[Treatment of heterotopic ossification after spinal cord injury - clinical outcome after single-dose radiation therapy].

Introduction: Heterotopic ossification (HO) is a common and serious complication after spinal cord injury, with an incidence of 5-50 %. Single-dose radiation therapy with 7 Gy is an established procedure for HO prophylaxis after total hip replacement. The aim of our study was to determine the clinical outcome after single-dose radiation therapy in the prophylaxis of HO in paraplegic patients.
Patients and Methods: Between January 2006 and July 2009, 75 paraplegic patients with heterotopic ossification were treated in our hospital. On the basis of the defined inclusion and exclusion criteria, 62 patients were included in our study, whereas 55 patients participated in our follow-up examination. All patients received a bi-weekly ultrasound of the hip for an attempt at early diagnosis of the condition. In case of an ultrasound suspicion of HO, a computed tomography (CT) or magnetic resonance imaging (MRI) of the hip was performed. After confirmation of HO, a single-dose radiation therapy with 7 Gy was performed. In group A, the patients were irradiated with an electrode voltage of 15 MeV (36 patients) and in group B with 6 MeV (26 patients). All patients were assessed with a standardised questionnaire with a mean follow-up of 30.6 months (range 6-78 months).
Results: The mean interval time between the initial spinal injury and HO development was 58,2 days (range 14-125). 69,4 % of all patients revealed a Brooker grade I, 27.4 % grade II and 3.2 % a grade III. No cases of Brooker grade IV (ankylosis) occurred. No patient showed side-effects after radiation therapy. However, in group A one patient (3,2 %) and in group B three patients (12.5 %) developed HO relapse. Those patients were treated again with a single-dose radiation therapy with 7 Gy and 15 MeV and, afterwards, they were free of complaints. Deep vein thrombosis was confirmed in 11 patients (32.3 %) in group A and in 8 patients (33.3 %) in group B.
Conclusions: Single-dose radiation therapy with 7 Gy in the treatment of heterotopic ossification is an effective option. A higher electrode voltage improves the effectiveness of the irradiation and the clinical outcome. Essential for the outcome is the early detection and treatment of HO with single-dose radiation therapy. Randomised, prospective studies should be undertaken in order to confirm these findings.
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