avascular necrosis
Introduction
Introduction to ischemic necrosis The characteristic pathological change of ischemic necrosis is the death of bone cells due to impeded blood supply. The severity of ischemic necrosis depends on the damage of the circulatory system. The femoral head (hip) is the most common lesion; the second is the femoral knee and the humeral head (shoulder). Less involved in the humerus, the scaphoid and the scaphoid. Avascular necrosis of the femoral head is a disease in which a series of clinical manifestations such as hip pain and limited mobility occur due to the destruction of the blood supply to the femoral head by different causes, resulting in femoral head necrosis, which can occur in all age groups. It is a very common disease in the clinic. basic knowledge The proportion of sickness: 0.01% Susceptible people: no specific population Mode of infection: non-infectious Complications: muscle atrophy
Cause
Cause of ischemic necrosis
Many situations can cause this disease:
1. A variety of primary diseases are associated with ischemic necrosis, and some have been shown to be predisposing factors.
2, the most common site of traumatic ischemic necrosis is femoral head, humeral head, humerus, wrist scaphoid. Trauma can cause ischemic osteonecrosis due to blocked blood supply. At the same time, in the supply of femoral head and A functional open anastomosis is formed between the small arteries of the humeral head, a phenomenon that is more common in the human population.
3, hip dislocation will tear the ligament and joint capsule, and the damaged blood vessels are mostly located in the joint capsule. When the hip dislocation is more than 12 hours, 52% of patients have ischemic necrosis, and within 12 hours The recovery rate of osteonecrosis was 22%. In patients with post-fracture fixation, the incidence of ischemic necrosis and collapse is 11% to 45%, independent of the surgeon's technique and fixture.
4, the most common part of ischemic necrosis is the hip joint, followed by the humeral head. There are two main theories about the pathogenesis: end-vascular occlusion caused by intravascular factors (such as fat embolism, sickle cell, decompression sickness) Deep sea diver blood vessel embolization in the blood vessels; extravascular factors such as Gaucher cell proliferation, bone marrow adipocyte hyperplasia increased bone marrow pressure. Spontaneous knee avascular necrosis is also more common in older women.
Prevention
Ischemic necrosis prevention
Specific preventive measures are:
1 Immediately brake after fracture, do not try to stand up and move the hip joint before treatment, in order to prevent aggravation of vascular injury, to move the patient to be stable, to avoid excessive traction of the hip joint.
2 After the fracture, it should be treated as soon as possible. The longer the time, the higher the head necrosis rate.
3 The reset should be accurate, the higher the quality of the reduction, the lower the head necrosis rate.
4 strive for a reset, repeated reduction to increase vascular damage.
5 strive for closed reduction, surgical reduction when failure, soft tissue peeling should be reduced during surgery to prevent further damage to blood supply.
6 Select a fixed method with small damage and good stability, and the minimum damage of multiple needle fixation is a good fixation method.
7 elderly patients with subtrochanteric fractures can directly undergo artificial joint replacement to shorten the treatment cycle.
Complication
Ischemic necrosis complications Complications muscle atrophy
In the late stage of avascular necrosis of the femoral head, the patient is limp-prone and gradually aggravated, showing a clear feeling of short legs, difficulty walking, pain, X-ray will see the femoral head flat, collapse, joint space narrow or disappear, cystic changes are obvious, The area of osteosclerosis is large. The femoral head cartilage is completely broken and the articular surface is rough.
Symptom
Symptoms of ischemic necrosis Common symptoms Talus necrosis greater trochanter pain Muscle necrosis Joint pain Muscle atrophy Ileum repetitive malformation
1. Early main clinical symptoms:
1 The first symptoms appear are hip pain, soreness and discomfort, which may be persistent or intermittent, and bilateral lesions may alternately appear pain.
2 The hip joint activity is normal or slightly lost, and the sinusoidal activity is limited.
3 intermittent limp.
4 large trochanter pain, local deep tenderness, tenderness of adductor muscles, positive for Thomas sign, positive for 4 words.
2. The activities of the late hip joint are limited, limb shortening, flexion, adduction contracture deformity, muscle atrophy, sub-dislocation signs may occur in the hip, and Trendelenburg sign is positive.
Examine
Examination of ischemic necrosis
X-ray inspection
It is the main basis for diagnosis, and sometimes it does not require other imaging methods to make a clear diagnosis. The classic Ficat staging divides it into the following five phases: No clinical manifestations in stage 0, normal X-ray examination, bone scan Reduced intake, no or only mild manifestations in stage I, normal X-ray examination, bone scan showed cold zone of femoral head, pathological findings of infarction of the femoral head weight area, biopsy showed a large number of dead bone marrow cells, osteoblasts, osteoblasts, Stage II clinical manifestations were mild, X-ray examination showed changes in femoral head density (hardening or cyst in stage IIA, normal femoral head contour; new lunar sign in stage IIB), bone scan showed increased intake, pathological findings of spontaneous repair in infarct, biopsy It can be seen that there is new bone deposition between the trabecular bone of the necrotic bone, mild to moderate clinical manifestation in stage III. X-ray examination shows that the femoral head loses its spherical contour, collapses, bone scan shows increased intake, pathological findings of subchondral fracture, and necrosis of collapsed area Fissures and biopsy showed trabecular bone and bone marrow cells on both sides of the fracture line. The clinical manifestations of stage IV were obvious. X-ray examination showed narrowing of joint space and acetabular changes. The increase in pathological changes found osteoarthritis, degenerative cartilage biopsy shows acetabular also changed.
X-ray tomography of the femoral head is of great value in the detection of early lesions, especially in the examination of the new moon. Therefore, X-ray tomography can be performed in patients with early avascular necrosis of the femoral head.
2. CT examination
CT can detect small lesions early in the X-ray film and identify whether there is a range of bone collapse and its extension, thus providing information for the choice of surgery or treatment options, early osteonecrosis, in the femoral head, primary pressure trabecular bone and The medial part of the primary tension trabecular bone combines to form a distinct area of bone density enhancement, which appears as a radial image on the axial image, called the stellate sign, which is the basis for the diagnosis of early osteonecrosis, and the late axial CT scan. The circular or reduced density zone of the middle or edge can be seen. The three-dimensional image displayed by CT scan can provide more accurate data for evaluating the degree of avascular necrosis of the femoral head.
3. Magnetic resonance imaging (MRI)
Magnetic resonance imaging is an effective non-invasive early diagnosis method. It has obvious sensitivity and specificity to osteonecrosis. It can detect lesions earlier than CT and distinguish normal, necrotic bone and bone marrow. In the repair zone, the necrotic bone and bone marrow in the T1 and T2 weighted images have high signal intensity, while the articular cartilage bone appears as dark stripes, forming a wavy or zigzag pattern.
4. Hemodynamic examination of bone
It is generally considered that for X-ray films with normal or only mild osteoporosis, clinical asymptomatic or mild pain, and hip mobility limitation, hemodynamic examination of the bone can help confirm the presence or absence of early femoral head defects. Blood necrosis, the accuracy rate of 99%.
5. Arteriography
At present, the etiology of avascular necrosis of the femoral head is considered by most scholars to be caused by damage to the blood circulation of the femoral head. The abnormal changes of the arteries found in arteriography can provide a basis for early diagnosis of avascular necrosis of the femoral head.
6. Radionuclide scanning
This test is a safe, simple, sensitive, painless, non-invasive method for the early diagnosis of avascular necrosis of the femoral head, especially when X-ray examination is not abnormal, but clinical It is also highly suspected that the possibility of osteonecrosis is greater, usually 3-6 months earlier than X-ray films.
7. Pathological examination
Only for surgical cases, the pathological diagnosis of osteonecrosis is based on myelofibrosis, fat cell necrosis, trabecular necrosis, and some repairs, such as microvascular regeneration and granulation tissue.
Diagnosis
Diagnosis and differentiation of ischemic necrosis
diagnosis
Patients with femur, knee or shoulder pain are powerful indications for early diagnosis.
Diagnosis depends mainly on the extent of the disease. Magnetic resonance imaging (MRI) (in the early stages of the disease) is one of the most specific and sensitive techniques to prevent collapse of the femoral head or other bones. If the course of the disease is not clear, proceed X-ray examination, CT scan to exclude other lesions. Bone scan is more sensitive than X-ray examination, but lacks specificity and is not as widely used as MRI.
There was no significant difference in X-ray examination between the months of the disease and the onset of the disease. The early X-ray showed mild bone sclerosis. In the femoral head, in addition to the above phenomenon, the new moon sign also appeared, and there was also bone collapse ( If the femoral head is flattened, the joint cavity narrows and osteonecrosis eventually appear.
Differential diagnosis
1, lumbar intervertebral protrusion
Lumbar disc herniation is a common disease in orthopedics and the most common misdiagnosis in the diagnosis of femoral head necrosis. This disease is caused by rupture of the annulus fibrosus of the lumbar intervertebral disc and prominent nucleus pulposus tissue after compression or strain, which is caused by compression and stimulation of nerve roots. In the case of low back pain, the pain of femoral head necrosis can also occur in the patient's lower back and legs. Symptoms are similar. Due to the high incidence of lumbar disc herniation, clinicians first consider the occurrence of lumbar disc herniation. While neglecting the necrosis of the femoral head, there is a missed diagnosis and misdiagnosis.
2, hip joint synovitis
The onset of this disease is related to trauma, which is characterized by pain in the hip joint. In severe cases, there may be local swelling, hip joint activity is limited, and MRI may indicate effusion in the hip joint cavity. This disease is associated with early femoral head necrosis in children. Confusing.
3, rheumatoid arthritis
The disease is a non-specific inflammation, manifested as multiple and symmetric chronic arthritis, characterized by joint pain and swelling repeated attacks to joint destruction, rigidity, deformity, if the disease invades the hip joint, causing clinical symptoms and The clinical symptoms of femoral head necrosis are similar and should be identified.
4, ankylosing spondylitis
The disease is a chronic progressive inflammation of the spine, invading the ankle joint, the facet joint, the proximal ligament and the large joint of the proximal torso, resulting in fibrosis or bony rigidity and deformity. This disease is a seronegative reaction disease of connective tissue. Rheumatoid arthritis is similar, this disease can also invade the hip joint, and there are symptoms similar to the femoral head necrosis. Clinicians are easily misdiagnosed and missed.
5, osteoarthrosis
It is a degenerative bone and joint disease characterized by articular cartilage degeneration, injury and bone hyperplasia. The origin of the joint cartilage occurs mostly in middle-aged and elderly people. The incidence of weight-bearing joints and hyperactive joints is high. Such as the spine, hip, knee, interphalangeal joint, the main clinical manifestations of slow-developing joint pain, stiffness, joint swelling and deformity with limited mobility, pain due to femoral head necrosis can be manifested in hip and knee pain, so It is more common clinically confused with this disease.
