Hip preserving surgery for avascular hip necrosis: does terminating exposure to known risk factors improve survival?

Introduction: Avascular necrosis of the hip is rarely detected in early pre-radiographic stages (Arlet-Ficat stages I and II) where conservative treatment would still be possible. Studies of risk factors were often merely descriptive. The aim of the present study was to make a retrospective assessment of treatment survival rate for conservative management of avascular hip necrosis according to whether exposure to avoidable risk factors is eliminated or not. The study hypothesis was that eliminating avoidable risk factors is effective and reduces the risk of failure, and hence of hip replacement. Material and method: A single-center retrospective study was performed for conservatively managed avascular hip necrosis. Thirty-seven consecutive hips in 34 patients underwent decompression drilling, with a minimum 3-year follow-up. Known risk factors for osteonecrosis were classified as avoidable or non-avoidable. Results were analyzed according to the elimination of avoidable risk factors. The main endpoint was survival, with failure defined as femoral head collapse and/or recourse to total hip replacement. Avoidable risk factors (corticosteroids, smoking, alcohol consumption, blood pressure elevation, hypercholesterolemia) persisted for 17 hips (45.9%) and were prevented for 15 (40.5%). Five patients (5 hips: 13.5%) did not show preoperatively identified risk factors. Groups were demographically comparable. Results: Mean follow-up was 7.5 ± 3.7 years (range, 3.1-16.0 years). At last follow-up, there was a significant difference in survival at cumulative 9-year follow-up between patients with no risk factors (100%), with risk factors eliminated (59.3%; 95% CI, 0.273-0.012), and with persisting risk factors (23.5%; 95% CI, 0.013-0.458) (p = 0.001). Discussion: No studies were found in the literature assessing the survival of hip preserving surgery according to persistence or elimination of known risk factors for osteonecrosis. Eliminating risk factors significantly improved the survival rate for conservative treatment of femoral head necrosis.