Chapter 20. Orthopedic deformities in children

Congenital hip dislocation

Congenital hip dislocation is the most common and severe developmental anomaly of the musculoskeletal system. Early diagnosis is of particular importance in the effectiveness of treatment; therefore, not only orthopedists but also pediatricians should be well acquainted with the symptomatology of this disease.

Anatomical and physiological features

In newborns and infants, the hip joint is significantly different from an adult joint. Its articular surfaces are underdeveloped and are represented by cartilaginous tissue.

The acetabulum changes its shape, depth, and spatial location not only during intrauterine life but also after birth. In newborns, it has an oval shape, its upper edge is sloped and consists of bone and cartilage. The acetabulum is formed with three ossification nuclei separated by Y-shaped cartilage, which ossifies by the age of 15-18. The acetabulum depth in newborns increases due to the acetabular labrum.

The proximal femur is also comprised of cartilaginous tissue, including the head, neck and greater trochanter; these femoral sections are not visualized during radiological examination. The ossification nucleus of the femoral head normally appears after 3-4 months, in case of dysplasia, ossification, as a rule, is delayed.

Insufficient coverage of the head with the acetabulum, as well as mismatch of articular surfaces are one of the predisposing factors to the subluxation and luxation development in the hip joint.

Preluxation is a condition of the joint when the capsule is s tretched, and the femoral head is easily and freely adjusted and dislocated from the acetabulum. This is the initial condition of the hip joint in case of this pathology in a newborn. The fate of the preluxation largely depends on the conditions of the child maintenance in the first days of life. In some children, spontaneous healing occurs - the joint capsule contracts, the femoral head is centered in the acetabulum, which ensures further correct development of the joint.

Hip subluxation is formed with the progression of the pathology. Femoral head remains in the acetabulum. It is decentered, displaced but does not yet fall outside the labrum.

Hip dislocation occurs when the head loses contact with the acetabulum and limbus interposition occurs. Even before ambulation initiation, the femoral head shifts upwards under the influence of muscle traction and is located at the acetabulum posterior external edge until about one year of the child's life. Since ambulation initiation, the hip displacement gradually progresses, and the femoral head shifts under the anteroinferior spine, where a new support is formed. The limit of its displacement is the posterior surface of the iliac wing (Fig. 20.1).

Fig. 20.1. Congenital hip dislocation: a) normal state; b) preluxation; c) subluxation; d) luxation

Etiology

One of the causes for congenital hip dislocation development is the delay in the normal hip joint development during fetal life. Most authors believe that due to the unfavorable position of the lower extremities in sharp adduction, the femoral head and acetabulum begin to develop without close contact, which leads to their dysplasia (Fig. 20.2). Therefore, hip dysplasia is most often found in newborns, and dislocation is formed later, but the cases are possible when a true developmental anomaly of the hip joint is present, and dislocation is formed in the first days of life. Hip dislocation on the left is more common, which is explained by the left-sided position of the fetus in the womb. Dislocation is more common in girls than in boys.

Fig. 20.2. The frequency of congenital hip dislocation in breech presentation

Diagnosis

For timely diagnosis, it is necessary to examine newborns in the maternity hospital.

The slipping sign ("click") is essentially the only clinical sign of hip preluxation in newborns. The femoral head "rolls" over the elevation of the acetabulum edge, easily dislocating from it and setting back with a tangible click. Manipulations should be performed very carefully, which requires a certain skill. The sign is detected as follows: the child's legs are flexed in the knee and hip joints at right angles, the doctor's thumbs are located on the inner surface of the thigh, and the rest - on the outer surface, with the third finger resting on the greater trochanter. The hip is abducted at a 30-40° angle conducting mild traction along its axis. With a slight finger pressure in the medial direction, the head is set, and when the thumb is pressed on the inner surface of the thigh - it is dislocated (Fig. 20.3). To detect this sign, relaxation of the shin muscles is important, so it is advisable to conduct an examination either during sleep, or after the child is acquainted with the doctor's hands and completely relaxes their muscles. With the child's growth, this sign loses its significance: it becomes unstable due to the progression of changes in the hip joint. The stretched capsule contracts rapidly, and the adduction contracture of the hip increases. Therefore, this sign is noted only in 25% of cases with children older than 2-3 weeks. Other signs of incongruence in newborns are not usually observed; they start to manifest in the first months of the child's life.

Fig. 20.3. Determination of the "slipping" sign

Limited abduction in the coxofemoral joint in most cases is noted due to an increase in the tone of the hip adductor muscles. However, it may be observed in many diseases including neurological disorders; so in this case, a consultation with a neurologist is required. Normally, with abduction in the coxofemoral joint of a newborn, the outer surfaces of the hips should touch the table surface, later in life, the abduction should be at least 60° (Fig. 20.4). In case of congenital hip dislocation, hip abduction is limited due to the femoral head rests on the ilium.