Medical Care
Medical management of avascular necrosis (AVN) primarily depends on the location and severity of disease, as well as the patient's age and general health. Treatment outcomes correlate directly with the stage of the disease. No medical treatment has proven effective in preventing or arresting the disease process.
Conservative measures include limited weight bearing with crutches, and pain medications. This may be beneficial and is a reasonable initial course of action if the involved segment is smaller than 15% and far from the weight-bearing region. Immobilization may be helpful in some cases (eg, AVN of the distal femur or tibia). In advanced AVN, the disease course is unaffected by activity and will eventually require surgery.
Treatment with bisphosphonates may be helpful. Although large-scale, randomized, double-blind studies have not been performed, a systematic review of eight articles involving 788 hips suggested that alendronate has short-term efficacy in reducing pain, improving articular function, slowing of bone collapse progression, and delaying the need for total hip arthroplasty in adults with AVN. [32]
Iloprost, a vasoactive prostaglandin analog that is approved for inhalational treatment of pulmonary hypertension, has shown clinical and radiographic benefits in early-stage AVN when administered intravenously. Iloprost produces vasodilation and increases microcirculation, reducing bone marrow edema and relieving pain and other accompanying symptoms; it inhibits platelet aggregation and diminishes the concentration of oxygen free radicals and leukotrienes. [33, 34]
Statin therapy to prevent corticosteroid-induced AVN may be helpful. Pritchett reported a 1% incidence of AVN in 284 patients who were on statin therapy during the entire period of corticosteroid treatment (average, 7.5 y). [35]
Extracorporeal shockwave therapy (ESWT) has shown beneficial effects in early AVN of the femoral head. ESWT may relieve pain and improve hip function of the hip, and induce regression of AVN. [36, 37] ESWT may be combined with alendronate therapy. [32]
Hyperbaric oxygen therapy (HBOT) has demonstrated beneficial effects in early AVN of the femoral head, leading to a reduction in self-reported pain scores, localized edema, and lesion size on radiographic imaging. [38, 39] The efficay of HBOT may result from modulation of inflammatory markers and reactive oxygen species. HBOT has also proved useful in treatment of osteonecrosis of the jaw. [40, 41]
Surgical Care
Several surgical procedures have been used in an attempt to treat AVN, with variable success. No surgical procedure is the consensual best among surgeons in the treatment of AVN. In early stages of AVN (precollapse), core decompression with or without bone graft is typically considered the most appropriate treatment. In late stages, characterized by collapse, femoral head deformity, and secondary osteoarthritis, total hip arthroplasty is the most appropriate treatment.
Core decompression
Researchers postulate that core decompression improves circulation by decreasing intramedullary pressure and preventing further ischemia and progressive joint destruction. The best results vary from 34-95%, which is significantly better than results of conservative treatment. [42] The best results are obtained when treating patients with early AVN (precollapse). Core decompression is also effective for pain control.
Bone graft
Bone graft options include structural cortical or medullary bone graft and vascularized bone graft with either a muscle-pedicle bone graft or free vascularized fibular graft. [43]
Bone grafting is combined with the following:
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Core decompression, which may interrupt the cycle of ischemia
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Excision of sequestrum, which may inhibit revascularization of the femoral head
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Period of limited weight bearing
The best results have been reported with free vascularized bone grafts. Success rates of 70% and 91% have been reported in two small series. [44, 45]
Advantages of free vascularized grafts compared with total hip arthroplasty include the following:
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Healed femoral head may allow more activity
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No foreign body–associated complications occur
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If performed during early AVN, lifelong survival of the femoral head is possible
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The patient has the option of total hip arthroplasty in the future
Disadvantages of free vascularized grafts include the following:
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Longer period of recovery
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Less complete pain relief
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Variable success rate
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Lack of effectiveness in advanced disease
In a review of bone grafting through a window at the femoral head-neck junction, Zuo et al found that factors predicting good clinical success were absence of femoral head collapse or degree of collapse < 2 mm (Association Research Circulation Osseous [ARCO] stage IIIa). Surgical failure rates were high in patients with femoral head collapse > 2 mm (ARCO stage IIIb and IIIc) and in those with necrotic lesions involving the lateral pillar (L2 and L3 type). Finally, patients 40 years of age and older had a worse prognosis than those younger than 40. [46]
Osteotomy
Several osteotomy procedures have been tried with variable success.
Intertrochanteric osteotomies have been performed in patients with posttraumatic AVN.
Transtrochanteric rotational osteotomy involves rotation of the femoral head and neck on the longitudinal axis. The necrotic anterosuperior part of the femoral head becomes posterior, and the weight-bearing force is transmitted to what was previously the posterior articular surface, which is not involved in the ischemic process. In 1992, Sugano and colleagues reported excellent results in 56% of patients who underwent this procedure. [47] Transtrochanteric rotational osteotomy is technically demanding.
Total hip arthroplasty
Most patients with advanced disease (stage III and above) require total hip arthroplasty. Total hip arthroplasty provides excellent pain relief for many years, although most young patients require repeat surgery. With high failure rates (10-50% after 5 years), patients with AVN will probably need a second total hip arthroplasty during their lifetime. [48]
Cheung et al reported excellent long-term survival of cementless total hip arthroplasty for managing AVN of the hip. In their review of 182 total hip arthroplasties, 117 of them for AVN, 19.1- year survival was 97.1% for AVN patients and 96.2% for non-AVN patients. [49]
Cell therapy
The use of stem cells implanted via core decompression has been studied for the treatment of early-stage (precollapse) AVN of the femoral head. [50, 51, 52, 53] For example, Pilge et al reported benefit with the application of autologous bone marrow concentrate, derived from iliac crest aspirates. In this study, compared with core decompression alone, the addition of bone marrow stem cells seemed to decrease pain and other joint symptoms, improve range of motion, and prevent collapse of the femoral head. [34]
Hernigou et al reported superior long-term outcome with core decompression plus bone marrow injection compared with decompression alone in the same patient. Their study included 125 consecutive patients (78 males and 47 females) with bilateral corticosteroid-induced AVN. [54]
All patients had AVN at the same stage in both sides (stage I or II); the hip with lower volume of osteonecrosis, as measured with MRI, was treated with core decompression, and the contralateral hip was treated with decompression and percutaneous injection of mesenchymal cells (MSCs) obtained from bone marrow concentration. The average total number of MSCs (counted as number of colony-forming units–fibroblast) in each injection was 90,000 ± 25,000 cells (range, 45,000 to 180,000 cells). [54]
On follow-up conducted an average 25 years after the first surgery (range 20 to 30 years), 35 hips (28%) treated with cell therapy had collapsed, compared with 90 (72%) treated with decompression only. Total hip arthroplasty had been performed in 30 hips (24%) in the cell therapy group, versus 95 (76%) in the decompression-only group (P < 0.0001). [54]
Houdek et al reported beneficial results from injecting the combination of bone marrow–derived mesenchymal stem cells and platelet-rich plasma into the femoral head after standard hip decompression in patients with corticosteroid-induced AVN. In their preliminary study of 35 hips in 22 patients, use of this technique improved pain and function, and more than 90% of femoral heads had not collapsed at a minimum of 2 years. [55]
Systematic reviews of studies with patient-reported outcomes have demonstrated clinical benefit with the use of stem cells for hip AVN, with a low rate of complications, but have highlighted the lack of standardization with this technique. Comparisons across studies have been complicated by differences in etiology and severity of AVN, cell sources and doses, adjuvant therapies used, and outcome assessment methodology. [51, 52]
Although the assumption is that the injected stem cells are taken up and differentiate into osteoblasts, Im points out that the survival of stem cells implanted into the hip has not been studied. In other organs, tracking studies have shown that injected or implanted stem cells usually exert paracrine effects and then largely die off. Measures to improve stem cell survival by enhancing the vascularity and osteogenic potential of the treatment site are currently under study, and include use of adipose stem cells and the addition of angiogenic factors, such as vascular endothelial growth factor (VEGF). [56]
Autologous platelet-rich plasma has been used in conjunction with core decompression in early-stage AVN of the femoral head. A systematic review concluded that adjunctive platelet-rich plasma improves the efficacy of core decompressoin in these patients, especially when combined with stem cells and bone grafts, by inducing osteogenic activity and stimulating the differentiation of stem cells in necrotic lesions. [57]
Other sites
AVN of the femoral condyles (knees) may respond to more conservative intervention such as arthroscopic lavage and debridement. AVN of the femoral condyles has a better prognosis than hip AVN, although osteoarthritis eventually develops.
In a study of 25 patients with 29 shoulders treated with arthroplasty for humeral head AVN, Ristow et al reported that both total shoulder arthroplasty and hemiarthroplasty are safe and effective treatments, regardless of etiology and radiographic staging. At a mean follow-up of 3.9 years (range, 1-8.5 years), all patients who underwent operative intervention showed statistically significant improvement in measurements of functionality. [58]
Consultations
Obtain consultation with an orthopedic surgeon. Early intervention can save affected joints and obviate the need for joint replacement.
Activity
In early AVN, patients should use crutches or other supports to avoid weight bearing. In advanced AVN, the disease course is unaffected by activity; surgery is the only option.
Prevention
The following precautions can be taken to minimize the risk of developing avascular necrosis (AVN) and to improve outcomes in these patients:
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Use the minimum effective dose of systemic corticosteroids; when possible, use steroid-sparing agents
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Early diagnosis and treatment are important; the earlier AVN is detected, the more treatment (and less invasive) options available to the patient
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Provide patient education for high-risk patients
For patients undergoing pelvic radiotherapy, a variety of pharmacological interventions for preventing AVN have been studied, including supplemental calcium and/or vitamin D, bisphosphonates, selective estrogen receptor modulators, hormone replacement therapy (estrogen or testosterone), denosumab, and calcitonin. However, a Cochrane review concluded that the evidence relating to those interventions is of very low certainty. [59]
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Avascular necrosis in the femoral head resulting from corticosteroid therapy.
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Avascular necrosis of the shoulder showing subchondral radiolucent lines (crescent sign).
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Avascular necrosis of both femoral heads. This T1-weighted image shows decreased signal intensity in both femoral heads.
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MRI of the distal femur and proximal tibia. This T2-weighted image shows increased signal intensity in the marrow.
Tables
Stage |
Clinical and Laboratory Findings |
Stage 0 |
Patient is asymptomatic. Radiography findings are normal. Histology findings demonstrate osteonecrosis. |
Stage I |
Patient may or may not be symptomatic. Radiography and CT scan findings are unremarkable. AVN is considered likely based on MRI and bone scan results (may be subclassified by extent of involvement [see below]). Histology findings are abnormal. |
Stage II |
Patient is symptomatic. Plain radiography findings are abnormal and include osteopenia, osteosclerosis, or cysts. Subchondral radiolucency is absent. MRI findings are diagnostic. |
Stage III |
Patient is symptomatic. Radiographic findings include subchondral lucency (crescent sign) and subchondral collapse. Shape of the femoral head is generally preserved on radiographs and CT scans. Subclassification depends on the extent of crescent, as follows:
|
Stage IV |
Flattening or collapse of femoral head is present. Joint space may be irregular. CT scanning is more sensitive than radiography. Subclassification depends on the extent of collapsed surface, as follows:
|
Stage V |
Radiography findings include narrowing of the joint space, osteoarthritis with sclerosis of acetabulum, and marginal osteophytes. |
Stage VI |
Findings include extensive destruction of the femoral head and joint. |
