Ultrasound of the hip joints in newborns
Last reviewed: 18.10.2021
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Certain skills and abilities are needed to conduct ultrasound (ultrasound) of the hip joints of newborns in order to exclude congenital hip dislocations. With the appropriate skill, the lower part of the ilium, the acetabulum, especially the upper part of the hip joint and the edge of the acetabulum can be visualized. An exact location of the femoral head can be determined, and any violation of the shape or size of the hip joint is detected.
If there are any doubts, or if there are even minor echographic signs of dislocation of the hip joint in a newborn, repeat the test at the age of 4-6 weeks. By this time most joints become normal.
Anatomy of the hip joint of the newborn
The hip joint is formed by the articular surfaces of the head of the femur and the acetabulum of the hip bone. The head of the thigh, cervix and most of the acetabulum in the newborn are composed of cartilaginous tissue. Cartilage tissue before ossification looks gipoehogennoy with ultrasound. In the formation of the acetabulum involved three bones: iliac, ischial and pubic, which in the newborn are connected by means of cartilage. The free edge of the acetabulum is attached to the acetabulum, which increases the depth of the cavity and covers the head of the femur.
Ultrasound examination of the hip joint in children
Congenital hip dysplasia occurs in about 10 cases per 1000 healthy infants. This abnormality is usually called an abnormality of the hip joint, which is detected at birth, when the head of the femur is completely or partially displaced from the acetabulum. There are different degrees of dysplasia: from subluxation of the hip, incomplete dislocation of the hip, to complete dislocation of the hip with a displacement and with varying degrees of underdevelopment of the acetabulum. The use of X-ray examination in newborns to diagnose this anomaly is inexpedient, since the X-ray method does not fully reflect the changes occurring in the cartilaginous tissues of newborns. On the contrary, with ultrasound cartilage structures are reliably displayed. Therefore, the ultrasound method is widely recognized as a method of choice in diagnosis and monitoring of treatment of hip dysplasia in newborns. The research method includes carrying out stress and dynamic tests to assess the position, hip joint stability and development of the acetabulum, based on the relationship between the head of the femur and the acetabulum.
Method of ultrasound examination
The standard ultrasound of the hip joint of newborns, according to published data of the American College of Radiologists, should include three stages. In the first stage, the position of the femoral head in relation to the acetabulum is evaluated in an ultrasound study. At the second stage, the stability of the hip joint is investigated. Evaluate the change in the position of the femoral head during movement and the stress test (after the Barlow and Ortolani tests). The Barlow test consists in pressing the knee of the baby, which is bent and bent at the knee joint, to the knee.
With this sample, the femoral head is displaced from the acetabulum. When carrying out the Ortolani test, the femoral head itself is inserted into the acetabulum when the knee is bent at the knee joint. It should be noted that up to 2 months in normal these tests can be positive. When subluxation (subluxation) of the head of the femur is noted, incomplete immersion in the acetabulum. With incomplete dislocation, the displacement of the femoral head from the acetabulum occurs only when a dynamic sample or a stress test is performed. When completely dislocated, the head is completely outside the acetabulum until samples are taken. At the third stage, morphological disturbances in the formation of bone and cartilaginous tissues of the acetabulum are revealed. Quantitative indices: the development of the angle of the acetabulum and the angle of immersion of the head of the femur into the acetabulum reflect the degree of dysplasia. The study is performed when the baby is lying on his back or on his side. To investigate this joint and surrounding soft tissues, use a 7.5 MHz sensor with a linear or convective working surface, in a 3-month-old baby it is better to use a 5 MHz sensor.
The sensor is installed longitudinally in the projection of the acetabulum. Bony landmarks are: the line of the ilium, the transition of the ilium to the acetabulum, the head of the thigh with the joint capsule. Normally the iliac line will be horizontal straight, when it passes into the cartilaginous part of the acetabulum, it forms a bend. In this projection, the corners are measured by the graph. The bend and the horizontal line form an angle a - the degree of development of the acetabulum, the second angle - the angle of immersion of the femoral head - b. Angle a has less error and variability than b. Normally the angle a is more than 60 °, with the subluxation the angle a decreases to 43-49 °, while the angle α is less than 43 °. Angle b with subluxation less than 77, with dislocation - more than 77.
Measurement of angles is not accepted in all clinics. In a number of cases, they are limited to describing the bending of the acetabulum, the configuration of the lateral margin of the ilium and the structure of the acetabulum. It is also possible to calculate the degree of immersion of the femoral head in the acetabulum (Morin et al.). Normally, more than 58% of the femoral head should be immersed in the acetabulum.
When carrying out a dynamic test: withdrawal - reduction, flexion - extension of the limb, the position of the femoral head should not change. When conducting a stress test, the head of the hip should not be displaced from the acetabulum. The head of the femur can be displaced laterally, upward, posteriorly, depending on the degree of dysplasia. To detect the direction of displacement, the sensor is moved in the antero-posterior direction, and also transverse sections of the hip joint are obtained.
When tested in a transverse section, the infant's legs are bent approximately 90 °. The sensor is installed in the projection of the acetabulum. A cut of the metaphysis of the femur, the head of the femur and the ischium is obtained. The head of the femur at this cut is normally immersed completely between the metaphysis and the ilium, which form the Latin letter U. In this position, a lead-off test is also conducted to exclude sublaxation. In the presence of bias, the femoral head is displaced and the metaphysis of the thigh approaches the ileum, forming the letter V.