Title: Radiation Therapy Prophylaxis for Heterotopic Ossification of the Elbow Following Trauma or Recurrent HO
Abstract: Heterotopic ossification (HO) involves the abnormal deposit of bone matrix in soft tissue around large joints causing loss of motion of the affected joint. The incidence of HO following trauma can be as high as 89% in some populations. Prophylactic radiation therapy (RT) for HO has been used successfully for over two decades. The purpose of this study was to review all cases of RT prophylaxis in the elbow following trauma or recurrent HO for occurrence of HO, treatment complications, and risk of HO in terms of patient and treatment characteristics. All cases of RT prophylaxis for HO of the elbow were reviewed over a five-year period. Twenty-five patients were treated post-operatively with 7Gy, opposing field radiation in 1 fraction. Twenty patients (80%) had clinical follow-up > 6 weeks. Of these, 5 (25%) had previous HO and 15 (75%) were trauma patients. Plain films were used to evaluate occurrence of HO and severity was graded using Graham and Hastings classification. Statistical analysis was performed for occurrence of HO. Data was separated into two groups, new onset HO and no HO, and compared for any significant differences in patient and treatment characteristics. Overall, 7 of 20 patients (35%) developed new HO. New HO occurred in 6 of 15 trauma patients (40%) and 1 of 5 (20%) patients with previous HO. 4 of 15 (26.7%) trauma patients had clinically significant HO. 2 (13.3%) patients developed G&H class I HO, 3 (20%) developed class IIA, and 1 (6.7%) developed class IIC. No patient with previous HO developed clinically significant HO. There was no significant difference in age, BMI, type of injury, and intervals from injury and operation to RT between patients who developed HO and those who did not. The length of hospitalization was significantly higher in patients with new onset HO compared to those without (12.14 ± 11.33 days vs. 4.0 ± 2.86 days, p = 0.02). The rate of complications was higher in patients who eventually developed new HO (5/7, 71.4%) compared to those who did not (1/13, 7.69%). Of significance, all patients with complications were trauma patients. There were more complications per patient in the new HO group as well (1.14 ± 1.07 vs. 0.07 ± 0.28, p = 0.0028). Overall, 3 patients (15%) had nonunion. RT is a safe and effective form of HO prophylaxis in the elbow following traumatic injury and excision of HO. Our data suggests significant correlation between the incidence of HO and both the length of hospitalization and number of complications. Our study included a large number of trauma patients. Of note, all patients with clinically significant HO and all patients with complications were trauma patients. Further research is needed to investigate the effect of length of hospitalization and treatment complications on the incidence of HO in trauma patients, as these factors appear to further increase risk.