Free Vascularized Fibular Grafting Improves Vascularity Compared With Core Decompression in Femoral Head Osteonecrosis: A Randomized Clinical Trial

Abstract

Background: Management of osteonecrosis of the femoral head remains challenging. Core decompression and free vascularized fibular grafting are commonly used surgical procedures for treatment of osteonecrosis of the femoral head. Few studies, however, have compared these two procedures in a randomized controlled study, in terms of improved vascularity of the femoral head, progression of disease, or hip scores. QUESTION/PURPOSES: (1) What is the effect of core decompression and fibular grafting on vascularity of the femoral head as measured by single-photon emission CT (SPECT)/CT? (2) Does one of these two methods lead to greater progression of Association Research Circulation Osseous (ARCO) stage as determined by serial MRI? (3) What is the relationship between the change in vascularity of the femoral head and hip function as measured by the Harris hip score (HHS) and progression to THA as an endpoint?

Methods: A randomized controlled trial was performed between June 2010 and October 2012 at Zhongshan Hospital, Fudan University. During the study period, 51 patients who presented with ARCO Stages I to IIIB bilateral osteonecrosis were potentially eligible for inclusion, and 33 patients were identified as meeting the inclusion criteria and offered enrollment and randomization. Six patients declined to participate at the time of randomization, leaving a final sample of 27 participants (54 hips). Bilateral hips of each patient were randomly assigned to surgical options: one side was treated with core decompression and the contralateral side was concurrently treated with fibular grafting. SPECT/CT examinations were performed to quantify radionuclide uptake to evaluate vascularity of the femoral head before treatment and at 6 and 36 months after surgery. With the numbers available, we found no differences between the groups regarding vascularity at baseline (64% ± 8% core decompression-treated hips versus 64% ± 7% in the fibular-grafted hips; 95% CI, -5% to 5%; p = 0.90). MR images of the hips were obtained before surgery and at 6, 12, 24, and 36 months postoperatively and staged based on the ARCO classification. All patients were assessed clinically before treatment and followed up at 6, 12, 18, 24, 30, and 36 months after treatment using the HHS. We considered a difference in the HHS of 10 as the minimal clinically important difference (MCID). Patient progression to THA was defined as the endpoint for followup. Six patients (22%) were lost to followup.

Results: By SPECT/CT analysis, decompression-treated hips had lower vascularity than fibular-grafted hips at 6 months (68 % ± 6% versus 95% ± 5%; mean difference, -27%; 95% CI, -32% to -23%; p < 0.001) and 36 months (57% ± 4% versus 91% ± 3%; mean difference, -34%; 95% CI, -37% to -32%; p < 0.001). MRI analysis showed no differences between decompression-treated hips and fibular-grafted hips regarding ARCO stage at 12 months (p = 0.306) and 24 months (p = 0.06). Progression of ARCO staging was more severe in the decompression group than the fibular grafting group at 36 months (p = 0.027). The mean HHS was lower in the decompression group than in the fibular grafting group throughout the followup period, although these differences were at or below the MCID of 10 points early on. However, by 18 months, the scores favored fibular grafting (72 ± 4 versus 84 ± 4; mean difference, -13; 95% CI, -15 to -7; p < 0.001), a finding that was maintained at 24, 30, and 36 months. We found no differences between decompression-treated hips and fibular-grafted hips regarding progression to THA at 36 months (two of 21; p = 0.893).

Conclusions: Hips that underwent a vascularized fibular grafting procedure fared better than hips receiving core decompression as measured by improved vascularity and less progression of osteonecrosis as measured by ARCO staging. The mean HHS of the fibular-grafted hips was better than that of the decompression-treated hips during the entire postoperative period, but the differences were modest early on, and for the early postoperative period the differences were unlikely to have been clinically important; by 18 months after surgery, the differences probably were clinically important. The mid-term outcomes associated with vascularized fibular grafting seen in our patients are associated with improvements in femoral head vascularity and the potential for bone revitalization.

Level of evidence: Level I, therapeutic study.

Fig. 1

The flow chart shows distribution of the study subjects from enrollment to the end of the study.

Fig. 2A–D

Core decompression and bone grafting are shown in these images. (A) A custom-made hollow reamer was used to broach the tunnel until 0.5 cm below the subchondral bone using the C-arm machine. (B) Necrotic bone was removed from the hollow reamer. (C) A custom-made curette was used to remove the rest of the necrotic bone along the tunnel. (D) Bone granules were tightly grafted to the necrotic area through a hollow reamer with a custom-made plugger.

Fig. 3

SPECT/CT analyses at 6 months and 36 months after surgery show hips that had core decompression (CD) had lower vascularity than hips that had free vascularized fibular grafting (FVFG).

Fig. 4A–I

The SPECT/CT images of the hips of a 43-year-old male patient are shown. The patient’s left hip was treated by free vascularized fibular grafting and the right was treated with core decompression. (A) The region of interest was drawn around the femoral head on both femoral heads on the CT image. (B) The region of interest would automatically appear on SPECT and (C) fusion images of SPECT/CT. (D) The coronal CT image shows the patient’s hips 36 months after surgery. (E) Radionuclide uptake of the patient’s hips is shown in this SPECT image. (F) Vascularity of the femoral heads can be seen on the fused SPECT/CT image. (G) We used radionuclide uptake in the first sacral vertebra as a reference to minimize the errors caused by radionuclide dose. (H) The SPECT image shows radionuclide uptake in the first sacral vertebra. (I) A fused SPECT/CT image of the first sacral vertebra is shown.

Fig. 5

Temporal trends for the Harris hip score showed that the mean score was lower in the core decompression (CD) group than in the free vascularized fibular graft (FVFG) group during the entire postoperative period.

Fig. 6

Survivorship curves for the hips in each treatment group, with conversion to THA as the endpoint are shown. Kaplan-Meier survivorship analysis showed no differences between the two groups in survival rates at 36 months after surgery. Log-rank test; p = 0.893; CD = core decompression; FVFG = free vascularized fibular grafting.