Overview
Congenital hip dislocation is one of the most common congenital malformations in children, posterior dislocation is more common and is present at birth. The lesion involves the acetabulum, femoral head, joint capsule, ligaments and nearby muscles, resulting in joint laxity, subluxation or dislocation. Sometimes it can be combined with other deformities, such as congenital oblique neck, hydrocephalus, meningocele, congenital dislocation or contracture of other joints, etc. Ding Sheng, Department of Pediatric Orthopedics, Ningbo Women’s and Children’s Hospital [Etiology
The etiology of congenital hip dislocation is still not completely clear. Certainly, multiple deformities with hip dislocation should be congenital deformities. In general, most scholars in recent years believe that the etiology is not single. This means that there are many factors that can cause this disorder.
(i) Genetic factors
There is an undeniable fact that there is a clear family history of this disorder, especially in twin births, where the incidence can be as high as 20-30% in the family of a patient with this disorder and is more common in sisters. The same disease can occur in sisters with three types of hip dislocation and subluxation and dysplasia. If detailed and early examination and X-ray diagnosis are not performed, except for the first type, the last two types can often be missed and the hip joint is completely normal by the age of 7 or 8.
(B) Ligamentous laxity
In recent years, there are more and more reports proving that laxity of the joint ligaments is an important factor. In animal experiments, after Smith removed the joint capsule and the round ligament from puppies, the percentage of hip dislocation was very high. Clinically, Andren pointed out that the separation of the pubic symphysis in the x-ray was twice as high as that of normal infants. Meanwhile, Andren and Borglin found changes in urinary estrone (Estrone) estradiol 17β (Estradil) excretion in newborn hip dislocation cases within 3 days compared to normal infants. However, Thieme found no difference when comparing month-by-month measurements using 16 sick infants with 19 normal infants, after statistical processing. Therefore, the theory that endocrine changes cause ligamentous laxity is not yet valid.
(iii) Position and mechanical factors
Hip dislocation cases have been reported as high as 16-30% of breech births and only 3% of normal births. Wikinson (1963) fixed the hip joint of young children in flexion, external rotation, knee extension, and gave estrogen and progesterone. Hip dislocation deformities can occur.
Postnatal position has also been suggested to be a factor in this condition. For example, the high incidence in Sweden and American Indians is due to the swaddling position applied to the infant.
[Typing Description
The most common type is typical or true congenital hip dislocation, which is a formed normal fetus that develops a malformation in the late embryonic period. The other type is teratogenic congenital hip dislocation, which is rare and is a teratogenic lesion during the growth of embryonic organs: there are other deformities at birth, and these cases are clinically manifested as bilateral hip dislocation, often with both knees hyperextended and flexed, and both feet flattened inward or outward. The upper limbs can also be deformed, such as the elbow joint can not be flexed, parallel fingers, missing fingers, thumb inversion, flexion deformity and so on. In fact, this type of congenital deformity is due to multiple joint contractures. The typical hip dislocation can be divided into three types.
(i) Hip dysplasia
This is also known as an unstable hip. This category can be found only in the examination. The acetabulum is poorly developed and the acetabular index is usually more than 25° but nothing else. In recent years Caffey believes that the acetabular index in newborns is 35° to 40°. It may still correct itself during growth and still fall within the normal range. After incorporating the femoral head into the acetabulum in such cases, the acetabulum quickly returns to normal at 6 months.
(ii) Subluxation of the hip joint
In these cases, the femoral head and acetabulum are poorly developed, and the femoral head is displaced outward and upward, but not completely out of the joint capsule. x-ray examination shows that the femoral head is displaced outward and upward, and the acetabular index is increased to 35° or greater. Clinically, the femoral head can be palpated at the intersection with the femoral artery anterior to the groin. Hip subluxation is a unique type rather than an intermediate transitional stage between hip dysplasia and hip dislocation, and it can be retained in this condition without converting to a total dislocation state unless there are external factors prompting this change. Hip arthrography shows that in a subluxation, the joint capsule and the disc cartilage (Limbus) are located outside the acetabulum, limiting the outward and upward movement of the femoral head without producing a total dislocation. If the femoral head can enter the acetabulum and make contact with the cartilage surface, normal muscle contraction and weight-bearing tend to cause the acetabulum to develop quickly and gradually a normal acetabulum, femoral head and hip joint emerge. In a few cases, due to the presence of discoid cartilage and incorrect repositioning, the hip joint subluxation continues to exist.
(iii) Hip dislocation
This type is more common. These children come to the clinic with symptoms when they start walking or after walking. The femoral head has clearly and completely dislocated upward and outward from the joint capsule. Early arthrography may show that there is soft tissue separating the femoral head from the acetabulum, making it difficult for the femoral head to enter the acetabulum. The upward and outward displacement of the femoral head increases with age.
[Epidemiological features].
The incidence of this disease is affected by many factors, such as geography, living habits and ethnicity, and its incidence varies greatly. The incidence is higher in northern Italy, France and southern Germany, and Mckeown et al. reported in 1960 that the incidence was 0.7% in Birmingham, England, and 1% in Sweden, and the incidence is also higher in Japan and American Indian tribes. Hodgson believed that our incidence in China is very low, he mainly refers to the southern region of China, because the habit of bringing up children is two hip separation; knee flexion, because this infant position can correct the hip dislocation, and in fact the incidence in different regions of China is not consistent, but the lack of complete statistics. However, the incidence is not too low. In the African region, the incidence is the lowest in the world.
The disease is more common in girls, and the ratio of men to women is 5-7:1. The incidence on the left side greatly exceeds that on the right side, which is 10:1.
Clinical manifestations
The mother of the child often finds that the child’s limbs are abnormal and comes to the hospital for consultation. The symptoms can be broadly summarized as follows.
(A) Restriction of joint movement
Congenital hip dislocation in childhood is usually characterized by painlessness and unrestricted joint movement. In infants and neonates, however, the opposite is true, with temporary joint dysfunction and a fixed posture. The typical symptoms are that the affected limb is flexed and does not dare to straighten, and the movement is poorer than that of the healthy side.
(B) Limb shortening
Shortening of the affected limb is common in unilateral hip dislocation.
(iii) Other common symptoms
There are asymmetric labia majora, increased skin folds on the buttocks, inner thighs or N fossa, deepening or asymmetry, widening of the perineum, and sometimes a “popping sound” or bouncing sensation when pulling the affected limb.
If some of the above symptoms can be detected in time and carefully examined, timely diagnosis and treatment can be made and the treatment effect will be greatly improved.
Experimental examination
Clinical examination is the first step in diagnosis, it only indicates that there is a problem with the hip joint, but the final diagnosis needs to be made by x-ray film. Within 2 to 3 months after birth, the epiphyseal ossification center of the femoral head has not yet appeared, so X-ray examination relies on the relationship between the proximal end of the femoral neck and the acetabulum to measure it. After the ossification center appears, the diagnosis can be determined by taking a pelvic film including the bilateral hip joints, and when the film is taken, both lower limbs are brought together, and the affected limbs are pushed up and pulled down to take a piece of comparative measurement each, so that the changes are more obvious and reliable. There are several methods of measurement as follows.
(a) The horizontal line connecting the Y-shaped cartilage of the acetabulum bilaterally (called Y line or Hilgenreiner line) and the vertical line from the lateral ossification edge of the hip edge (called Perkin line or Ombredarne line), the two lines cross to divide the acetabulum into four zones, the normal femoral head ossification center should be in its inner lower zone, if it is located in other areas, it is dislocation. The ossification center is often smaller on the subluxation side (Figure 97-26).
(B) Acetabular index
The angle between this line and the Hilgenreiner line is called the acetabular index, which indicates the obliquity of the acetabulum and the degree of acetabular development (Figure 97-27). The acetabular index at birth ranges from 25.8 to 29.4°, and for 6-month-old infants it ranges from 19.4° to 23.4° (Caffey 1956). 20° or less for those over 2 years of age. Most scholars believe that more than 25° is abnormal, while some believe that more than 30° has a clear tendency to dislocation. In recent years, the acetabular index in normal newborns has been found to be as high as 35-40°, while the majority of them later transform into normal hips. Therefore, the acetabular index should not be considered alone in the diagnosis. However, a greater than normal value indicates an increase in the tilt of the acetabular roof and acetabular dysplasia.
(iii) Determination of epiphyseal exostosis
The distance between the epiphyseal center of the femoral head and the central plumb line of the pubic symphysis is called the paracentral distance. This method is valuable in measuring mild subluxation. Before the appearance of the epiphysis, the medial edge of the femoral neck can also be used as a point for measurement.
(iv) Von Rosen line
Bilateral thighs are abducted at 45-50° and internally rotated, and orthopantomographs are taken including the upper femur to the pelvis bilaterally. The VonRosen line is a line that extends proximally to the middle axis of the femur. In normal cases, this line passes through the superior external angle of the acetabulum; in dislocation, it passes through the anterior superior iliac spine. It has some reference value for diagnosis until the ossification center of the femoral head is present (Figure 97-28).
(V) Shenton line
The arc of the inferior border of the pubic bone and the arc of the medial femoral neck in the normal pelvic X-ray can be connected into a complete arc called Shenton’s line. In all cases of hip dislocation and subluxation, the integrity of this line is lost.
This line disappears in any dislocation, so it cannot distinguish between inflammation, trauma, congenital and other conditions. However, it is still one of the simplest diagnostic methods.
(vi) Anterolateral angle of femoral neck
Occasionally, radiographs are needed to further clarify the anterior angle. The easiest way is to make an orthopantomogram of the pelvis with the child lying flat and the hip up. Similarly, if the thigh is fully internally rotated and then the orthopelvic radiograph is taken, a comparison of the two films will show that the full length of the femoral neck appears when fully internally rotated, the femoral head is clear, and the femoral head is superimposed on the size of the trochanter when the hip is upward, so the presence of the anterior tilt angle can be estimated.
(vii) Arthrography
In general, arthrography is rarely necessary to make a definitive diagnosis, but it is occasionally necessary in some cases when the cause of disc cartilage, joint capsule stenosis, or reset failure needs to be clarified. Under general anesthesia, the hip joint is sterilely disinfected, and 1 to 3 ml of 35% iodine oil contrast (diodone diodast) is injected as a puncture in front of the joint. Under fluoroscopy, it is possible to find out whether there is any obstruction at the outer edge of the acetabulum, the condition of the cartilage at the outer edge of the acetabulum and whether there is any narrowing of the joint capsule. If necessary, after the manual repositioning, it is possible to re-imaging to clarify whether the femoral head is completely into the acetabulum and the repositioning and deformation of the disc cartilage. Due to the complexity of the operation, insufficient filling of the contrast and difficulty in reading the film, less people have applied contrast diagnosis in recent years.
(H) Central marginal angle (CE angle)
The degree of femoral head entry into the acetabulum is often measured during follow-up cases. Wibeng takes the center of the femoral head as a point and the outer edge of the acetabulum as a point, and even these two points form a straight line. The outer edge of the acetabulum is a vertical line downward, and the two lines form an obtuse angle at the outer edge of the acetabulum, which is called the central angle of the rim. The normal range of this angle is 20-46°, with an average of 35°; 15-19° is suspicious; less than 15°, or even a negative angle, indicates that the femoral head is displaced and is dislocated or subluxed (Figure 97-29).
[Diagnosis description
It mainly relies on physical signs and x-ray examination and measurement. The following points are also noted in the examination of newborns.
(a) Appearance and skin pattern
In multiple malformations with hip dislocation, the examiner often finds a disproportion between the thighs and calves, with short and thick thighs but slender calves, often with wide hips and short or indistinct inguinal wrinkles. Different skin lines on both sides are seen during hip examination, and the affected side is usually elevated or increased by one. The whole lower limb often feels shortened when the affected limb is turned out 15-20° when it is put flat and aligned.
(B) The femoral head cannot be touched to flex the hip
Bend the knee 90° each, hold the upper end of the calf with one hand, place the thumb of the other hand at the inguinal ligament and the other 4 fingers at the hip ring jump, when the hand rotates the calf, the activity and protrusion of the femoral head can be found in the front under normal circumstances. In the case of dislocation, the femoral head is felt to be active in the front while the four fingers behind the hip are empty.
(C) Galeazzi’s sign (Galeazzi)
When the child is lying flat, the two lower extremities are flexed to between 85° and 90°, and the two ankles are placed in a flat symmetrical position, it is found that the two knees are high and low, which is called Galeazzi’s sign. Shortened femur and hip dislocation are seen in this sign (Figure 97-22).
(iv) Abduction test (Otolani’s sign)
Lie the child flat, bend the knee and hip at 90°, and the physician will grasp both knees with both hands facing the child’s hip and abduct both knees at the same time. However, one side of the hip dislocation cannot reach 90°, often between 65° and 70°, and the adductor muscle is obviously bulging, which is called a positive abduction test. There is a sliding or jumping sensation between abduction to 75° and 80°, but later it can be more abducted to 90°, called Otolani jumping sound, which is an important basis on diagnosis. Sometimes the popping sound inside and outside the acetabulum and the meniscal beating sound of the knee must be distinguished during the examination and not confused with each other (Figure 97-23, 24).
(E) Joint loosening test
The prerequisite for checking joint loosening is that the soft tissues around the femoral head are loose, the muscles are not tense, and the femoral head can move up and down, into as well as out of the acetabulum. These tests include the following three methods.
1. Thomas test (Thomas)
In newborns, the healthy leg is flexed to the abdominal wall so that the anterior lumbar convexity disappears and the affected leg can be perfectly straight when it is straightened. Normal infants still have about 30° of flexion when straightened, and can be completely flattened into a straight line.
2, Barlow test (Barlow)
Bend the affected limb at the knee so that the heel touches the buttock. One hand holds the ankle joint and the ipsilateral large and small bulge, and the other hand pushes the thumb against the pubic symphysis and the other 4 fingers against the sacrum. At the midway point of abduction, the femoral head is dislocated posteriorly with thumb pressure, and the bone reenters the joint when the thumb is relaxed. A positive Barrow test indicates that the joint is relaxed and easily dislocated but not hip dislocation (Figure 97-25).
3.Sleeve test
The child lies flat, flexes the hip 90° flexes the knee 90°, holds the knee joint with one hand, the other hand presses the anterior superior iliac spine on both sides of the pelvis, pushes the knee joint downward, can feel the femoral head protruding backward, when lifting upward, the femoral head reenters the acetabulum, it is called a positive socket test.
The above three groups of joint loosening examination method is generally applicable to newborns, and can cooperate without crying and quarrelling to be correct, otherwise it often cannot be examined, therefore, there are still some limitations.
(F) Limp gait
Although early diagnosis is very important, there are still many cases that come to the clinic with lameness. This type of gait can be seen with a little analysis during walking. In children walking, the pelvis sags and sways when the affected limb is in the weight-bearing phase and does not rise; it is not evident in the swing phase. The diagnosis is usually made only after the child walks, at the earliest at the age of 2 years or more, but is treated later. The child with bilateral hip dislocation has a very obvious movement on both sides of the pelvis during walking, often called the duck-step swinging posture, with the hips protruding backward and the lumbar vertebrae protruding forward, so it is easy to think of hip dislocation during examination.
(vii) flexor test (Trendelenurg’s sign)
This is an old method, which is rarely applied now. Children stand, when the healthy side stands on one leg, the affected leg is lifted up and the pelvis is elevated upward ipsilaterally. On the contrary, when the affected limb stands on one leg, the pelvis sags downward because the femoral head on the affected side is not in the acetabulum, and the hip joint is unstable due to the atrophy of the gluteus muscle.
(H) Rise of the greater trochanter
In normal babies, a straight line from the anterior superior iliac spine through the apex of the greater trochanter to the sciatic tuberosity is called Nelaton’s line. If the femoral head is not in the acetabulum and dislocates upward, the greater trochanter rises and the three points are not in a straight line.
[Treatment Description
The treatment of congenital hip dislocation should emphasize early diagnosis, and the treatment effect is best in infancy, and the older the age, the worse the effect. Up to 35 years of age and beyond, hip pain will occur. Therefore, most scholars emphasize the need for census of newborns so that early diagnosis and treatment are important measures to obtain healing. In teratogenic dislocations, there is no good treatment available, and incision and repositioning is usually required, but the results are not good. Typical congenital hip dislocation, if treated early and correctly, has a high possibility of developing into a normal hip joint under normal functional stimulation. Those treated within 3 years of age have a high cure rate. With age, the bony components of the femoral head and acetabulum increase, plasticity decreases, and pathological changes worsen, making it difficult to achieve normal function despite correct treatment.
Treatment methods include closed reduction + brace, closed reduction + frog cast; closed reduction + rotational osteotomy to correct the anterior tilt angle; incisional reduction, and additional acetabular reconstruction and various osteotomies according to different situations. Specific treatment principles are as follows.
(i) Birth to 2 months
Without traction and anesthesia, the hip can be repositioned by flexing both hips to 90° and then gradually abducting them, placing the thumb at the greater trochanter and pushing it forward and inward, avoiding violence during repositioning. The stent should be removed after the radiographic examination. There are many types of stents, including the abductor urinary pillow (Figure 97-30) and the Begg plastic stent (Figure 97-31). Barlow stent (Fig. 97-32) and Rosen stent (Fig. 97-33) are effective, but they have pressure on the skin, which may cause pain and pressure sores, and may cause ischemic necrosis of the femoral head. complications, it uses the two lower extremities to flex 90°, the natural position of the two lower extremities themselves to reach abduction, so that it can naturally reset and maintain the reset position, which is beneficial to both the development and the shaping of the hip joint and has a certain range of hip movement. The disadvantage is that because it is made of canvas, it is relatively hard, and if the shoulder and chest are wrapped too tightly, it affects breathing and too loosely, it is easy to slip off and affect the treatment.
(II) Over 3 months, under 2 to 3 years old
In this group of cases, because of the long time of dislocation, the soft tissues around the hip have different degrees of contracture, therefore, before the reset, traction is made first, usually not more than 2 weeks, if there is a muscle contracture is more obvious, it must be loosened before the reset, such as the cut off of the adductor muscle and the lengthening of the iliopsoas muscle, etc., and later, when the position of the femoral head has been confirmed by bedside X-ray to be at the level of the acetabulum, it is reset by manipulation under general anesthesia, if the position is satisfactory after the reset, then Frog cast fixation is applied. In order to accommodate the growth and development of the child, the cast should be replaced once every 2 to 3 months, and each time an X-ray should be taken to confirm the position of the femoral head in the acetabulum. If it is found that the cast is dislocated after replacement, it must be repositioned again. Each time the cast is replaced, the thighs are gradually internalized until the acetabulum develops normally, and then the cast is removed. If the reset fails, the presence of fatty fibrous tissue hyperplasia, round ligament hypertrophy and dumbbell-shaped joint capsule in the acetabulum should be considered, which prevents the femoral head from entering the acetabulum and thus requires incisional reset.
(iii) From 3 years old to 8 years old
This group of children has been dislocated for a long time, the soft tissue contracture is more obvious, the acetabulum development is worse, often small and shallow, and there is a large amount of fatty fiber tissue at the bottom of the socket, so it is extremely difficult to reset by manipulation, therefore most of them need to be repositioned by incision. However, traction must be done for 2 to 3 weeks before the incisional repositioning, until the femoral head is tractored to the acetabular plane before surgical treatment can be performed. After incision and repositioning, other surgeries are performed according to different situations.
1, the femoral head cover surgery is generally applicable to children with subluxation, poor acetabular development, the femoral head can not be completely covered. There are three main types of these surgeries.
(1) pelvic osteotomy (Salter operation): there must be a good reset before the operation, if there are difficulties in the manual reset, an incision must be performed during the operation to reset, and then the pelvic osteotomy must be performed, and the lower osteotomy piece must be pulled forward and downward during the operation to increase the coverage of the femoral head and the stability of the hip joint.
(2) Pelvic osteotomy (Chiari operation): this operation must be performed on a traction bed with X-ray surveillance, and the positioning must be correct, and the attachment point of the joint capsule must be clearly identified.
(3) Peri-articular capsule osteotomy (Pemberton procedure): This procedure allows the upper part of the acetabulum to be folded forward and laterally to increase its coverage. A bone fragment is taken from the iliac bone and embedded in the pried open osteotomy to stabilize the acetabular reconstruction. Postoperative plaster fixation (Figure 97-37).
2. Zahradnick’s operation The acetabulum is deepened by first making an incision and repositioning. After resetting, the lower limb can only be reset in extreme internal rotation because of the large anterior tilt angle of the femoral neck, so a rotational osteotomy must be made under the ramus, and then fixed with plate screws.
For children over 8 years of age, it is difficult to perform incisional repositioning and there are many complications, so incisional repositioning is generally not performed, and some conservative procedures aiming at stabilizing the hip joint are used, such as acetabular implant capping (Figure 97-38) and osteotomy of the femur at the mouth (Figure 97-39). In recent years, shortening of the femur followed by incision and repositioning has been applied with fair short-term results. For adult congenital hip dislocation, it is usually seen more often in postpartum women and is more often semi-dislocated. Due to the long-term abnormal hip weight-bearing situation, it is easy to cause traumatic arthritis and produce hip pain. For such cases, the use of closed-hole nerve cutting can temporarily relieve the pain, and if the function of the hip joint has been affected, then artificial total hip replacement surgery can be applied.
Complications】
Most of the complications of congenital hip dislocation after treatment are due to rough manipulation, insufficient traction, failure to grasp the surgical indications, failure to understand the factors preventing reset and improper fixation. Most of them can be avoided. Common complications are.
(i) Re-dislocation
(1) Re-dislocation is often caused by the failure to eliminate the factors that hinder the repositioning, the appearance of artifacts on X-ray, carelessness when replacing the cast, excessive anterior tilt angle or dysplasia of the acetabulum, which makes it easier to re-dislocate even after repositioning.
(B) Ischemic necrosis of femoral head
This kind of complication is mainly due to rough manipulation or excessive surgical trauma, which damaged the blood supply of the femoral head; strong extreme abduction during fixation; insufficient traction or failure to release the adductor and iliopsoas muscles before resetting, and excessive pressure on the femoral head after resetting and some other unknown causes.
(c) Osteoarthrosis of the hip joint is a late complication, usually in older children after surgery, and it is often difficult to avoid such complications when they reach adulthood.
(d) Separation of the femoral epiphysis, fracture of the upper femoral segment and sciatic nerve injury are caused by insufficient traction, use of violence during repositioning or too shallow anesthesia, etc., which can generally be avoided.
Attachment: Evaluation of the long-term efficacy of anterior hip dislocation.
1. This evaluation standard is applicable to the evaluation of the efficacy of congenital hip dislocation in all age groups after surgery or conservative treatment; the evaluation time of the efficacy can be evaluated at least 2 years after treatment, and too short a time is of little significance; this standard can reflect both the results of follow-up and the prognosis, and has the characteristics of easy to use, easy to judge and more accurate evaluation.
2. The criteria consist of two major parts, both of which are scored in a total of 30 points.
(1) Evaluation of clinical function (15 points): subjective sensory and clinical examination (2) Evaluation of X-ray radiography (15 points).
3.Evaluation method.
4.Evaluation.
30-26 points …… excellent 25-21 points …… good 20-16 points… …may <15 points ...... poor
5, Description.
(1) Trendelenburg sign is a marker of the degree of hip stability and is an important element in the evaluation. It is positive when the hip joint is subluxated or when the treatment is complicated by short hip deformity due to ischemic necrosis of the femoral head.
Sharp’s angle is also a response to the developmental status of the acetabulum and is used when the Y-shaped cartilage is not closed, so it is difficult to measure the acetabular angle accurately. Sharp’s angle.
(3) Acetabular head index AHI (Acetabular-Head-Index) AHI = A/B, A is the distance from the inner edge of the femoral head to the outer edge of the acetabulum; B is the transverse diameter of the femoral head. Its value was negatively correlated with age.
(4) Measurement of joint space: The joint space is evaluated according to a 5-grade system, with grade 4 being the normal joint space; grade 3 being 1/4 narrower than the usual gap; grade 2 being 1/2 narrower; grade 1 being 3/4 narrower; and grade 0 having a total loss of joint space. The measurement of joint space should be compared with the healthy side, and in bilateral cases, with the hip joint of an aged child. The joint gap is an important reference indicator of the presence or absence of damage to the articular cartilage.