Super-acute massive osteolysis of the femoral head after acetabular fracture fixation : a comparative study with conventional post-traumatic osteonecrosis requiring total hip arthroplasty.

Abstract

Super-acute massive osteolysis of the femoral head (MOFH) is a rare but devastating complication following acetabular fracture, characterized by rapid femoral head destruction within weeks. This study aimed to characterize and compare the clinical and radiological features of super-acute MOFH with those of conventional post-traumatic osteonecrosis of the femoral head (ONFH) requiring total hip arthroplasty (THA). This retrospective study included adult patients who underwent acetabular fracture osteosynthesis at a single Level I trauma centre between January 2021 and December 2025 and subsequently required THA. Patients were classified into super-acute MOFH or conventional ONFH groups. Demographic data, injury patterns, surgical variables, and radiological findings were reviewed. Reduction quality was assessed using postoperative radiographs and CT-based articular gap and stepoff measurements. Groups were compared using non-parametric and exact tests; Firth penalized logistic regression identified factors independently associated with super-acute MOFH. Overall, 31 patients met the inclusion criteria: 12 with super-acute MOFH and 19 with conventional ONFH. Patients with super-acute MOFH were significantly older (p = 0.010). Fracture pattern, hip dislocation, recurrent dislocation, time to reduction, time to fixation, surgical approach, revision fixation, and overall reduction quality showed no association with super-acute MOFH. CT-based articular gap measurements were similar between groups. Greater postoperative axial stepoff in posterior wall fractures occurred in the super-acute MOFH group but were not independently predictive. Multivariable analysis showed increasing age was independently associated with super-acute MOFH (odds ratio 1.14 per year; 95% CI 1.01 to 1.29; p = 0.037). Super-acute MOFH is a distinct, aggressive post-traumatic entity that can occur despite satisfactory acetabular reduction and fixation. Its development is unrelated to fracture morphology or surgical factors, but associated with older age in middle-aged trauma patients, suggesting host-related biological vulnerability. Early recognition, close postoperative imaging surveillance, and timely THA preparation are recommended for at-risk patients.