**4.4. Sagittal balance and alignment**

In recent years, the spinopelvic parameters and sagittal spinal balance have been found to be more important than the coronal curves in relation to clinical outcomes [26, 37–39]. Glassman et al. evaluated the relationships between radiographic parameters and health status. They found that the severity of symptoms is linearly related to the extent of sagittal spinal imbalance [29]. Anterior translation of the trunk, with the SVA in excess of 7 cm is associated with an increase in clinical symptoms [29]. Similarly, Lafage et al. showed a correlation between the SVA and Scoliosis Research Society (SRS) total scores and Oswestry Disability Index (ODI) [35]. Schwab et al. found that a SVA in excess of 47 mm, in combination with a pelvic tilt in excess of 22° and pelvic incidence-lumbar lordosis (PI-LL) mismatch in excess of 11° was closely correlated with disability [40].

The present study showed that SBP exercises did not impact the thoracic kyphosis and lumbar lordosis significantly. The findings concurred with previous findings [41, 42] in AIS patients. Weiss and Klein found that the Physio-logic® program did not improve the thoracic kyphosis [42] and Noh et al. found that Schroth exercises did not improve the thoracic kyphosis and lumbar lordosis [41]. The findings are not unexpected, in view of the fact that the spine of adult scoliosis patients is generally more rigid than that of AIS patients and improvement of curves is less likely.

Yet, the present study found that SBP exercises increased the sacral slope, decreased the pelvic tilt, and improved the SVA significantly (**Table 4**). It is noteworthy that the improvement involved two of the three key radiographic parameters correlated with disabilities [40]. At baseline, the mean sacral slope was 25.3°, which is lower than the mean sacral slope of 39 and 40.9° reported in normal volunteers by Troyanovich et al. and Duval-Beaupere et al., respectively [43, 44]. Our results, however, compared well with the results reported by Iida et al. in adult scoliosis patients. They reported a sacral slope of 26.6° of the DLS patients group and 27.5° for the adult AIS group, respectively [9]. Yang et al. reported a mean sacral slope of 32° in the 99 adult patients with spinal deformities (ASD) with a median age of 67 years [45]. The difference between our data and that of other studies may be related to the magnitude of the scoliosis [9, 45], as progression of lumbar scoliosis has been found to reduce the sacral slope [35, 46].

Duval-Beaupere et al. suggested that a reduction in sacral slope reduced the stability of the pelvis [47]. At the conclusion of the study, the sacral slope increased significantly from a mean of 25.3–28.8°, suggesting that the intervention may improve the stability of the pelvis requiring less hip extensor activity to maintain balance [47].

The pelvic tilt reduced from 20 to 16.2° post intervention. The difference was statistically significant. A study has shown that a pelvic tilt angle of above 22° correlated with disability [43]. Similarly, a number of studies have shown that a large pelvic tit is associated with increased pain and decreased function [35, 38]. A study which analyzed the pre and postoperative differences in spinopelvic parameters and their relationship to postoperative pain showed that patients with a larger postoperative pelvic tilt were likely to have postoperative residual pain than patients with a smaller postoperative pelvic tilt [38]. Similarly, Lafage et al. showed clear evidence that an increased pelvic tilt was associated with increased pain and decreased function [35]. Thus, the reduction of pelvic tilt after intervention may be associated with a better clinical outcome.

PI-LL mismatch has also been found to strongly correlate with disability [40]. A mismatch suggests that the lumbar lordosis does not compensate adequately [40]. The mismatch is clinically significant when it is in excess of 10°. At baseline, 5 had PI-LL mismatch, whereas after 9 months, only 2 had any significant PI-LL mismatch. Yet, the pre- and post-intervention differences were not statistically significant.

Positive sagittal spinal imbalance has also been found to correlate with the severity of symptoms and disability [29, 40]. Duval-Beaupere et al. showed that an anterior translation of the center of gravity in excess of 30 mm in front of the coxofemoral joints require the contraction of the hip extensors for balance [44]. This may be related to the increase in symptoms in patients with positive sagittal spinal imbalance. In the present study, it was shown that the SVA reduced significantly after intervention, suggesting that the patients had an improved global sagittal spinal balance. This may be clinically significant as Schwab et al. showed that a SVA in excess of 47 mm correlated with disability [40].
