[Prevention of heterotopic ossification by radiotherapy following total hip prosthesis]

Clinically relevant heterotopic bone formation (HBF) following total hip arthroplasty (THA) occurs in about one third of all high risk patients. HBF can reduce the functional result of surgery by pain and limited range of motion. The experience with patients treated with postoperative radiation therapy after THA with or without removal of HBF is reported.

Between November 1986 und June 1993, postoperative irradiation was performed on 238 hips of 216 patients (117 men, 99 women, median age 66 years, range 38-86 years) with defined risk factors using 10 Gy in 5 fractions (n = 176) or 7 Gy in one fraction (n = 62) with a cobalt unit. In general, irradiation was performed during the first four postoperative days after primary THA alone in 182 hips or removal of HTB in 56 hips with (n = 28) or without (n = 28) revision surgery. Risk factors for HBF were preexisting ipsi- or contralateral HBF in 105 hips (group 1) or hypertrophic osteoarthritis, previous operative procedures of the hip and others in 134 hips (group 2). After a follow-up of at least 6 months patients were examined and radiographs of the hip were performed to classify HBF.

New or progressive ossifications had developed in the interval in 15 of 104 hips of group 1 (14.4%), compared with 19 of 134 hips in group 2 (14.2%). Clinically significant new HBF (grade 3 or 4) occurred in none of group 2, and in 3 hips of group 1 (2.9%). After radiation with 10 Gy HBF of all grades occurred in 23 of 176 hips (13.1%), and in nine of 62 hips after 7 Gy (14.5%). The lowest number of treatment failures was found in patients irradiated during the first 4 postoperative days.

These results demonstrate that immediate postoperative radiation is efficacious for prevention of clinically relevant HBF following THA and removal of HBF.