Single-Fraction Postoperative Radiation Therapy for Post-traumatic Radioulnar Synostosis.

Post-traumatic radioulnar synostosis is a rare complication of forearm trauma, characterized by heterotopic bone formation between the radius and ulna, resulting in loss of forearm rotation. Surgical excision is the primary treatment, but recurrence through reformation of heterotopic bone remains a concern, particularly in patients with a prior osteogenic predisposition. Surgical removal of this bone bridge is the main treatment, but the condition can recur. We report the case of a man in his late 50s with post-traumatic left forearm radioulnar synostosis who underwent surgical excision followed by a single dose of radiation therapy (RT) (7 Gy) given within 48 hours of surgery to prevent recurrence. The patient experienced immediate improvement in passive forearm rotation after surgery, without neurovascular compromise, and tolerated radiation therapy without acute complications. This case adds to the small, published literature supporting postoperative low-dose RT in high-risk patients following radioulnar synostosis excision. It demonstrates the feasibility of same-day CT simulation and radiation delivery in the inpatient setting.