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Ultrasound examination of the hip joint is a mandatory component of newborn screening. Screening (medical examination) is a set of measures aimed at identifying/preventing diseases. It must be carried out at the age of one or two months. The main purpose of ultrasound is to confirm or refute the diagnosis of hip dysplasia. What you need to know about the disease, how exactly is the study carried out and is ultrasound safe for the baby’s body?
Peculiarities of pediatric diagnostics
The hip joint is a spherical, multiaxial joint of the human body. It is formed by the semilunar surface of the pelvic bone and the articular surface of the femoral head. The main properties are circular rotation, flexion, extension, abduction, adduction of the hip. The functionality of the musculoskeletal system largely depends on intrauterine development. Initially, the baby is born with “soft” bones in order to safely pass through the birth canal and be born. But already in the first months of life, the bone skeleton becomes stronger, which makes it possible to track the norms and pathologies.
Ultrasound of the hip joint is a mandatory procedure as part of newborn screening. It is carried out at 1 or 1,5 months to confirm / refute dysplasia. Diagnostics helps to identify changes in the structure, position of the articular cavity, the degree and features of the formation of the femoral head, flexibility of the ligaments, and so on.
In the treatment of dysplasia, the age of the child and the timeliness of diagnosis are fundamentally important. In the period from the first to the sixth month, the therapy will consist of massage, soft swaddling or its absence, wearing the baby in a sling and other comfortable manipulations. After six months, to get rid of dysplasia, the child will have to wear rigid plaster spacers. They limit mobility, and when worn for a long time, they start the process of muscle atrophy. This disrupts the natural development of the baby and can affect psychological health.
Do not ignore preventive examinations and provide your child with qualified medical care. Timely diagnosis will speed up the treatment process without affecting the quality of life of the baby.
Hip dysplasia
Dysplasia is a congenital defect of the hip joint. Pathology is caused by abnormal development of the movable bone junction and leads to dislocation/subluxation of the femoral head.
According to statistics, the disease is diagnosed in 2-3% of newborns worldwide. In 80% of cases, dysplasia occurs in girls. Most often, problems occur with the left hip joint (60%), less often with the right (20%) or with both at the same time (20%).
With dysplasia, a change in the shape / size / structure of the joint is diagnosed. The load is distributed unevenly, which determines the slowdown / acceleration of bone growth. Manifestations, final shape and general condition of the bones are determined on an individual basis. In newborn babies, the hip joint is an immature biomechanical structure. His ligaments are too elastic, and the glenoid cavity is thickened and vertical. The overall functionality of the body depends on the nature of the development of the mobile bone joint. That is why early diagnosis is so important for the full health of the musculoskeletal system.
There are several stages of dysplasia – pre-luxation, subluxation, dislocation. With pre-dislocation, the joint cannot be held within the boundaries of the articular cavity. Subluxation is characterized by partial displacement of the femoral head. With a dislocation, the head of the femur is completely displaced. Ultrasound examination helps to identify all stages of dysplasia. If diagnostics and treatment are ignored, the child begins to limp, feel severe pain, growth/development disorders are possible, which leads to serious problems in the future.
How does an ultrasound machine work?
Ultrasound is powerful sound waves. Human hearing organs can perceive a frequency from 16 to 20 kHz, so ultrasonic vibrations (from 20 kHz) are beyond our acoustic perception. However, some groups of animals (whales, dolphins, bats, and others) communicate with ultrasound. Each wave is characterized by an oscillation period, frequency and length. All of them depend on the elasticity/density of the medium through which this wave propagates. Any environment, including the tissues of the human body, prevents the propagation of sound vibrations. This is called acoustic impedance. The speed and density of sound waves depend on the magnitude of acoustic resistance.
As soon as a sound wave reaches the boundary of two media with different acoustic impedance (for example, soft and hard tissues), one part of it propagates in the new medium and is absorbed by it, while the other part is reflected. The intensity of the reflection depends on the magnitude of the acoustic impedance. The higher the indicator, the brighter and lighter the signal that the ultrasonic equipment receives. Additionally, the technique records the distance to the separation boundary, the time it takes the wave to pass, the speed of movement, the difference in densities, and so on.
Human skin reflects 99,99% of sound vibrations, making ultrasound impossible. That is why the scanned area is lubricated with a special aqueous jelly, which acts as a transition medium.
The reflected sound wave enters the amplifier and special reconstruction systems. They process the received information and transform it into slices of the studied part of the body. The picture is painted in black and white, which uses at least 64 different gradients of the black and white scale. The maximum intensity of sound vibrations is fixed in white, and the minimum intensity in black.
There are three operating modes of ultrasound – A, B, M. A-mode provides a one-dimensional picture, B-mode – a two-dimensional image of anatomical structures in real time. M-mode is a one-dimensional image with a time coordinate. It is used to diagnose the functionality of the heart.
To make the image as informative and accurate as possible, contrast agents (echo contrast) are used. The contrast agent contains free microbubbles of gas (less than 5 µm in diameter). They improve the visualization of blood flow or individual organs, increase the contrast between tissues and increase the accuracy of diagnosis.
Indications/contraindications for
Indications for examination of the hip joint in newborns (in addition to screening):
- the birth of a baby at a period of less than 37 completed weeks;
- increased tone of the lower extremities;
- heterogeneity of symmetry / depth of skin folds on the baby’s body (special attention should be paid to the area of the hips and buttocks);
- unequal length of the limbs;
- dysembryogenesis (disorders of embryonic development that occur due to genetic or teratogenic factors);
- excessive clicking or cracking in the joints;
- limited functionality of the hip (for example, it is impossible to completely spread the hips during the massage);
- neurological abnormalities;
- the birth of twins / triplets (one fetus gets unlimited access to the resources of the mother’s body, and several children have to share nutrients among themselves).
There are no contraindications for ultrasound examination. Ultrasound is sound waves that the human ear simply cannot perceive. They do not affect the performance of our body in any way, which means they are absolutely harmless.
What are the advantages of the method
Since 1989, ultrasound has been used in pediatrics. It is noteworthy that the first studies were aimed at studying the hip joint. The problem of dysplasia was found everywhere, and therefore required an effective solution and constant monitoring. Ultrasound examination still does not lose popularity and remains the safest, most informative and accurate diagnostic method. The production and use of ultrasound equipment is strictly regulated by the World Health Organization, so parents can be sure of their quality and functionality.
The main advantage of ultrasound is safety. Unlike X-rays or computed tomography, after which radiation doses accumulate in the body, ultrasound does not affect a person in any way. It is this type of diagnosis that suits the most vulnerable categories of patients – newborns, pregnant / lactating women and the elderly.
The second advantage is maximum patient comfort. During the study, the baby does not need to be fastened with soft belts or forcibly held in his arms so that the device fixes the state of the body. On the contrary, activity within the normal range will help the doctor to better examine the hip joint and will not overshadow the mood of a small patient. Additionally, a specialist can track the dynamics of changes, fix inflammatory processes or defects in muscles, ligaments, tendons, joint capsule and cartilage.
Preparation and conduct of the study
No specific preparation is required. The main thing is that the baby is full and calm, because excessive activity, crying or fear simply will not allow the doctor to diagnose. Parents should think over the child’s outfit in advance – the lower part of the costume should be easily and quickly removed so as not to waste time.
The baby is placed on a couch, previously covered with a diaper, lubricated with a special gel and the sensor of the ultrasound machine is leaned against. The doctor gently moves the sensor from side to side, examining the joint. The device simultaneously emits sound waves, captures their characteristics and displays an image of the internal cavity on a computer. The doctor and parents can watch what is happening in real time through the computer screen. The uzist scans both hip joints with adjacent soft tissue and bone areas. Periodically, the doctor turns the baby on the left or right side / back / stomach, raises or lowers the limbs, twists them slightly in order to study in more detail the condition and functionality of the bone skeleton.
A convex transducer is used to diagnose the hip joint. Its frequency varies from 1,8 to 7,5 MHz. Yes, the device is minimal, which ensures complete adherence to the patient’s skin. A feature of the sensor is the size of the final image. Its width is several centimeters larger than the sensor itself. Doctors must take into account this discrepancy in order to navigate the anatomical structures and understand their real size. Typically, convex probes are used to diagnose deeply located organs (the hip joint, organs of the gastrointestinal tract, reproductive or urinary systems).
The study lasts only a few minutes. Once all the information is collected, the doctor completes the examination, erases the liquid gel, prints the necessary pictures and talks with the parents about the norms and pathologies of the hip joint.
Norms and pathologies
At least two specialists are engaged in deciphering the image. The doctor who conducted the study makes a preliminary diagnosis, and the orthopedist who wrote out the referral for diagnosis studies in more detail and compares the anamnesis with the ultrasound results. Specialists evaluate the angle of the femoral head relative to the acetabulum, the general condition of the bone and tissues that are located around. The doctor draws two lines along the joint, which form angles, and classifies them according to the Graph table. The first angle indicates the elevation of the acetabular fossa and should be greater than 60°. The second angle characterizes the development of the cartilaginous space of the cavity and should be less than 55°.
These figures are calculated for newborn babies up to three months old. Each age category has its own norms and pathologies. For more detailed information, contact your doctor.
In general, there are 4 variations of the diagnosis – the norm, developmental delay of the joint, subluxation or dislocation. Based on the diagnosis, the doctor draws up an individual therapeutic plan and informs his parents. Massage and daily activity are usually sufficient for newborns. For older children, more stringent methods of correction are suitable. Remember, the earlier the pathology is detected, the faster and easier the therapy will be.
Ultrasonography of the hip joint is a standard diagnostic procedure that is prescribed before the age of three months. It is carried out as part of the screening of newborns in order to study the norms and pathologies of the child’s body. Ultrasound is the best alternative to X-ray, which is carried out for babies up to the sixth month of life. Unlike x-rays, ultrasound is absolutely safe, accurate and informative. An ultrasound referral can be obtained from an orthopedist or you can independently choose a specialized medical center for diagnostics. Enjoy the benefits of modern medicine and be healthy!