In this study we aimed to analyze the coronal and sagittal parameters after surgical treatment of AIS by the technique of DVR with type 1 and type 2 Schwab osteotomies. The main results showed that use of the technique yielded significant improvements in sagittal and coronal parameters, such as reductions in the proximal and distal Cobb angles as well as with the lumbar Cobb angle, in addition to an increase in segmental (T5-T12) and total thoracic kyphosis (T1-T12). The surgical technique for DVR is popular for correcting AIS, with efficacy on clinical and radiological parameters. However, the literature offers little with regard to its effectiveness in adolescents with AIS before and after the surgical procedure with DVR.
Using the DVR surgical technique associated with an osteotomy, a 68% correction of the main thoracic curve was observed in the coronal plane, with positive and significant improvement. This is similar to that observed in the study performed by Urbanski et al. [21], in which the authors evaluated 21 patients who underwent the DVR surgical procedure with researchers observing a 69% correction of the main thoracic curves. However, the divergence among related studies has been debated, especially with regard to sample standardization, surgical correction technique, and fixation materials used, as well as standardized surgery time for evaluations. These points lead to difficult comparisons. Thus, there is still a large divergence in post-surgical results using the DVR technique.
A recent meta-analysis carried out by Son et al. [22] has shown benefits with the DVR technique when compared to the simple spinal defeat technique. In this study, the association of the DVR technique with osteotomy was beneficial for increasing the correction of the thoracic curvature with an increase in kyphosis, but the risk-benefit of their choice must be weighed, given the possible post-surgical complications. Such care for surgical consideration is based on studies in which the authors did not find improvement in thoracic kyphosis using Schwab’s type 2 osteotomy [23, 24, 25], but rather increased rates of bleeding during the procedure. Despite this, Seki et al. [11], using uniplanar screws, showed gains in correction of intervertebral rotation with the association of periapical Schwab type 2 osteotomies in relation to facetectomies, especially at lumbar levels. In this study, despite not having considered the parameters of rotational correction, we can observe benefits of performing osteotomy for the correction of thoracic kyphosis, in that it can benefit the patient’s lung capacity.
Another important finding observed in this study was in the sagittal plane, with a considerable gain in segmental and total thoracic kyphosis, especially in patients classified by Lenke et al. [14] as hypokyphotic (eight patients with thoracic kyphosis T5-T12 < 10°) with a preoperative average of 6.8° of kyphosis to 20.1° postoperatively. It is worth reiterating that all patients reached the normal range of kyphosis, according to the classification by Lenke et al. [14]. A study carried out in the past decade by Bernhart [26] revealed an important discussion about normality values for thoracic kyphosis (T3-T12) being between 9° and 53°, while Stagnara [27] referred to the range of 7° and 43°. The Spinal Deformity Study Group [28] offered a reference of 10° to 40° (T5-T12). Although the purpose of this study was not to verify normality parameters, the correction of the coronal and sagittal parameters among adolescents was positive, except for the parameters of lumbar lordosis, pelvic incidence, sacral slope, and pelvic tilt. These points can be explained by the DVR technique associated with osteotomy, since when correcting thoracic kyphosis, little change affects the region of the lumbar spine and pelvic segment. These findings are in agreement with the study by Urbanski et al. [21], in which the authors also did not observe significant changes in lumbar lordosis, but an increase in thoracic kyphosis with DVR in patients with AIS.
The use of DVR has been a source of disagreement regarding the maintenance or increase of thoracic kyphosis. Mladenov et al. [29] observed a decrease in thoracic kyphosis and lumbar lordosis in patients undergoing DVR compared to patients undergoing simple vertebral defeat. Urbanski et al. [21] showed improvement in the coronal plane with the DVR technique, but without differences in the sagittal plane compared to the group of patients submitted to simple defeat. Kim et al. [10], evaluating patients undergoing DVR, observed a lower number of arthrodesis and a lesser amount of intraoperative bleeding, despite not seeing significant differences in postoperative kyphosis in relation to the control group.
In a review study with meta-analysis, Son et al. [22] reported no significant differences in postoperative thoracic kyphosis between the groups undergoing DVR and those undergoing simple defeat. The differential of this study was to observe that perhaps the improvement of thoracic kyphosis was primarily due to type 2 osteotomy associating with the DVR technique, since none of the authors of the studies mentioned previously found significant increases in thoracic kyphosis using only the DVR technique.
One of the limitations of this study was that we did not consider postural parameters referring to the symmetry of the shoulders, nor did we consider the different types of AIS according to Lenke’s classification. Consideration was not given to the rotation of the vertebrae in the pre- and postoperative periods or their implications for improving the quality of each patient’s life and/or respiratory function.
The clinical relevance of this study points to the positive effect of the DVR technique associated with osteotomy in improving the parameters of thoracic kyphosis in patients with hypokyphotic predominance (T5-T12 < 10°). According to Johnston et al. (2011) [30], hypokyphotic patients are associated with decreased lung function, especially in early onset curves. Still in this line of reasoning, Fuji et al. [31] observed an improvement in the pulmonary functioning of a patient with severe scoliosis (main thoracic curve of 96°) with hypokyphosis (T5-T12: 6°), with correction of the curve to 28° in the coronal plane and to 14° of kyphosis (T5-T12), while in this study we found 6.8° of kyphosis which increased to 20.1° in the postoperative period in hypokyphotic patients.