Radiation therapy or radiotherapy, which is the use of ionizing radiation for therapeutic ends, has been proposed as a possible adjunct treatment for HO.
Sautter-Bihl et al. (2000) studied 36 patients with HO of whom 27 patients (32 joints) received radiotherapy when ossification was minimal. 11 patients (13 joints) had obvious ossifications, which had to be resected. Post-op radiotherapy was performed 24-36 hours post-operatively. Two patients received radiotherapy both before and after surgery. The mean duration of follow-up was 23.6 months. 30 of the 36 irradiated patients showed no progression of HO. In three patients, re-ossification after therapy resulted in a moderate decrease in joint mobility.
In the follow-up case series by Sautter-Bihl et al. (2001), the authors examined the effectiveness of radiotherapy administered to 52 SCI patients. Radiotherapy effectively prevented primary and secondary HO post-surgical excision in 71% of patients. However, treatment did not result in regression of HO once developed, as measured by the Brooker scale. Two joints increased in Brooker score, although neither of them developed any functional impairment. Another case series by Museler et al. (2017) used either 15 MV or 6 MV radiotherapy to target HO at the hip in 244 patients. Recurrence of HO was found to be very low (5.3%), and of those that experienced recurrence, HO was initially present in both hips.
In a case control study by Honore et al. (2020), patients with SCI and traumatic head injury underwent either excision and radiotherapy before surgery (at a dose of 7.5 Gy, with 15 or 18 MV X-ray photons; case group) or excision only (control group). The results revealed no differences between the odds ratios for HO recurrence between the case group and the control group. In addition, the case group patients were found to be significantly more likely to develop sepsis after surgical excision requiring surgical revision, compared to the control group patients. Based on these findings, the authors concluded that radiotherapy should not be combined with surgery in patients with hip HO undergoing excision.
A case study by Cramarossa et al. (2013) reported on the use of radiation therapy on a patient who had previously experienced an SCI at the C5-C6 level and had been diagnosed with dysphagia due to HO-induced osteophytes. One day after surgical intervention, which involved anterior cervical decompression and drilling of the osteophytes, the patient received a single treatment of radiation at 8 Gy. At follow-up, the patient reported that they were not experiencing any recurrence of dysphagic symptoms. The authors add that radiation should only be considered for patients at high risk of HO due to the risk of creating a radiotherapy-induced malignancy and that an expansion of the literature is required to better assist treatment decisions.
There is level 3 evidence (from one case control study: Honore et al. 2020) that combining radiotherapy with surgery in patients with hip HO undergoing excision may not prevent HO recurrence and may be associated with an increased risk of postoperative sepsis.
There is moderate Level 4 evidence (from three case series studies: Sautter-Bihl et al. 2000; Sautter-Bihl et al. 2001; Museler et al. 2017) that radiotherapy reduces the progression and recurrence of heterotopic ossification.