Developmental dysplasia of the hip (DDH), also known as developmental hip dislocation, is the most common hip disorder in pediatric orthopedics, with an incidence rate of about 1 per 1,000, about 6 times higher in girls than in boys, about twice as high on the left side as on the right side, and about 35% bilaterally. The name “congenital hip dislocation” is more representative of all the deformities of the disease.
I. Etiology.
Caused by multiple factors. Risk factors for the disease are: girls, first births, multiple births; those with family history; fetal malposition, such as breech position, low amniotic fluid; having plantar inversion deformity of the foot or myotonic plagiocephaly, etc.; wrong swaddling method-candle wrap.
Second, clinical manifestations.
Depending on the age of the child, the degree of dislocation, unilateral or bilateral onset, the clinical manifestations can be different, mainly as follows.
1. Children with unilateral dislocation can have asymmetry of hip and thigh lines in the early stage, but the specificity is not strong. One side of the hip joint is internalized. The perineum becomes wider in children with bilateral dislocation.
2. Children with unilateral dislocation have unequal lower limbs, and children with bilateral hip dislocation during the walking period have a limping gait and duck gait.
Bilateral thigh pattern asymmetry; positive left abduction test; positive Allis sign.
III. Examination.
1.Physical examination.
Ortolani’s sign is the abduction of the hip joint, the elevation of the greater trochanter, and the repositioning of the femoral head back into the acetabulum, which produces a popping sound and a sense of repositioning. A positive Ortolani sign confirms the diagnosis of hip dislocation, whereas a positive Barlow sign only indicates hip instability. In the late stage, there is limited hip abduction and unequal limb length.
2.Ultrasound examination.
There are several methods of ultrasonography, and the most widely used one is Graf method.Graf method is by measuring α angle and β angle, which represent the angle of bony acetabulum and the angle of cartilage part respectively. Based on the different indices, the hip joint is classified into four types, and several subtypes. Ultrasonography is mainly used for infants up to 6 months of age.
(1) Advantages
(1) High specificity and sensitivity, both greater than 90%, with few false negatives.
(ii) Diagnosis of dislocation, subluxation and acetabular dysplasia is possible.
③The treatment of DDH can be dynamically observed.
(iv) There is no radiation damage.
(2) Disadvantages: large variation in results and high demands on the examiner.
Ultrasonography.
3.X-ray examination.
It is more suitable for those who are more than 6 months old, and X-ray examination is not recommended for those who are less than 3 months old. The radiographic findings of children with DDH include increased acetabular index, interruption of Shenton’s line, and normal femoral head ossification center not located in the inner lower 1/4 quadrant of the square formed by Hilgenreiner and Perkins lines. The acetabular index becomes smaller with age and should be within 24° at 2 years of age. In children younger than 8 years of age, the acetabular index is a reliable indicator of acetabular development. When the child is older than 5 years, measuring the CE angle is of great value, and in adult patients, it is one of the most useful indices. The Sharp acetabular angle is also a useful indicator for measuring acetabular dysplasia when the Y-shaped cartilage is closed.
4. Magnetic resonance imaging (MRI) examination.
It is used to show the correspondence between the femoral head and the acetabulum after closed repositioning or incisional repositioning, and it can show both cartilage and glenoid lip, the disadvantage is that it is expensive and the child needs to be sedated.
5.Electron computed tomography (CT) examination.
The 3D reconstruction of CT is more valuable for older children, and the cross-sectional scan of CT is good for observing whether the hip joint is reset.
IV. Diagnosis.
1, early diagnosis.
Relying on physical examination and ultrasonography, a positive Ortolani sign can diagnose hip dislocation, while acetabular dysplasia requires ultrasonography to confirm the diagnosis.
2.Late diagnosis.
For those with limited hip abduction, unequal lower limbs, limp and duck gait, orthopantomogram of the hip joint can confirm the diagnosis.
Differential diagnosis.
It needs to be differentiated from multiple joint contractures, cerebral palsy, hip dislocation combined with multiple syndromes, and hip dislocation combined with septic hip osteoarthritis.
Multiple joint contractures, cerebral palsy and multiple syndromes combined with hip dislocation are easier to differentiate because they have some characteristics of their original disease. In the case of hip dislocation combined with septic hip osteoarthritis, ask about the history of high fever and impaired hip movement in the past, and the X-ray may show signs of destruction of the femoral head and acetabulum.
V. Treatment.
The goal of treatment for DDH is to obtain concentric repositioning of the hip joint, which is the only way to provide good conditions for the development of the femoral head and acetabulum, and to prevent ischemic necrosis of the femoral head. Treatment varies according to the age of the child and the severity of the lesion. The earlier the treatment, the better the results. Conversely, as age and treatment complexity increase, the risk of complications such as ischemic necrosis of the femoral head increases and the child may develop degenerative changes of the hip and osteoarthritis in the future.
The treatment options by age are as follows.
1. Neonates and children younger than 6 months of age.
The diagnosis is best made in the neonatal period and treated immediately upon detection. The most commonly used treatment is the Pavlik dressing device, which has a 95% recovery rate for Ortolani’s sign positive hip. The Pavlik dressing should be reviewed weekly for 3 weeks prior to treatment and ultrasound should be performed, and if the hip is repositioned and stable, the review period should be extended until the ultrasound is normal. The complications of Pavlik dressing and brachial plexus nerve palsy, ischemic necrosis of femoral head, etc.
2. Children from 6 months of age to 18 months of age.
For children in this age group, subluxation or dislocation of the hip joint should be treated by closed reduction or incisional reduction, which is the first choice of treatment, and for those with acetabular dysplasia, brace treatment can be used. Closed resetting must be performed under basic anesthesia, and if intraoperative arthrography shows satisfactory and stable resetting, human position cast fixation should be given, requiring hip flexion at 100-110° and abduction not more than 60°, excessive abduction cast and brace fixation may easily cause ischemic necrosis of the femoral head; if closed resetting is unsatisfactory or unstable, hip incisional resetting should be done, generally simple hip incisional If the closed repositioning is satisfactory or stable, then the hip needs to be repositioned by hip arthrotomy, usually by simple hip arthrotomy plus human plaster fixation; after the plaster fixation, the hip joint is repositioned by fluoroscopy in the operating room. Before discharge, review the orthopantomogram of the hip joint, and if necessary, CT or MRI examination to understand the reset situation. Ultrasound examination can be used for part of the review after discharge to reduce the number of X-ray examinations. Usually, the hip is fixed in plaster for about 3 months and then replaced with a brace for about 3 months. The potential for acetabular development after closed or incisional repositioning is great and can last until 4 to 8 years after repositioning, and most children with DDH do not need a second acetabular or femoral surgery.
3. Children aged 18 months to 8 years.
Most children with DDH older than 18 months of age have poor acetabular development potential, and most of them need to do pelvic osteotomy at the same time of hip arthrotomy and reset. Children with DDH within 4 years of age can choose Salter, Pemberton, Dega and other pelvic osteotomies, and for children with high dislocation, high joint pressure after reset, large anterior tilt angle and neck stem angle need to do shortening of the proximal femur, de-rotation and internal rotation at the same time. Osteotomy. For children older than 4 years of age, a triple pelvic osteotomy can be performed for complicated cases such as re-dislocation after surgery. The choice of the specific surgery method should be decided by the doctor according to the pathological changes of the hip joint, the age of the child and other factors.
4.Children over 8 years old.
For children above 8 years old, if the dislocation is bilateral, no treatment will be performed. unilateral Pemberton, Dega and triple pelvic osteotomy can be done before the Y-chondral closure, and Ganz pelvic osteotomy can be performed if the Y-chondral closure. Chiari pelvic osteotomy is a kind of palliative surgery, which can also achieve good treatment results for some children.
VI. Prognosis.
One of the most common problems in the treatment of DDH is ischemic necrosis of the femoral head, once the ischemic necrosis of the femoral head occurs, it can recover on its own in mild cases, but in severe cases, it will produce femoral head deformities of different degrees, and some children also have residual deformities of different degrees after DDH surgery, which will affect the prognosis of DDH treatment These may affect the prognosis of DDH treatment. Therefore, the children with DDH should be followed up for a long time until the skeletal development stops in adolescence, and the problems found during the follow-up should be treated in time to improve the prognosis of DDH treatment.
VII. Prevention.
The “candle wrap” swaddling method of stroking and binding the legs of the child during the neonatal period is wrong and can increase the incidence of DDH by more than ten times.
The correct method of swaddling is popularized, and the swaddling method of letting the child’s legs abduct freely can greatly reduce the incidence of DDH. For those with other risk factors causing DDH, physical examination and ultrasound should be given in the neonatal period to intervene early if there are any abnormalities, which can maximize the cure rate and reduce the disability rate of DDH.
4 steps for proper swaddling.
1.Fold back the top corner of the blanket and place the baby on top of the blanket with the head in a position above the folded corner.
2.Lift one side of the blanket, stick to one shoulder of the baby, wrap the body and press it under the other side.
3.Fold up the end of the blanket under the baby’s feet and fold it toward the chest, paying attention to leave some space under the feet so that the baby’s legs and feet have room to move.
4.Lift the other side of the blanket, wrap it around the baby’s body, and press the end under the baby’s body.