Impact of hip synovitis on the long-term outcomes of free vascularized fibular grafting for osteonecrosis of femoral head

Objective·To observe the impact of hip synovitis on the long-term outcomes of free vascularized fibular grafting (FVFG) for osteonecrosis of femoral head (ONFH).Methods·Between October 2001 and December 2013, 370 patients diagnosed with ONFH (556 hips) underwent FVFG. Preoperative synovitis was assessed using magnetic resonance imaging (MRI) and quantified with the Hip Inflammation MRI Scoring System (HIMRISS). Patients were divided into no synovitis group, moderate synovitis group, and severe synovitis group. Harris hip scores and the incidence of total hip arthroplasty were collected with an average follow-up duration of 90.5 months (range: 5‒215 months). Hip survival failure (defined as a Harris hip score lower than 80 at the final follow-up or the occurrence of total hip arthroplasty) was calculated. Multivariable Cox regression analysis was adopted to compare the influence of different degrees of synovial inflammation on long-term prognosis.Results·The proportion of hip survival failure was 28.0% in patients without synovitis and 28.5% in those with moderate synovitis, whereas it was significantly higher (60.4%) in patients with severe synovitis. The results of multivariable Cox regression analysis showed that severe synovitis was an independent risk factor for poor prognosis (HR 2.06, 95%CI 1.21‒3.53) after adjusting for age, gender, education level, marital status, ONFH type, affected side of ONFH, smoking history, baseline Harris hip score and other hip MRI-based covariates (collapse, bone marrow edema, and degeneration).Conclusion·Severe synovitis in patients with ONFH significantly increases the failure rate of hip preservation after FVFG, and the severity of synovitis should be considered in surgical decision-making.