[Prevention of periarticular ossification following endoprosthetic hip replacement using postoperative irradiation].

The development of heterotopic ossification (HO) after total hip replacement or other surgical hip procedures can considerably impair the functional result and quality of life in up to 73% of all patients. Predisposing high risk factors for heterotopic ossification are severe pre-intra- and/or postoperative hip trauma, previous development of ipsi- and/or contralateral heterotopic ossification, hypertrophic osteoarthritis, active rheumatoid spondylarthritis as well as male sex. Over the past two decades a variety of surgical, pharmaceutical and radiotherapeutic prophylactic measurements have been proposed and tested in clinical trials. Since June 1988, we have treated 77 patients or 80 hips respectively with prophylactic irradiation. Individual risk factors included severe coxarthrosis grade IV, ipsi- or contralateral heterotopic ossification and severe hip trauma. As of July 1991 60 patients with a minimum follow-up of six months could be analyzed using clinical and radiological scoring systems. The patients had been prospectively randomized in two different treatment arms: 32 patients were treated with low dose (LD), five times 2 Gy daily fractions to a total dose of 10 Gy, whereas 28 patients were treated with high dose (HD), ten times 2 Gy (eight patients) or five times 3.5 Gy (20 patients). Operative procedures and individual risk factors were equally distributed in both groups. 23 patients (38% received indometacin three times 25 mg for six weeks, 19 patients (32%) diphosphonate EHDP 20 mg/kg body weight and 18 patients (30%) had no additional medication. 56/60 (93%) patients developed no significant heterotopic ossification and/or remained without impairment of their postoperative radiological and clinical hip status according to the applied Brooker and Harris Scores. Only 4/60 (7%) patients demonstrated treatment failures developing postoperative worsening one grade of Brooker score in two patients and two and three grades of Brooker score in the two others. Only 1/49 patients experienced a treatment failure, when radiotherapy had been initiated before and at postoperative day 4 compared to 3/11 patients initiated after postoperative day 4 (p less than 0.001). 3/32 patients (9.4%) in the LD group and 1/28 (3.6%) in the HD group were scored as treatment failures (nonsignificant). Radiotherapy treatment duration and additional medication had no impact on the outcome. In conclusion postoperative radiotherapy has shown high efficacy in prevention of heterotopic ossification as long as the treatment is initiated within the first four days after surgery. With respect to acute toxicity postoperative radiotherapy seems to be without any competition compared to surgical and pharmaceutical approaches including corticoid, diphosphonate and nonsteroid antiphlogistic drugs.