Rapidly progressive avascular necrosis of the hip joint: too important to miss!

Abstract

Introduction: Avascular necrosis (AVN) is the most common aetiology leading to total hip arthroplasty in Hong Kong. A subset of AVN patients exhibit alarmingly rapid disease progression with significant collapse of the femoral head or acetabular erosion. Our objectives were to identify the incidence of rapidly progressive AVN (RPAVN), radiologically characterise and define RPAVN, and evaluate if any of these patients had underlying septic arthritis. Methods: This retrospective study evaluated 147 cases of AVN out of 572 patients who were on the waiting list for total hip arthroplasty in Hong Kong West Cluster between January 2014 and June 2019. Radiographs, investigation results, and clinical notes were reviewed. We defined RPAVN as a collapse of the femoral head of ≥25% or acetabular erosion within 6 months. Results: In all, 23 hips in 20 patients met our radiological criteria for RPAVN (15.6%). Within the timeframe, 11 cases had complete collapse of the femoral head and 13 cases had acetabular erosion. Preoperative joint aspiration was performed in 13 hips and intra-operative tissue culture was performed in 12 hips, but all cultures were negative. Steroid and alcohol use were identified in 17.4% and 13.0% of these patients, respectively. Fifteen cases had total hip arthroplasty done, with five requiring acetabular reconstruction using either bone graft or metal augment. Conclusion: Rapidly progressive avascular necrosis is a distinct hip pathology that requires early surgical intervention after exclusion of infection to prevent rapid functional deterioration and increasing surgical difficulty.