A total of 348 initial hits were obtained from six databases. In total, 268 unrelated and 22 duplicate titles were excluded after their titles and abstracts were screened (Fig. 1). Up to 48 of 58 full-text articles were excluded because of the following reasons: 1) ineligible study designs (single-arm study: n=8, retrospective study: n=5, observational study: n=2, and feasible study: n=3); 2) incorrect interventions (head positioning: n=1, general stretching: n=5, core muscle training: n=7, spinal manual therapy: n=3, electrostimulation therapy: n=2, and traction: n=1); 3) inappropriate patient population (n=3, adult participants); 4) inappropriate outcomes (n=2, Cobb angle was not compared); 5) full-text was not in English (n=4); and 6) duplicates (n=2, same cohort with multiple publications). Finally, 10 articles were included in this review (Fig. 1).
Evidence hierarchy and methodological appraisal
Eight articles with an RCT methodology (80%) were classified as providing level II evidence(35-37, 41, 45-48), and two articles with prospective CCT methodology (20%) were classified as providing level III evidence(38, 40) (Table 1). The PEDro scale was ranked from 5 to 9, with an average score of 6.9/10 for overall articles (Table 1). Specifically, the average scores of Schroth studies(35-38, 45), scientific exercise approach to scoliosis (SEAS) studies(41, 47, 48), and alternative SSE(40, 46) studies were 6.4 (n=5, score: 5–8), 8 (n=3, score: 8–9), and 6.5 (n=2, score: 6–7), respectively. Criteria 4 (blinding subjects) and 5 (blinding therapists) were not met for 80% (n=8) of studies(35-38, 45-48). However, one RCT(41) reported participant blinding, whereas one CCT(40) reported therapist blinding.
Characteristics of included studies
Five trials adopted the Schroth method (Table 2). In particular, three RCTs compared the Schroth method alone with standard care(45), Pilates(35), and home exercise(37); one CCT compared the Schroth method and bracing with bracing alone for moderate scoliosis (38); one RCT compared the Schroth method and respiratory exercises with the Schroth method alone for mild to moderate scoliosis (36). Three trials adopted the SEAS method (Table 2). These included one RCT comparing SEAS with core stabilization exercises in patients with moderate scoliosis(47), one RCT comparing SEAS with bracing for moderate scoliosis(48), and one comparing SEAS with traditional exercises for mild scoliosis(41). Another two studies adopted alternative SSE (body awareness, and Xinmiao approach)(40, 46): one was an RCT comparing traditional exercises and body awareness exercises with traditional exercise alone for both mild and moderate scoliosis(46); a CCT study grouped participants by age (<10 years, 10–12 years, and 13–15 years) to determine the relationship of age, skeletal maturity, and gender with intervention effects(40).
Variations in intervention dosage were found, from daily to every other day (Table 2). Four trials reported >1-year follow-up, whereas six trials had study periods of 2–6 months (Table 3). However, only five studies reported exercise compliance in percentage values of prescribed dosage (Table 3).
Six studies compared the truncal asymmetry pre- and post-intervention (Table 3). Four of them showed that SSE was not superior to core exercises, traditional exercises, and bracing for ATR improvement(38, 46, 47) or shoulder balance(48). Two studies showed better improvement of ATR in the study group(37, 41). For QoL (Table 3), five studies adopted the SRS-22 questionnaire(38, 41, 46-48), and one study adopted the SRS-23 questionnaire(37). However, a high initial score (mean score: 3.8–4.2) was noted in all studies (Table 3), with three studies reporting better QoL outcomes in terms of function and mental domain, favoring the SSE group(41, 46, 48). Two studies found no significant differences of QoL between the groups in either adding SSE to bracing treatment or comparing supervised SSE with home exercises(37, 46). Another study found improved pain domain outcomes in the core exercise group only(47).
- Can SSE improve scoliotic deformity?
Ten studies with 494 participants were enrolled in this review (Table 2). Five trials (three RCTs and two CCTs) with moderate study quality showed significant curve regression in terms of reducing Cobb angles beyond the measurement error of 5° (Table 3). Three studies(35, 40, 41) enrolled participants with mild scoliosis (Cobb angle: 10°–27°): Monticone et al. reported a decrease of 5.3° with SEAS but an increase of 1.7° with general exercise at skeletal maturity(41); Kim et al. found a large curve regression from 23.6 ± 1.5° down to 12.0 ± 4.7° in the Schroth group, whereas a reduction from 24.0 ± 2.6° to 16.0 ± 6.9° was observed in the Pilates group after 3 months of exercises(35); Liu et al. grouped participants according to age and revealed that notable curve regressions were favored in patients younger than 13 years (a decrease of Cobb angle: 6.8 ± 5.5° for age <10 years; 3.1 ± 4.2° for age 10–12 years) and with Risser stage 0 (a decrease of Cobb angle: 5.7 ± 5.6°) at 2-year follow-up(40). Another two studies involved brace-wearing patients with moderate scoliosis(38, 46). Kwan et al. found that 17% of the participants showed improvement with Schroth exercises, whereas only 4% improved with no exercise at 1.5-year follow-up(38). Yagci et al. adopted body awareness exercise with bracing and revealed a significant Cobb angle reduction (−7.33 ± 2.78° vs 0.63 ± 4.34°, p < 0.05) of the thoracic curvature between the groups(46).
Three RCTs showed statistically significant reductions in Cobb angle, but differences were not of clinical significance (Table 3). Kim et al. conducted an 8-week-long study and reported a reduction of Cobb angle by 4.26 ± 1.36° after Schroth with respiratory exercises(36). Schreiber et al. conducted a 6-month-long study and demonstrated a 3.5° decrease in the largest curves but only a decrease of 0.4° in the sum of curves (root mean square value) with Schroth therapy(45). Kuru et al. performed a 6-month-long study with three groups and found greater Cobb angle reduction (−2.53°, p = 0.03) in those who relied on supervised Schroth therapy(37).
Furthermore, two RCTs concluded that SSE was not superior than either bracing or core muscle exercises in improving scoliotic deformity (Table 3). Yagci et al. compared the SEAS with core muscle exercises in participants wearing a brace and revealed comparable effects between the thoracic (−5.3 ± 2.2° vs 4.8 ± 2.6°) and lumbar (−4.1 ± 2.5° vs −3.5 ± 3.0°) curvatures(47). Zheng et al. compared the SEAS alone with bracing for moderate scoliosis and suggested that a notable reduction in Cobb angle only favored the bracing group (bracing: 5.58 ± 6.37° vs SEAS: 2.24 ± 3.19°, p = 0.01)(48).
- Effects of age, skeletal maturity, curve magnitude, and exercise compliance with SSE in reducing Cobb angle.
Two studies investigated the relationship between age and intervention effects(40, 41). One RCT with a high study quality (PEDro: 9) revealed that in the SEAS group, participants aged ≥ 13 years had better results than younger patients (−5.8° vs −4.8°)(41). One CCT with moderate study quality (PEDro: 6) revealed the opposite result in terms of better outcomes (−6.8 ± 5.5°/−3.1 ± 4.2° vs −1.5 ± 4.8°), favoring younger patients (<13 years)(40).
One study analyzed the interaction effect of skeletal maturity, in the form of Risser sign, with SSE in improving scoliotic deformity(40). This study suggested that subjects with Risser stage 0 significantly benefited from SSE in curve regression compared with those with Risser stage 3 (Risser stage 0: 5.7 ± 5.6° vs Risser stage 3: 2.1 ± 4.7°).
Two studies compared decreasing values in Cobb angle between thoracic and lumbar curves (Table 3). One study demonstrated that only body awareness therapy could significantly improve thoracic curvatures, and yet, no difference was detected in comparison with the traditional exercise group(46). Another study revealed that both thoracic and lumbar Cobb angles decreased in all participants wearing braces regardless of the exercise strategy (SEAS vs Core muscle training)(47).
No study investigated the correlation of exercise compliance with intervention effects. Five studies reported exercise compliance in the percentage value of the prescribed dosage (Table 3: 58 ± 0.27% to 88%)(38, 45-48), of which three trials reported significant intergroup differences in Cobb angles that were beyond measurement error(38, 46, 48): one study showed greater Cobb angle reduction in patients undergoing brace with exercise(38); another study showed that bracing was superior to exercise alone for moderate scoliosis(48); and the third study suggested body awareness exercise with bracing could effectively improve scoliosis(46).