Osteonecrosis of the femoral head (ONFH), also known as ischemic necrosis of the femoral head (AVN), is a common and intractable disease in the field of orthopedics.
I. Definition: ONFH is a disease in which the blood supply to the femoral head is interrupted or damaged, causing the death and subsequent repair of bone cells and bone marrow components, which then leads to structural changes in the femoral head, femoral head collapse and joint dysfunction.
ONFH can be divided into two categories: traumatic and non-traumatic. The former is mainly caused by hip trauma such as femoral neck fracture and hip dislocation, while the main causes of the latter in China are corticosteroid application and alcohol abuse.
Second, the diagnostic criteria
Experts suggest that the diagnostic criteria proposed by the Japanese Ministry of Health and Welfare Osteonecrosis Research Society (JIC) and Mont be integrated to develop our diagnostic criteria.
(A) The main criteria
1.Clinical symptoms, signs and history: arthralgia mainly in the groin and hip and thigh area, limited internal rotation of the hip joint, history of hip trauma, history of corticosteroid application, history of alcoholism.
2.X-ray changes: femoral head collapse without joint space narrowing; sclerotic zone with demarcation within the femoral head; subchondral bone with transverse X-ray zone (crescent sign, subchondral fracture).
3.Nuclear scan shows a cold zone in the hot zone within the femoral head.
4, T1-weighted phase of MRI of the femoral head shows banded low signal (banding type) or T2-weighted phase with double line sign.
5, Bone biopsy shows more than 50% osteocyte vacuolation fossa in bone trabeculae and involvement of multiple adjacent bone trabeculae with bone marrow necrosis.
(II) Secondary criteria
1.X-ray shows femoral head collapse with narrowing of joint space, cystic degeneration or speckled sclerosis in the femoral head, and flattening of the outer upper part of the femoral head.
2.Nucleotide bone scan shows cold or hot areas.
3, MRI shows a band type with homogeneous or heterogeneous low signal intensity without T1 phase.
The diagnosis can be confirmed if two or more major criteria are met. Meeting one major criterion, or the number of positive secondary criteria ≥ 4 (including at least one positive radiographic change), is likely to be diagnosed.
(C) Key points of each diagnostic method
The diagnosis of femoral head necrosis can be made by asking medical history, clinical examination, X-ray radiography, magnetic resonance imaging (MRI), nuclear scan, computerized tomography (CT), and other methods.
(iv) Clinical diagnosis
Medical history should be carefully inquired, including history of hip trauma, application of corticosteroids, alcohol consumption or anemia. The clinical symptoms should be clarified in terms of pain location, nature, relationship with weight bearing, etc. Physical examination should include the rotational activity of the hip joint.
Early clinical symptoms of femoral head necrosis are not typical, and internal rotation of the hip joint leading to pain is the most common symptom. After the femoral head collapses, the range of hip joint activities may be limited.
(E) Physical signs :Local deep pressure pain, pressure pain at the stop of the internal rotator muscle, and axial percussion pain may be positive in some patients. In the early stage, the hip joint pain, Thomas sign and 4-character test are positive; in the late stage, the femoral head collapse, hip joint dislocation, Allis sign and single-leg independent test sign may be positive. Other signs include limited abduction, external rotation or internal rotation, shortening of the affected limb, muscle atrophy, and even signs of subluxation. In the presence of hip dislocation, there may also be an upward shift of the Nelaton line, the base of Bryant’s triangle is less than 5 cm, and the Shenton line is discontinuous.
The T1-weighted phase of typical ONFH is characterized by the residual epiphysis of the femoral head, sinuous bands of low signal adjacent to or crossing the epiphysis, and low signal bands encircling high signal areas or mixed signal areas. The recommended scanning sequence is T1 and T2-weighted, with additional T2 lipid suppression or short T1 inversion recovery (STIR) sequences for suspicious lesions. Coronal and cross-sectional scans are generally used, and additional sagittal scans may be added for more accurate estimation of necrosis volume and for clearer visualization of the lesion. Roll-enhanced MRI is particularly effective for early ONFH detection.
(F) Nuclear scan Nuclear scan is highly sensitive and low specificity for the diagnosis of early ONFH. The diagnosis can be confirmed by using 99Tc diphosphate scan if there is a cold area in the hot zone. However, the concentration of nuclide alone (hot zone) should be differentiated from other hip diseases. This test can be used to screen for lesions and to look for multi-site necrotic foci. Single photon emission tomography (SPECT) may enhance sensitivity, but specificity is still not high.
(VII) CT For stage II and III lesions, CT examination can clearly show the boundary, area, sclerotic zone, self-repair of the necrotic foci and subchondral bone, etc. The clarity and positive rate of CT showing subchondral fracture are better than MRI and X-ray, and the addition of two-dimensional reconstruction can show the overall situation of the coronal position of the femoral head.
Differential diagnosis
Differentiation of lesions with similar X-ray changes or MRI changes should be noted.
(a) Differential diagnosis of diseases with similar X-ray changes 1. intermediate and advanced osteoarthritis: it may be confused when the joint space is narrowed and subchondral cystic changes appear, but its CT shows sclerosis with cystic changes and MRI changes are mainly low signal, which can be differentiated accordingly. 2. acetabular dysplasia secondary to osteoarthritis: the femoral head is not fully wrapped, the acetabular line is in the upper part of the femoral head, the joint space is narrowed and disappears, the bone 3, ankylosing spondylitis involving the hip joint: common in adolescent males, mostly bilateral sacroiliac joint involvement, characterized by HLA-B27 positive, the femoral head remains round, but the joint space becomes narrower, disappears or even fuses, so it is not difficult to distinguish. Some patients with long-term application of corticosteroids can be combined with ONFH, the femoral head can appear collapsed but often not serious. 4, rheumatoid arthritis: mostly seen in women, the femoral head remains round, but the joint space is narrowed and disappeared. Erosion of the articular surface of the femoral head and acetabular bone is common, and identification is not difficult.
(B) Differential diagnosis of diseases with similar MRI changes
1, temporary osteoporosis sign (ITOH): can be seen in middle-aged male and female patients, is a temporary painful bone marrow edema. x-ray shows the femoral head, neck and even rotor bone volume reduction. mri can see T1-weighted phase uniform low signal, T2-weighted phase high signal, the range can be to the femoral neck and rotor, no band low signal, can be distinguished from ONFH. This disease can be healed within 3-6 months.
2, subchondral insufficiency fracture: Mostly seen in elderly patients over 60 years old, without obvious history of trauma, showing sudden onset of hip pain, inability to walk, and limited joint movement. x-ray shows slightly flattening of the upper outer femoral head, T1 and T2-weighted phase of MRI shows subchondral low signal lines, surrounding bone marrow edema, and T2 lipid suppression phase shows lamellar high signal.
3, pigmentation choroidal nodular synovitis: mostly in the knee joint, hip joint involvement is rare. CT and X-ray may show cortical bone erosion of the femoral head, neck or acetabulum, and mild to moderate narrowing of the joint space. MRI shows extensive synovial hypertrophy with uniform distribution of low or moderate signal.
MRI shows a T1-weighted phase with moderate signal and a T2-weighted phase with high signal, more medially. 5. synovial herniation pit: This is a benign lesion in which the synovial tissue has proliferated and invaded the femoral neck cortex. MRI shows small round lesions with low signal in T1-weighted phase and high signal in T2-weighted phase, mostly eroding the upper femoral neck cortex, usually asymptomatic.
A reasonable treatment plan should take into account the stage, necrosis volume, joint function, as well as the patient’s age and occupation.
Non-surgical treatment of femoral head necrosis It is important to note that the efficacy of non-surgical treatment of ONFH is still unpredictable.
1, protective weight-bearing Academics are still debating whether this method can reduce femoral head collapse. The use of double crutches can effectively reduce pain, but the use of wheelchairs is not advocated.
2.Medication For early stage (0, I, II) ONFH, non-steroidal anti-inflammatory and analgesic agents can be used, for high coagulation and low fibrinolysis state, low molecular heparin and corresponding traditional Chinese medicine can be used, such as sodium alun phosphate can prevent femoral head collapse, vasodilator drugs also have certain efficacy.
Physical therapy includes extracorporeal shock wave, high-frequency electric field, hyperbaric oxygen, magnetic therapy, etc., which are beneficial to relieve pain and promote bone repair.
Surgical treatment of femoral head necrosis Most ONFH patients will face surgical treatment, which includes two types of surgery to preserve the patient’s own femoral head and artificial hip joint replacement. Surgery to preserve the femoral head includes medullary core decompression, bone grafting, and osteotomy, and is indicated for patients with ONFH in ARCO stages I, II, and early stage III, with a necrosis volume of 15% or more. If the method is appropriate, artificial joint replacement can be avoided or postponed.
I. Femoral core decompression (core decompression) It is recommended to use a fine needle of about 3 mm in diameter and drill multiple holes under fluoroscopic guidance. Autologous bone marrow cell transplantation and bone morphogenetic protein (BMP) implantation can be performed in conjunction. This therapy should not be used in advanced stages (stages III and IV).
Second, autologous bone grafting with blood vessels There are more applications such as fibula grafting with blood vessels and iliac bone grafting with blood vessels, which are suitable for stage II and III ONFH, and have good efficacy if applied appropriately. However, these procedures may lead to complications in the donor area, and they are very traumatic, have a long operation time and vary greatly in efficacy.
Without vascular bone grafting, there are more applications such as transfemoral rotor decompression bone grafting and femoral head neck bulb decompression bone grafting. Bone grafting methods include compression bone grafting and support bone grafting. The bone grafting materials used include autologous cancellous bone, allograft bone, and bone replacement materials. These procedures are suitable for ONFH in stage II and early stage III, and have better results in the middle stage if applied properly.
Osteotomy The necrotic area is moved out of the weight-bearing area of the femoral head, and the non-necrotic area is moved out of the weight-bearing area. The osteotomies applied in clinical practice include internal or external osteotomy and transfemoral rotational osteotomy. This method is suitable for ONFH with moderate necrosis volume of stage II or early or middle stage III. This procedure will bring more technical difficulties for the future artificial joint replacement.
V. Artificial joint replacement Once the femoral head has collapsed heavily (late stage III, stage IV, stage V), and joint function or pain is heavy, artificial joint replacement should be selected. For patients under 50 years of age, limited femoral head surface replacement, metal-to-metal surface replacement, or double-action femoral head replacement are available. These arthroplasty procedures are transitional and can preserve more bone for later revision, but each has its own indications, technical requirements and complications and should be chosen carefully.
Arthroplasty has a positive effect on advanced ONFH, and it is generally believed that non-cemented or hybrid prostheses have better medium- and long-term outcomes than cemented prostheses. Artificial joint replacement for femoral head necrosis is different from arthroplasty for other diseases, and some related problems should be noted: 1. Patients have been applying corticosteroids for a long time, or have underlying diseases that need to continue treatment, so the infection rate is elevated; 2. Long-term non-weight bearing, osteoporosis and other reasons lead to easy penetration of the prosthesis into the acetabulum; 3. Having performed surgery to preserve the femoral head can bring various technical difficulties.
There are also: dead bone removal bone cement filling femoral head reconstruction
In addition, there is controversy in academic circles about the treatment of asymptomatic ONFH. Some studies have concluded that ONFH with large necrotic volume (>30%) and necrosis located in the weight-bearing area should be treated actively and should not wait for symptoms to appear.
Treatment options for different stages of femoral head necrosis
For stage 0 non-traumatic ONFH, if the diagnosis is confirmed on one side and stage 0 is highly suspected on the opposite side, close observation is advisable and MRI follow-up is recommended every 6 months.
Stage I, II ONFH if it belongs to asymptomatic, non-weight-bearing area, lesion area <15%, can be closely observed, regular follow-up; symptomatic or lesion >15%, should be actively carried out to preserve the joint surgery or drugs and other treatment.
Stage IIIA, IIIB ONFH can be treated by each implant osteotomy, osteotomy, limited surface replacement, or conservative treatment for those with mild symptoms.
Among patients with stage IIIC and IV ONFH, if the symptoms are mild and the age is young, joint-preserving surgery can be chosen, while other patients can choose surface replacement and total hip replacement.
Efficacy evaluation
The evaluation of the efficacy of ONFH can be divided into clinical evaluation and imaging evaluation. Clinical and imaging changes are not completely synchronized in the same patient, so they should be evaluated separately. Clinical evaluation uses hip function score (such as Harris score, SF-36 score, etc.) and should be evaluated on a case-by-case basis according to the same stage, similar necrosis area, and the same treatment method. Imaging evaluation can be done by applying X-ray films and using concentric garden templates to observe changes in femoral head shape, joint space and acetabulum. MRI examination data should be available for the evaluation of lesions within stage II.