Femoral head necrosis, also known as ischemic necrosis of the femoral head, is a pathological process resulting from disruption of the blood supply to the bone. Each year, more than 500,000 patients worldwide undergo total hip replacement, 5 to 18 percent of which are due to femoral head necrosis. Femoral head necrosis has many causes and is associated with genetic factors and certain extrinsic risk factors. Fractures of the femoral neck and dislocation of the hip joint can destroy the main nutrient vessels of the femoral head, and increased intracapsular pressure due to hematoma in the joint capsule can lead to osteonecrosis of the femoral head.
The use of corticosteroids is the most common risk factor for femoral head necrosis, accounting for 10-30% of all cases. Koo found that the total dosage from the start of prednisone use to MRI findings of femoral head necrosis ranged from 1,800 to 15,500 mg (mean 5,928 mg) or its equivalent. The time from initiation of hormone use to diagnosis of femoral head necrosis generally ranges from 1 to 16 months (mean 5.3 months), with most patients diagnosed within 12 months of hormone use.
Excessive alcohol intake has been shown to be a cause of osteonecrosis of the femoral head. A prospective study showed a 9.8-fold increase in the risk of osteonecrosis with an alcohol intake >400 ml per week. Occasional drinkers (< 8 ml per week and not daily) and regular drinkers (8 ml per day) had a higher risk of osteonecrosis compared to those who never drank alcohol. A significant dose-response relationship between femoral head necrosis and alcohol intake was found, with relative risks of 2.8, 9.4, and 14.8 for those who consumed <320g, 320-799g, and 800g of alcohol per week, respectively.
Smoking is also a risk factor for osteonecrosis of the femur. Hirota et al. found that smoking increased the incidence of osteonecrosis of the femur, but the evidence suggests that it took more than 20 pack-years of smoking (packs per day * years of smoking) for a cumulative effect to occur.
Several hemoglobinopathies including hemoglobin SS (sickle cell disease), hemoglobin SC and thalassemia are associated with osteonecrosis of the femoral head. The incidence of femoral head necrosis in these populations ranges from 4% to 20%, and studies have shown an association with a hypercoagulable and hypofibrinolytic state of the patient’s blood.
HIV-infected patients are also at increased risk of osteonecrosis. However, it is still unclear whether the cause is the virus or the medication used for treatment. Recent studies have suggested that osteonecrosis of the femoral head may also be an autosomal dominant disorder, with chromosomal localization of a mutation in a type II collagen gene (COL2A1 gene). Certain genetic polymorphisms have also been found to be associated with femoral head necrosis, such as alcohol metabolizing enzymes and the drug transport protein P-glycoprotein. glueck found that endothelial cell nitrogen oxide synthase polymorphisms may be associated with idiopathic osteonecrosis. The importance of these studies is to genetically screen families of patients with osteonecrosis of the femoral head, identify gene carriers, and take steps to slow disease progression.
Staging or grading
The success of treatment of osteonecrosis of the femoral head is directly related to the stage of the disease, so it is important to use reliable staging. There are many staging systems for osteonecrosis of the femoral head, but there is no standardized staging system to assess the extent and location of osteonecrosis of the femoral head. Currently, the commonly used ones are Ficat staging, ARCO staging, Steinberg staging, Pittsburg staging and so on.
Each staging system has its limitations and is difficult to be universally accepted to guide treatment individually. Most orthopedic surgeons plan treatment by four basic x-ray presentations: whether the femoral head is collapsed; the size of the necrotic portion; the degree of femoral head collapse; and whether the acetabulum is involved with osteoarthritic manifestations.
Treatment methods
Non-surgical treatment
Non-surgical treatment methods include weight restriction, medication and various in vitro biophysical treatments, which are generally less effective.
Weight restriction slows the progression of the disease. Femoral head collapse eventually occurs in more than 85% of cases, and only small lesions limited to the interior of the femoral head may be effective.
Drugs currently reported for the treatment of femoral head necrosis include statins (lipid-lowering drugs), pro-protein-synthesizing steroids (stanozolol), low-molecular-weight heparin, prostacyclin derivatives (iloprost), bisphosphonates, and pro-adrenocorticosteroids.
Other controversial treatments such as electromagnetic stimulation, extracorporeal shock wave and hyperbaric oxygen therapy are also available.
Surgical treatment
Medullary decompression: This is the most commonly used surgical procedure for early stage femoral head necrosis. The aim is to reduce the pressure in the femoral head and restore normal blood supply to relieve hip pain.
In a prospective randomized controlled study, Stulberg treated 55 cases of femoral head necrosis with core decompression alone. According to the Harris score, the power of the surgical group for femoral head necrosis (Ficat stages I, II, and III) was about 70%, and that of the non-surgical group was only 20%.
Hernigou and Beaujean used marrow core decompression combined with autologous bone marrow cell transplantation to treat pre-collapse femoral head necrosis with a success rate of 94%. cui used a genetic marker technique to demonstrate direct osteogenesis by injecting ex vivo expanded bone marrow stem cells into the osteonecrosis site. Lieberman reported the use of osteogenic protein to treat 17 cases of osteonecrosis of the femoral head, with success in 14 cases and no patients requiring total hip arthroplasty.
Free avascular fibula graft: The use of avascular bone graft in the treatment of osteonecrosis of the femoral head can prevent femoral head collapse and promote vascularization of the necrotic area. The use of free vascularized fibular grafts is a reasonable option for the treatment of patients <50 years of age with osteonecrosis without femoral head collapse. However, its use in the treatment of patients with already collapsed femoral head necrosis is currently controversial. In order to avoid arthroplasty, a vascularized fibular graft may still be a treatment option for patients under 20 years of age with 2-3 mm of collapse and acetabular involvement.
To obtain the optimal placement of the graft, the Ioannina technique uses continuous CT scanning to determine the proximal femoral profile and the location, extent, and morphology of the necrotic area, and the implant is completed with a specially designed positioning device. Investigators have reported that only 55% of conventional fibular grafts are placed randomly in the desired position, while 89% can be achieved with the special Ioannina positioning device.
Many research centers have reported successful cases treated with free vascularized fibula grafts, with 10-year survival rates ranging from 74% to 82%. Patients who have collapsed preoperatively have a poorer prognosis, and the percentage of patients requiring total hip replacement ranges from 13 to 28%.
Bone grafting without blood vessels: Bone grafting without blood vessels is theoretically advantageous in the treatment of patients with pre-collapse and early collapse with relatively intact articular cartilage. There is no consensus on the indications for non-vascular bone grafting. Most scholars recommend this approach for patients with femoral head collapse <2 mm or failed medullary core decompression surgery and no acetabular involvement. Some authors have reported good results with this approach in patients with collapsed femoral head necrosis, but the number of cases is small. However, with further research on growth factors and different bone graft substitutes, the indications for this procedure may be relaxed in the future.
Osteotomy: Osteotomy is the removal of the necrotic portion from the weight-bearing area. One study reported a success rate of 78% in 474 patients treated with rotational osteotomy. The patients with higher success rates were mainly those with early-stage femoral head necrosis (89%, 73%, and 70% for stages II, III, and IV, respectively) and those with less extensive necrosis. The success rate was 93% for patients with less than 1/3 of the articular surface involved; and 64% for patients with more than 1/3 of the surface involved. Angular osteotomy is more effective in patients who are younger, more active, not taking hormones, have a single hip lesion, have a smaller lesion, and have good preoperative hip motion and no femoral head collapse.
Tantalum rods: Tantalum rods are a biomaterial with unique physical and mechanical properties and high porosity (>80%), which facilitates rapid and safe bone ingrowth.Tsao et al. reported the same or even better early clinical results with tantalum rods for femoral head necrosis compared with medullary core decompression and fibula graft with vascularization (92% success rate at 4 years of follow-up).
Total hip arthroplasty: Total hip arthroplasty is an effective treatment modality for ischemic necrosis of the femoral head in Ficat stage III and IV. Diseases associated with the underlying femoral head necrosis have an impact on prosthetic longevity, and hormone use, alcohol abuse, systemic lupus erythematosus, and organ transplantation have a negative impact on prosthetic longevity.
Success rates for cemented and uncemented total hip arthroplasty vary from study to study, but there is general agreement that: cemented prostheses are prone to postoperative loosening; uncemented prostheses are prone to polyethylene wear and periprosthetic osteolysis.
The advent of modified polyethylene as well as other types of articular surfaces (ceramic-to-polyethylene, ceramic-to-ceramic, metal-to-metal) has reduced or even eliminated the production of polyethylene particles, but has produced ceramic and metal particles.
Femoral head surface replacement: Ficat stage III, necrotic angle >200. or femoral head necrosis more than 30% in extent, collapse >2 mm, and no destruction of acetabular cartilage detected as indications for femoral head surface replacement.
In general, satisfactory results are still available 10 years after surface replacement. However, a small number of recent studies have shown a 3-year prosthetic survival rate of only 75.9%.
Hemiarthroplasty: The success rate of hemiarthroplasty for femoral head necrosis has been reported in the literature to vary. Complications of this procedure are more frequent, mainly loosening of the femoral prosthesis, wear and tear invagination of the acetabulum, osteolysis and polyethylene wear, with a failure rate of 42% as shown by X-rays.
Treatment principles
The following should be the main considerations when developing a treatment plan for a patient with femoral head necrosis: the patient’s age, activity level, general physical condition, coexisting diseases, and life expectancy. The surgeon’s surgical proficiency is also a factor to be considered when choosing a treatment option. Different treatment methods are appropriate for different stages of femoral head necrosis.
Physical examination assesses pain, claudication and limitation of activity to determine the extent of hip pathology. Patients with systemic disease or short life expectancy should avoid major surgery. Patients with complex disease are better suited for definitive surgery (total hip replacement) rather than other palliative treatments. Studies have found that the duration of symptoms affects the outcome of head-preserving treatment. In a study of 45 patients with Ficat stages I-II who underwent percutaneous multiple fine-needle medullary decompression, the success rate was higher in patients with preoperative symptoms lasting 6 months than in those with symptoms lasting 11 months. beaulé et al. compared the results of femoral head surface replacement in patients with preoperative symptoms <12 months versus >12 months, with the former having a better prognosis.
In conclusion, patients with asymptomatic pre-collapse femoral head necrosis are more suitable for pharmacological or biophysical treatment. In slightly advanced cases where the articular cartilage has not yet separated, osteotomy or bone grafting combined with bone marrow stem cell transplantation to promote repair of the necrotic area, or tantalum rod implantation, may be an option. If there is minor destruction of the femoral cartilage but no acetabular involvement, surface replacement of the femoral head is an option. The only viable treatment option after acetabular involvement is total hip arthroplasty. Ceramic-to-polyethylene, metal-to-metal, and ceramic-to-ceramic prostheses should be chosen for young patients with high activity.