The results are consistent with the experimental hypothesis: those subjects who were treated during four years with the Chêneau brace would report at the end of treatment a reduction in lateral deviation and rotation compared with before the start of treatment. Also, there was a significant increase in the trunk length after four years of treatment compared with before the start of treatment. The paired (dependent) t-test results for lateral deviation, rotation and trunk length showed significant differences in topography values when using the Chêneau brace. When the subjects’ topographies were measured, the means were 17.73 mm and 10.13 mm before and after treatment respectively for the lateral deviation, 7.77 degrees and 5.90 degrees before and after treatment respectively for the rotation, and 393.84 mm and 421.60 mm before and after treatment respectively for the trunk length. The standard error in the experiment was small, hence it did not effect the results.
Perhaps the most reasonable explanations for these findings are concerned with the design of the Chêneau brace and the skeletal age of the subjects. The strategically placed pressure points with the large expansion rooms permit the correction of many aspects of the deformity. Maximum deflection is obtained by optimum location and shape-direction of the pressure points. The expansion areas of the brace allow small voluntary and involuntary movements as well as the patients own growth provides an active mechanism of correction. Also, in the thoracic region the expansion area has an additional advantage, in that the space was important for respiratory movement and for active correction in the direction of derotation and rekyphosis (reduction of flatback).
The lateral deviation results suggested that the Chêneau brace could correct curvature in the coronal plane. Conventionally, good scoliosis correction was considered when the vertebral column in the coronal plane, was as close as possible to vertical. However, the three-dimensional deformity of scoliosis needs to be evaluated and treated in all three anatomical planes. When more influence was put on the sagittal plane and rotation, the coronal plane deformity does not become less important, due to the coronal X-ray still being considered as standard good correction. There is support here for the experimental hypothesis. Furthermore, the placement of the pressure at the apex of the curve seems to play an important role. Chêneau (1996a) reported, that the curve pressure is placed two vertebras above and two vertebras below the apex of the thoracic curve and one vertebra above and one vertebra below the apex of the lumbar curve, therefore, maximal coronal plane correction is obtained.
The rotation results show that the Chêneau brace can correct the trunk rotation. Perhaps the most reasonable explanations for this finding were concerned with the three-dimensional design of the brace. The direction and location of the pressure points with their corresponding expansion chamber provides space for the correction of the rotation.
All the subjects in this study were measured by Rasterstereography and evaluated by means of surface reconstruction of the trunk utilising the Formetric system. Therefore less X-rays were required and a greater account of the three-dimensional aspects of scoliosis were taken into consideration when evaluating back shape. The use and effectiveness of the Formetric system for the evaluation of back shape has been reported by Weiss and Rigo (1994). However, Rigo (1999a) at present is the only author that has published work using the Formetric system to evaluate topography changes with treatment of the Chêneau brace. Rigo (1999a) presented at the meeting of the International Research Society of Spinal Deformities in Burlington, Vermont, that the Chêneau brace has significantly decreased the following topography parameters: trunk imbalance, lateral deviation and rotation. The results of this study were similar to those results found by Rigo (1999a), however, some of the subjects measured by Rigo (1999a) have been utilised in this experiment. Therefore, a direct comparison of this experiment with the study by Rigo (1999a) would be misleading. Consequently, there is no research to compare the consistency of these parameters, however, additional parameters have been evaluated in this experiment.
There was a significant change in trunk length after treatment when compared with before the start of treatment, this may seem obvious as these children would grow during their four years of Chêneau brace treatment. However, there seems to be a correlation between the growth and correction. For this reason, brace treatment is normally applied to the end of skeletal maturity because the body is normally more flexible and correctable during growth. After skeletal maturity the body is normally more rigid and as a result more difficult to correct.
The Risser sign (skeletal age) and magnitude of the curve play an important roll in evaluating the course of idiopathic scoliosis. The useful cross-correlation of incidence rates of progression of curves under 29 degrees was reported by Lonstein et al., (1995). The two factors considered were the curve magnitude and maturity as assessed by the Risser sign (table 2.2). These figures are used to record the natural history and incidence of progression when evaluating the effectiveness of treatment.
For curves of 20 to 29 degrees in an immature child with a Risser sign of 0 or 1, the incidence of progression was 68 %. On the other extreme, for curves under 19 degrees in a mature adolescent with a Risser sign of 2 or more, the incidence of progression was 1.6%. In the other two groups, that is, smaller curve (less than19 degrees) in an immature child (Risser 0 or 1), and larger curve (20 to 29 degrees) in a mature child (Risser 2 or more), the incidence of progression is approximately the same at 22 to 23% (Lonstein et al., 1995).
The subjects in this study who have Risser 0 and Risser 1 were 61% and 26% respectively, and 37.43 degree Cobb angle means, therefore the incidence of progression, if untreated was at least 68%. This was assuming that greater than 30 degree curves would have a greater progression percentage than that of curve less than 30 degrees. However, the possibility of correction in these low Risser subjects was worse as they had a higher growth potential compared to Risser 3 or 4. There is a significant reduction between before and after topography values. Therefore, when these topography values are compared with the incidence of progression, it could be assumed that the Chêneau brace has significantly changed the prognosis of the subjects in this study.
It is possible that the treatment time was insufficient to differentiate the long term effect of the orthotic treatment. However, considering that long term idiopathic scoliosis treatment should be continued until the completion of skeletal growth, approximately 18 years of age in girls, with the average follow-up time of 2 years, the difficulties in scoliosis research could be understood.
There is support here for the experimental hypothesis, however, the subjects were additionally provided with physiotherapy treatment. Unfortunately, it is not possible to assess the extent of physiotherapy, as this experiment failed to explore this question. Future work should therefore check on this possibility, and additionally evaluate the effects of Chêneau brace treatment with and without physiotherapy. Nevertheless, Weiss and Werkmann (1996) have reported the favourable values of physiotherapy in scoliotic patients, and Rigo (1999a, 1999b) claims this could improve the actions of the Chêneau brace by making the curve more flexible and preventing muscle atrophy.
6.2 MAJOR AND MINOR COBB ANGLE VALUES
The results are consistent with the experimental hypothesis: that the Chêneau brace would prevent the progression of the major and minor Cobb angles. The paired (dependent) t-test results for major and minor Cobb angles showed significant reductions when using the Chêneau brace. When the subject’s X-ray values were measured, the means were 37.43 degrees and 24.22 degrees before and after treatment respectively for the major Cobb angles as well as 25.04 degrees and 16.95 degrees before and after treatment respectively for the minor Cobb angles. The standard error in the experiment was small, hence it did not affect the results.
6.3 MAJOR AND MINOR TORSION VALUES
The results are consistent with the experimental hypothesis: that the Chêneau brace would prevent the progression of the major and minor torsion angles. The paired (dependent) t-test results for major and minor torsion angles showed significant reductions when using the Chêneau brace. When the subject’s X-ray values were measured, the means were 14.61 degrees and 10.74 degrees before and after treatment respectively for the major torsion angles as well as 6.56 degrees and 4.17 degrees before and after treatment respectively for the minor torsion angles. The standard error in the experiment was small, hence it did not affect the results.
Perhaps the most reasonable explanations for these findings are concerned with the design of the Chêneau brace. The strategically placed pressure points with large expansion rooms allow for correction of many aspects of the deformity. Maximum deflection is obtained by optimal location and shape-direction of the pressure points. The expansion areas of the brace permit small voluntary and involuntary movements, as well as the patients own growth providing an active mechanism of correction. Also in the thoracic region the expansion area has another advantage, in that the space is important for respiratory movement, which provides active correction in the direction of derotation and rekyphosis.
6.4 COMPARISON OF COBB ANGLE MAGNITUDE AND RISSER SIGN
The results are consistent with the experimental hypothesis: those subjects who had a Cobb angle 30 degrees or less would report a significant correction of the scoliotic deformity compared to those subjects who had a Cobb angle greater than 30 degrees.
The paired (dependent) t-test results for vertebral rotation, major Cobb angle, minor Cobb angle, major torsion angle and minor torsion angle showed significant differences in subjects who had a Cobb angle 30 degrees or less compared to subjects who had a Cobb angle greater than 30 degrees when using the Chêneau brace. The subjects who had a Cobb angle 30 degrees or less had no significant improvement of correction of the lateral deviation compared to subjects who had a Cobb angle greater than 30 degrees when using the Chêneau brace. However, a significant correction of the scoliotic deformity, which refers to the parameters, lateral deviation, vertebral rotation, major and minor Cobb angles as well as major and minor torsion angles, found a significant difference when analysed as a group.
Studies of the natural history of untreated scoliosis have presented a clear indication that scoliotic curves with Cobb angles greater than 30 degrees show a significant increase in progression compared to Cobb angles less than 30 degrees (Clarisse, 1974, Fustier, 1980, Lonstein and Carlson, 1984, Bunnell, 1986,). Therefore in this study, it was assumed that subjects with Cobb angles less than 30 degrees would produce a better correction compared to subjects with Cobb angles 30 degrees or greater. Although, this study shows a significant difference in all parameters, the roll of natural history was evaluated in subjects who used the Chêneau brace. This was done by accepting the hypothesis that the Chêneau brace had a significant effect on the scoliosis. However the natural history of untreated scoliosis also facilitated good results in subjects with less than 30 degrees Cobb angles because in this group of patients, there was a percentage of subjects that had a favourable natural history. This implies that the group of subject with less than 30 degrees Cobb angle obtained superior correction due to not only the positive effects of the Chêneau brace, but also because the natural history shows in general less progression. Also, generally larger curves are more rigid compared to smaller curves and therefore they are more difficult to correct. The opposite occurs with smaller curves as they are more flexible and therefore normally have better correction.
The correction of the Cobb angle while using a Chêneau brace with the cross-correlation of curve magnitude and Risser sign showed that subjects with Cobb angles less than 30 degrees and low Risser signs (Risser signs 0 and 1) had a greater percentage of Cobb angle correction (44%) compared with subjects with Cobb angles greater than 30 degrees and low Risser signs (Risser signs 0 and 1), which had 32% of Cobb angle correction.
Also, the correction of the Cobb angle while using a Chêneau brace with the cross-correlation of curve magnitude and Risser sign showed that subjects with Cobb angles greater than 30 degrees and high Risser signs (i.e.: Risser signs 3) had a greater percentage of Cobb angle correction (48%) compared with subjects with Cobb angles greater than 30 degrees and low Risser signs (Risser signs 0 and 1), which had 32% of Cobb angle correction.
Therefore, the results of this study demonstrate that subjects with lower Risser signs (i.e. the greater the growth potential) presented less Cobb angle correction compared to subjects with higher Risser signs (i.e. less growth potential). These results correspond with those reported by Goldberg et al., (1993); Lonstein et al., (1995); Peterson and Nachemson, (1995), which claim that when analysing the growth potential and curve progression, it is generally true that the younger the child (i.e. the greater the growth potential), the greater the incidence of progression if untreated. Hence, this also was true for subjects who were treated with the Chêneau brace, in which the younger the child, the greater possibility of less correction compared to an older child.
Although Dickson (1984) claimed that there is no evidence which demonstrates conclusively that wearing a spinal brace affects the natural history of scoliosis, this study demonstrates that the Chêneau brace was effective in changing the natural history of progressive scoliosis. This was evaluated in the cross-correlation of curve magnitude and Risser sign, which showed that although the Chêneau brace significantly corrected the parameter of the subject, the natural history of scoliosis could have improved the results in subjects with higher Risser signs (i.e. Risser sign 3) and lower Cobb angles (i.e. less than 30 degrees). However, 85% and 65% of the subjects in this study had Risser signs 0 or 1 and Cobb angles greater than 30 degrees respectively. As a result, it was valued by using the cross-correlation by Lonstein (1995), of curve magnitude and Risser sign that the majority of these subjects had approximately 68% possibility of curve progression if left untreated. Nevertheless, this study reported a statistically significant difference in all parameters, therefore correction and not progression was effectively obtained.
This study showed significant differences in all parameters (except lateral deviation) for subjects who had a 30 degrees Cobb angle or less compared to subjects who had greater than 30 degrees Cobb angle when using the Chêneau brace. However it was interesting to observe that the subjects who presented greater than 30 degrees Cobb angle had significantly better correction of lateral deviation (48% correction) compared to those subjects who had less than 30 degrees Cobb angle (29% correction). This phenomenon was first noted by Rigo (2000), it was stated that Cobb angles with larger magnitudes produced greater changes in lateral deviation. This was because not all the forces produced by the Chêneau brace could produce changes in the vertebral column, however these forces were capable of causing greater changes to the trunk shape, in which the increased correction of lateral deviation was obtained. Therefore, the greater the Cobb angle, the greater the lateral deviation, which allows a greater percentage of correction of the trunk deformities.
The Cobb angle results of previous Chêneau brace studies (Hopf and Heine, 1985, Liljenqvist et al., 1998) were slightly better than this study, however, this could be attributed to the fact that their subjects had lower initial Cobb angles. Hence, a greater probability of an increased Cobb angle correction.
This study presented better results than the studies presented by Rigo (1999a, 1999b) in all of the following parameters, lateral deviation, vertebral rotation, major Cobb angle, minor Cobb angle, major torsion angle and minor torsion angle. However, approximately 11 subjects from that study were also utilised in this study. Also the studies by Rigo (1999a, 1999b) reported 49 and 105 subjects respectively, therefore it is difficult to compare this study with those studies presented by Rigo (1999a, 1999b). Nevertheless, it was observed that the study presented by Rigo (1999a, 1999b), had a significant number of subjects who had previous brace treatment. Rigo (1999a, 1999b) claimed that this could have affected the end result, due to the spinal rigidity produced by the previous failed brace treatments from other clinics.
6.5 COMPARISON OF PREVIOUS BRACE WEARERS
The results are not consistent with the experimental hypothesis: those subjects who had no previous brace treatment would report a significant correction of all parameters of the scoliotic deformity compared to those subjects who had previous brace treatment. The paired (dependent) t-test results showed no significant differences in subjects who had previous brace treatment compared to subjects who had no previous brace treatment when using the Chêneau brace.
Although Rigo (1999a, 1999b) claimed that his study had subjects with rigid curve due to poor previous brace treatment, this study found no significant difference in the group who had previous brace treatment. Generally in Spain, patients who go to a private clinic (Instituto Elena Salva) from another clinic (national health service or private) would be because they were not satisfied and had poor results from the previous brace treatment. It was assumed that the failed treatment produced a larger curve and therefore more rigid vertebral column. However this study found no significant difference in the subject who had previous brace treatment compared to those who had no previous brace treatment. This implies that the poor previous brace treatment was due to poor previous brace type and design, as a result these subjects were capable of obtaining a significant correction of all parameters. The brace type and design plays an important roll in the individual patient results, however the Chêneau brace evaluation, design and rectification processes were very complicated and required a great amount of time.
6.6 INTERPRETATION AND IMPLICATIONS OF THE CLASSIFICATION OF CHÊNEAU AND THE CLASSIFICATION OF KING PATTERNS
There was a significant difference of the percentage of correction of the 3-curve scoliosis compared to the 4-curve scoliosis pattern. This implies that the Chêneau brace system was more effective for 3-curve patterns compared to 4-curve patterns. These results agree with Lonstein (1995), who reported that double-curve pattern (which could be considered as a 4-curve pattern) had a greater possibility of progression compared to single curves (which could be considered as a 3-curve pattern). Therefore, these results show that the Chêneau brace had a significant effect on the scoliotic deformity (all parameters), however the subjects with 3-curve scoliosis patterns reported better results than the 4-curve scoliosis patterns.
The King type III, King type IV and King type V curve patterns presented a higher percentage of correction compared with King type I and King type II curve patterns. The King type III, King type IV and King type V patterns could be considered as 3-curve scoliosis and the King type I and King type II could be considered as 4-curve scoliosis (Chêneau, 1996a, Rigo, 1997). Therefore these results show a relationship between King type III, IV and V to 3-curve patterns, also, King type I, and II patterns to 4-curve patterns. As a result, when grouped together they both show 3-curve and King type III, IV and V had greater percentage of correction compared to 4-curve or King type I and II pattern.
The Cobb angle results show that the Chêneau brace can prevent progression of the coronal plane curvature. Due to the introduction of X-rays, the coronal plane radiographic view has become the standard for the evaluation of the severity of scoliosis. Therefore, conventionally, good scoliosis correction was considered when the vertebral column, was as close as possible to vertical in the coronal plane and the Cobb angle was as close as possible to 0 degrees. Although the rotation is often measured in the coronal plane X-ray and the sagittal plane X-ray is sometimes taken, this still falls short of a three-dimensional evaluation and correction.
The three-dimensional deformity of scoliosis should be evaluated and treated in all three anatomical planes (Winter et al., 1975; Dubousset 1992; Chêneau, 1990, 1996a, 1996b; Rigo and Chêneau, 1997; Aubin et al., 1997; Wood and Rigo, 1999). As a result, the Cobb angle measurement is insufficient to optimally assess and evaluate idiopathic scoliosis.
The good coronal plane results that are often reported by conventional TLSOs (Boston, Malaga, Lyon) and casting braces appear at first sight to be positive with a good correction of the deformity. However, this could be a major mistake when considering the three-dimensional model. Aubin et al., (1997) have claimed that the Boston brace produces a lordotic effect in the thoracic region. The normal physiological curve in the thoracic region is kyphotic and therefore this has a negative effect, which occurs in all of the conventional TLSOs, as their upper shapes are very similar.
Generally, bracing theories consider three different thoracic pad locations. The most common location is utilised in the Lyon and Malaga braces. In these braces the thoracic pressure pad is placed covering the entire length of the curve, with the width extending from approximately the lateral midline to the vertebra (posterior midline). The Boston brace thoracic pad is located below the apex of the curve with the width being similar in the Malaga and Lyon braces. However, the most different thoracic pressure is in the Chêneau brace, which normally does not use pads, but instead relies on direct contact of the thermoplastic brace against the patient. This provides a smoother surface for deflexion and derotation (Chêneau et al., 1997). The location is also different, with the pressure being two vertebras above and two below the apex of the curve and the width extending from the lateral midline to approximately 60% of the distance between the lateral midline and the posterior midline. This is much less than the previous braces. Also the direction of the forces are more oblique than in conventional braces with pads that are more laterally and anteriorly directed. This shorter width leaves space for derotation and deflexion of the trunk, also the alignment of these forces facilitates these actions. Therefore, as the thoracic curve is reduced, more of the patient’s back becomes in contact with the brace.
These theories of the Chêneau brace pressure placement and direction seem to produce a reduction of the Cobb angle in patients with idiopathic scoliosis. However the effect of each component is difficult to measure due to the numerous amounts of variables in a scoliosis deformity. Therefore, the effectiveness of the pressure pad placement and direction can be measured as a whole using the Cobb angle. However, caution must be applied when using only the Cobb angle, as a decrease in the Cobb angle with increase of hypokyphosis would not be the objective of the three-dimensional correction outlined by Dubousset (1992).
Similar theories are applied by the Boston, Lyon and Malaga braces for the lumbar curve pressure pad placement and direction of forces. The pads of the Malaga and Lyon braces are the same shape, covering the entire curve and extending from the lateral midline to just before the posterior midline. The Boston brace again places that pressure pad just below the apex of the curve and extends from lateral midline to just before the posterior midline. The Chêneau brace applies pressure that is located one vertebra above and one vertebra below the apex of the curve and is applied directly to the patient via the plastic brace. The pressure comes from the ventral aspect of the brace and extends between 25% from the posterior midline to crossing over the posterior midline, depending on the lumbar lordosis of the patient. Therefore, it can be seen that the Chêneau brace has taken into consideration the sagittal plane deformity as well as the pelvis rotation.
These results are consistent with those of Chêneau (1990), Hopf and Heine (1985), as well as Liljenqivist et al., (1998). However, the results of Chêneau (1990), and Hopf and Heine (1985), are from the Chêneau brace model 1992, therefore, due to the substantial changes in the current design, it would be difficult to compare the 1992 model with the present one. The Cobb angle results of the Chêneau brace could be compared with long term result of Milwaukee brace and Boston brace (Carr et al., 1980; Emans et al., 1986), however these early studies were only a single plane study and therefore are insufficient when compared to the three-dimensional Chêneau brace. Also, these studies evaluated the percentage of initial Cobb angle correction of the brace, as well as to the end of brace treatment. Whereas this study could not evaluate all the subjects’ initial correction because many of them were previously treated patients, who came from other clinics with failed brace treatment. As a result, many of the patients in this study had initial corrections that were measured using a brace other than the Chêneau brace.
Based on these observations, future research on the Chêneau brace would include a larger sample, measured from start of treatment, until two years after treatment has finished, and a group of subjects that have had no previous brace treatment.
Also, the initial correction of scoliosis when wearing the Chêneau brace could be compared to that of the Boston, Milwaukee and Lyon braces. Further investigation is then warranted to analyse sagittal plane X-ray values to evaluate the long term effect of the Chêneau brace in hypokyphosis.