagnosed at follow up) make up 2-18% of all pediatric fractures. When radiographic findings are nonspecific, but the index of suspicion for fracture remains high, standard practice is to apply a long-arm splint and arrange follow up. This can lead to unnecessary cost and discomfort when follow-up reveals no fracture. MRI is an expensive and time-consuming alternative for more detailed fracture evaluation and is impractical with young children who require sedation for the study.
Recent literature suggests point-of-care ultrasound may aid in clinical diagnosis of supracondylar fractures. A high-resolution linear probe with frequencies ranging from 6-13 MHz should be used. With the elbow held at 90 degrees, the examiner should scan along the distal posterior humerus in longitudinal and transverse axes looking for cortex disruption, a bulging posterior fat pad (elevated above the humeral line) and lipohemarthrosis (a collection of hypoechoic blood with hyperechoic fat floating on top). With this technique, ultrasound has been shown to have a sensitivity of between 88 and 100%, a specificity of between 70 and 100%, a positive predictive value of between 95 and 100%, and a negative predictive value of between 86 and 100% in the diagnosis of occult supracondylar fractures. Point of care ultrasound is thus an effective, low-cost and time-saving tool when evaluating supracondylar fractures.
References