Response to letter to editor regarding ‘In-brace alteration of pulmonary functions in adolescents wearing a brace for idiopathic scoliosis’ by Yagci et al. (2019)

Response to Letter

My coauthors and I thank the author(s) for their inquiry and remarks regarding our recent study reporting in-brace alteration of pulmonary functions in adolescents with idiopathic scoliosis. ¹ Your comments highlight several important points that need to be clarified.

We would first like to point out that pulmonary function is not always expected to decrease in patients with scoliosis, regardless of brace wearing. ² The possible alterations in pulmonary functions may depend on many factors such as curve pattern (single thoracic, single lumbar or double curve), curve magnitude, severity of rotational deformity, progression of scoliosis, scoliosis history (scoliosis presence years) and age. ³ Recent studies have reported deteriorated pulmonary functions in patients with severe scoliosis and in long-term outcomes.^2–4 Second, this single-group study aimed to investigate the effects of the brace on pulmonary functions in the in-brace condition (while patients were wearing the brace). The study was not a follow-up study, and therefore, it did not aim to test a hypothesis or determine the effects of bracing on pulmonary functions with time. As such, the methodology of this study did not require a control group. The long-term effects of wearing a spinal brace on pulmonary functions may be the aim of future studies as you recommended.

We did not aim to affect kyphosis with a spinal brace. When designing and manufacturing a spinal brace, the experienced orthotist is careful about generating a three-point corrective force system.

For the correction of the curve in the frontal plane, one force was applied from the posterio-lateral side of the apex of convexity and a high counter-force was applied from the opposite side. This was defined by an oblique vector with a ‘dorso-lateral to ventro-medial’ direction. For correcting the curve in the horizontal plane, that is, de-rotation, the force applied from the dorsal rib hump acts as a counter-force to the pad on the ventral rib hump in order to form a pair of forces as well as for the reconstruction of the normal thoracic kyphosis. Therefore, a correctly applied force system should actively correct the lateral deviation and rotation deformity while protecting physiological sagittal curves.^5,6 This issue has already been reported in the article, where we state that,

The proper biomechanical principles for orthotic correction was applied regarding corrective forces against spinal column lateral deviation and axial rotation, while protecting the physiological lumbar lordosis and allowing thoracic expansion and free movement ability to the trunk and four extremities.

The authors of the letter also address issues related to the biomechanical properties of the spinal brace. There are many scoliosis braces that are commonly used in the treatment of idiopathic scoliosis. The Cheneau brace, ⁷ Boston brace and modifications of this ⁸ are some of them. The brace used in this study was a modification on the Boston brace. While maintaining original body shape, the brace also facilitated a symmetrical posture and, by achieving this, a three-dimensional action of correction. All of the aforementioned braces are total contact braces that distribute the load being transferred from the brace into the spine in order to correct the scoliosis curve. Only the brace design, biomechanics of correction, and treatment application changed from brace to brace, not the aim of the brace itself. The Cheneau brace is another type of scoliosis brace that has been used. There are many studies, which show the effectiveness of the aforementioned orthosis in scoliosis rehabilitation,^7,8 while there is no consensus about which brace is the most suitable brace for scoliosis rehabilitation. ⁹ The brace described in our study has been used for many years in Turkey to manage patients with scoliosis. We also treat our patients with this brace. Therefore, the study aimed to investigate the effect of this brace on pulmonary functions in patients with idiopathic scoliosis.