To evaluate the risk factors and duration of femoral head collapse after free vascularized fibular graft (FVFG) for the treatment of avascular necrosis of femoral head (AVN).

Data of the patients who underwent FVFG for the treatment of AVN between January 2006 and December 2012 at Department of Orthepedics, Shanghai Sixth People’s Hospital were studied retrospectively. Inclusion criteria : age between 18 to 55 years, AVN of Ficat-Arlet stage II~III, follow-up according to the plan and reach the end-point. Exclusion critera: severe complications, being failed to follow up on schedule, incomplete data. Univariate and multivariate Logistic regression analyses were used to analyze the risk factors for the progression of femoral head collapse after FVFG. Age, gender, causes of AVN, sides of AVN, stages of AVN and presence of femoral head collapse were recorded.

A total of 215 cases (307 hips) with a mean follow-up duration of (51±26) months were included in the study. Femoral heads of 260 hips (84.7%) did not collapse at the last follow-up, and femoral head collapse was observed in the remaining 47 hips (15.3%). Femoral head collapse was observed between three months and 24 months after the operation, and the first, second, and third quartile of the time point of femoral head collapses following the operation were three months, six months after operation, and 15 months after the operation, respectively. The results of univariate and multivariate binary logistic regression analyses demonstrated that age ≥ 40 years (P=0.021) and AVN of Ficat-Arlet stage III (P=0.003) were the risk factors of femoral head collapse after FVFG for AVN.

FVFG could provide excellent outcomes for the treatment of AVN. The risk duration of femoral head collapse after FVFG for AVN is within postoperative 15 months, and the risk factors are age≥40 years old and Ficat-Arlet stage III. For the patients with risk factors, the follow-up interval should be shortened, and the rehabilitation exercise intensity should be reduced.