October 2007 • Vol. 3, No. 4
	Advancing Orthotic and Prosthetic Care Through Knowledge

Post-Operative Orthotic Management After a Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis

Bryan Malas, MHPE, CO
Kevin Meade, PhD

Keywords: Selective thoracic fusion, decompensation, compensatory curve

Introduction

For patients with adolescent idiopathic scoliosis (AIS) and curve magnitudes in excess of 50 degrees, non-operative management is unlikely to remain a reliable treatment option for curve stabilization. Surgical management is considered the gold standard of treatment for curve magnitudes in excess of 50 degrees for the AIS population. For thoracic curves in the presence of a compensatory lumbar curve, selective thoracic fusion is a surgical option but remains controversial. For selective thoracic fusion, the surgical goals are curve reduction, spine stability, preservation of spinal motion segments, and avoidance of coronal decompensation.^1,4 In some cases, an unintended post-operative outcome is a resulting coronal decompensation in which the head is malaligned over the pelvis in the coronal plane and as measured from the spinous process of T1 and S1.^2,3 Spontaneous correction of the compensatory lumbar curve and subsequent reduction of coronal decompensation has been reported by some authors, but little evidence is present to suggest which curves will spontaneously correct. Additionally, spontaneous curve correction results have been inconsistent.¹ In another study, 37 percent of King Type IV compensatory lumbar curves showed progression.⁴ An alternative solution to consider is post-operative orthotic management in which the intent is to reduce the curve magnitude of the compensatory curve and address coronal decompensation.

This case presents an alternative solution to compensatory lumbar curves and concomitant decompensation that may not exhibit spontaneous curve correction after a selective thoracic fusion in a patient with AIS. Further evidence is needed to determine if and when spontaneous curve correction occurs and if orthotic management is a viable treatment option. Until then, orthotic management of post-operative selective thoracic fusions should be carefully considered for compensatory lumbar curves and prolonged decompensation that do not spontaneously correct.

Methods

This case outlines the surgical and post-operative orthotic treatment of a 16-year-old female diagnosed with adolescent idiopathic scoliosis. At the time of surgery, the patient presented with an atypical left thoracic curve (T4-T12) and right lumbar curve (T12-L4). The curve magnitudes were 45 degrees and 30 degrees respectively (see figure 1). Sagittal films revealed hyperlordosis, hypokyphosis, and a significant anterior tilt of the sacrum (see figure 1a). The patient showed radiographic evidence of pelvic obliquity but no decompensation at the time of surgery. However, there was evidence of significant transverse plane rotation in the lumbar spine.

The surgeon performed a selective thoracic fusion using a two-rod and screw construct. Intervertebral screws were used at T9 and T10 and bilaterally at T3, T11, and T12. The construct included one distraction hook. At one-month post selective thoracic fusion, a coronal plane x-ray indicated that the thoracic curve had decreased from 45 degrees to 24 degrees, and the lumbar curve magnitude had decreased from 30 degrees to 21 degrees. At nine months, there was an increase in the lumbar curve magnitude from 21 degrees to 35 degrees, and at 14 months the same curve had progressed from 35 degrees to 39 degrees (see figure 2). There appears to be little change in the transverse plane rotation in the lumbar spine. A decision was made to address the lumbar curve and decompensation with orthotic management on the same day as the final radiograph study.

Upon evaluation, the patient presented with shoulder symmetry. The soft tissue had a markedly full appearance in the area of the compensatory lumbar curve. Remarkable findings included decompensation to the right of 35mm and right-arm gap. The patient also presented with a 10mm leg length discrepancy (LLD) on the right side that the physician elected not to manage. In addition, the Cobb angle and decompensation radiographic findings showed mass vertebral distribution to the right of the center sacral line (CSL).

A bi-valve impression was taken of the patient in a recumbent position using six-inch plaster splints. The anterior and posterior impressions were taken supine and prone respectively. A translational force was applied to the right axilla and right compensatory curve apex during the impression process in order to reduce curve magnitude and the decompensation. The patient was subsequently fit with a custom-molded anterior opening TLSO with axillary and trochanteric extensions on the right. Additionally a right lumbar pad was suspended on an internal sling within the TLSO to increase transverse loading. A pad was added to the trochanteric extension to further decrease decompensation (see figure 3).

Results

After receiving the custom-molded TLSO, the patient received an in-orthosis coronal plane radiograph indicating a curve reduction from 39 degrees to 20 degrees, nearly 50 percent correction. Decompensation was reduced to 3mm and, after several adjustments were made to the orthosis, eliminated completely (see figure 4). Moreover, there appears to be a significant reduction in transverse plane rotation in the lumbar spine. Sagittal films revealed some decrease in the sacral tilt (see figure 4a). The duration of orthotic treatment lasted approximately one year with dosage being limited to nighttime wear only. Approximately one year after completion of orthotic treatment and a little over two years post-surgery, the patient was seen for follow- up and out-of-orthosis radiograph (see figure 5). Results showed that the curve had stabilized close to its initial post-operative curve magnitude at 34 degrees and had leveled off to 18mm of decompensation (see table 1). Sagittal films revealed a significant tilt of the sacrum and hyperlordosis (see figure 6).

Discussion
Curve Magnitude

Despite some initial reduction of the compensatory lumbar curve immediately following surgery, the radiographic evidence suggests that the curve not only went back to its original pre-operative magnitude, but it also exceeded that amount and reached as high as 39 degrees. A final radiograph one year post orthotic treatment suggests that the curve had stabilized to 34 degrees, but the transverse plane rotation remained in the lumbar spine. If ± 5 degrees of measurement error is taken into account, the treatment could be considered successful by Scoliosis Research Society (SRS) standards. There was some residual loss (7 degrees) of curve correction within the span of the surgically fused curve that may or may not have impacted stabilization of the more inferior compensatory curve. Therefore, it remains difficult to determine the degree of effectiveness of orthotic treatment exclusively. A bigger question is whether or not the compensatory lumbar curve in the presence of a selective thoracic fusion continues to exhibit the same behavioral characteristics of an idiopathic curve.

The terminal point of the fusion inferiorly presents a stress riser in the first motion segment and may have short-term effects that lead to curve progression or longer term effects such as arthritic changes at the junction between fused and non-fused segments. Paradoxically there are reports suggesting that spontaneous correction is possible. Dosage and time of orthotic intervention are also important considerations to determine the efficacy for orthotically managing these curves.

Decompensation

At the time orthotic treatment was initiated, the patient presented with 35mm of decompensation to the right at a difference of 30mm from the pre-operative value. This resulted in an 86 percent increase in decompensation. A substantial increase in decompensation is known to increase the likelihood of progression of the deformity. When combined with the stress riser as described previously, this may have a profound negative effect on stability of the spine. For the patient and family alike, the increased decompensation resulted in dissatisfaction specific to the aesthetic appearance of the patient and self-image concern. As a result the head was misaligned over the pelvis in standing, and the patient presented with a more obvious arm gap on the right side. An additional consideration is the effect of decompensation on the lower limbs and in particular joint articulations. As decompensation increases, the weight on the lower extremity on that same side increases. While no long-term studies have considered the effects of prolonged decompensation, the importance of overall balance may be an important consideration for not only the critical load on the spine, but the effects on the lower extremity as well. For this patient the decompensation was reduced from 35mm to 3mm in orthosis. A year after orthotic treatment, the decompensation had increased to 18mm, but remained 17mm less than the pre-orthosis value. Overall this resulted in approximately a 50 percent decrease in decompensation and within the acceptable range of decompensation as described by the SRS (less than 2cm).

Although the decompensation post-orthotic treatment was considered successful, further success might have been gained by orthotically addressing the LLD on the right. Through accommodation of the LLD, the pelvic obliquity and inferior endpoint tilt of the lumbar compensatory curve may have reduced and subsequently decreased the decompensation. Moreover this accommodation is likely to have decreased the deforming moment in the coronal plane and provide a better overall balance.

Conclusion

Orthotic management of the compensatory lumbar curve and or decompensation after a selective thoracic fusion for patients with AIS may be an important treatment option that may address issues related to cosmesis and overall self-image for the patient, spinal stability, and long-term effects of arthritis. While the curve magnitude and cause-and-effect relationship is difficult to determine, for this case the orthosis appears to have addressed the issues related more specifically to decompensation. Further evidence is necessary to make a determination as to the effectiveness of orthotic treatment for these patients but should not be abandoned as it may prove to be a viable part of the overall treatment for this population.

References

1. Edwards CC, Lenke LG et al. Selective thoracic fusion for adolescent idiopathic scoliosis with c modifier lumbar curves: 2- to 16-year radiographic and clinical results. Spine 2004; 29(5), pp 536-546.

2. McCance S, Denis F, Lonstein J, et al. Coronal and sagittal balance in surgically treated adolescent idiopathic scoliosis with the King II curve pattern. Spine 1998; 23:2063-73.

3. Bridwell K, McAllister J, Betz R, et al. Coronal decompensation produced by Cotrel-Dubousset ‘derotation’ maneuver for idiopathic right thoracic scoliosis. Spine 1991; 16:769-77.

4. Suk S, Lee SM, Chung ER et al. Selective thoracic fusion with segmental pedicle screw fixation in the treatment of thoracic idiopathic scoliosis. Spine 2005; 30(14), pp 1602-1609.

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