- See:
Pseudoachondroplasia
- Cervical Spine:
- stenosis of foramen magnum:
- all patients with achrondroplasty will demonstrate some radiographic stenosis of foramen magnum, and many can be shown to
demonstrate either some at least some clinical symptoms or some somatosensory abnormalities;
- may contribute to hypotonia, ventilatory insufficiency such as sleep apnea, and/or sudden death in infants;
- in working up stenosis of the foramen magnum recognize that respiratory abnormalities may be due to restrictive lung disease (from chest shape abnormalities);
- Spine:
- spine is affected by progressive decrease in distance between pedicles of lumbar vertebra, which diminishes size of vertebral canal and
may cause lower extremity paralysis and bladder dysfunction;
- prominent lumbar lordosis is seen in achondroplasia and in many other skeletal dysplasias;
- it generally does not respond to bracing but is not of sufficient concern to warrant surgery.
-
thoracolumbar kyphosis:
- present in most infants, resolves in 90% of affected pts as they begin to walk;
- some authors distiguish between supple kyphosis (most patients) and rigid kyphosis (which has a worse prognosis);
- initial treatment is to delay sitting in infancy;
- most flexible kyphotic curves resolve once the patient starts walking (generally delayed until age 2);
-
bracing:
- if flexible kyphosis persists, however, it should be treated w/ extension orthosis (generally after 3 yrs);
- bracing is also indicated for rigid curves with kyphosis greater than 30 deg;
- ref: Achondroplasia: Effectiveness of an orthosis in reducing deformity of the spine. Arch Phys Med Rehabil 68:384-388, 1987 Siebens AA, Hungerford DS, Kirby NA:
-
indications for surgery:
- progressive kyphosis that occurs despite bracing requires early surgery;
- persistent angular thoracolumbar kyphosis w/ vertebral wedging of 40 deg or more by age 5 is aggressively treated w/ surgery;
-
surgical treatment:
- combined anterior strut grafts and posterior fusions should be performed, w/ anterior strut grafts & posterior fusions;
- anterior decompression is reserved for those pts w/ neurologic comprimise;
- surgical options include decompression and fusion for severe kyphosis (most will correct spontaneously but anterior decompression and
strut grafting & posterior fusion w/o instrumentation are indicated for kyphosis > 60 deg;
- lumbar stenosis:
- compared to normal pts, there is 30% decrease in cross-sectional area secondary to both abnormal endochondral ossification of posterior
vertebral growth centers and degenerative changes;
- stenotic deformity in the lumbar spine of pts w/ achondroplasia tends to woresen w/ increasing age;
- mild pre-existing thoraclumbar kyphosis further narrows the space available for the neural elements;
- hip flexion contractures seen in these patients may cause increase lumbar lordosis and aggravate the thoracolumbar kyphosis;
- non operative treatment should include wt loss (typically problem), bracing, and exercises (unpredictable);
- nonsurgical brace rx of spinal stenosis are aimed at decreasing lumbar lordosis w/ flexion, thereby "opening up" spinal canal;
- if myelography is necessary for evaluation of neurologic deficit, it should be performed via cisternal puncture above suspected lesion
to avoid the technical difficulty of inserting a needle into a small canal;
- also, removal of CSF may exacerbate neurologic symptoms in already compromised small spinal canal;
- multilevel decompression for stenosis (recommended for inter-pedicular distances of < 20 mm at L1 and < 16 mm at L5);
