Prevention of heterotopic ossification in high-risk patients by radiation therapy.

Heterotopic ossification (HO) is a frequent occurrence after cemented and cementless total hip arthroplasty (THA). Patients at risk for this complication include those with preexisting ipsilateral or contralateral HO, diffuse idiopathic skeletal hyperostosis, hypertrophic osteoarthrosis, posttraumatic arthritis, and ankylosing spondylitis. Low-dose radiation therapy effectively prevents HO in this high-risk group when treatment is begun early in the postoperative period. A prospective evaluation has established the efficacy of fractionated and single-dose radiation therapy protocols. Limited radiation portals are used in patients receiving cementless prostheses. A rectangular radiation portal obliquely oriented to the prosthesis enables radiation treatment of the periarticular soft tissues while avoiding exposure of the bone-prosthesis interface. Radiation therapy to this interface may inhibit or delay bony ingrowth. Radiation therapy is the only treatment used to prevent HO that is delivered locally and not systemically. Low-dose radiation therapy using a limited radiation portal is the treatment of choice to prevent HO in high-risk patients after cementless THA.