Case report
Avascular osteonecrosis of the hip in patient after adjuvant radiotherapy for rectal cancer

Avascular necrosis (AVN) refers to the death of osteocytes and osteoblasts. AVN is encountered mostly among men in their 4^th or 5^th decade of life. The basic treatment for osteonecrosis is surgery, and the choice of procedure is based on preoperative staging. AVN is a very rare complication in radiotherapy (RT), but it presents an important clinical problem, still underestimated in oncological practice.

Case report: This report documents an extensive symmetric avascular necrosis with acetabular protrusion and femoral head deformities in a 71-year-old woman with unresectable, poorly differentiated adenocarcinoma of the recto-sigmoid region, after therapeutic pelvic irradiation. The pelvic radiography, performed 24 months after the RT, due to bilateral hip pain, revealed advanced acetabular protrusions, with secondary deformities of both femoral heads.

It is necessary to take into account the bone structures, among organs at risk (OAR), involved in irradiation fields. The detailed analysis of the dose distribution, and the use of collimators, allow a decrease in the total RT dose to OAR. Osteoradionecrosis risk awareness, early diagnosis, adequate management and prompt, appropriate treatment could probably protect patients against long-term morbidity.