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Post-Polio Health (ISSN 1066-5331)

Vol. 8, No. 4, Fall 1992

 

Special Feature on Scoliosis, continued

Polio Network News (Vol. 8, No. 2) featured articles by two polio survivors experiencing scoliosis. Doris S. Benedict, Deposit, NY, compiled responses from other Polio Network News readers, and Linda Bieniek, Chicago, IL, wrote about exploring your options when considering scoliosis surgery. The article below provides a professional point of view.
Poliomyelitis and Scoliosis

Serena S. Hu, MD
Department of Orthopedic Surgery
University of California-San Francisco

Scoliosis is an abnormal, side-to-side or lateral, curvature of the spine. It can be caused by
1) congenital structural abnormalities,
2) neuromuscular conditions such as poliomyelitis, spinal cord injury, or cerebral palsy, or
3) without known cause, also called idiopathic scoliosis, which is most often seen in the adolescent population.

Although the lateral curvature is that which is commonly measured, scoliosis produces a rotational deformity as well. This rotational deformity results in the most clinically evident aspect of scoliosis, the rib hump. In addition, the side-view (sagittal plane contour) is also important in assessing the spine. Kyphosis (hunchback) is defined as the forward curvature in this plane; normally the spine has a gentle kyphosis in the thoracic spine or chest region. Lordosis, or backwards curvature, is seen as the swayback aspect of the lumbar spine or low back. Increased or decreased kyphosis or lordosis relative to normal may have effects on spinal alignment, depending upon the person and his/her spines' ability to compensate.

While scoliosis is relatively common in people with neuromuscular conditions such as poliomyelitis, the need for treatment may vary. The prognosis for progression and eventual curve magnitude is
related to the age of onset of the curvature, as well as the extent of muscle involvement and muscle imbalance.

In young patients, that is those who have not completed their adolescent growth spurt, bracing is a useful option. Custom-molded braces, including the Milwaukee brace, as well as less cumbersome types such as the Boston brace, or the TLSO (thoracic-lumbosacral orthosis), can be used to prevent or slow progression of curvature in younger patients. For curves of higher magnitude, the amount of force which must be applied can result in chest wall deformity and should be observed for and avoided. In the adult population, bracing is not effective in preventing progression of scoliosis; however, it may be used in certain instances, as will be described below.

Treatment of scoliosis in the poliomyelitis population may be indicated for pain, progression, curve magnitude, or compromise of cardiopulmonary function. The worsening of cardiopulmonary function may be secondary to the magnitude of a thoracic curve or because the collapsing spine prevents adequate breathing. Collapse of a spine can also result in the increasing need for upper extremity support, thereby decreasing mobility of the arms.

Gait and its effect on the spine

There are several unique aspects of the polio patient which make treatment additionally complex.
Firstly, distinctive gait patterns are often developed by the polio survivor, depending upon the specific muscle groups and strengths available. Trunk motion may be an important factor in these adaptations, and, therefore, immobilizing part or all of the spine can affect gait. In many patients, stabilizing a collapsing spine may improve gait mechanics and efficiency. In others, the spine's hypermobility may be used to advantage in gait. However, it may be questioned as to whether this increased motion may accelerate degenerative changes in the spine.

Ambulatory ability may also be affected by muscle deconditioning which can quickly develop in the polio patient after several days of bedrest following surgery. Although most polio patients after spine fusion have unchanged or improved overall function, many need increased ambulatory aids in the early post-operative period, and a few continue to do so.

It may occasionally be useful to brace a surgical candidate pre-operatively, to assess how they might be able to alter their gait patterns. Gait concerns should be balanced with the disability associated with an increasing spinal curvature and associated pulmonary compromise.

Post-polio syndrome

Post-polio syndrome, or the deterioration of muscle strength and stamina long after the initial illness, may lead to impairment of the person's muscle and lung function. Although the presence of post-polio syndrome cannot be correlated with increase risk of progression of scoliosis, increased trunk muscle weakness may contribute to spinal collapse. Pulmonary function tests should be performed if surgery is considered, and may give information as to a person's risk for surgery, and the potential need for post-operative ventilatory assistance.

Degeneration of the spine

Adult scoliosis of the idiopathic type may present with pain secondary to degenerative changes. The pain can often be successfully managed with conservative measures, particularly muscle and
cardiovascular strengthening programs. Low back pain, for example, is quite common in the adult
population, and recovery from such episodes is also usual. This recovery can be facilitated by
physical therapy and/or exercise programs which strengthen the abdominal musculature as well as
the spine extensors.

Flexibility can be increased where needed by appropriate stretching of tight muscle groups.
Strengthening of the arms and legs, as well as aerobic training – walking, swimming, bicycling
– are also recommended for idiopathic scoliosis. A physical therapist should help design the exercise program appropriate to the specific symptoms and muscle involvement and should teach and/or supervise the performance of the exercises to ensure that they are done properly and for maximal benefit.

Although this treatment is useful in post-polio scoliosis, one may be limited as to strength gains
possible because of the polio involvement. If post-polio syndrome is present, some contend that
overexertion should be avoided, although monitored exercise programs do appear to be beneficial.

Because of the complex issues which can be involved in a person with post-polio scoliosis, it can
often be helpful if a multidisciplinary approach is applied. An orthopedic surgeon experienced in the care of patients with scoliosis, particularly those with poliomyelitis sequelae, may have pulmonary medicine colleagues evaluate patients and work closely with them in post-operative management.

Physical therapists can provide assistance and input regarding gait training, ambulatory aids, and
adaptations. Rehabilitation medicine specialists can be of assistance in optimizing the patient's function even if surgery is not indicated.

Indications for spine fusion

Spine fusion may be indicated for progression of curve, curve magnitude, or loss of pulmonary
function secondary to these changes. Pain may be a relative indication for surgery if conservative
measures fail to reduce it.

Should a person with a paralytic scoliosis secondary to poliomyelitis be indicated for surgery, several approaches may be offered. Early results of spine fusion with older techniques suggest that both anterior and posterior spine fusion were necessary to obtain a solid fusion in many patients with postpolio scoliosis. Halo-traction, either halo-femoral or halo-pelvic, was applied in many cases to improve the correction obtained with fusion. Today this method is generally recommended only for severe curves with significant cardiopulmonary compromise. In these cases, pre-operative halo-traction may result in improvement of cardiopulmonary function. (A halo is a metal or composite ring which is applied to the patient's head via several pins. Appropriate weights can be attached and countered either by weights attached to the person's pelvis or by their own body weight.)

Posterior fusion, in the back of the spine, was combined with posterior instrumentation and later
with anterior instrumentation and fusion. Harrington rods (instrumentation) permitted greater
correction, better maintenance of correction, and improved fusion rates than with fusion alone.
Harrington rods, until recently the gold standard of posterior spine instrumentation, utilized hooks at
either end of a ratcheted rod, across which distraction (lengthening) forces were applied for correction of the curvature. However, rods were less effective if the curve extended to the pelvis, that is, if there was pelvic obliquity.

Sublaminar wires (Luque technique)

The Luque technique, a system of multiple wires attached to rods, was devised to obtain better fixation to the spine. Luque wiring requires the placement of wires at each vertebral level under the lamina, into the spinal canal, and carries an increased risk of neurologic damage. However, damage is uncommon and usually temporary. The application of multiple fixation sites along the spine appears to give stronger fixation and better correction in osteoporotic spine.

The sublaminar wire technique (above) and the variable hook-rod system to be described below
can be combined with the Galveston technique for pelvic fixation. This involves placement of the end of a specially-bent rod – the top of which is attached to the rest of the spine via the aforementioned wires – between the sides of the pelvic bone and appears to afford the best pelvic fixation available at this time, as well as the better correction of pelvic obliquity.

Continued ...

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