Congenital Hip Dislocation in Children

　　There are many causes of congenital hip dislocation in children, but the specific causes are not yet clear. Factors such as mechanical factors, joint laxity induced by endocrine factors, primary hip dysplasia, and genetic factors all play important roles in the occurrence of the disease. Abnormal flexion of the hip during breech presentation can lead to posterior dislocation of the femoral head. Laxity of the ligaments was once considered an important etiological factor. Increased estrogen secretion in the later stages of pregnancy can cause pelvic relaxation, which is beneficial for delivery but also causes the ligaments of the fetus in the uterus to become correspondingly relaxed, making it easier for the femoral head to dislocate 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 defect may play an important role in the onset of the disease. The hip joint of the fetus begins as interstitial cartilage forming a cleft, initially呈深凹圆形, then gradually becomes shallower,呈半圆形. At birth, the ilium, ischium, and pubis are only partially fused, and the acetabular fossa is very shallow, so the fetal hip joint has a large range of motion during delivery to facilitate the passage of the fetus. Therefore, the hip joint of the fetus is most susceptible to 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 easily placed deeply in the acetabulum, making dislocation more likely.

　　Congenital hip dislocation often results in complications after treatment, most of which are caused by粗暴的手法, insufficient traction, lack of understanding of surgical indications, not clarifying the factors hindering reduction, and improper fixation, among other reasons. Most of these complications can be avoided. Common complications include:

　　1. Recurrent dislocation:It is often caused by the failure to eliminate factors hindering reduction. When there is a false appearance on X-ray, the cast is changed carelessly, the anterior oblique angle is too large, or the acetabulum is dysplastic, even after the hip joint is reduced, it is still easy to dislocate again.

　　2. Ischemic necrosis of the femoral head:This type of complication is mainly due to rough manipulation or excessive surgical trauma, causing damage to the blood supply of the femoral head. The extreme abduction during fixation, insufficient traction before reduction or insufficient relaxation and reduction of the adductor muscles and psoas muscle, and excessive pressure on the femoral head after reduction can all lead to the occurrence of this disease.

　　3. Osteoarthritis of the hip joint:Late complications. Generally, in older children after surgery, it is often difficult to avoid some types of complications after they grow up.

　　4. Separation of the femoral head epiphysis, fracture of the upper segment of the femur, sciatic nerve injury, etc.:These are all caused by insufficient traction, the use of force during reduction, or too shallow anesthesia, which can generally be avoided.

　　The clinical manifestations of congenital hip dislocation in children are different at different stages, and the types are also different, and the specific clinical manifestations are described as follows.

　　One, Manifestations in neonates and infants

　　1. Joint movement disorder:The affected limb is often in a flexed position, the activity is worse than that on the healthy side, and the power of stepping is located on the other side. The abduction of the hip joint is limited.

　　2. Shortening of the affected limb:The femoral head epiphysis on the affected side is displaced upwards and outwards, and it is common to have corresponding shortening of the lower limb.

　　3. Changes in skin creases and perineum:The skin creases on the buttocks and the inner side of the thigh are asymmetric, the skin creases on the affected side are deeper than those on the healthy side, and the number increases. The labia majora of female infants are asymmetric, and the perineum is widened.

　　Two, Manifestations in infancy

　　1. Limping gait:Limping is often the only complaint of parents when children visit the doctor. When there is unilateral dislocation, it is manifested as limping; when there is bilateral dislocation, it is manifested as 'duck walk', the buttocks of the child are obviously突出，lumbar prominence increased.

　　2. Shortening and deformity of the affected limb:In addition to shortening, there is also an inward deformity.

　　Three, Classification

　　1. Classification according to the relationship between the femoral head and the acetabulum generally can be divided into the following 3 types.

　　(1) Congenital dysplasia:The femoral head is only slightly displaced outwards, the Shenton line is basically normal, but the CE angle can decrease, the acetabulum becomes shallow, and Dunn calls this congenital hip joint dislocation Grade Ⅰ.

　　(2) Congenital subluxation:The femoral head is displaced upwards and outwards, but still forms a joint with the lateral part of the acetabulum. The Shenton line is discontinuous, the CE angle is less than 20°, the acetabulum becomes shallow, and it belongs to Dunn classification Grade Ⅱ.

　　(3) Congenital complete dislocation:The femoral head is completely outside the true acetabulum, forming a joint with the lateral aspect of the ilium, gradually forming a pseudoacetabulum. The original joint capsule is interposed between the femoral head and the ilium, belonging to Dunn classification Grade Ⅲ.

　　2. Classification according to the degree of dislocation can be divided into the following 4 degrees.

　　(1) Grade Ⅰ dislocation:The femoral head epiphysis is located below the Y-line and outside the vertical line from the superior lateral margin of the acetabulum.

　　(2) Grade Ⅱ dislocation:The femoral head epiphysis is located between the parallel line to Y-line and the superior margin of the acetabulum.

　　(3) Grade Ⅲ dislocation:The capital epiphysis is at the height of the parallel line of the acetabulum margin.

　　(4) IV degree dislocation:The capital epiphysis is located above the parallel line of the acetabulum margin, and a pseudoacetabulum is formed.

　　Congenital hip dislocation is an abnormal condition caused during pregnancy, so pregnant women should not bend over and work during pregnancy to avoid their children being born with congenital hip dislocation. During the 10 months of pregnancy, pregnant women should sit up straight.

　　Congenital hip dislocation is a common deformity disease in the neonatal period. Early detection, early diagnosis, and early treatment can achieve good results after timely treatment.

　　The examination of children with congenital hip dislocation includes hip flexion and abduction test, Ortolani and Barlow test, ultrasound examination, and X-ray examination, etc. The specific examination methods are described as follows.

　　1, Hip flexion and abduction test:When both hips and knees are flexed to 90°, the hip joints of normal newborns and infants can be abducted about 80°. If abduction is restricted within 70°, it should be suspected that there is a hip dislocation. If the hip dislocation is reduced, it can be indicated by the ability to abduct to 90° after hearing a sound.

　　2, Galeazzi sign or Allis sign:Both hips are flexed to 90°, the legs are brought together, and the bilateral malleoli are aligned. The level of the patient's knee is lower than the shoulder side.

　　3, Ortolani and Barlow tests (‘Pop-in’ and ‘Pop-out’ tests):The above methods are not suitable for infants over 3 months old, as they may cause damage.

　　4, The adductor muscle on the affected side is tense and contracted.

　　5, Ultrasound examination:This method can be used to detect congenital hip dislocation in newborns early, which is a useful and non-invasive method. It is the most convenient and effective method for mass screening.

　　6, X-ray examination:For patients suspected of having congenital hip dislocation, anteroposterior pelvic X-ray films of both hips should be taken after 3 months of age (before this, most of the acetabulum is still cartilage). Abnormal development of the acetabulum, plate subluxation, or dislocation can be found on the X-ray film. When taking X-ray films, an adrenal protective plate should be added.

　　Patients with congenital hip dislocation should increase their 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, and bananas. Avoid spicy foods such as chili and mustard; bad habits such as smoking and drinking should be戒除.

　　The treatment principle for children with 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, with the hope of obtaining a hip joint that is close to normal function. The older the age at the start of treatment, the worse the effect.

　　One, conservative treatment

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

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

　　2. Choose supports, splints, or plaster casts according to the different ages of the patient, requiring stability, comfort, convenience, and ease of urinary and fecal management, and it is best to allow the hip joint to maintain appropriate activity.

　　3. Choose the most suitable age for hip joint development, the younger the better, generally it is suitable for children under 3 years old.

　　4. The ratio of the head and 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 the fixation is removed, dislocation will not occur again. Generally, it takes 3-6 months, and the shorter the patient's age, the shorter the fixation time.

　　Second, surgical treatment

　　1. Salter pelvic osteotomy:Salter surgery, in addition to reducing the femoral head, is mainly to change the abnormal acetabular direction to a normal physiological direction, relatively increase the depth of the acetabulum, so that the femoral head and acetabulum reach concentricity. This surgery can be used for patients with hip joint dislocation aged 1-6 years, including those who have failed to reduce by manual method.

　　2. Pemberton acetabuloplasty:Osteotomy is performed parallel to the hip joint superior margin 1-1.5cm from the top of the acetabulum, lifting the acetabular end downward to change the inclination of the acetabular roof, so that the acetabulum fully contains the femoral head and reaches a normal shape. This procedure can be chosen for patients over 7 years old, or those under 6 years old with an acetabular index over 46°.

　　3. Femoral rotational osteotomy and femoral shortening osteotomy:Femoral rotational osteotomy is suitable for those with an anteversion angle of 45° to 60° or more, and should be performed simultaneously with the aforementioned surgery. Generally, osteotomy is performed below the lesser trochanter, usually using a hacksaw, and after osteotomy, the near osteotomy end is internally rotated or the far osteotomy end is externally rotated, fixed with a 4-hole plate, but attention should be paid not to overcorrect. Femoral shortening osteotomy is suitable for older patients, grade III dislocation, especially those who have not reached the traction position before surgery, and also osteotomy below the lesser trochanter, shortening about 2 centimeters, and can also correct excessive anteversion at the same time, and then also fixed with a 4-hole plate.