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The Impact of Lateral Pads versus Posterolateral Pads in the Management of Idiopathic Scoliosis

Zach Harvey, BSc, CO
Megan Chamis, BSc, CO
Robert Lin, BSc, CPO

ABSTRACT

The Boston-low profile thoracolumbar sacral orthosis (TLSO) is a common treatment for idiopathic scoliosis (IS). Some have found that the forces applied in the brace are not optimal. For example, hypokyphosis, inherent to IS curves, is sometimes amplified by orthotic treatment. Hypokyphosis is a major concern with IS and it is important to reduce. Proper pad placement is therefore critical in achieving optimal correction in the coronal plane while not accentuating hypokyphosis in the sagittal plane. In correction of the thoracic spine, pads are placed either laterally or posterolaterally, pushing against the ribs, thereby correcting lateral curvature of the spine. The decision to use either lateral (L) pads or posterolateral (PL) pads) has raised some discussion. The current study evaluates the pads in the Boston brace in relation to percentage of thoracic correction and degrees increase in hypokyphosis. Charts and x-rays of 38 first-time bracing patients with adolescent and juvenile IS, between the ages of 7 and 15 years, from two ABC-certified orthotists, were examined. As a cross-sectional, retrospective analysis, it was hypothesized that the PL pads would offer no difference in desired coronal plane thoracic correction compared with L pads and that PL pads would create more unwanted increase in hypokyphosis than L pads. Results indicate that practitioners varied in their preference to pad styles, that there was no difference between pad styles for thoracic scoliosis correction (significant at p < 0.10, but not at p < 0.05), and that the PL pad induced more hypokyphosis than the L pad (p < 0.10 and p < 0.05). In conclusion, the use of L pads should be considered in the majority of IS cases, with the exception of scoliosis curves with excessive kyphosis. Scoliosis curves that are hyperkyphotic should be treated with a PL pad to induce thoracic extension.

Keywords: Scoliosis, idiopathic, Boston, TLSO, hypokyphosis

Idiopathic scoliosis (IS) is a multiplane deformity, the evolution of which is quite variable and patient specific.¹ Rotation is apparent on x-ray (the pedicles and spinous processes of the vertebrae rotate) and clinically as a rib hump (for thoracic curves only). It is longitudinal in that there is shortening of the trunk. The longitudinal aspect is not treated orthotically, as would be the case in the use of a halo, because traction is effective mostly for large curves, outside the parameters of orthotic use.² Lateral aspects of the IS deformity can be viewed from the coronal and sagittal perspectives. A right-thoracic, left-lumbar, S-shaped curve is the typical coronal plane pattern, although other curve patterns are prevalent. Sagittal deviations may include hypokyphosis or flat-back in the thoracic vertebrae. Translation may occur in the IS spine in the form of disorientation of the ribs or decompensation, the head being unbalanced in relation to the center of the pelvis.

The normal spine has less than 10° of lateral curvature in the coronal plane.³ Normal kyphosis is about 20-40°; 35° is average in the population^4,5 (37° in another study⁶). Kyphosis <20° could be said to be hypokyphotic and >40° as hyperkyphotic. Lumbar lordosis is about 50° on the average, with considerable variation.⁶ An orthosis becomes a viable option when a curve reaches 25° in the coronal plane with documented progression and immature growth plates.⁷

The Milwaukee brace [i.e., the cervicothoracic lumbosacral orthosis (CTLSO)] has been the "standard of comparison" of IS bracing since its development in 1946 by Blount and Schmidt.² The CTLSO is still the only orthosis adequate in treating high thoracic curves. The Boston low-profile TLSO and similar full-time thermoplastic TLSOs, such as the Wilmington, Rosenberger, and Miami, have since proven useful in helping to prevent the progression of most IS curves and have become the primary treatment modality for orthotic treatment in North America. The effectiveness of coronal plane correction by the Boston brace has been well documented.^8-10 Some have found the Boston brace to actually be superior to the Charleston bending brace (CBB) and the CTLSO in curve correction.¹¹ Others have found the CTLSO to be superior to the TLSO in treatment of the thoracic curve.¹² One study suggests using the Boston brace as a preferred treatment choice with the exception of smaller single lumbar and single thoracolumbar curves. In these cases, a nighttime-only CBB may be adequate.¹³ The Providence orthosis shows some promise as another type of nighttime-only orthosis.¹⁴ Nighttime orthoses may be more acceptable to the patient, but studies show that the more hours per day the brace is worn, the better the results.^11,13 Although the use of TLSOs has limitations, including its ineffectiveness in treating high thoracic curves, patient and social acceptance of the orthosis is generally much better than the higher profile Milwaukee.² Compliance, however, may be the same between the two.¹⁰

In the Boston brace, the pads are placed so as to most effectively reduce the size of the scoliotic curve when the brace is worn. In the lumbar spine, the pad is placed to push against the paraspinal musculature and the transverse processes, to derotate the curve. Therefore, the lumbar pad is located on the posterior wall of the orthosis, extending laterally to the waist groove. The 15° of lordosis built into the Boston Brace modules acts to decrease lordosis, unlocking the facet joints, making the lumbar pad more effective. For thoracic curves, it has been found that pads inside the orthosis are ineffective in derotation, at least in a standing position.¹⁵ Others found small yet significant changes in rotation in supine Boston brace wear.¹⁶ In the thoracic spine, the ribs are used as leverage, and proper placement of the thoracic pad is critical. Pad shape, size, and position are determined from x-ray and clinical evaluation. It should not extend higher than the rib corresponding to the apical vertebrae, which has been shown to decrease correction.¹³ Thoracic pads are traditionally placed either laterally only (L pads), or posterolaterally (PL pads), (Figure 1 and Figure 2 ). The decision to use L or PL pads has raised some discussion about what is optimal for coronal plane correction, hypokyphosis, patient acceptance, and pressure distribution.

Over the years, Boston Brace International has changed their modules from 0° lordosis (which is still available, but not standard) to 15°, and they have advocated the use of an L pad rather than a PL pad. Some studies suggest that the forces in the current Boston brace are not applied in an optimal way.^15,17,18 The purpose of the current research was to determine which pad style offers the best overall correction. Radiographic-assessment of in-brace correction is the best prognosticator of outcomes^13,19 and was the basic premise for the design of the study. "If curves reduce in the brace to less than 50 per cent of the initial measurement, there is a good chance of obtaining significant permanent correction."²⁰ In clinical practice, some practitioners have found that the medial directed force from a lateral pad yields as much coronal plane correction without the associated augmentation of hypokyphosis. Other opinions differ.²¹ Some believe that by pushing on all of the deformity (i.e., rotational and lateral aspects), there would be a better chance of obtaining greater correction.

It was hypothesized in the current study that coronal correction would be similar between L and PL pads. Similarity in patient population and brace correction was proposed to exist between the two practitioners.

Another factor is the amount of hypokyphosis. Sagittal x-rays often reveal a hypokyphotic thoracic spine in this population of patients wearing an orthosis. It is important to note the amount of hypokyphosis before and after bracing. "With true thoracic lordosis (less than -5 to 10°), orthotic treatment is probably contra-indicated."²² Thoracic lordosis is detrimental in that it can possibly lead to pulmonary dysfunction.²³ Hypokyphosis is said to be inherent to thoracic IS, and scoliosis curves that are not hypokyphotic are possibly not idiopathic.⁷ Furthermore, hypokyphosis and rotation in the thoracic spine have been stated to be the primary deformities of IS, rather than the lateral curvature in the coronal plane.^24-26 Many authors believe that hypokyphosis is the generating factor in IS.¹⁵ This undesirable hypokyphosis has been shown to increase with the use of a TLSO.^27-30 The anteriorly directed force from the PL pad was hypothesized to induce hypokyphosis more than the L pad.

A third factor to consider is patient acceptance. Based on unpublished data, patients have found the L pad more tolerable than the PL pad. Creating a brace that is as comfortable as possible is important, considering that the majority of patients are instructed to wear the brace full-time (18 to 23 hours per day). It is advantageous to maximize the in-brace curve correction without compromising patient acceptance and comfort.

A fourth factor is pressure distribution. Since Pressure = Force/Area, the larger the area of skin contact, the less the pressure. Therefore, the larger PL pad would theoretically help to distribute pressure more than the smaller L pad. This becomes important with younger, less developed children whose ribs are still malleable and can be deformed by the forces of the orthosis. This is especially disconcerting because it is known that "prolonged wearing [of a TLSO] can produce a tubular thorax deformity."³

Considering these four factors (coronal plane correction, hypokyphosis, patient acceptance, and pressure distribution), the decision to use an L or a PL pad becomes unclear. It was the goal of the current study to clarify the use of the L pad versus the PL pad in the Boston low-profile orthosis.

METHODS

A retrospective, cross-sectional comparison was performed from patient charts and radiographs. Patients of two ABC-certified orthotists at Connecticut Children's Medical Center and the former Newington Children's Hospital were evaluated from August 1992 to March 2000. Data were grouped into two separate categories: a category comparing practitioners and a category comparing the two pad styles. Children and adolescents between the ages of 7 years, 2 months and 15 years were chosen with the following inclusion criteria: 1) they used a Boston brace with no history of prior treatment, 2) they had a diagnosis of IS, 3) they had no prior associated surgeries, 4) they had a right thoracic curve treated at the apex of T8 or below, with a Boston brace, 5) they had sufficient radiographs and chart information, and 6) they had a hypokyphotic curve either in or out of the Boston brace. Two hundred and five patient charts were reviewed and narrowed to the 39 patients who met the inclusion criteria. From these patients, in-brace and out-of-brace x-rays in the coronal and sagittal planes were compared.

Because these were first-time x-rays taken at the time of delivery of the orthosis, the pads may have been moved after the in-brace x-ray to optimize correction. However, the next films would have been taken 4-6 months later; because the design of this research was a cross-sectional rather than longitudinal, it was decided not to introduce the extraneous variable of time in the orthosis.

Cobb angle measurements were obtained for single, double, or, in some cases, triple curves. However, the magnitude of the treated thoracic curve was the only curve considered, and in-orthosis percentage correction was compared. In the sagittal plane, the degrees increase in hypokyphosis was determined for each pad style.

Data were compiled using Microsoft Excel. For statistical analysis, two series of tests were performed. The first was between the two practitioners. Two-tailed independent t-tests were performed for coronal and sagittal changes. Two-tailed tests were used because no direction was implied in the hypotheses. The second series of tests compared the pad styles. A two-tailed independent t-test was performed for percentage of thoracic coronal correction and a one-tailed independent t-test was performed for degrees increase in hypokyphosis. Significance testing was performed for p values less than 0.05 and 0.10.

RESULTS

The first certified orthotist had recorded data from 17 patients; the second had recorded data from 21 patients. Among the 38 patients, 23 had L pads and 15 had PL pads. The first practitioner had a 1:16 ratio of PL to L pads, and the other had a 14:7 ratio. Riser sign, which is a measurement of bone-age, ranged from grade 0 to 2.

Table 1 and Figure 3 and Figure 4 summarize the practitioners and pad styles in comparison with the means of the independent variables. Between practitioners, significance testing was inconclusive. Between pad styles, it was found that PL pads offered no difference in desired coronal plane correction compared with L pads for p < 0.10 (but not for p < 0.05), and that PL pads created more undesired hypokyphosis than L pads for p < 0.10 and p < 0.05.

CONCLUSION

Patient groups between practitioners were not homogenous based on significance testing. The reason might be that each had a certain preference of pad style and a different ratio of PL to L pads existed in the data. Because there were significant differences between pad styles, it is not surprising that practitioner 1, who had a preference for L pads (16:1) varied in patient data with practitioner 2, who had a more even distribution of L to PL pads (14:7). It might be noted that one practitioner trained under the other, and each used standard methods to correctly fit the Boston brace. A controlled design in which patients were selected from a single practitioner would have been ideal but, given the selection criteria, would not have been feasible for the current research. Nevertheless, the existence of two practitioners introduced an extraneous variable into the study.

In the comparison of thoracic curves in the coronal plane, correction was not different between the pad styles (significant at p < 0.10, but not at p < 0.05). Significance testing for p values suggests that conclusions must be made with caution, because there is a 5-10% probability that the results could be due to chance alone. It is most likely, therefore, that the posterior aspect of the pad is not needed to sufficiently correct the spine in the coronal plane. In the sagittal plane, the PL pad enhanced unwanted hypokyphosis more than the L pad for p < 0.10 and p < 0.05. This was congruent with the original hypothesis. The anteriorly directed force from the PL pad created an undesired moment on the spine. This evidence should be considered for IS curves that are hypokyphotic or at risk of becoming hypokyphotic. For cases of scoliosis and concomitant hyperkyphosis, the forces of the PL pad would encourage a more normal kyphotic angle by straightening the spine in the sagittal plane. Therefore, based on the outcomes of the current study, PL pads should be used solely in the case of hyperkyphotic scoliosis curves, which is uncharacteristic of IS.

Future research demands extra effort in record-keeping to assess the clinical effectiveness of scoliosis bracing. A single-practitioner research study that compared thoracic pad styles would add more validity to the results of the current study. Patient acceptance, vertebral rotation, and pressure distribution related to pad styles might also be examined. Other variables associated with the subtleties of orthosis design must also be analyzed to develop the most effective scoliosis treatment.

ACKNOWLEDGMENTS

I thank the radiology department at the Connecticut Children's Medical Center for supplying me with patient radiographs and the statistics department for helping to analyze my data. I thank Don Katz, CO, for reviewing and editing the initial draft.

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ZACH HARVEY, BSc, CO, is affiliated with Hanger Prosthetics and Orthotics, Ft. Myers, FL.

MEGAN CHAMIS, BSc, CO, is affiliated with the Connecticut Children's Medical Center, Hartford, CT, and Hanger Prosthetics and Orthotics, Ft. Myers, FL.

ROBERT LIN, BSc, CPO, is affiliated with is affiliated with the Connecticut Children's Medical Center, Hartford, CT, and Hanger Prosthetics and Orthotics, Ft. Myers, FL. Correspondence to: Zach Harvey, BSc, CO, Hanger Prosthetics and Orthotics, 12591 Creekside Ln., Ft. Myers, FL 33919; E-mail: zzharv@yahoo.com