OUTCOMES OF CAGE REINFORCEMENT OF THE ACETABULUM AFTER PREVIOUS PELVIC IRRADIDATION.

Abstract

Acetabular components of total hip joint replacement (THJR) in previously irradiated pelvis show high rates of failure. We present a literature review and a retrospective series evaluating the survival of acetabular cages in this difficult situation. Our hypothesis was that cage reinforcement of the acetabulum after previous pelvic irradiation would lead to early failure.

A cohort of 11 patients (12 hips) was identified, who had undergone THJR utilising an acetabular cage, after previous pelvic irradiation for malignant tumours. All operations were performed by a single surgeon in Waikato over the period of 1997–2007. Six patients (six hips) died within one year of their operation, the further five patients (six hips) were analysed for survival and radiograpical loosening of the acetabular component. Complications attributed to previous irradiation are also reported.

There is a paucity of literature of THJR survivorship after pelvic irradiation. The first series from the 1970’s showed 50% acetabular loosening at 5 years in cemented cups. Two conflicting series are published with 44% vs. 0% failure of uncemented cups. Only one previous series (22 hips) reports the use of acetabular reinforcement rings, and showed a 20% loosening and 10% deep infection rate at 4 years. In our cohort of 12 hips in 11 patients, only five patients survived greater than one year after joint replacement. The average follow up of the remaining six hips is five years (two to ten years). Two out of six of the acetabular cages have catastrophically failed. Of the remaining four cages, one is probably, and three are possibly radiologically loose. Two out of six have raised concerns in regards to deep infection that were not proven microbiologically. Overall of the patients who survived greater than one year after their THJR for pelvic irradiation, only four out of six of the acetabular cages remained insitu, and all had concerns raised in regards to radiographical loosening.

We report a high rate of clinical and radiographic failure of cage reconstruction of the acetabulum after previous pelvic irradiation. A superior method of acetabular reconstruction in this difficult situation is yet to emerge. Alternative methods of reconstruction continue to develop, with trabecular metal options a possible consideration.