Pediatric Developmental Dislocation of the Hip

Introduction to developmental dislocation of the hip in children Developmental dislocation of hip (DDH), formerly known as congenital dislocation of the hip, is a relatively common form of malformation. If left untreated or mishandled, it can cause hip and lower back pain and affect labor. In fact, the clinically seen children have different degree of dislocation, and some have no real dislocation but only the possibility of potential dislocation. Therefore, in recent years, some scholars have advocated that this disease is developmental hip dislocation (DDH) or congenital hip dysplasia. basic knowledge Sickness ratio: 0.0001% Susceptible people: children Mode of infection: non-infectious Complications: pediatric fracture

Causes of developmental hip dislocation in children

(1) Causes of the disease

The cause of this disease is not fully understood. Genetic factors play an important role. Through dominant gene transfer, the main cause of this disease is the abnormality of the bony structure of the hip joint and the developmental defects of the soft tissue around the joint. Some authors support the hip. In terms of dysplasia, some authors believe that the joint capsule is slack and the femoral neck anteversion angle is too large.

(two) pathogenesis

It is currently believed that this disease is the result of both genetic and environmental factors.

1. Genetic factors Wynne-Davies proposed in 1970 that one of the main genetic mechanisms of developmental dislocation of the hip is hereditary ligament relaxation, and another suggestion that the genetic phenomenon is if one of the monozygotic twins has developmental dislocation of the hip. The chance of another illness is 34%, while the double-oval twins are 3%. In addition, during the delivery, the mother produces relaxing hormones that cause the ligaments to relax and expand the pelvis for delivery. This hormone enters the baby through the placenta. Similarly, the ligaments are loosened by the baby girl, and the effect on the baby boy is small. Epidemiological investigations have found that the incidence of Asian-African people is significantly lower than that of the Eastern European whites.

2. Pathological changes can vary with age, weight bearing and degree of dislocation. Changes in bone, articular surface, and soft tissue around the hip are difficult to distinguish between abnormal sequence or causal relationship.

(1) Changes in bones:

1 The acetabulum is shallow and narrow, with a large slope. The stimulating of the femoral head on the flap can form false sputum.

2 femoral heads are not commensurate with the acetabulum, and the femoral head can be deformed.

The 3 femoral necks can be short and thick, or the dry angle of the femoral neck can be increased, and the anteversion angle is increased.

4 pelvis can develop abnormalities, such as narrow humeral wing, thickened acetabular floor, and separation of ischial tuberosity.

5 The spine may have a lumbar protrusion in the large age and bilateral dislocation.

3. Changes in soft tissue

(1) The labrum of the acetabular rim can be turned down due to compression of the femoral head.

(2) The joint capsule can have different degrees of relaxation, elongation, thickening, and the pressure on the front of the iliac crest muscle can be a gourd shape.

(3) The round ligament can grow, thicken, hypertrophy or break or even disappear.

(4) Muscles around the joints such as the iliopsoas, adductor, rectus femoris, and gluteal muscles may also have different degrees of contracture.

Developmental prevention of hip dislocation in children

Measures to prevent fetal malformation

1, early pregnancy, avoid fever and cold. Women who have had high fever in early pregnancy, even if the child does not have obvious appearance deformity, brain tissue development may be adversely affected, manifested as mental retardation, poor learning and reaction ability, this mental retardation can not be restored. Of course, fetal fever caused by high fever is also related to the sensitivity of pregnant women to high fever and other factors.

2. Avoid getting close to dogs and cats. Few people know that cats with bacteria are also a source of infectious diseases that are a great threat to fetal malformation, and cat feces are the main route of transmission of this malignant infectious disease.

Pediatric developmental hip dislocation complications Complications, pediatric fractures

This disease can cause lameness and low back pain.

Dislocation

It can occur at the time of manual reduction or after resetting, the degree of dislocation can range from mild subluxation to complete dislocation, and late dislocation can occur during gypsum fixation or after removal of plaster.

Factors that hinder the resetting can also cause dislocation. When the gypsum is replaced, the sickness or rough examination can cause re-dislocation. The excessive anteversion angle is the cause of dislocation in the later stage. It occurs after the walk begins, and the dislocation occurs in the gypsum. Remove the plaster for joint angiography, if you are not satisfied with the reset, you need to cut open again.

2. Avascular necrosis of the femoral head

For iatrogenic complications, the mechanical compression of the cartilage and bone, or the trauma of open reduction and reduction, and the strong active hip joint after removal of the plaster may be caused by the closure of the cast gypsum fixed to the excessive outreach and the adductor muscle tension. Before the occurrence of the femoral skulling center, X-ray photographs show that the ossification center appears late, and the femoral neck becomes wider. If it occurs in the femoral skull center, it will first show an increase in the density of the nucleus, followed by absorption. Changes, the final femoral head flat, late ischemic necrosis, due to trochanter compensatory development and hip varus.

3. Fracture

Closed or open reduction can cause femoral condyle separation due to violence, femoral neck or subtrochanteric fracture, large children often occur in long-term traction, bone atrophy, once fracture occurs, after the fracture is healed, then dislocation, If the anteversion angle is too large before surgery, it can be corrected in the treatment of iatrogenic fractures.

4. Neural paralysis

At the time of reduction, the force of the femoral head and the pelvis can be damaged by over-loading or manipulation. The sciatic nerve or femoral nerve can be damaged. If it can be diagnosed early, it should be dislocated to reduce the nerve tension.

5. Postoperative joint mobility or rigidity

The reasons are mostly due to the destruction of the articular cartilage surface by surgery. The soft tissue around the joint is loose before or during surgery. The postoperative cast immobilization is too long, the premature weight bearing or postoperative traction is insufficient, and the infection is too old for the sick child. Scarred physique is also a factor in joint stiffness.

Pediatric developmental hip dislocation symptoms common symptoms "duck step" gait

There are risk factors such as women, positive family history, breech presentation and oligohydramnios.

Clinical manifestations may vary due to age, dislocation, and unilateral or bilateral lesions, but the main signs are as follows:

1. Gait: The only complaint is that the unilateral person sways to the affected side. Both sides have obvious "duck steps" to sway from side to side. At the same time, lumbar protrusions and hips are seen.

2. Double lower limbs are not equal: seen in unilateral dislocation, unilateral femoral line, hip pattern asymmetry, bilateral perineal widening.

3. Large trochanter changes: Large trochanter rises, prominent, above the Nelaton line (the anterior superior iliac spine to the ischial tuberosity).

4. Examination of several signs

(1) Ortolani (Ortolani) sign: more commonly used in the neonatal period of bilateral hip joint routine examination, in order to early diagnosis and treatment, positive for the supine position of the hip 90 °, the examiner's grip can cause downward Hip dislocation, hip can be reset during abduction, the intrinsic is to check whether the hip is easy to reset.

(2) Galeazzi (Alias) or Aris (Allis) sign: positive for unilateral dislocation, supine, hip, knee and knees on the two-legged table, showing the height of the knees.

(3) Barlow test: used to check newborns, 90° hips, knees to make the heels touch the buttocks, one hand to hold the tendon and the femur, small trochanter, the other hand to fix the pelvis, the hip from the neutral position Adduction and light force or downward pressure on the small trochanter can cause the femoral head to recede backwards, then abduct the hip and slightly pull it to reset, which is unstable hip.

(4) Telescope test: The examiner's left hand supports the hip trochanter, and the right hand holds the affected limb up and down, and the left hand can feel the big trousers moving up and down.

(5) Trendelenburg test: The child stands on one leg with normal weight. When normal, the contralateral pelvis rises to maintain balance. When dislocated, the contralateral pelvis subsides due to weak relaxation of the gluteus medius. Developmental dislocation of the hip can be achieved. Coexisting torticollis, humerus adduction and other posture deformities.

Examination of developmental dislocation of the hip in children

Blood, urine, routine examination is normal.

1. X-ray examination: It can be confirmed whether there is dislocation, unilateral or bilateral, subluxation or total dislocation, and the acetabular dysplasia of the affected side can be seen. The femoral humeral center of the femur is delayed or smaller than the healthy side. False sputum can be seen above the acetabulum after dislocation. To further understand the development and deformation of the acetabulum and femoral head, some measurements can be made:

(1) Y line: the horizontal connection of the midpoint of the Y-shaped cartilage at the deepest point on both sides of the acetabulum.

(2) Perkin line: through the vertical line of the outer edge of the acetabulum, this line intersects the Y line to form four quadrants, and the normal femoral head is located in the inner lower quadrant.

(3) acetabular index: the angle between the upper edge of the acetabulum and the deepest line of the acetabulum and the Y line. The normal newborn is 27.5°, 20° at 2 years old, and the hip dislocation is greater than 30°.

(4) CE angle: the angle of intersection between the center of the femoral head and the upper edge of the acetabulum and the Perkin line. This angle measures the degree of outward movement of the upper end of the femur, less than 15° or disappears in the subluxation, and disappears at the full dislocation. In the opposite angle.

(5) Shenton line: the inner edge of the femoral neck is connected with the upper edge of the obturator. Normally it should be a smooth parabola. When it is dislocated, it will lose its proper curvature.

(6) von Rosen filming: used for the examination of pre-dislocation cases, double-bone abduction 45°, and extreme internal rotation filming. If the axis of the femoral shaft passes through the center of the acetabular fossa, there is no dislocation, such as located at the outer edge of the acetabulum. For the dislocation signs.

2. B-ultrasound: In 1984, Graf first reported the use of ultrasound to check whether the baby had hip dysplasia. After comparing the autopsy, X-ray findings and ultrasound results, it was found that there were few echoes of articular cartilage, joint capsule and The muscles have moderate echoes, while the fibrocartilage-like lips, the cartilage-like femoral neck and the upper end of the femur have strong echoes. The sensor is placed in the large trochanter. From the lateral view, the ossified tibia is always white. The inner wall of the ossified acetabulum and labrum is the clamshell, the straight line of the ossified outer wall of the tibia, the angle of intersection with the straight line passing through the bony cap and the line passing through the line of the cartilage cap. They are called alpha angle and beta angle respectively. According to the size of this angle, they are classified and their corresponding pathological features and treatment principles are proposed. However, these principles have not been unified in clinical application.

Most studies have shown that ultrasound is more sensitive than X-ray films in examining abnormal hip development in infants. Ultrasound screening can detect clinically undiagnosed hip dysplasia and mildly dysplastic hips that can be improved on their own. There is no increase in the rate of misdiagnosis, but some authors believe that the results of ultrasound examination are too sensitive, and the diagnosis of small infants under 3 months is false positive, which leads to mistreatment. Some authors choose ultrasound screening for infants with predisposing factors. It was found to be of no value in reducing the incidence of future hip dislocation.

Therefore, although ultrasonography can be used to check whether newborns and small babies have hip dysplasia, it should be applied properly to avoid mistreatment of minor abnormalities. Ultrasound is also useful for early detection of the success of Pavlik sling treatment. In recent years, it has been reported that the use of non-invasive B-ultrasound is beneficial to sick children.

Diagnosis and diagnosis of developmental dislocation of the hip in children

diagnosis

According to clinical characteristics and auxiliary examination results, and whether there are predisposing factors, such as women, positive family history, breech production and oligohydramnios, can be diagnosed as the disease.

Differential diagnosis

1. From the signs of joint dislocation: the diseases that need to be identified are:

(1) Suppurative hip arthritis: such as infantile septic hip arthritis can be caused, pathological hip dislocation, each with a history of hip swelling, pain, X-ray film sometimes shows bone destruction, acetabular development can be better.

(2) Paralytic hip dislocation: caused by poliomyelitis, mainly based on medical history and gluteal muscle paralysis weakness, X-ray film hip joint development is still normal.

2. From the lower extremity adduction, the characteristics of abduction limitation should be differentiated from the following diseases:

(1) Congenital hip varus: Most children with claudication who are 3 to 4 years old or older, the telescope test is negative, and the X-ray film shows that the femoral head is in the acetabulum, the femoral neck dry angle is small, and the large trochanter position is high. Hip abduction is limited.

(2) cerebral palsy: due to the tension of the adductor muscle, the hip joint can not be abducted. Each has the characteristics of high muscle tension and hyperreflexia, and it can also have poor mental performance.

(3) Cartilage dystrophy: X-ray films show normal hip position, but bone development is not normal.

(4) multiple joint contracture: multiple deformities, so that the lower limbs can not be abducted, but there are other signs of joint contracture, this disease can be combined with hip dislocation, treatment is more difficult, in addition, the newborn's hip, knee joint is not easy Straightening, hip abduction is only about 20 °, these are normal phenomena, we must pay attention to identification.

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