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Delaying radiation after traumatic acetabular fractures can significantly increase incidence of heterotopic ossification
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A retrospective study has concluded that any increase in the time interval between the occurrence of traumatic acetabular fractures and the delivery of radiation therapy correlates with a significant increase in the incidence of heterotopic ossification.
The single-institution study of 716 patients referred for radiation therapy (RT) to prevent heterotopic ossification (HO) found that 452 (63.1%) had no HO and 264 (36.9%) had HO. The risk of HO development increased from 10.3% for RT delivered in 3 days or less to 15.1% when RT was delivered in 7 days or less.
Further delay of RT resulted in even higher incidences of HO: 21.7% for 14 days or less, 25.5% for 21 days or less, and 91.1% for over 21 days.
“Radiation therapy is usually given postoperatively within 72 hours of surgery,” principal investigator Waleed Fouad Mourad, MD, a senior radiation oncology fellow at the University of Mississippi Medical Center in Jackson, said. “However, according to the literature, preoperative RT within 1, 2, 4, 16 and 18 hours of surgery has also been advocated for HO with similar outcomes. How can pre- and postoperative RT yield the same results? That’s when I realized that there must be other factors affecting the HO incidence other than the RT timing from surgery.”
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These Brooker IV images represent a patient who developed severe HO despite radiation therapy as described above. However, the patient was treated with radiation therapy 10 days after his accident. Images: Mourad WF |
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The authors speculated that as the time from trauma was prolonged in some of the patients, “the early osteoprogenitor cells and the pluripotent mesenchymal cells infiltrating the area of trauma had already entered a more differentiated and less radiosensitive phase of their growth,” Mourad told Orthopedics Today. “Thus, these patients were likely more resistant to the prophylactic effect of RT.”
Early intervention
Outcomes of the study, which were presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons in New Orleans, underscore that the time interval from traumatic acetabular fractures (TAF) to surgery and RT (with or without indomethacin) “is prognostic and predictive of HO,” Mourad said. “Patients undergoing RT 3 weeks or more after TAF should be informed of their higher risk — about 90% — of developing HO.”
Mourad, who is also an instructor in the Department of Radiation Oncology and Nuclear Medicine at Ain Shams University in Cairo, Egypt, noted that all study patients had RT delivered within 72 hours of the orthopedic surgical intervention; thus, “surgical intervention as early as possible should be advocated.”
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This patient had a right traumatic acetabular fracture and underwent open reduction and internal fixation, this was followed by single fraction of 700 cGy, prescribed at midplane , as shown above, the patient was treated supine with beam entry anterior-posterior and opposing posterior-anterior. The blocks were drawn to keep at least a 2-cm margin from the desired area of treatment. |
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In the literature
Cooley and Goss in 1958 and Craven and Urist in 1971 were the first to demonstrate the inhibitory influence of ionizing radiation on bone repair and growth in rats, he reported.
“The effects were more pronounced when treatment was initiated close to the time of the fracture,” Mourad said. “These authors hypothesized that the early osteoprogenitor cells involved in bone repair were more radiosensitive than the more mature or differentiated cells seen later.”
Mourad plans on conducting a follow-up study by investigating the influence of time interval from date of fracture to date of surgical repair, followed by RT on fractured sites around the elbow joint — in the distal humerus, elbow joint and forearm — shoulder joint, wrists, ankles and knees. “The rational of this upcoming study is to explore and identify, if any, the site preference for HO formation due to delayed definitive treatment,” he said. – by Bob Kronemyer
Reference:
- Mourad WF; Russell GV Jr.; Qin Z, et al. Novel concepts in prevention and formation of heterotopic ossification post acetabular fracture. Paper # 222. Presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons. March 9-13. New Orleans.
Waleed Fouad Mourad, MD, 350 W. Woodrow Wilson Ave., Suite 1600, Department of Radiation Oncology, Jackson, MS 39213-7681; 601-815-6886; e-mail: wmourad@umc.edu.
