Alternative Orthotic Management of the Spine in Children with Severe Spinal Muscular Atrophy

Scott M. Savage, CPO


Orthotically treating the severely involved SMA child for spinal deformity can be quite a challenge for the orthotist. Bracing has historically been the most conservative form of treatment but with poor results. Circumferential orthosis designs compress and limit thoracic and abdominal expansion required for maintaining the patient's VC (Vital Capacity or lung volume). Also, studies have shown that the curvatures will inevitable increase by a mean of twelve degrees annually despite intervention. For those reasons, spinal instrumentation with fusion has become the treatment of choice to address this problem. However, there are a small population of SMA patients in which surgery is not an option. Attempts are usually made to place them in spinal orthoses of limited tolerance or seating systems which may not fully provide optimal positioning and support required for comfort and function. With these factors in consideration, an alternative approach to orthotically managing severe SMA scoliosis without limiting the patient's VC will be presented.

Three subtypes of this disease have been identified in the literature; type I (acute infantile), type II (chronic infantile), and type III (chronic juvenile). The focus of this discussion will concern the type I group. Regardless of the type of SMA a person may have, expiration usually results from secondary complications affiliated with pulmonary insufficiency. This insufficiency lowers the individual's VC.

Factors influencing the VC deficit may be general respiratory weakness, lack of pulmonary expansion due to decreased chest wall movement, decreased pulmonary volume, deformity of the chest wall, and scoliosis. Respiratory infections are common and each are considered life threatening. Scoliosis occurs in 90% of SMA cases and 60% of these are paralytic in pattern. Rapid progression of the curve is the norm. Orthoses commonly used in treating this population include corsets, various total contact TLSO designs, and for historical purposes the TSO or thoracic suspension orthosis. Unfortunately, use of circumferential spinal orthoses has a major impact on the patient's already limited VC. The study published by Noble-Jamieson, et'al. did reveal that of sixteen neuromuscular patients with circumferential TLSO's there was mean decrease in VC of twenty two per cent. Seven of those sixteen had greater than twenty five percent decrease in their VC. From experience, restriction of pulmonary function typically leads to rejection of the orthosis. Surgical intervention does seem to be the answer to this population's problems. Spinal instrumentation can maintain VC status, increase comfort, independence, and cosmesis and eliminates the need for bracing. Unfortunately not all severe type I SMA are surgical candidates.

The most severely involved SMA patients, such as the acute or chronic infantile, tend to have extremely poor VC status initially and surgical intervention would compromise this even more. Skeletal immaturity or osteopenic structures render a spine in which effective instrumentation may not be possible. Their curvatures are quite high in magnitude and are associated with rotary components and pelvic obliquity's which are rigid in nature. Tolerance of circumferential compression and aggressive corrective forces associated with standard TLSO use are very limited. Seating systems may not fully address optimal positioning or comfort. Presented with this type of patient, the orthotist must examine the goals specific to this population. These include improved positioning in space while maintaining or increasing ADL function, providing comfort, and delaying further progression of the spinal deformity. With these factors in consideration an alternative approach to orthoti-cally managing the severe SMA patient will be presented.

The SMA-TLSO is essentially a posterior shell TLSO which wraps anteriorly but not completely. It utilizes the standard 3-4 point force systems associated with more conventional TLSO's but does not incorporate abdominal compression or increase in hydrostatic pressure. It is designed to lock into the pelvis by gripping the waist and encompassing the ASIS's anteriorly, maintaining the spine in as much correction as tolerated by the patient, and applying an infra-axillary stabilizing force opposite the convexity of the curve. Suspension is achieved from flexible abdominal and chest traps.

Promising results from use of this type of orthosis include less pulmonary restriction (maintains or improves the patient's VC), satisfactory comfort, and more optimal alignment in conjunction with an existing seating system, resulting in increased ADL functioning. One main compromising factor of this orthosis, as well with conventional TLSO's is that aggressive correction of the scoliosis is not well tolerated. These children typically present, as mentioned previously, with curvatures high in magnitude with excessive rotary components and pelvic obliquities. Accommodating these dramatic spinal shifts and bony prominences are necessary for overall patient comfort. In-brace correction may not be "orthopedically" optimal. Of the five patients fit with the SMA-TLSO, the average OOB (out of brace) Cobb angle measurement at the time of brace initiation was 50 degrees, with a range of 42 to 85 degrees. The average IB (in brace) findings were 52 degrees from a range of 48 to 71 degrees. In contrast, VC status when tested has not been reduced while wearing the orthosis. To day, only three of the five patients have had FVC (Forced Vital Capacity) tests done in and out of their orthosis. One patient demonstrated no change of VC status. Two revealed an increase of VC status in their orthoses. One of those two has had a FVC test done previously in a Boston type TLSO which was never accepted.

In conclusion, the SMA-TLSO appears to be an effective alternative solution in treating patients with severe neuromuscular scoliosis in conjunction with limited lung capacity. It does not follow the standards of true TLSOs, however it does utilize similar biomechanical principles. Positive feedback has been received form the patients and their parents in regards to the orthosis's function and simplicity. Brace tolerance has increased and VC status has been maintained.

References:
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Address correspondence to:
Scott M Savage, CPO Texas Scottish Rite Hospital for Children, 2222 Welbom Dallas, TX 75219 Tel. (214) 559-7440 Fax. (214) 559-7428