What are the Surgical Options?
Orthopedic surgery is often recommended when spasticity and stiffness are severe enough to make walking and moving about difficult or painful. The spine is monitored for scoliosis, and the hips for progressive dislocation. In younger children, lengthening or transfer of contracted tendons may suffice. This surgery is typically supplemented by bracing to prevent early recurrences. For older children with bony deformities, corrective osteotomies (cutting and resetting of the bony alignment) may be required. If surgery becomes necessary, it is wise to do as much as possible at one setting (single event multilevel surgery (SEMLS)) both to keep multiple levels in balance as well as to avoid having to operate too frequently through childhood. Indications for surgery are generally different in ambulatory as opposed to non-ambulatory children.
The goal here is to improve walking, though the spine and hips must still be monitored as in the non-ambulatory child. Typically the children are ambulating but with some issue such as toe walking, a poor stride length, scissoring (hips crossing over while walking) or crouching (the knees bent while walking). At times the feet may not be aligned with the way that the child is walking and there may be toeing in or toeing out. Instrumented three dimensional gait analyses may be helpful in identifying which muscles are contributing to the abnormalities, and examination can determine if there are twists in the bones that need to be addressed. Scissoring may be caused by tight adductor muscles of the hips or flexion at the knees and internal rotation at the hips. A crouch gait may be related to simple weakness, or balance issues, or can be due to contractures of the hips and/or knees. For the ankle level the issues are tightness or weakness of the triceps surae, or both. In the past heel cords were released as necessary, but now we recognize that the gastrocnemius may be tight without the soleus being involved. The latter is important in lifting the heel at the end of stance (‘push of’) so that when possible it must be preserved. Otherwise, there is a risk of further crouching at the ankle as the child ages. The exception is the child with hemiplegic, where toe walking may be treated (after conservative measures such as casting and or botulinum toxin) by tendon achilles lengthening without concern for later crouching which is a risk only for children with both lower extremities involved (i.e. diplegia).
The goal is to promote ease of care by preventing contractures, the development of significant scoliosis and progressive hip subluxation. This is done to promote useful sitting and transfers, if possible, and to prevent pain and pressure difficulties which may eventually accompany poor sitting postures, and subluxed hips. To ensure good sitting height and lung development, scoliosis surgery is postponed as late as possible by sitting modification and at times bracing. Likewise, hip abduction bracing or chair ‘pom pom’ modifications may be useful to control hip subluxations. Both of these areas are monitored by x-rays. Spinal fusion may be offered for curves in older children that exceed 50 degrees when sitting. The mere presence of hip and knee contractures in individuals who utilize a wheelchair are not in itself an indication for surgery. For progressive hip subluxation, iliopsoas release and adductor tendon lengthening may stabilize the situation, but when there is bony deformity of the hip joint itself, or when spasticity is particularly severe, proximal femoral varus osteotomy (cutting and redirecting the thigh bone) and/or acetabuloplasty (deepening or reorientation of the socket) may be necessary. For foot deformities, the goal is to perform procedures that allow the child to wear comfortable shoes and to be able to place them properly in a wheelchair foot platform. This may require tendon lengthening, particularly the triceps surae (heelcord) and the posterior tibialis muscles (responsible for inverting or turning the foot in), but may require bony realignments and fusions in more severe cases.
Although not readily apparent to the untrained eye, the position of the foot with respect to the leg is helpful in extending the knee. When distorted, this relationship is often referred to as ‘lever arm’ disease. Likewise, the position of the knee with respect to the axis of the hips is also important in gait progression so there is not excessive ‘kneeing in.’ Why correct such deformities? Severe kneeing in or scissoring may impede one leg from moving ahead of the other. Further, if an otherwise uninvolved individual were to attempt to walk in a crouched manner, he or she would experience great fatigue in a short amount of time. Similarly, if they were to take half steps all day long, they would likewise feel very fatigued. Half steps or a shorted stride may result from tight hamstrings. Thus, correction of such abnormalities may result in a more efficient gait, with a greater stride length, greater self-selected velocity and less fatigability.
Because there can be a combination of bony deformity and soft tissue contractures, along with weakness, deciding how much and which abnormalities to address can at times be challenging. Once a decision to address a gait aberration has been made, the trend among orthopedic surgeons is to do more at a single sitting and not less. This discussion did not touch on some of the nuiances, such as hyperextension of the knees, or patella alta, but when severe and symptomatic, these abnormalities may at times require complex reconstruction as well.
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Dystonia Medical Research Foundation
Metachromatic Leukodystrophy Foundation
Pelizaeus-Merzbacher Disease Foundation