Fracture Through a Bone Cyst

Description

This is a break through a weak spot created by a benign (non-cancerous) bone cyst — a fluid-filled or fibrous cavity that had hollowed out part of the bone, most often in the upper arm. The cyst is usually silent until the fracture reveals it.

How it happens (the mechanism)

A benign cyst gradually hollows out the inside of the bone, thinning its walls. That weakened area can then break under a force that would not harm normal bone — sometimes a minor injury. In this way the fracture is often what first brings a silent, benign cyst to attention, and occasionally the healing response that knits the fracture also helps the cyst fill in with bone.

What matters

The reassuring headline is that these cysts are benign — not cancer. The fracture itself typically heals like other childhood fractures, and the pace afterward is unhurried: confirm the diagnosis, heal the break, then decide whether the cyst needs treatment to lower the chance of another fracture.

Symptoms

Pain, swelling, and reluctance to use the arm after an injury that may have seemed minor; sometimes the cyst is found incidentally on an X-ray.

Doctor examination and imaging

X-rays show the fracture and the cyst; occasionally additional imaging is used to confirm the cyst is benign.

Treatment

First the fracture is treated, usually as that bone would be treated normally — often without surgery. Then the cyst is addressed, which may be watched, or treated with an injection or a minor procedure to help it fill in, depending on its type, size, and location.

Recovery and long-term outlook

The outlook is good; these cysts are benign, and the fracture heals well. The cyst is followed with X-rays over time.

When to call the doctor

Call if pain is severe or worsening, your child will not use the arm at all, the area becomes very swollen, red, or warm, your child develops a fever, or things are not improving as expected.

Learn more

OrthoInfo (AAOS) — Growth Plate Fractures: orthoinfo.aaos.org

This information is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. For specific concerns about your child, consult a board-certified, fellowship-trained pediatric orthopaedic surgeon.