Congenital hip dislocation

　　There are many theories explaining the etiology of congenital hip dislocation, such as mechanical factors, joint laxity induced by endocrine factors, primary acetabular dysplasia, and genetic factors, etc. Abnormal flexion of the hip during臀位产 can lead to posterior dislocation of the femoral head. Joint laxity was once considered an important pathogenic factor. Increased estrogen secretion in the late pregnancy period of the mother can cause pelvic relaxation, which is beneficial for delivery, but also causes the ligaments in the fetus in the uterus to produce corresponding relaxation, making it easier to dislocate the femoral head in the neonatal period. However, it is difficult to explain the cause of the disease with a single factor. It is generally believed that genetic and primary embryonic quality defects may play an important role in the pathogenesis. The hip joint of the fetus begins as an interstitial cartilage formed gap, initially presenting as a deep凹圆形, then gradually becoming shallower, presenting as a semicircle. At birth, the ilium, ischium, and pubis are only partially fused, and the acetabular fossa is very shallow, so the hip joint of the fetus has a large range of motion during delivery to facilitate the passage of the fetus. Therefore, the fetus is most susceptible to hip dislocation during this period before and after birth. If the lower limbs of the fetus are placed in an extended adducted position, the femoral head is not easy to be placed deeply in the acetabulum, and it is very prone to dislocation.

　　For hip dislocation, whether conservative treatment or surgical treatment, complications such as ischemic necrosis of the femoral head may occur. After surgical treatment, redislocation and joint stiffness may also occur, and prevention should be paid attention to during treatment. The following is a specific introduction to common complications.

　　1. Ischemic necrosis of the femoral head

　　This is a iatrogenic complication, mainly caused by mechanical pressure leading to arterial ischemia. Salter proposed 5 diagnostic criteria:

　　(1) One year after reduction, the ossification nucleus of the femoral head still does not appear.

　　(2) One year after reduction, the growth of the epiphysis is stagnant.

　　(3) One year after reduction, the neck of the femur becomes wider.

　　(4) Flattening of the femoral head, increased density, or appearance of fragmentation.

　　(5) Residual deformity of the femoral head, including flattening and enlargement of the head, flat hip, varus femur neck, and short and wide femoral neck.

　　2. Redislocation after surgery

　　Although the incidence rate of redislocation after surgery is not high, once it occurs, the prognosis is poor, and complications such as femoral head necrosis and joint stiffness may occur. Efforts should be made to prevent this. The main cause is the unsatisfactory tightness of the joint capsule, which is the most common cause; secondly, the anterior tilt angle is too large and has not been corrected. There are also reasons such as asymmetry of the head and acetabulum and improper treatment. Prevention should be strengthened, and early surgery should be performed if it occurs.

　　3. Limited or stiff hip joint movement

　　This complication is relatively common. The older the patient, the higher the incidence rate. The higher the position of the dislocated femoral head, the more severe the contracture around the hip joint. If not corrected, it is easy to develop restricted hip joint movement or stiffness, especially for those who are immobilized with a hip orthopedic brace after surgery. It is necessary to strengthen early joint function exercises after surgery, adopt hip abduction plaster splint fixation, and practice sitting up and moving around after one week. It is also possible not to use plaster fixation and to use continuous passive motion for joint function exercise after surgery.

　　Congenital hip dislocation is a disease whose etiology is not yet fully understood. It has various symptoms, and its symptoms are relatively obvious through many experiments. The following is a specific introduction to the symptoms of this disease:

　　1. Unilateral dislocation in infancy

　　The asymmetry of the gluteal wrinkles and thigh skin folds, the deep and high-lying inguinal creases, and the shorter affected limb. In cases of bilateral dislocation, the perineum becomes wider, and some careful mothers, in addition to discovering the above changes, may also find that the baby's thighs are difficult to separate, often discovering a bouncing phenomenon in the hip joint when changing diapers.

　　2. Ortolani test

　　It is an effective and simple method for early detection of congenital hip dislocation. The specific method is: let the child lie on his back and flex the hip and knee to 90°, the examiner places the thumb on the inner side of the child's thigh, and the index and middle fingers on the greater trochanter. Gradually abduct and externally rotate both thighs; if there is a dislocation, you can feel a click or a jump sound, and the hip can be abductively and externally rotated to 90°. If you adduct and internally rotate the thigh, push the thumb outward, the femoral head can be dislocated again, and there will be a click or a jump sound again, which is called a positive Ortolani test (click-in and click-out test), which is suitable for newborns.

　　3. Barlow test

　　Also known as the 'stability test', it is an improvement of the Ortolani test. The baby lies flat, the examiner's middle fingers are placed on both greater trochanters, and the thumbs are placed near the small trochanter on the medial side of the thigh. The hip is flexed to 90°, and the knee is completely flexed, then the hips are abducted to 45°. If the examiner feels the femoral head sliding into the acetabulum with the middle fingers, it indicates a dislocation. Then, using the thumb placed near the small trochanter on the medial side of the thigh, push the femoral head posteriorly and laterally. If the femoral head slips out from the posterior edge of the acetabulum, after releasing the thumb, the femoral head slides back into the acetabulum, indicating that the hip is unstable, and it is called a positive Barlow test. This test is not suitable for older children.

　　4. Dislocation period

　　The time when the child begins to walk is later than that of normal children. The abnormality in walking is painless limping. In patients with bilateral hip dislocation, the gait is like a duck, that is, swinging from left to right, the pelvis is anteriorly inclined when standing, the buttocks are raised, and the waist is anteriorly convex. In patients with unilateral dislocation, the affected limb is shortened, when lying flat, the knees are flexed to 90°, and the tops of the two knees are not on the same plane. The lower side indicates a dislocation. This is the positive Allis sign.

　　5. Trendelenburg test

　　When the child stands on one foot, the opposite pelvis cannot be lifted to maintain body balance, indicating that the hip on the standing foot has a lesion, which is a positive Trendelenburg test.

　　What we usually refer to as dislocation is joint dislocation, which means that the normal connection of the body's skeletal part has been lost. Joint dislocation can be divided into many types, which are divided according to different parts. Hip joint dislocation is one type of joint dislocation, and when hip joint dislocation occurs, it can affect motor function. So, how to prevent it? The following are some methods of hip joint dislocation prevention:

　　1. Limit the extension of the hip joint, and other activities are not restricted. In addition to a few cases with hindrance to reduction within the hip joint, the vast majority of children can achieve reduction treatment without developing aseptic necrosis of the femoral head. There are also methods such as the one-piece sock suit method and the abduction cradle support method, which are maintained for more than 4 months.

　　2. Under general anesthesia, the child is in a supine position, with the hip and knee of the affected side each flexed 90° along the long axis of the thigh. Traction is applied along the long axis of the thigh, while the greater trochanter is compressed to bring the femoral head into the acetabulum. After reduction, since the frog plaster can easily affect the development of the femoral head and produce ischemic changes, currently, pediatric orthopedics in China and abroad no longer use the frog plaster and instead use the 'human character plaster', that is, the hip joint is only abducted by about 80°, the knee is slightly flexed, and the child is allowed to walk on the plaster after the plaster is applied.

　　4, As the degree of dislocation increases, the secondary changes of bone and soft tissue are also more serious, and manual reduction is difficult to be successful, so surgical treatment should be adopted. Salter pelvic osteotomy should be performed. For those with a femoral neck anteversion angle greater than 45°, additional femoral rotation osteotomy should be performed.

　　3, A part of the mild children can still use the traction吊吊带法 for treatment. If it cannot be复位 after using 4-6 weeks, it can be changed to manual reduction and cast fixation method.

　　Congenital hip dislocation is a disease whose etiology is still unclear to this day and usually occurs in the neonatal period. If parents suspect that their child may have hip dislocation, several examinations can be done to finally determine it.

　　1, Von-Rosen (abduction and internal rotation) film method

　　The infant lies on his back, his two hips are extended and abducted 45°, and the internal rotation position is photographed as much as possible. Normally, the upward extension of the femoral shaft axis intersects below the lumbar sacral plane. However, when the hip joint is dislocated, this line intersects above the lumbar sacral plane through the anterior superior iliac spine. However, the hip joint dislocation of some children has the possibility of natural复位 in the position of abduction and internal rotation, resulting in normal appearance. This method of measurement is more reliable and is suitable for newborns whose ossification center of the femoral head has not yet appeared.

　　2, Perkin quadrant

　　After the ossification center of the femoral head appears, the Perkin quadrant can be used to judge the dislocation of the hip joint. That is, a straight line is drawn between the centers of the two acetabula, known as the H line, and a perpendicular line (P line) is drawn from the outer margin of the acetabulum to the H line, dividing the hip joint into four quadrants. Normally, the ossification center of the femoral head is located in the lower inner quadrant, and it is subluxation in the lower outer quadrant, and complete dislocation in the upper outer quadrant.

　　3, Acetabular index

　　The acute angle formed by the line from the outer margin of the acetabulum to the center of the acetabulum intersecting with the H line is called the acetabular index, and its normal value is 20° to 25°. After children start walking, this angle decreases year by year and is basically constant at about 15° by the age of 12. When the hip joint is dislocated, this angle is significantly increased, even over 30°.

　　4, CE angle

　　Also known as the center edge angle (center edge angle), that is, the angle formed by the perpendicular line from the center point of the femoral head to the YY' line and the line connecting the outer margin of the acetabulum and the center point of the femoral head. Its significance is to detect the relative position of the acetabulum and the femoral head, which is valuable for the diagnosis of acetabular dysplasia or hip subluxation. It is normally below 20°.

　　5, Shenton line

　　Normally, the arc line at the superior margin of the obturator foramen connects with the inner arc line of the femoral neck to form a continuous arc line, known as the Shenton line. When the hip joint is dislocated, this line is interrupted.

　　6, Simon line

　　It is a continuous longitudinal arc line formed along the outer margin of the iliac bone to the superior outer margin of the acetabulum, then downward and outward along the outer margin of the femoral neck. When the hip joint is dislocated, this arc line is also interrupted.

　　7. Hip arthrography

　　In infancy, the femoral head has not ossified, and most of the hip joint is cartilage, which does not show up on X-rays. Therefore, arthrography is conducive to observing the transparent parts of the joint and soft tissue structure. The method is: the child lies flat, is under general anesthesia, and an 18-gauge needle with a needle core is inserted 1.5 to 2 cm below the anterior superior iliac spine under sterile conditions, directed downward and inward towards the acetabulum until it touches the acetabulum, then turned outward into the joint capsule. Inject contrast agent. In a normal hip joint, the following can be observed:

　　(1) The size and shape of the femoral head.

　　(2) The cartilage edge of the acetabulum.

　　(3) Circular area, that is, the area surrounding the joint capsule, where a transparent area surrounds the femoral neck, dividing the contrast agent into two.

　　(4) Transverse ligament, manifested as a depression below the contrast agent.

　　(5) Round ligament.

　　When the acetabular labrum is inverted during congenital hip dislocation, there may be a filled defect between the femoral head and the acetabulum, the joint capsule is obviously contracted, and there is a striped shadow in the acetabulum, indicating a thickened round ligament.

　　8. CT examination

　　Recently, some scholars have used CT to examine congenital hip dislocation in infants and young children, and can see bone defects, acetabular deformation causing dislocation, and can see changes in bone, soft tissue adhesion, anteversion of the femoral neck, and the degree of femoral head dislocation.

　　When congenital hip dislocation is found, surgical treatment is usually adopted for treatment. In order to achieve better recovery from the disease, patients should pay attention to the following dietary taboos and preferences:

　　1. Eat more food

　　Increase nutrition, eat more protein-rich foods such as fish, eggs, and soy products, and appropriately increase calcium. Drink more water, eat more vegetables and fruits, such as: green vegetables, celery, bananas, etc.

　　2. Avoid eating food

　　Avoid spicy foods. Such as chili, mustard, etc. Smoking and drinking should be戒除.

　　The treatment principle for congenital hip dislocation is to diagnose and treat it as early as possible. Once the diagnosis of congenital hip dislocation is established after birth, treatment should be started immediately, hoping to obtain a hip joint that is close to normal function. The older the age at the start of treatment, the worse the effect. Now let me talk about the specific process of conservative treatment methods.

　　1. The theoretical basis of conservative treatment

　　The theoretical basis of conservative treatment is Harris' law, that is, the concentricity of the head and acetabulum is the basic condition for the development of the hip joint. In order to achieve the stability of the hip joint after reduction, the following conditions must be met:

　　(1) Choose a posture to maintain the stability of the hip joint. The traditional frog position is the most ideal posture, but it is not conducive to the blood supply of the femoral head.

　　(2) Choose orthopedic devices, splints, or plaster casts according to the different ages of the patient, requiring stability, comfort, convenience, and ease of urine and defecation management. It is best to keep the hip joint appropriately active.

　　(3) Choose the most suitable age for the development of the hip joint, the younger the better, generally 3 years old or younger is recommended.

　　(4) The ratio of the head to the acetabulum should be proportional. If the ratio is unbalanced, it cannot maintain the stability of the hip joint, and even the treatment may fail.

　　(5) Maintain reduction for a certain period of time to allow the joint capsule to retract to nearly normal, and after removing the fixation, it will not dislocate again. Generally, it takes 3 to 6 months, and the shorter the patient's age, the shorter the fixation time.

　　2, Method

　　Manual reduction and various splints, plaster fixation: after manual reduction, various adjustable splints or braces can be used for fixation for patients under 1 year old; for patients over 1 year old, due to their older age, the reduction is more active and stronger, which can cause the splint and brace to be unstable and lead to dislocation, so plaster fixation for 2 to 3 months is required before changing to splint or brace fixation. If manual reduction is possible, in order to prevent the occurrence of avascular necrosis of the femoral head, the following various measures should be adopted to prevent it.

　　Firstly, pre-reduction traction before reduction should be performed to overcome the contraction of the soft tissues around the hip joint, relax the muscles, and reduce the pressure between the head and the socket after reduction. Usually, suspended skin traction is performed, and for patients aged 2 to 3 years with III degree dislocation, bone traction can also be selected, generally for 2 to 3 weeks.

　　Secondly, cut the adductor muscle. The running path of the internal artery of the femur runs between the adductor muscle and the iliac psoas muscle. When in the frog position, this artery is compressed and affects the blood supply of the femoral head, therefore, cutting the adductor muscle not only overcomes the spasm of the adductor muscle but also has a certain effect on preventing femoral head necrosis.

　　Third, gentle manipulation under general anesthesia. After general anesthesia, the muscles relax, which is conducive to reduction, but the manipulation should be gentle and the principle of single reduction should be adopted, that is, if the reduction is not successful, it is forbidden to repeat the reduction, as this will cause repeated trauma to the femoral head, so for those who have not succeeded in single reduction, surgical treatment should be performed in principle.

　　Fourth, use the human position fixation method, that is, starting from 90° abduction and external rotation, gradually adduction to the angle of dislocation, and the range between these two angles is the safe range, choose the middle value of this angle. If dislocation occurs when abduction and external rotation are 90° and adduction to 60°, the safe range is 30°, so the human position is 75° abduction and external rotation. Ramsey pointed out that the safe range is related to the degree of adductor spasm, the more severe the spasm, the smaller the safe range. The human position is conducive to preventing the occurrence of avascular necrosis of the femoral head, and generally needs to be fixed for 6 months.