Achondroplasia is a congenital disease in which the process of growth of the bones of the skeleton and the base of the skull is disrupted. The cause of the pathology is a genetic mutation. Part of the fruit dies in utero. At birth, disorders are noticeable from the first days of life: the head is enlarged, the limbs are shortened. Subsequently, there is a pronounced lag in the growth of arms and legs with a normal size of the trunk, there are valgus and varus deformities of the limbs, deformities of the spine. Pathology is diagnosed according to examination data, special measurements and radiography. Treatment is symptomatic, aimed at preventing and eliminating gross deformities.
Achondroplasia (congenital chondrodystrophy, Parro-Marie disease, diaphyseal aplasia) is a genetic disease in which there is a shortening of the limbs in combination with the normal length of the trunk. Characteristic features are low height (130 cm or less), a forward-curved spine, a saddle-shaped nose and a relatively large head with protruding frontal bumps. According to experts in the field of traumatology and orthopedics, achondroplasia occurs in one out of 10 thousand newborns, women suffer more often than men. There are currently no ways to completely cure achondroplasia by restoring the growth and proportions of the body. Treatment is aimed at minimizing the negative consequences of the disease.
The pathology is based on a violation of bone development due to genetically determined dystrophy of epiphyseal cartilage. The cause of the disease is a mutation of the FGFR3 gene. In 20% of cases, achondroplasia is inherited, in 80% it develops as a result of a mutation that has arisen for the first time. Due to the chaotic arrangement of the cells of the germ zone, a violation of the normal ossification process occurs. As a result, bone growth slows down. At the same time, only bones growing according to the enchondral type are affected: tubular bones, bones of the base of the skull, etc. The bones of the cranial vault, growing from connective tissue, reach the required size, which leads to a discrepancy in the proportions between the head and the body, which causes a characteristic change in the shape of the skull.
The violation of anatomical proportions is noticeable already at birth: the child has a relatively large head, short arms and legs. The forehead is convex, the cerebral part of the skull is enlarged, the occipital and parietal tubercles protrude. In some cases, hydrocephalus is possible. There are violations of the structure of the facial skeleton, which arose as a result of improper development of the bones of the base of the skull. The eyes of patients with achondroplasia are widely spaced, located deep in the orbits, there are additional folds near the inner corners of the eyes. The nose is saddle-shaped, flattened, with a wide upper part, the frontal bones protrude noticeably forward, the upper jaw also protrudes significantly above the lower one. The language is rough, the palate is high.
The lower and upper limbs of achondroplasia patients are uniformly shortened, mainly due to the proximal segments (hips and shoulders). The handles of a newborn baby reach only to the navel. All segments of the limbs are somewhat curved. The feet are wide and short. The palms are wide, the II-V fingers are short, almost the same length, the I finger is longer than the others. In the first months of life, patients with achondroplasia have fat pads and skin folds on the extremities. The trunk is normally developed, the chest is not changed, the abdomen is protruding forward, and the pelvis is tilted posteriorly, so the buttocks protrude more strongly than in healthy children.
Infants with achondroplasia are more likely than their healthy peers to develop sudden death in their sleep. It is assumed that the cause of death in such cases is compression of the medulla oblongata and the upper part of the spinal cord due to an anomaly in the shape and size of the occipital foramen. In addition, children suffering from achondroplasia are characterized by respiratory disorders due to the features of the structure of the face, large tonsils and a small chest.
At 1-2 years of life, due to a violation of muscle tone, patients with achondroplasia may develop cervical-thoracic kyphosis, which disappears after the start of walking. All children have some lag in physical development. They begin to hold the head only after 3-4 months, learn to sit at 8-9 months and later and begin to walk at 1.5-2 years. At the same time, the intellectual development of patients with achondroplasia usually remains within the normal range, there are no mental abnormalities.
As they grow older, due to the perversion of epiphyseal bone growth, with normal periosteal growth, the bones thicken, bend, and become lumpy. Due to the increased elasticity of the epiphyseal and metaphyseal sections of the tubular bones, varus deformities of the limbs occur, rapidly progressing with early loading. The curvature is further aggravated due to excessive traction of well-developed muscles and a significant mass of a normally developing trunk. Due to the violation of the normal axis of the limbs, patients with achondroplasia form flat-toed feet, knee joints become loose.
There are a number of deformations characteristic of achondroplasia. The femoral bones bend and twist inward in the lower parts. Due to the uneven growth of the bones of the tibia, the fibula in the upper part “pushes” upwards and ceases to articulate with the tibia, and in the lower one “skews” the fork of the ankle joint. As a result, the ankle joint turns 10-15 degrees inward, the foot goes into the supination position at an angle of 10-20 degrees. The upper limbs are also curved, especially in the forearm area. Shortening of the upper extremities persists, however, in adult patients with achondroplasia, the fingers no longer reach the navel, but the inguinal fold.
In adult patients, there is a growth deficit caused mainly by shortening of the lower extremities. The average height of women is 124 cm, men – 131 cm. Changes in the head and facial skeleton persist and even become more pronounced: an enlarged cerebral part of the skull, a protruding and overhanging forehead, a deep bridge of the nose, a visible malocclusion. Strabismus is possible.
Patients with achondroplasia are prone to obesity. Due to narrowed nasal passages, they often develop otitis media, and conductive hearing loss is formed. Due to obstruction of the upper respiratory tract, signs of respiratory failure may be detected. With achondroplasia, narrowing of the spinal canal is often observed. It usually occurs in the lumbar, less often in the cervical or thoracic spine. It may manifest as sensitivity disorders, paresthesia and pain in the legs. In severe cases, pelvic organ dysfunction, paresis and paralysis may occur.
The diagnosis of achondroplasia is made by a pediatric orthopedist, does not cause difficulties due to the characteristic appearance and proportions of the patient’s body. All children are examined in detail to assess the degree of deviations from the normal development of the skeleton, the data are entered in the table. This table is regularly updated as the child grows, and the data entered in it are compared with a standard table specially compiled for patients with achondroplasia.
To assess the condition of various organs and systems, a comprehensive examination is carried out, consultations of various specialists are appointed. To exclude hydrocephalus, newborn children with achondroplasia are examined by a neurosurgeon, if hydrocephalus is suspected, an MRI of the brain or a more accessible computed tomography is prescribed. To study the condition of the nasal passages and ENT organs, achondroplasia patients are referred for consultation to an otolaryngologist. You may also need to consult a pulmonologist.
Skull x-ray reveals a disproportion between the facial and cerebral parts. The occipital foramen is reduced in size, the lower jaw and the bones of the cranial vault are enlarged. The Turkish saddle has a characteristic shoe-shaped shape and a flat, elongated base. Chest X-ray in achondroplasia is usually unchanged, in some cases the sternum protrudes forward and is somewhat curved. It is possible to thicken the ribs and their deformation in the area of transition to cartilaginous arches. Sometimes there are no normal anatomical bends of the collarbones.
As a rule, no gross changes are detected on the spine images of patients with achondroplasia, physiological bends are less pronounced than in healthy people, while lumbar hyperlordosis may be detected. Radiography of the pelvis indicates a change in the size and shape of the wings of the iliac bones – they have a rectangular shape, unfolded and shortened. The horizontal location of the roof of the acetabulum is also determined.
Radiography of tubular bones in patients with achondroplasia reveals shortening and thinning of the diaphyses, thickening and goblet-shaped expansion of the metaphyses. The epiphyses are immersed in metaphyses by the type of hinges. Joint radiography shows deformity and incongruence of articular surfaces, expansion of articular gaps and violation of the shape of the epiphyses. Radiographs of the knee joint of patients with achondroplasia indicate an elongation of the fibula, rotation and supination are determined during radiography of the ankle joint. The reliability of the clinical diagnosis is confirmed with the help of genodiagnostics.
A complete cure of patients by the forces of modern orthopedics is not yet possible. Attempts have been made to carry out treatment using growth hormone, but reliable evidence of the effectiveness of this technique in achondroplasia could not be obtained. At an early age, conservative therapy is carried out aimed at strengthening muscles and preventing limb deformity. Patients with achondroplasia are prescribed exercise therapy, massage, recommended to wear special orthopedic shoes, etc. Prevention of obesity is carried out.
Surgical interventions in achondroplasia are indicated with pronounced deformities of the limbs and narrowing of the spinal canal. Osteotomy is performed to correct deformities, laminectomy is performed to eliminate spinal stenosis. In some cases, operations are also performed to increase growth. Limb elongation in achondroplasia is usually carried out crosswise, in two stages: first, the thigh is lengthened on one side and the lower leg on the other, then surgical interventions are performed on the remaining segments.
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