Vascularized Fibular Grafting for Osteonecrosis of the Femoral Head

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CHAPTER 31 Vascularized Fibular Grafting for Osteonecrosis of the Femoral Head

Introduction

The first documented report of osteonecrosis of the femoral head (ONFH) appeared more than a century ago, yet, since then, few definitive conclusions have been reached regarding its causes or treatment. Approximately 20,000 new cases are diagnosed each year, and ONFH accounts for 5% to 12% of total hip replacements performed in the United States annually. The natural history of ONFH is subchondral collapse with a squaring of the femoral head that leads to hip degeneration. Because of this natural history and the fact that ONFH has a proclivity to manifest in younger patients, most surgeons have traditionally believed that procedures aimed at preserving the native hip are preferable to joint replacement.

Conceptually, the ideal procedure would remove the necrotic bone within the femoral head and replace this void with healthy bone that is replete with a nascent vascular source to improve the likelihood of restoring a vital subchondral plate. Such a procedure would relieve the patient’s pain, preserve or restore the sphericity of the femoral head, and ultimately prevent the deterioration of the hip. Fulfilling these criteria would likely prevent the need for a second surgery (i.e., arthroplasty); this is an important objective, particularly for younger patients. We feel that the free vascularized fibular graft more closely addresses these objectives as compared with any other biologic-preserving procedure currently available; it is our preferred method for the treatment of ONFH. We have outlined our indications, contraindications, results, and surgical technique, and we have highlighted some of the critical steps that we feel are paramount to obtaining successful results with this procedure.

Basic science

There are more than 100 conditions or factors that are known to activate intravascular coagulation and to potentially cause osteonecrosis. A growing body of evidence supports the theory that ONFH in adults and Legg-Calvé-Perthes disease in childhood is related to an underlying thrombophilia or hypofibrinolysis. A recent study reported that 136 of 206 patients (66%) with osteonecrosis revealed abnormal clotting values of the tested factors. In a follow up study of patients with ONFH, activated protein C resistance was the most frequent abnormality found, with a 50% prevalence. Lipoprotein A is also thought to play a role in the development of osteonecrosis, with a reported prevalence of 32% in one study of 124 subjects with ONFH.

Aberrant microvascular anatomy has also been implicated in the development of ONFH. With the use of digital subtraction angiography, one study showed that 94% of 99 hips with osteonecrosis demonstrated abnormal hip vasculature as compared with 31% (5 out of 16) abnormal findings in the control group. Regardless of the cause, we know that the eventual pathway ends with bone death that results from inadequate perfusion.

Despite this wealth of associated conditions and known risk factors, no one factor has proven to have a direct causative effect. In fact, the ultimate development of ONFH is more likely the unfortunate nexus of multiple risk factors that individually fall short of causing osteonecrosis but that collectively tip the scales toward an intraosseous ischemic event.

We have studied the efficacy, both clinically and in the laboratory, of the free vascularized fibular graft (FVFG) for the treatment of ONFH. With the use of a canine model in which ONFH was induced with cryotherapy, we implanted into the canine femoral head core either nonvascularized bone grafts, pedicled muscular flaps, or vascularized bone grafts. The necropsy femoral head analysis at 1 year demonstrated statistically significant increased trabecular thickness only in the vascularized bone grafts.

Indications

For all patients, as adjuncts to this list of objective criteria, we include the patient’s “hip health,” which is determined by the degree of limp, the limitation of motion, and the degree and frequency of pain. For example, if we are equivocal about the benefit of the FVFG for a certain patient on the basis of radiographic analysis alone but discover that the patient has only mild groin pain and nearly full or full range of hip motion, we are inclined to offer the procedure. Conversely, if this same patient reports severe hip pain with limited hip motion and a severely antalgic gait, we are more likely to recommend arthroplasty for that hip.

In our hands, core decompression alone is effective only for patients who are less than 50 years old with a stage I or stage II central lesion of dense bone (not cystic) that involves less than 20% of the femoral head. If the procedure is performed for conditions outside of these parameters, we believe that core decompression may exacerbate the already compromised vascular status of the femoral head and ultimately hasten the progression of the condition and the subchondral collapse.

Surgical Technique

Fibular Graft Harvest

With the use of tourniquet control, a straight, lateral, 15-cm longitudinal incision is made coincident with the natural sulcus between the lateral and posterior compartments of the leg. The incision is begun at least 10 cm distal to the fibular head, and it ends at least 10 cm proximal to the lateral malleolus. The peroneal muscles are reflected in an extraperiosteal fashion off of the lateral aspect of the fibula, working from posterior to anterior and stopping when the anterior intermuscular septum is visualized (Figure 31-2).

The anterior intermuscular septum is then divided to expose the anterior musculature, which is reflected bluntly off of the fibula. At this point, the interosseous membrane is easily visualized, and the adjacent anterior musculature, with its accompanying deep peroneal nerve and anterior tibial artery, is gently swept off of the interosseous membrane and away from the fibula. With the use of a specially designed right-angle beaver blade, the interosseous membrane is divided close to its fibular attachment along the entire length of the proposed fibular graft. The posterior intermuscular septum is then divided to expose the posterior muscles: the soleus proximally and the flexor hallucis longus distally.