The Case
A very “acrobatic” 13 year old male was jumping on a trampoline at his buddy’s house. In an attempt to do a flip he landed on his back, then bounced off of the trampoline landing awkwardly on his left arm. His friend screamed an expletive because the patient’s upper arm was swollen. After getting their stories straight, and alerting a grown-up, the friend’s mom called an ambulance.
The initial exam revealed a swollen upper arm with swelling. His strength in the hand appeared to be normal – including grip, extension, opposition of thumb to little finger, and thumb abduction. Wrist flexion and extension were normal, as were his radial and ulnar pulses. Sensation in the branches of the radial, median and ulnar nerves was normal. After providing analgesia you order an X-Ray.
A broken arm and nothing more…
The Diagnosis
The radiographs don’t lie. Mr. Tramampoline has a midshaft fracture of the humerus. In children, this is generally a fracture that looks worse than it is (though a tough sell for the patient I agree). Why? Well, despite displacement and angulation these fractures heal readily with immobilization alone in most cases. The thick periosteal layer of the humerus as well as robust healing in children are responsible for these Wolverine-esque recovery. Most children with mid-shaft humerus fractures have pain and swelling and limited deformity.
The risk of vascular injury is exceedingly low, but radial nerve injuries can be seen. The radial nerve supplies sensation to the dorsum of the hand between the first and second metacarpal and motor control of thumb and wrist extension and supination of the forearm. Neurapraxias do occur, but almost all resolve in less than six months. The risk of a radial nerve palsy is <4%.
The radial nerve and its course in relation to the humerus
Management
Since midshaft fractures generally do well on their own and are often not associated with angulation/displacement, immobilization alone is sufficient. Incomplete fractures in children and adolescents can be managed with sling & swathe.
Sling and swathe and dress shirt
Complete or moderately displaced fractures can be optionally treated with an upper arm sugartong splint (coaptation splint) or a hanging arm cast which takes advantage of gravity and helps reduce deformity by fatiguing flexor muscles.
Proximal sugar tong splint (from: Shaw, DC, Heckman, JD. Principles and techniques of splinting musculocutaneous injuries. Emerg Med Clin North Am 1984; 2:391.)
Reduction is rarely indicated unless neurovascular compromise exists, or there is a concern for compartment syndrome. Open fractures are even more rare. Kids who have been immobilized alone should follow up with an orthopedic surgeon familiar with pediatric fractures within 7 to 10 days.
Immediate Orthopedic consult is recommended for:
- Open fractures
- Neurovascular compromise
- Completely displaced fracture
- Angulation more than 20 degrees in children and 10 degrees in adolescents
- Evidence of compartment syndrome (rare)
If the mechanism is suspicious, the history inconsistent, or if you are concerned consider evaluation for non-accidental trauma. Mid-shaft humerus fractures are not necessarily pathognomonic for abuse though. See this article for more information.
