Computerized tomography-based radiotherapy improves heterotopic ossification outcomes

Fifteen years’ experience of radiation therapy for resected advanced heterotopic ossification following motor vehicle accidents: outcome and side effects

Background

Surgical resection is the primary treatment for advanced-stage heterotopic ossification (HO), with a high incidence of local recurrence reaching up to 50%. Postoperative radiotherapy (PORT) and indomethacin are commonly used prophylactic strategies following surgery. The study aims to assess the safety and effectiveness of PORT in advanced-stage HO patients having motor vehicle accidents (MVA).

Methods

Medical records of patients having HO following MVA between 2006 and 2021 were retrospectively reviewed. Thirty-nine patients with advanced disease (35 had hip HO and 4 had elbow HO) were included in the study.

Results

Excision of HO with joint preservation was performed for 82% of patients, while 18% had a joint replacement. Seven to 8 Gy radiation was given to all patients within 3 days postoperatively. A ninty seven percent of patients regained partially the movement range. The mean follow-up time was 74 months. Six patients had treatment failure, with only one having a recurrence of HO. The 8-year treatment failure-free rate (8-y TFFR) was 79.3±9%, and the 5-year HO failure-free rate (5y-HOFFR) was 97.2±3%. Acute side effects were experienced in 13% of patients but resolved without any consequences. Despite the relatively long follow-up time, we did not report any absolute infertility or secondary malignancies related to the radiation. The testicular mean calculated dose was 33±44 cGy, and the mean measured dose was 58±40 cGy. Of the 35 patients who received radiation to the pelvis, 26 were married, and all did not experience infertility post-treatment.

Conclusion

PORT proved an effective and safe treatment for advanced-stage HO disease. The treatment failure is mainly related to surgical difficulties due to advanced disease. Treatment using a 3-dimensional or intensity-modulated radiation therapy is not associated with serious side effects like second malignancy or absolute infertility.

Burn-induced heterotopic ossification from incidence to therapy: key signaling pathways underlying ectopic bone formation

Burn injury is one of the potential causes of heterotopic ossification (HO), which is a rare but debilitating condition. The incidence ranges from 3.5 to 5.6 depending on body area. Burns that cover a larger percentage of the total body surface area (TBSA), require skin graft surgeries, or necessitate pulmonary intensive care are well-researched risk factors for HO. Since burns initiate such complex pathophysiological processes with a variety of molecular signal changes, it is essential to focus on HO in the specific context of burn injury to define best practices for its treatment. There are numerous key players in the pathways of burn-induced HO, including neutrophils, monocytes, transforming growth factor-β1-expressing macrophages and the adaptive immune system. The increased inflammation associated with burn injuries is also associated with pathway activation. Neurological and calcium-related contributions are also known. Endothelial-to-mesenchymal transition (EMT) and vascularization are known to play key roles in burn-induced HO, with hypoxia-inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF) as potential initiators. Currently, non-steroidal anti-inflammatory drugs (NSAIDs) and radiotherapy are effective prophylaxes for HO. Limited joint motion, ankylosis and intolerable pain caused by burn-induced HO can be effectively tackled via surgery. Effective biomarkers for monitoring burn-induced HO occurrence and bio-prophylactic and bio-therapeutic strategies should be actively developed in the future.

A Retrospective Analysis of 287 Patients Undergoing Prophylactic Radiation Therapy for the Prevention of Heterotopic Ossification

Purpose

Heterotopic ossification (HO) is a potentially disabling disorder of ectopic bone formation secondary to orthopedic surgery or trauma. In this retrospective analysis we evaluated the outcomes of patients who received radiation therapy (RT) for HO prophylaxis.

Methods and Materials

A total of 287 patients who received RT for HO prophylaxis at a major trauma center from 2007 to 2018 were analyzed. Data collected included types of injury, surgery, time intervals between key events, development of postprophylaxis HO, and secondary malignancies. Associations between various factors and the risk of developing HO were analyzed. Kaplan-Meier analysis was used to estimate failure rates.

Results

The most common indication for RT was traumatic acetabular fracture (83.3%). Twelve patients (4.2%) developed postprophylaxis HO with a median time to failure of 8.6 months (2.8-24.5). Kaplan-Meier 1-, 2-, and 5-year failure rates were 3.7%, 4.4%, and 7.4%, respectively. Injury type and timing of RT were not associated with the risk of failure, but we observed a trend of increased risk of failure in patients with longer time between surgery and RT (odd ration [OR] 1.68, P = .056). Current or former smokers (51.7%) were less likely to fail (OR 0.10, P = .03). There was no incidence of in-field secondary malignancy.

Conclusions

There was no significant association between injury and fracture type, surgical approach, or timing of RT and development of HO, contrary to published reports of increased HO risk with certain surgical approaches and longer time intervals between injury and surgery, suggesting that prophylactic RT might play a role in mitigating these effects. Decreased risk of postprophylaxis HO among former or current smokers was unexpected. No secondary malignancy in the RT field was identified, although the median follow-up was only 17 months. Compared with published HO incidences (17%-39%) in patients who receive no prophylaxis after traumatic acetabular fractures, our results are highly suggestive of the efficacy of prophylactic RT.

Testicular Dose During Prophylaxis of Heterotopic Ossification with Radiation Therapy

AIM

A single-institution, retrospective study was performed to investigate potential techniques to minimize radiation exposure to the testicles during heterotopic ossification (HO) prophylaxis. We report the impact of split-beam technique (SBT) and different photon energies on the total dose of radiation received by the testicles during prophylaxis of HO.

MATERIALS AND METHODS

Between 2008 and 2010, we identified 64 patients with traumatic acetabular fractures who underwent surgery followed by radiation therapy (RT) without testicular shielding. Postoperative RT was delivered within 72 h in a single fraction of 700 cGy using 6-18 MV photons, without testicular shielding due to patient refusal. All patients underwent 3-D RT planning in which the testicles were contoured as a region of interest and dose-volume histograms (DVH) were generated. Additional treatment planning trials were created for each patient by utilizing a SBT medially and by using different photon energies (6, 10 and 18 MV) to study the effects of these maneuvers on the delivered dose to the testicles.

RESULTS

In reviewing the DVH, it was noted that the mean dose delivered to the testicles was 10 cGy (range=3-40). The maximum dose was 31 cGy (range=7-430). When SBT was utilized, a significant reduction in the mean (44%) and maximum (47%) doses delivered to the testicles was noted. Further reductions in the mean (26%) and maximum (14%) doses were achieved by using higher-energy (10-18 MV) beams. The radiation doses to the testicles from the CT simulation and the two portal images were estimated to be 4 and 1.5 cGy, respectively.

CONCLUSION

Low-dose prophylactic RT to prevent HO around the hip causes a low, but likely biologically meaningful, radiation dose to be delivered to the testicles. This dose could be further reduced by using a medial SBT and photon energies above 6 MV. Testicular shielding should be offered to all male patients receiving such RT. In addition, all patients should be informed about the consequences of testicular radiation as part of their informed consent.