title: Safety and efficacy of radiation therapy as secondary prophylaxis for heterotopic ossification of non-hip joints.
abstract: BACKGROUND
  Prophylactic radiation therapy (RT) is an established adjuvant therapy for heterotopic ossification (HO) of the hip when delivered in the immediate pre- or postoperative setting. Its role in prevention of recurrence after excision of HO is supported by randomised trials for HO of the hip, but there is scant evidence to demonstrate the safety and efficacy of a similar approach in non-hip joints. In the current study, we evaluate radiological and functional outcomes after prophylactic RT for prevention of HO of the knee and upper extremity.
  
  
  METHODS
  With institutional review board (IRB) approval, patients treated at our institution with prophylactic RT for non-hip HO from 1998 to 2009 were identified. Records were reviewed, including pre- and postoperative records, operative reports and radiography. The primary objectives were to determine the safety of RT and rate of treatment failure, as defined by need for further surgical intervention.
  
  
  RESULTS
  A total of 30 patients received prophylactic RT for HO of the elbow (n=21), MCP joint (n=1) and knee (n=8). Twenty-nine of the 30 patients were treated within 24-48h postoperatively, and one patient was treated within 24h preoperatively. Based on institutional policy, only patients considered to be at high risk of recurrence were selected to receive prophylactic RT. Patients were treated to a dose of 7Gy in one fraction, with two parallel opposed. Complications following treatment included two patients with postoperative wound infections, one patient with a ruptured triceps tendon and one patient with a fracture within the treatment field. Follow-up information was available for 26 of 30 patients, with a median follow-up time of 16months (range, 2-143months). Recurrent HO, requiring surgical re-excision, developed in 10.5% (n=2) of patients who were followed for upper extremity HO (n=19). For patients followed after RT for HO of the knee (n=7), there were no recurrences of HO that required further intervention.
  
  
  CONCLUSIONS
  In this group of patients at high risk for developing further HO, prophylactic RT appears to be a safe adjunct to surgery and is effective in prevention of HO recurrence. Results are similar to published reports of HO of the hip and support the use of surgical excision and perioperative, prophylactic RT for HO of non-hip joints.
authors.affiliation: Department of Radiation Oncology, Kimmel Cancer Center and Thomas Jefferson University Rothman Institute, Thomas Jefferson University Hospital, Philadelphia, PA19107, USA.
authors.forename: Mark V
authors.initials: MV
authors.lastname: Mishra
authors.forename: Luke
authors.initials: L
authors.lastname: Austin
authors.forename: Javad
authors.initials: J
authors.lastname: Parvizi
authors.forename: Matthew
authors.initials: M
authors.lastname: Ramsey
authors.forename: Timothy N
authors.initials: TN
authors.lastname: Showalter
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004551:Elbow Joint / Q000528:radiation effects*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000528:radiation effects*; D008297:Male; D008662:Metacarpophalangeal Joint / Q000528:radiation effects; D008875:Middle Aged; D009999:Ossification, Heterotopic / Q000517:prevention & control* / Q000532:radiotherapy* / Q000601:surgery; D011183:Postoperative Complications / Q000517:prevention & control*; D055502:Secondary Prevention; D055815:Young Adult