This study points on the discrepancy between surface image of the trunk and radiologically assessed curvature (Cobb angle) in adolescent girls submitted to the treatment of progressive scoliosis with a corrective spinal orthosis. Taking into consideration the same gender, age, type of scoliosis and the Cobb angle – the differences in clinical parameters found in between groups should be attributed to the influence of orthosis on the trunk shape. Although the study is not a longitudinal study, we compared the values of the angle of trunk rotation before start of bracing and under brace treatment. We found a significant decrease of rotation in the main curvature (8.4 ± 2.7° versus 10.2 ± 2.9°). This finding is an additional argument that the brace was responsible for the lower values of the ATR in the braced group. In our study the rotation deformity, evaluated with the scoliometer (ATR) and with surface topography (HS) was diminished in the braced group. The rotation deformity in the transverse plane of the body remains the essential expression of idiopathic scoliosis. Stokes et al. reported that the measurement of the back surface asymmetry with surface topography that gave the highest correlation with the skeletal deformity was the axial rotation (back surface axial rotation versus vertebral axial rotation) [8]; the natural history patients being considered. Correlation coefficient of the ATR (clinical parameter) versus Cobb angle (radiological parameter) revealed lower values in the patients wearing the brace, which may reflect the increased discrepancy of surface versus skeletal deformity under brace treatment. In more severe structural scoliosis, usually with the Cobb angle greater than 50 degrees, the trunk rotation may spread out of the main curve proximally or distally. In our patients we did not find the situation, that the trunk rotation was oriented towards the same side at two adjacent levels (for example right main thoracic and right proximal thoracic). Therefore, to obtain the sum of rotation, we simply added the values read at three levels of the trunk: proximal thoracic, main thoracic and thoracolumbar/lumbar. There was no significant difference in parameters describing frontal plane asymmetry, namely the POTSI index, C7 plumb line and axillary plumb line. Usually, single curves cause more important clinical deformity than double curves. James stated that in double scoliosis "clinically the pattern is not very deforming for each of the structural curves balances the other" [9]. In this study the groups presented the same proportion of curve pattern: thoracic, thoracolumbar or double (thoracic and lumbar). There was a slightly higher proportion of single curvatures in the group managed with a brace, but not significant; a better clinical image of the back was noted in this group, in spite of such proportion. It was somewhat surprising, that both groups did not differ significantly according to the parameters describing frontal plane asymmetry (C7 plumb line, axillary plumb line, POTSI index). Possible reason is a small deformity in the non-braced group, the mean POTSI being within the normal range [10]. Another explication is, that it is the scoliotic curvature to straighten with brace, not the shoulders, scapulae, waists or other distant body parts. Voluntary imbalance of the shoulders or waist lines is sometimes introduced by the brace, in order to achieve better curve correction. The girls in the brace-treated group were slightly older (p = 0.046). According to Grivas et al. [6], they should present a better correlation between the Bunnell angle and the Cobb angle, than the non-treated group, which was not the case in our study (r = 0.22 versus r = 0.36). The interpretation of this finding is that the deformity in the treated children is corrected to a certain degree, due to applied conservative treatment using a brace.
Clinical to radiological discrepancy in idiopathic scoliosis was pointed out by James [9] who published the photos of the back of four girls with 70 degrees of curvature each, having largely different cosmetic appearance due to different curve location. The weak relationship of the rib prominence and Cobb angle was already reported by Thulbourne and Gillespie [11] however the influence of conservative treatment on further weakness of this relation has not been exploited. Ono [12] presented results of radiographic exam and surface topography in 504 patients with untreated idiopathic scoliosis and found the discrepancy between the Hump Sum and the Cobb angle. Grosso and Negrini [13] found no correlation between Cobb angle and clinical parameters (ATR, hump height, distance of the spinous process from the plumb line) in a cohort of 116 patients with moderate degree scoliosis. Goldberg et al. [14] identified significant but not complete correlation between Cobb angle and topography angle and supported surface topography as an adjunct to radiography. The same team developed better understanding of the fact that Cobb angle and surface parameters are not measuring the same aspect of the deformity, by proposing and testing new surface topography measures to quantify left-right asymmetry [15]. Grivas et al. indicated that the rib hump is not wholly a secondary effect, as the ribs themselves are asymmetric, and postulated that the deformity of the thorax develops first and this of the central axis succeeds [16].
In spite of an apparent consensus that Cobb angle cannot stand for surface deformity, the published results of brace treatment for progressive idiopathic scoliosis are most often based on the analysis of plane radiographs only, with special respect to the Cobb angle [17–19]. Coillard et al. [20], who previously proposed a valuable Freepoint system to evaluate relationship among various parts of the body, presented the results of the SpineCor brace limited to the Cobb angle analysis. Emans et al. [21] developed a detailed analysis of the results of the Boston bracing system, discussing the influence of various morphological parameters, such as curve type, curve apex location, vertebral axial rotation and in-brace initial correction on the final outcome however the radiological data were exclusively considered. Katz and Durrani [22] studied the curves of 36 to 45 degrees managed with the Boston brace to determine factors influencing the outcome but they limited the clinical data to gender, age, menarchial status, height, weight and brace wear schedule, avoiding any information on the shape of the patients' trunk.
One of the most important recent publications in the field is the SRS Committee report on standardization of criteria for adolescent idiopathic scoliosis brace studies [23]. The proposed criteria of outcome include: (1) Cobb angle progression, (2) Cobb angle exceeding 45°, (3) surgery recommended or undertaken. The authors analyzed 32 contributive brace studies but did not reported any clinical parameters assessing the brace effectiveness. In the analysis of "potentially useful additional variables" the SRS Committee enumerated curve pattern, curve magnitude, curve rotation, menarchial status, in-brace correction, skeletal maturation and peak height velocity. The parameters describing the shape of the body of children with idiopathic scoliosis were not considered.
The minority of authors reporting on bracing results for idiopathic scoliosis consider both clinical and radiological data. Rigo used Cobb and Perdriolle angles for radiographic evaluation while the lateral deviation, rotation, trunk imbalance, pelvis tilt and torsion were applied for surface evaluation [24]. The same author published a case report on a durable Cobb angle correction with a brace combined with Bunnell angle correction and surface topography lateral deviation correction [25]. Grivas et al. considered the Bunnell angle to assess the effect of Dynamic Derotation Brace [26]. The fundamental study of Nachemson and Peterson on the effectiveness of bracing included plumb line balance assessment, increase in height during the first year of observation and the presence and extent of a rib hump [27].
Few papers were found that discuss directly the question whether the management of scoliotic patients with a corrective orthosis can influence the difference in the clinical versus radiological outcome. Pham et al. reported on a series of 63 patients managed with Cheneau orthosis who presented significant reduction of the rib hump but not accompanied by a reduction of radiological rotation at the final follow-up 2 years after discontinuing the brace [28]. Weiss reported a case of radiological progression under brace treatment but combined with reduction of surface trunk rotation and surface lateral deviation [29].
Our study demonstrates that the phenomenon of discrepancy of clinical versus radiological measures should be considered by the physicians. The current inexplicable tendency seem to be to omit clinical data describing how the patient feels and how she looks like. Instead the ciphers read by the physician from the radiograph are supported. Nevertheless the improvement of the back shape is a recognized factor influencing the compliance.
From the patient's perspective it seems essential to realize that bracing is capable not only to stabilize radiological parameters but to improve cosmetic appearance. External image of the deformity have the impact on the general health perception, self-estimation as well as on emotional and social functioning. Clinical correction combined with the radiological stabilization appears as an attractive therapeutic option for patients with moderate curves which otherwise are known not to interfere with the patients' health and function throughout their life [30].
On the other hand we would like to stress that all patients in both groups presented radiologically progressive scoliosis, and at the same time these curves were at risk for further progression due to incomplete maturation. The therapy was not undertaken for cosmetic reasons and we do not have intention to recommend such an annoying management if the risk of progression is sufficiently low.
