Zygomatico-coronoid ankylosis secondary to heterotopic bone formation: combined treatment by surgery and radiation therapy--a case report.

Zygomatico-coronoid ankylosis is a rare, extra-articular form of ankylosis of the jaws. An unusual case is presented in which true bony zygomatico-coronoid ankylosis was produced by a mass of heterotopic bone. Surgical treatment consisted of an oblique ostectomy across the mandibular ascending ramus, with interposition of Silastic sheeting to form a pseudarthrosis. Since surgery is often the stimulus for this condition, 2000 rads were delivered to the surgical site postoperatively in order to inhibit recurrent heterotopic bone formation. The rationale and indications for this form of treatment are discussed.