One complication that can occur after surgery on the acetabulum is the development of bone in abnormal places such as muscle and soft tissues. There is some evidence that a single dose of radiation to the surgical site within 3 days of surgery will prevent this abnormal bone from forming. However, there are no high quality studies proving that radiation works any better than doing nothing at all. The purpose of our study is to determine whether there is a difference in abnormal bone formation after acetabular surgery when patients are treated with external beam irradiation versus no treatment.

Heterotopic ossification (HO) is a common complication after surgical fixation of acetabular fractures, with incidence rates reported as high as 90%. HO can be a debilitating complication and surgical excision for more severe cases carries a high complication rate. Numerous strategies have been employed to prevent HO formation but results are mixed and the optimal treatment strategy remains controversial.

The most common modalities used to prevent HO formation are oral administration of indomethacin or single-dose external beam irradiation therapy (XRT). Despite the common use of indomethacin and observational data to support its use, more recent randomized controlled trials (RCTs) have failed to demonstrate any significant reduction in the incidence of severe HO when patients were administered 6 weeks of indomethacin versus placebo. Similarly, XRT has been shown to be effective against HO formation in smaller observational studies, but there are no adequately powered RCTs to support its use compared to placebo.

Given the high incidence, impact on outcomes, and controversy regarding treatment, there remains a need for continued research to determine optimal treatment strategies for HO prophylaxis. While XRT remains standard of care for prophylaxis at many centers, including our own, there are no RCTs to support its use. Given the associated cost and resources, and potential risk even if minor, our study will help determine the feasibility of a larger RCT to help determine if the use of XRT is justified.

For this feasibility study, eligible patients will be randomized to XRT versus control. Both arms will receive gluteus minimus debridement in the OR, which is the standard of care at Shock Trauma. If randomized to the treatment group, patients that undergo surgical fixation of an acetabular fracture via a posterior or combined anterior and posterior approach will undergo a single fraction of external beam radiotherapy to the surgical site within 72 hours of surgery. This treatment is currently the standard procedure performed for all patients who undergo a posterior or combined approach at our institution. The control treatment arm will only include gluteus minimus debridement in the OR and will not receive XRT. We will have 30 patients randomized to each group. We will look at consent rate, power, and HO formation on 3 month post-op radiographs.

Inclusion Criteria:

• Adult aged 18+ with an acute acetabular fracture
• Indicated for surgical fixation via a posterior or combined anterior and posterior approach

Exclusion Criteria:

• Contraindication to radiotherapy such as history of cancer/RT
• Patients that are getting an acute total hip arthroplasty at the time of fixation of the acetabular fracture
• Not English speaking
• Not a Maryland resident or likely to have difficulty returning for post-op follow up(s) (i.e. homeless, incarceration)

Adverse event data was collected over a period of 3 months post-op for each patient.

A limitation of the current study is the fourteen-patient crossover from the XRT treatment arm to no XRT. These 14 patients were randomized to the XRT group, but did not receive XRT at all, thus crossing over to the no XRT group. Additionally, although the sample size was adequately powered, there were a relatively few number of study events. Lastly, although the study is multicenter, it is only 2 centers.