In this article, two surgeons well known for their work in this area review the spinal manifestations of achondroplasia. Their specific focus was on the treatment of spinal problems linked with this condition.
Achondroplasia is a genetic disorder that results in a common type of dwarfism. Children who are born with this condition have a variety of deformities, including several in the spine. The most common spine problems include foramen magnum stenosis, thoracolumbar kyphosis, lumbosacral hyperlordosis, and spinal stenosis.
The authors discuss the treatment of each one of these conditions. They review previous studies done and summarize their findings. The first deformity to appear in the infant or young child is foramen magnum stenosis. This refers to narrowing of the opening at the base of the skull where the spinal cord exits.
Many problems can occur when the narrowing is enough to cause pressure on the spinal cord. Children may have difficulty swallowing, reduced muscle tone, muscle weakness, and delays in development. Surgery is often needed to take pressure off the neurologic structures. This type of procedure is referred to as surgical decompression.
Thoracolumbar kyphosis is a curved mid-lower back from the way the children slump-sit. If uncorrected, the anterior (front) section of the vertebrae get pushed into a wedge-shape. Surgery isn’t usually needed but prevention is important.
As the child grows and develops, he or she assumes an upright position. This has the effect of improving trunk strength. The child starts to walk. Both of these factors work to overcome the forces that created slumping and wedging. Bracing is used during the interim. The child is not allowed to sit unsupported.
When these efforts fail to prevent progressive kyphosis, then surgery is done to stabilize the spine. Multiple pedicle screws are used to fuse vertebral segments together. Screw size and angles are important in this population.
The authors describe the successful results of previous studies they have done using a two-stage anterior and posterior spinal fusion for this problem. They also discuss studies done by other surgeons using a one-stage anterior procedure, posterior alone surgery, and reconstructive surgery for adults with thoracolumbar kyphosis from achondroplasia.
Lumbosacral hyperlordosis is an increase in the normal swayback position of the low back area. The more thoracic kyphosis is present, the more the body tries to compensate with increased lordosis. When viewed from the side, the child with these two features has a prominent abdomen (belly) and buttocks.
The best way to treat lumbosacral hyperlordosis is unknown. Conservative (nonoperative) care with muscle stretching has not helped. Surgeons have tried releasing hip flexor muscles and bone lengthening procedures without success. This is an area for future study.
Spinal stenosis (narrowing of the spinal canal) is the final spinal manifestation of achondroplasia that is presented. In this condition, not only is the spinal canal narrow, but the vertebral bodies are also short and thick.
The effect of these changes is to reduce the distance between the vertebrae, discs, ligaments, and other soft tissues. At the same time, the spinal cord and spinal nerves are all a normal size. The mismatch between these structures increases the risk that the stenosis will cause painful symptoms.
Children can be affected by spinal stenosis, but more often, this condition develops during the adult years. Most of the time, it’s the lumbar spine that’s involved. But stenosis can also affect the cervical (neck) spine, too. When symptoms are severe, surgery may be needed. This happens in about one-fourth of the achondroplasia patients with cervical or lumbar stenosis.
Studies show that simple decompression is not successful with these patients. There are many complications reported such as dural tears, wound breakdown, and infections. Instrumentation used to fuse the spine such as screws or plates are also at risk for breaking, shifting position, or coming loose. Kyphosis (forward curvature of the spine) is a typical complication in children. This is especially common after decompression at multiple levels.
The authors conclude there are many difficulties in treating spinal problems in children with achondroplasia. Even so, it is possible to manage this condition safely and effectively. Treatment at a center where the surgeons and staff have experience with this diagnosis is strongly advised.