Acute poliomyelitis is a viral infection that damages the anterior horn cells motor nuclei, causing paralysis. From a human host, the disease is spread by the oropharyngeal route. Most develop only a mild gastroenteritis. About 1% develop paralysis.
Stages of Poliomyelitis
Acute stage After an incubation period of 3 weeks, a systemic flu-like illness develops. Rarely, the infection spreads to the nervous system, causing inflammatory changes with varying degrees of neuronal degeneration. Over a period of 2 weeks, a progressively increasing paralysis develops without sensory involvement. Muscles with motor nuclei extending over several segments are most likely to be affected. About twice as many muscles become weak as become totally paralyzed.
Convalescent stage This recovery phase extends over a period of about two years. Most recovery occurs during the first few months. Contractures start to develop during this period.
Chronic stage After about two years, the disease becomes chronic. Muscle imbalance, contractures, and growth cause increasing deformities. Most severe deformities are seen in severely affected younger patients with many years of growth. Limb atrophy and shortening are characteristic deformities. Without management, children develop methods of mobility that take a variety of forms. Muscle imbalance causes pelvic obliquity, and scoliosis may occur. Walking with aids may occur in those less involved.
Postpoliomyelitis syndrome (PPS) causes slowly progressive weakness, atrophy, muscle pain, and fasciculations that occur 15 or more years following the original disease. Management is usually conservative.
Orthopedic Management of Chronic Poliomyelitis
Assessment requires a careful evaluation, which includes grading strength of muscle groups, determining the range of active and passive motion, assessing contractures, determining limb length differences, and documentation of deformity. Function may be improved by tendon transfers. This requires a preoperative assessment of specific muscles to determine which have adequate strength to function effectively in a rerouted position. Prognosis is better for the young, with minimal paralysis. Sensation and IQ are unaffected, improving prognosis as compared with children with cerebral palsy or myelodysplasia.
Deformity correction is by gentle stretching and splinting. An overcorrected position may improve or prevent progression of deformity. Stretching must be performed carefully to avoid fractures of the fragile bone.
Operative correction procedures may be very effective in correcting deformity and restoring function.
Tendon transfers These transfers are effective if applied for the appropriate indications.
Upper limb The objective is to place the hand in a position for optimum function and for stability to facilitate transfers and crutch walking. Children with little hand function may still use crutches and have prehension between the arm and the chest. These important adaptive functions should be preserved. Shoulder stability is more important than mobility. Elbow and hand require mobility for optimal function. Establish motion and correct deformity before performing tendon transfers.
Spine Scoliosis occurs in about a third of children with paralysis. Curve patterns are usually either a double-major or long paralytic type. Pelvic obliquity is common. Bracing may slow progression for 20°–40°curves. For curves 40°–60°, a posterior segmental instrumentation and fusion are often indicated. Curves >60° may require anterior and posterior instrumentation and fusion.
Lower limb requires most attention, as paralysis is more common and corrective procedures are most effective. The objective is to provide stability and symmetry for walking with or without a brace. The foot should be plantigrade, the knee extended, and the hip stable. Symmetry requires an absence of significant pelvic obliquity and leg length inequality. With good medical care, about 60% of these children can become community ambulators and 30% household ambulators.
Common procedures in poliomyelitis include shoulder fusions, tensor fascia releases, correction of knee flexion contractures, rotational osteotomies, correction of calcaneus and cavus deformities, and limb length equalization procedures.