Abstract
The management of osteonecrosis of the femoral head ranges from symptomatic therapy to total hip replacement. Conservative treatment is effective only in small, early-stage lesions. Free vascularised fibular grafting has provided more consistently successful results than any other joint-preserving method. It supports the collapsing subchondral plate by primary callus formation, reduces intra-osseous pressure, removes and replaces the necrotic segment, and adds viable cortical bone graft plus fresh cancellous graft, which has osseoinductive and osseoconductive potential. Factors predisposing to success are the aetiology, stage and size of the lesion. Furthermore, it is a hip-salvaging procedure in early pre-collapse stages, and a time-buying one when the femoral head has collapsed.
Osteonecrosis of the femoral head is a disease in which bone death usually progresses to structural failure leading to collapse of the femoral head and intractable pain. There are many causative factors, some of which are well recognised and others less widely known. Excessive steroid or alcohol use, haemoglobinopathy, Gaucher’s disease, pregnancy, hyperbaric exposure, auto-immune disease and trauma to the hip are the most commonly recognised causes.1,2
Although a century has elapsed since osteonecrosis was first described, the pathogenetic mechanisms involved in various forms of the disease are still unclear and little is known about the early pathophysiology of this puzzling condition. Various causes have been suggested including primary vascular abnormalities, fat embolism, cumulative stress, hypertrophy of fat cells, intramedullary haemorrhage and intravascular coagulation. Some causes may coexist, and rather than considering osteonecrosis as a single disease, it is now most considered to be a heterogeneous group of disorders leading to a common pathway of necrosis of the femoral head.
Treatment is currently based not on knowledge of the pathogenesis and disease prevention, but rather on the end-stage changes of the bone. Its increasing incidence in the young, often with bilateral involvement, necessitates reliable hip-salvaging procedures and the avoidance of hip replacement, which may fail due to poor biological fixation of the femoral implant. Early diagnosis before articular collapse, and hip salvage should be the treatment of choice.
This article reviews the indications, technique, results, factors influencing the outcome, and major complications of free, vascularised fibular grafting for the treatment of osteonecrosis of the femoral head. Traditional and new methods of treatment which are currently under investigation are also addressed.
Treatment alternatives
In order to delay the progress of the disease, many surgical techniques have been described. Core decompression, vascularised or non-vascularised autologous bone grafts and various osteotomies have been used.3–7 The existence of a large number of procedures suggests that none is entirely effective, and none offers predictable results. It is difficult to evaluate the efficacy of these procedures as there have been few prospective controlled studies.
The effectiveness of core decompression with or without bone grafting for structural support, performed before the articular collapse, remains controversial with unpredictable results.8 Intertrochanteric or rotational osteotomies of the proximal femur aim to move the affected areas of the femoral head away from the main weight-bearing regions of the joint.9 However, these are technically demanding procedures with inconsistent results. They often alter the gait pattern, and significantly complicate subsequent total hip replacement (THR). Recently, a proximal femoral osteotomy combined with free vascularised fibular grafting has been reported for the treatment of osteonecrosis of the femoral head caused by nonunion of a fracture of the femoral neck.10
Primary THR is an excellent option in the older patient, with collapse and deformity of the femoral head.3–11 In younger patients, however, arthroplasty with its limited life-span and increased morbidity is a poorer option.12,13 Surgical alternatives for a young patient with a large osteonecrotic lesion are limited to femoral resurfacing arthroplasty and bipolar hemiarthroplasty. Candidates for these procedures are patients with Ficat stage 3 disease, a change in femoral head contour of more than 2 mm, normal acetabular cartilage, and a combined necrotic angle of more than 200° or more than 30% involvement.14
The porous tantalum implant procedure is a minimally invasive technique with no associated donor-site morbidity and few major device-related complications. It is indicated mainly for the management of early-stage osteonecrosis of the femoral head in patients who do not have chronic systemic disease.15 However, large series with longer follow-up periods are needed to determine its clinical value.
Biological agents which promote neoangiogenesis, such as vascular endothelial growth factor (VEGF) to preserve the femoral head from osteonecrosis, are under investigation. In order to promote neoangiogenesis in an animal model of osteonecrosis, Yang et al16 introduced recombinant plasmid pCD-hVEGF165 mixed with collagen through a drill hole in the osteonecrotic lesion. New bone formation was observed six and eight weeks after transfection with the VEGF gene. The implantation of autologous bone-marrow mononuclear cells into the lesion area in patients with early-stage disease also showed promising results.17
Free vascularised fibular graft
The use of free bone grafts has been extensively reported, but the results were not encouraging, probably because the grafted bone does not revascularise.18 Since Meyers19 first described a muscle pedicle graft technique for the treatment of osteonecrosis of the femoral head, many salvage procedures using pedicled bone grafts have been proposed.
With the advances in microsurgery during the last 30 years, free vascularised fibular grafts have increasingly been used in an attempt to salvage the necrotic femoral head.1 The presence of a symptomatic stage 2 to stage 4 lesion in a patient younger than 50 years of age is the main indication for fibular grafting. Narrowing of the joint space and acetabular involvement are contraindications to surgery which is designed to preserve the femoral head. Collapse of the femoral head and depression of more than 2 mm are relative contraindications for a free vascularised fibular graft.
A vascularised fibular graft can provide suitable length and substantial cortical support, and is relatively easy to harvest. The fibula, with its large peroneal vascular pedicle, nutrient artery and periosteal blood supply, became a favoured source of vascularised bone.20 With the nutrient blood supply preserved, osteocytes and osteoblasts within the graft can survive, and incorporation of the graft to the recipient bone is facilitated without the usual replacement of the graft by creeping substitution. The viability of the vascularised fibula is particularly important in the grafting of the osteonecrotic femoral head, as the subchondral bone is itself necrotic and cannot contribute to union. Thus, the rich vascularity and biological potential of this graft allows callus formation from the deliberately exposed cortex and the periosteal cambial layer of the cephalad end of the graft to the cancellous bone and the remaining subchondral bone of the osteonecrotic femoral head.
Operative technique.
A modification of the operative procedure described by Urbaniak21 and Aldridge et al22 is usually used. With the patient in the lateral decubitus position, the affected hip is exposed through a curved anterolateral incision. An interval is created between tensor fascia lata and gluteus medius, followed by dissection between the rectus femoris and the vastus intermedius. The lateral aspect of the proximal femur is exposed and the ascending branch of the lateral circumflex artery, with its two accompanying veins, is prepared for the anastomosis with the peroneal vessel pedicle of the fibula.
The ipsilateral fibula is exposed through a lateral incision, by a second surgical team working simultaneously. The middle third of the fibula, containing the nutrient vessels, is harvested (Fig. 1). The length of the fibular graft is based on the diameter of the femoral head. The amount of the fibula that is harvested is calculated intra-operatively with fluoroscopic help.
A Steinmann pin is passed into the osteonecrotic lesion under fluoroscopic control and a cylindrical tunnel 16 mm to 19 mm in diameter is made by progressive reaming to a distance of 5 mm from the articular surface. Necrotic bone is then removed under fluoroscopic guidance using a long curette. Cancellous bone from the reaming procedure is packed into the cavity created by the removed necrotic bone. The periosteum of the end of the fibular graft to be implanted is reflected and sutured. The graft is inserted into the cylindrical tunnel within the femoral head. Correct placement is confirmed fluoroscopically (Fig. 2). The graft is stabilised using a 1.5 mm Kirschner (K−)wire. Microsurgical techniques are used for end-to-end anastomoses of the artery and vein (Fig. 3).
Precise placement of the graft in the centre of the lesion and within 3 mm to 5 mm of the subchondral plate is necessary for optimal results.23 A computer-assisted system has been used by the authors for several years to optimise the length and position of the fibular graft within the femoral head.23 A three-dimensional (3D) reconstruction of the hip is created after computerised analysis of CT images. Slices of 1 mm thickness every 3 mm from the articular surface of the femoral head to the lesser trochanter are reconstructed to produce a 3D model of the proximal femur, the necrotic area and the optimal canal within the femoral head. Using these parameters, a custom-made aluminium alloy targeting device is manufactured. The personalised aiming device is designed to match exactly the lateral surface of the lesser trochanter, and a drill hole of 2 mm diameter for guiding the K-wires ensures the placement of the fibular graft in the ideal position. The lateral surface of the proximal femur is prepared carefully, so that the aiming device can be locked firmly to the outer surface of the greater trochanter. Therefore, most of the musculotendinous origin of the vastus lateralis with its periosteum is retracted. Once the aiming device is placed in the correct position, a guiding K-wire is introduced through the pre-made canal. The ideal position of the guide wire is confirmed fluoroscopically, and the aiming device is removed to allow for drilling a cylindrical tunnel.
Non-weight-bearing mobilisation starts on the second postoperative day and continues for six weeks and then weight-bearing increases gradually until full weight-bearing at six months. Follow-up clinical and radiographic examinations are performed at three and six months, and yearly thereafter.
Data analysis.
Data analysis has shown good to excellent results.6 It is now generally agreed that osteonecrosis of the femoral head can be arrested in most patients if the procedure is performed before the development of a subchondral fracture6 (stage 1 and 2, Steinberg classification24) (Fig. 4). The results are more unpredictable when there is collapse of the femoral head.25 In stage 3, fibular grafts may arrest or delay the progression of the disease.25 Even in patients with advanced osteonecrosis, including those with collapse of the articular surface, free vascularised fibular grafting may provide symptomatic relief and postpone the requirement for THR.25–27
Urbaniak et al28 described 224 patients with osteonecrosis of the femoral head treated with free vascularised fibular grafting with a follow-up period of between 4.5 and 12.2 years. The classification of the disease ranged from stage 2 to stage 5, according to the modified Marcus-Enneking system.29 They reported a probability of conversion to THR within five years after the primary procedure of 11% for the stage 2 hips, 23% for the stage 3 hips, 29% for the stage 4 hips, and 27% for the stage 5 hips. In another study, Urbaniak and Harvey30 described an 83% survival of the fibular graft in 646 procedures after follow-up ranging from one to 17 years.
Soucacos et al6 described 228 hips in 187 patients who underwent grafting for osteonecrosis of the femoral head, of which 184 were assessed at a mean follow-up of 4.7 years using the Steinberg classification system. A total of 101 hips (55%) did not progress, 69 (38%) had progression, and 14 (8%) were converted to THR. Results were significantly better for patients in stage 2 than for those in stage 5. In particular, 95% of the hips with stage 2 osteonecrosis did not progress, whereas only 39% of the hips in stage 5 remained stable. None of the hips with stage 2 lesions underwent conversion to THR. In contrast, 2% of the hips with stage 3, 12% of those with stage 4, and 17% of those with stage 5 osteonecrosis underwent conversion to THR.
In a study by Yoo, Chung and Hahn31 in 121 patients treated with vascularised fibular grafting with a follow-up ranging from three to 10 years, good or excellent results were seen in 91%. The overall satisfactory outcome was similar (90%) in a study conducted by Sotereanos, Plakseychuk and Rubash32 who reported conversion to THR in 23% of hips after a mean of five years. Marciniak, Furey and Shuffer33 assessed 101 hips treated with vascularised fibular grafting which were followed for a minimum of five years when the survival rate for Markus-Enneking stage 2, 3 and 4 hips was 57%, 70%, and 59%, respectively.
Plakseychuk et al,34 in an attempt to compare vascularised with non-vascularised fibular grafting for the management of osteonecrosis of the femoral head, presented 220 hips treated by vascularised grafting with a minimum follow-up of three years. In patients with pre-collapse stages 1 and 2, the rate of survival of the femoral head at seven years was 86%. Similar results were observed in a review of 1303 vascularised fibular grafts performed at seven centres with a minimum follow-up of two years.26 The survival rate for patients who were treated before collapse of the femoral head was 88%.
Vascularised fibular grafting provides the most consistently successful results14 of any joint-preserving methods, such as core decompression, conventional bone grafting and osteotomy. In patients who are operated on in a pre-collapse stage, there is complete functional recovery and relief of pain.6,28 In severely affected hips, there is relief of pain and increased function despite the gradual development of radiographic changes of osteoarthritis.35 Although some hips eventually require conversion to arthroplasty, the authors believe that the method should be used as a hip-salvaging procedure, even in advanced stages in patients under 30 years of age.
The success of the procedure may be due to: (1) decompression of the femoral head, which may halt the ischaemia caused by increased intraosseous pressure; (2) excision of the necrotic bone beneath the weight-bearing region that might inhibit revascularisation of the femoral head; (3) buttressing of the articular surface with the vascularised graft by primary callus formation, augmented by cancellous bone graft, which has osseoinductive and osseoconductive factors; and (4) protection of the healing construct by a period of limited weight-bearing.
The technique of free vascularised fibular grafting does not violate the joint capsule as other bone grafting procedures such as pedicled iliac crest and quadratus femoris pedicle grafts do. It has an advantage over non-vascularised autogenous grafts as it supports the subchondral surface with a viable cortical strut and enhances the revascularisation and osteogenesis of the femoral head.36 Furthermore, it is a hip-salvaging procedure in the early stages, and a time-buying procedure in minimally collapsed femoral heads. Additionally, ultimate conversion to a THR in a patient previously treated by free vascularised fibular grafting is not difficult.
Factors influencing the outcome
Various factors influence the success of free vascularised fibular grafting.6 These include the aetiology of the necrosis, the stage of the disease and the size of the necrotic segment.
The stage of the disease is an important prognostic factor in the outcome of free vascularised fibular grafting and treatment in the early pre-collapse stages has been associated with improved outcome.6,25,26,32 Patients with post-collapse, pre-degenerative osteonecrosis of the femoral head benefit from vascularised fibular grafting.6,37 In a study of 224 free vascularised fibular grafts performed in 189 patients with post-collapse, pre-degenerative osteonecrosis, the overall survival rate was 67.4% at an average of 4.3 years post-operatively.37 Likewise, Soucacos et al6 reported a survival rate of 88% in hips with Steinberg stage 4 and 98% of hips with stage 3 lesions of the femoral head. Based on their data, the authors suggested that free fibular grafting is a valuable means of postponing THR in the majority of patients with stage 3 or 4 disease.
Both clinical outcome and survival of the femoral head appear to benefit from vascularised fibular grafting, even in post-collapse stages. According to Berend et al,25 the amount of flattening or pre-operative linear collapse does not significantly affect survival or functional outcome. The negative effect of pre-operative femoral head collapse may be diminished by reduction of the collapsed segment intra-operatively and support with the vascularised fibular graft. Conversely, Marciniak et al33 observed more encouraging results for stage 3 and 4 lesions than for stage 2 disease. They suggested that there is no relationship between the initial radiographic stage of the disease and the functional outcome or the rate of graft survival. In order to improve function, relieve pain and maintain options for secondary procedures in patients with advanced stages of osteonecrosis, the aetiology of osteonecrosis, the patient’s age, the size of the osteonecrotic segment and the condition of the acetabular articular cartilage should all be considered.
Although the aetiology of osteonecrosis remains elusive, it is related to outcome of treatment by vascularised fibular grafting. Idiopathic and alcohol-related osteonecrosis of the femoral head has a worse prognosis than steroid-induced necrosis, or necrosis secondary to pregnancy, infection, slipped capital femoral epiphysis or Legg-Calvé-Perthes’ disease.25 According to the same study, post-traumatic osteonecrosis is associated with an intermediate relative risk of fibular graft failure and conversion to THR.25 Moreover, patients with osteonecrosis secondary to treatment of neoplasia or renal transplantation are relatively poor candidates for vascularised fibular grafting. Although the pathogenesis of osteonecrosis has recently been associated with thrombophilia and hypofibrinolysis, there is no current evidence that increased intravascular coagulation results in poor outcome after femoral head-preserving surgery.37,38
Some authors have emphasised that both survival of the hip after grafting and clinical outcome are strongly related to the size of the necrotic area.32,39 However, according to a recent study, although larger lesions have an increased risk of conversion to THR, the size of the lesion does not directly affect survival of the hip after free vascularised fibular grafting.25 After femoral head-preserving surgery, survival of the hip may not be completely predicted by the size of the necrotic segment alone, but rather by the combination of the size, the aetiology of the osteonecrosis, and the linear femoral head collapse.25 Moreover, in contrast to Steinberg et al,39 who noticed better clinical results in patients with smaller necrotic lesions, Berend et al25 found that although pre-operative clinical symptoms were directly related to the size of the lesion, significant clinical improvement should be expected after free vascularised grafting, regardless of the size of the necrotic area.
Furthermore, the location of the femoral head lesion may affect the prognosis after free vascularised fibular grafting, especially for lesions involving the weight-bearing area. In order to surgically overcome the effect of the lesion site as the outcome, Beris and Soucacos23 showed that precise placement of the graft to support the subchondral plate mechanically might be the most important factor in deterring subchondral collapse.
Although success or failure of the free vascularised fibular graft procedure has been more closely correlated with the size of the lesion and the amount of collapse of the femoral head, the patient’s demographic factors should also be considered when formulating a treatment plan. Age, general health status, activity level, the range of movement of the hip and comorbidities appear to influence the functional outcome. The duration of symptoms has been found to correlate with the outcome in patients who have received core decompression or hemi-resurfacing of the femoral head.40,41 However, the relationship between the duration of symptoms and outcome has not been evaluated in patients undergoing vascularised fibular grafting.
Although the prognosis after preservative surgery for osteonecrosis of the femoral head is affected primarily by factors related to the stage of the necrosis, the orientation of the acetabulum may influence the outcome42 as it influences the contact stresses about the hip.43 Therefore, less than optimal acetabular cover, as seen in patients with developmental dysplasia, is correlated with higher stresses on the femoral head and an increased incidence of adverse outcomes, including progression of femoral head collapse or conversion to THR. Periacetabular osteotomy combined with free vascularised fibular grafting may be the treatment of choice in osteonecrosis of the femoral head in dysplastic hips.
Complications
Free vascularised fibular grafting has become a standard surgical technique. However, complications are often underestimated, especially when the fibula is harvested. Free vascularised fibular grafting for osteonecrosis of the femoral head has been associated with proximal femoral fracture, prolonged rehabilitation, and donor-site morbidity, including sensory abnormalities, motor weakness and ankle pain.44,45
In maxillofacial reconstruction, approximately 25 cm of fibula can be harvested, leaving remnants of bone proximally and distally. These remnants do not provide stability, especially at the ankle. For osteonecrosis of the femoral head only 12 cm to 15 cm of fibula is resected and the distal osteotomy is at least 10 cm above the lateral malleolus, ensuring stability.46
Garrett et al47 reported that 42.9% of patients had difficulty walking on uneven terrain, stairs or inclines following free vascularised fibular grafting, and 7.1% had limitation of flexion of the ankle. Bodde et al44 reported that 60% of patients had pain, 50% dysaesthesia, 30% a feeling of instability of the ankle, and 20% could not run.
Zimmermann et al45 reported a 38.1% rate of wound healing complications after free vascularised fibular grafting in cancer patients and major healing complications have been reported in patients with cancer, systemic lupus erythematosus, tobacco use and alcohol consumption.48,49 Wound breakdown at the donor site is rare in patients treated for osteonecrosis of the femoral head.
A flexion contracture of flexor hallucis longus has also been reported as a minor complication after fibular harvesting.44,49 It has been seen in less than 3% of our patients, and can be treated by ‘Z’ lengthening of the flexor hallucis longus at the level of the ankle joint.6
Conclusions
The management of osteonecrosis ranges from symptomatic pain relief to THR. The current hip-preserving strategies are effective in early-stage small lesions and thus early diagnosis and accurate identification of the extent and localisation of the lesion is essential. Although there is as yet no consistently satisfactory method of treatment for osteonecrosis of the femoral head, the salvage technique of free vascularised fibular grafting has been more successful than any other procedure short of THR. It supports the collapsing subchondral plate, reduces intra-osseous pressure and replaces the necrotic segment, and, with fresh additional cancellous bone graft augments revascularisation and neo-osteogenesis of the femoral head.
Fig. 1
The tip of the forceps indicates the origin of the peroneal vessel pedicle. At this stage the tourniquet is deflated and the graft remains in situ until the preparation of the hip has proceeded.
Fig. 2
The correct placement of the fibular graft is confirmed intra-operatively with the image intensifier.
Fig. 3
End-to-end microvascular anastomoses between the ascending branch of the lateral femoral circumflex artery (arrow) and the concomitant vein (arrowhead) and the peroneal vessels are performed using 8-0 interrupted nylon sutures.
Fig. 4a, Fig. 4b, Fig. 4c
a) Pre-operative radiograph of a 31-year-old man with Steinberg stage 2 osteonecrosis of the left femoral head secondary to alcohol abuse. b) Postoperative radiograph obtained at four months shows adequate placement of the fibular graft. c) A radiograph taken 16 years after the operation showing no progression of the disease. The joint space is preserved and the patient remains asymptomatic.
References
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