Abstract
Purpose
Surgical intervention is the preferred approach to prevent further progression of deformity for patients with adolescent idiopathic scoliosis (AIS); among existing surgeries, posterior spinal fusion is predominant. The minimal clinically important difference (MCID) of the total score of the Scoliosis Research Society (SRS)-22r questionnaire is an increase of ≥ 0.4 in surgically treated patients. However, to the best of our knowledge, there is no research exploring the factors influencing SRS-22r total scores exceeding MCID at 2 years postoperatively.
Methods
Patients who underwent posterior spinal fusion between February 2019 and November 2023 and had a minimum follow-up duration of > 2 years were included. The radiological data and SRS-22r scores were assessed preoperatively and postoperatively. Based on the SRS-22r total scores, the patients were divided into two groups: ‘I’ = Improvement group (∆ Score ≥ 0.4) and ‘NI’ = Non-improvement group (∆ Score < 0.4). Demographic characteristics, radiographic data, and SRS-22r scores were analyzed using chi-square tests and t-tests for comparison. Multivariate logistic regression analysis was used to determine influencing factors.
Results
A total of 66 patients with AIS underwent posterior spinal fusion surgery were included in the study. The major Cobb angle decreased from 52.9 ± 12.3° preoperatively to 12.3 ± 8.6° (p < 0.001) at 2 years postoperatively, while the SRS-22r total score improved from 3.9 ± 0.4 to 4.2 ± 0.5 (p < 0.001). Overall, 32 of 66 of patients (48.5%) achieved MCID. Preoperatively, the Improvement group trended toward a larger Cobb angle (p = 0.042). Postoperatively, patients who achieved a greater Cobb angle correction in degrees were more likely to attain the MCID (p = 0.003).
Conclusion
Postoperative MCID attainment in patients with AIS is influenced by both the preoperative Cobb angle and the degree of its surgical correction.
Supplementary Information
The online version contains supplementary material available at 10.1186/s13018-025-06225-w.
Keywords: Adolescent idiopathic scoliosis, Minimal clinically important difference, SRS-22r, Quality of life
Introduction
Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis among adolescents, with an incidence rate of approximately 1–3% [1]. Severe AIS not only leads to three-dimensional spinal deformities but also significantly affects patients’ quality of life (QoL). For patients with a Cobb angle exceeding 40°, surgical intervention is typically the preferred approach to prevent further progression of deformity, with posterior spinal fusion being the predominant treatment method [2]. The goals of treatment for AIS extend beyond radiographic correction of deformities to include substantial improvement in subjective QoL [3–5].
Although posterior spinal fusion surgery for AIS can correct visible deformities, not all patients experience improved QoL postoperatively. The long-term impact of curve location on QoL may also differ [6]. The Scoliosis Research Society (SRS) has developed the SRS-22r questionnaire, widely used for assessing QoL in patients with AIS [7–9]. However, the improvements in statistical scores of questionnaires do not always equate to clinically meaningful changes. The concept of minimal clinically important difference (MCID), defined as the smallest measurable change in outcome score that makes a meaningful difference to the patient’s life, provides a more intuitive and quantitative threshold of questionnaire for evaluating treatment outcomes [10]. Bennett et al. utilized the MCID value of the appearance domain in the SRS-22r questionnaire to discuss factors influencing patients’ postoperative QoL [11]. The MCID of total scores of SRS-22r is increase of 0.4 [12]; however, studies applying MCID to evaluate surgical outcomes in AIS are limited. Currently, research lacks a systematic exploration of the association between radiographic data and QoL improvement based on MCID in patients with different curve types of AIS.
This study, based on a 2-year follow-up cohort, utilizes MCID as a marker for evaluating QoL improvement. It aims to investigate how posterior spinal fusion surgery affects QoL in patients with AIS across curve types and identify factors linked to the improved MCID.
Methods
Study population
This single-center retrospective study analyzed prospectively recorded data from patients with AIS who underwent posterior spinal fusion surgery between February 2019 and November 2023. Questionnaires were collected through online tools. Clinical and radiographic data of patients were standardized and collecte under the framework of the Deciphering disorders Involving Scoliosis and COmorbidities (DISCO) study. All surgeries were performed by the same surgical team. All patients or their legal guardians provided informed consent, and the study obtained approval from the hospital ethics committee (No. I-24PJ0473).
The inclusion criteria were: (1) clinical diagnosis of AIS and treatment with posterior spinal fusion; (2) age at surgery between 10 and 18 years; (3) availability of radiographs preoperatively, at 1 week, and at 2-year follow up; and (4) complete questionnaire data (including the SRS-22r and short form survey 36 [SF-36]) before surgery and at 2-year follow-up. Exclusion criteria included non-idiopathic scoliosis, history of spinal surgery, irregular follow-up and preoperative SRS-22r total score higher than 4.6 (to avoid ceiling effects). All questionnaires were completed by patients with guidance.
Outcome measure
Radiographic Measurements: Standard standing posteroanterior and lateral spinal radiographs were obtained preoperatively, at 1 week, and at 2 years postoperatively. Coronal plane assessments included major coronal curve of Cobb angle, coronal balance (CB), Nash-Moe rotation of the major curve (NM), apical vertebral translation (AVT), shoulder tilt (ST), radiological shoulder height (RSH), and Risser classification. Sagittal plane measurements included lumbar lordosis (LL, L1-S1), thoracic kyphosis (TK, T5–T12), sagittal vertical axis (SVA), and sacral slope (SS). Spinal flexibility was assessed using bending radiographs.
Questionnaire measures
Questionnaires included the SRS-22r (1 indicating worst and 5 indicating best QoL) [13] and the SF-36 (0 indicating worst and 100 indicating best) [14]. The MCID of the total scores of the SRS-22r was 0.4 [12].
Based on the SRS-22r total scores, the patients were divided into 2 groups: the Improvement group (I; Δ total score ≥ 0.4) and the Non-improvement group (NI; Δ total score < 0.4). The two groups were compared using clinical and radiographic measures. According to the Lenke classification, patients were divided into those with primary thoracic curves (Lenke 1–4) and those with primary thoracolumbar/lumbar curves (Lenke 5–6).
Statistical analysis
Data were checked for normality using the Shapiro-Wilk test. Descriptive statistics were presented as means ± standard deviations (SD). For continuous variables, the independent t-test was employed for parametric data, while the Mann-Whitney U test was used for non-parametric data. Paired statistical tests were applied to compare preoperative and postoperative data for the same group of 66 patients. For normally distributed continuous variables, a paired t-test was conducted. For non-normally distributed continuous variables, Wilcoxon signed-rank test was used. The Bonferroni correction was used to mitigate the possibility of Type 1 error (α = 0.05/15). Variables with P values < 0.05 in univariate analyses were included in a multivariate logistic regression model. Data analysis was performed using SPSS (version 26.0).
Results
A total of 89 patients who underwent surgical treatment for AIS at PUMCH between February 2019 and November 2023 were enrolled (Fig. 1). Preoperative data, including SRS-22r, SF-36, as well as clinical and radiographic information, were collected. At 1 week postoperatively, all patients completed clinical and radiographic follow-ups. At the 2-year postoperative follow-up, 71 patients completed clinical and radiographic evaluations, with 68 patients returning the SRS-22r and SF-36 questionnaires. Due to follow-up periods of less than 2 years, 18 patients were excluded from the 2-year follow-up analysis. Additionally, 3 patients did not return the questionnaires, and 2 were excluded due to a preoperative SRS-22 score greater than 4.6. Ultimately, 66 patients were included in this study with an average age of 14.3 ± 2.1 years, comprising 9 men and 57 women. Demographics and spinal characteristics are presented in Table 1. According to the NM classification, 58% of participants were at 2. Regarding skeletal maturity, 32% were Risser grade 3, and in the PUMC classification, 50% were PUMC type 3. According to the Lenke classification, 24% had Lenke type 5 curves. In addition, baseline characteristics of the 23 patients excluded from the study were analyzed and compared with those who completed the study. No statistically significant differences were found between the two groups (Supplementary Table 1).
Fig. 1.
Flow diagram of the study population
Table 1.
Main demographics of participants
| Total (n = 66) | |
|---|---|
| Age, year | 14.3 ± 2.1 |
| Sex, male/female | 9/57 |
| Height, cm | 163.7 ± 6.8 |
| BMI, kg/m2 | 19.4 ± 3.4 |
| Flexibility, % | 50.4 ± 26.9 |
| NM, n | |
| 1 | 16 |
| 2 | 38 |
| 3 | 10 |
| 4 | 2 |
| Risser, n | |
| 0 | 14 |
| 1 | 5 |
| 2 | 5 |
| 3 | 21 |
| 4 | 13 |
| 5 | 8 |
| Lenke classification, n | |
| 1 | 9 |
| 2 | 14 |
| 3 | 6 |
| 4 | 10 |
| 5 | 16 |
| 6 | 11 |
| PUMC classification, n | |
| 1 | 14 |
| 2 | 19 |
| 3 | 33 |
| Blood loss, ml | 347.6 ± 204.3 |
| Fused segments | 10.0 ± 3.3 |
| Complications | 0 |
PUMC classification: Peking Union Medical College classification, NM: Nash-Moe rotation of the major curve
Radiological data of the patients are shown in Table 2. Compared to preoperative data, significant deformity correction were observed at 2 years postoperatively in the main Cobb angle (12.3 ± 8.6° vs. 52.9 ± 12.3°, p < 0.001), CB (10.1 ± 7.8 mm vs. 17.6 ± 11.5 mm, p < 0.001), and AVT (12.0 ± 5.6 mm vs. 43.9 ± 15.2 mm, p < 0.001). We also observed changes of LL (53.4 ± 12.8° vs. 57.8 ± 11.7°, p = 0.003) and SS (37.1 ± 10.2° vs. 42.2 ± 9.6°, p < 0.001). Additionally, when compared to data at 1 week postoperatively, no significant differences were observed in radiological data at 2 years postoperatively, except for CB (10.1 ± 7.8 mm vs. 13.4 ± 9.1 mm, p = 0.045), TK (25.5 ± 12.5° vs. 21.6 ± 9.9°, p = 0.002), and SVA (11.7 ± 27.2 mm vs. 20.8 ± 29.8 mm, p = 0.013). Compared to preoperative data, significant improvements were observed at 1 week postoperatively in the main Cobb angle (12.4 ± 8.4° vs. 52.9 ± 12.3°, p < 0.001), CB (13.4 ± 9.1 mm vs. 17.6 ± 11.5 mm, p = 0.007), and AVT (12.3 ± 7.7 mm vs. 43.9 ± 15.2 mm, p < 0.001). Changes were also noted in SVA (20.8 ± 29.8 mm vs. 7.6 ± 27.4 mm, p < 0.001) and SS (39.7 ± 10.6° vs. 42.2 ± 9.6°, p = 0.006). No significant variations were observed in RSH and ST.
Table 2.
Radiological data
| Radiological data | Preoperative (A) |
1 week Postoperative (B) |
2 yr fellow-up(C) |
A VS B | A VS C | B VS C | |
|---|---|---|---|---|---|---|---|
| Main Cobb, ° | 52.9 ± 12.3 | 12.4 ± 8.4 | 12.3 ± 8.6 | < 0.001a* | < 0.0011a* | 0.801a | |
| RSH, mm | 10.4 ± 8.7 | 9.8 ± 8.8 | 9.1 ± 6.2 | 0.662a | 0.462a | 0.733a | |
| ST, ° | 2.2 ± 1.7 | 2.1 ± 2.0 | 2.0 ± 1.3 | 0.461a | 0.600a | 0.828a | |
| CB, mm | 17.6 ± 11.5 | 13.4 ± 9.1 | 10.1 ± 7.8 | 0.007a* | < 0.001a* | 0.045a* | |
| AVT, mm | 43.9 ± 15.2 | 12.3 ± 7.7 | 12.0 ± 5.6 | < 0.001a* | < 0.001a* | 0.692a | |
| LL, ° | 57.8 ± 11.7 | 56.0 ± 12.5 | 53.4 ± 12.8 | 0.217b | 0.003b* | 0.050b | |
| TK, ° | 24.2 ± 11.0 | 21.6 ± 9.9 | 25.5 ± 12.5 | 0.094b | 0.387b | 0.002b* | |
| SVA, mm | 7.6 ± 27.4 | 20.8 ± 29.8 | 11.7 ± 27.2 | < 0.001b* | 0.323b | 0.013b* | |
| SS, ° | 42.2 ± 9.6 | 39.7 ± 10.6 | 37.1 ± 10.2 | 0.006a* | < 0.001a* | 0.169a | |
CB: Coronal balance, AVT: Apical vertebral translation, ST: Shoulder tilt, RSH: Radiological shoulder height, LL: Lumbar lordosis (L1-S1), TK: Thoracic kyphosis (T5–T12), SVA: Sagittal vertical axis, SS: Sacral slope, Yr: year, aMann-Whitney U test, bTwo Sample t-test, *p < 0.05
SRS-22r total scores (4.2 ± 0.5 vs. 3.9 ± 0.4, p < 0.001), self-image (3.9 ± 0.8 vs. 3.2 ± 0.6, p < 0.001), mental health (4.2 ± 0.5 vs. 4.0 ± 0.5, p = 0.035), and satisfaction domain scores (4.4 ± 0.6 vs. 3.7 ± 0.9, p < 0.001) significantly improved from preoperative to the 2-years postoperative period. Compared to preoperative data, the general health (GH: 68.6 ± 20.1 vs. 75.2 ± 19.0, p = 0.004), mental health (MH: 56.6 ± 12.6 vs. 73.2 ± 13.7, p < 0.001), and health transition (HT: 48.9 ± 19.8 vs. 73.9 ± 23.3, p < 0.001) criteria in the SF-36 significantly improved 2 years postoperatively (Table 3).
Table 3.
SRS-22r scores at preoperative and final follow-up
| Preoperative | 2 year follow up | p-value | |
|---|---|---|---|
| SRS-22r | |||
| Total | 3.9 ± 0.4 | 4.2 ± 0.5 | < 0.001a* |
| Function | 4.0 ± 0.6 | 4.0 ± 0.6 | 0.990a |
| Pain | 4.5 ± 0.6 | 4.5 ± 0.4 | 0.551a |
| Self-image | 3.2 ± 0.6 | 3.9 ± 0.8 | < 0.001a* |
| Mental health | 4.0 ± 0.5 | 4.2 ± 0.5 | 0.035a* |
| Satisfaction | 3.7 ± 0.9 | 4.4 ± 0.6 | < 0.001a* |
| SF-36 | |||
| PF | 89.6 ± 12.3 | 85.8 ± 11.6 | 0.018a* |
| RP | 78.8 ± 32.6 | 78.8 ± 30.8 | 0.843a |
| BP | 90.2 ± 17.0 | 91.3 ± 13.5 | 0.532a |
| GH | 68.6 ± 20.1 | 75.2 ± 19.0 | 0.004a* |
| VT | 77.9 ± 13.2 | 73.3 ± 12.6 | 0.025a* |
| SF | 86.2 ± 17.8 | 87.7 ± 19.8 | 0.495a |
| RE | 82.8 ± 29.4 | 89.4 ± 25.6 | 0.072a |
| MH | 56.6 ± 12.6 | 73.2 ± 13.7 | < 0.001a* |
| HT | 48.9 ± 19.8 | 73.9 ± 23.3 | < 0.001a* |
Yr: years, PF: Physical functioning, PR: Physical role functioning, BP: Bodily pain, GH: General health, VT: Vitality, SF: Social functioning, RE: Role-Emotional, MH: Mental health, HT: Health transition, aMann-Whitney U test, *p < 0.05
Patients were divided into two groups based on the SRS-22r total scores: the improvement group (“I”) with a Δ total score ≥ 0.4 and the non-improvement group (“NI”) with a Δ total score < 0.4 (Table 4). The basic characteristics of the 2 groups, including age, height, surgical fusion segments, and blood loss volume, showed no statistically significant differences (Supplemental Table 2). We found that patients in the “I” group had significantly better postoperative outcomes compared to the “NI” group across multiple domains in both Lenke 1–4 and Lenke 5–6 subtypes. For Lenke 1–4, the “I” group showed significant improvements in total score, function, mental health, and satisfaction at the two-year postoperative follow-up compared to the preoperative values (p < 0.05). The corrective values in these domains were also significantly higher in the “I” group than in the “NI” group (p < 0.02). In patients with Lenke 5–6 classification, similar trends were observed, with the “I” group demonstrating significant improvements in total score, function, self-image, mental health, and satisfaction at 2 years postoperatively (p < 0.05). Interestingly, although overall improvements in pain scores were modest, the corrective values were significantly higher in the “I” group than the “NI” group (p = 0.014).
Table 4.
Comparison of SRS-22r results between “I” and “NI”
| Total | Lenke 1–4 | Lenke 5–6 | |||||||
|---|---|---|---|---|---|---|---|---|---|
| I(n = 32) | NI(n = 34) | p | I (n = 21) | NI (n = 18) | p | I (n = 11) | NI (n = 16) | p | |
| SRS-22r | |||||||||
| Total | |||||||||
| Pre | 3.8 ± 0.3 | 3.9 ± 0.4 | 0.052a | 3.8 ± 0.3 | 3.9 ± 0.4 | 0.076a | 3.9 ± 0.4 | 3.9 ± 0.4 | 0.882a |
| 2 year Post | 4.4 ± 0.3 | 3.9 ± 0.5 | < 0.001a* | 4.4 ± 0.3 | 4.1 ± 0.4 | 0.004a* | 4.5 ± 0.3 | 3.9 ± 0.5 | 0.001a* |
| Function | |||||||||
| Pre | 3.9 ± 0.5 | 4.0 ± 0.6 | 0.243a | 3.8 ± 0.6 | 4.1 ± 0.5 | 0.074a | 4.1 ± 0.5 | 4.0 ± 0.7 | 0.601a |
| 2 year Post | 4.2 ± 0.4 | 3.7 ± 0.6 | 0.001a* | 4.2 ± 0.4 | 3.9 ± 0.4 | 0.027a* | 4.2 ± 0.5 | 3.6 ± 0.7 | 0.044a* |
| Correction | 0.3 ± 0.4 | -0.3 ± 0.5 | < 0.001a* | 0.3 ± 0.4 | -0.2 ± 0.5 | < 0.001a* | 0.1 ± 0.3 | -0.3 ± 0.6 | 0.042a* |
| Pain | |||||||||
| Pre | 4.4 ± 0.6 | 4.5 ± 0.6 | 0.643a | 4.5 ± 0.5 | 4.6 ± 0.4 | 0.708a | 4.2 ± 0.8 | 4.4 ± 0.6 | 0.653a |
| 2 year Post | 4.7 ± 0.3 | 4.3 ± 0.5 | < 0.001a* | 4.6 ± 0.4 | 4.5 ± 0.4 | 0.127a | 4.6 ± 0.4 | 4.3 ± 0.4 | 0.057a |
| Correction | 0.3 ± 0.5 | -0.2 ± 0.4 | < 0.001a* | 0.1 ± 0.5 | -0.1 ± 0.4 | 0.136a | 0.4 ± 0.6 | -0.1 ± 0.3 | 0.014a* |
| Self-image | |||||||||
| Pre | 3.2 ± 0.6 | 3.2 ± 0.6 | 0.505a | 3.0 ± 0.6 | 3.2 ± 0.5 | 0.190a | 3.6 ± 0.5 | 3.2 ± 0.6 | 0.098a |
| 2 year Post | 4.2 ± 0.6 | 3.7 ± 0.9 | 0.008a* | 4.1 ± 0.6 | 3.8 ± 0.8 | 0.109a | 4.3 ± 0.6 | 3.5 ± 0.9 | 0.012a* |
| Correction | 1.0 ± 0.6 | 0.4 ± 0.6 | 0.001a* | 1.1 ± 0.7 | 0.5 ± 0.5 | 0.004a* | 0.8 ± 0.6 | 0.3 ± 0.6 | 0.165a |
| Mental health | |||||||||
| Pre | 3.9 ± 0.3 | 4.1 ± 0.6 | 0.009a* | 4.0 ± 0.3 | 4.1 ± 0.6 | 0.389a | 3.8 ± 0.4 | 4.1 ± 0.7 | 0.149a |
| 2 year Post | 4.4 ± 0.5 | 3.9 ± 0.5 | < 0.001a* | 4.4 ± 0.4 | 4.0 ± 0.5 | 0.048a* | 4.4 ± 0.5 | 3.8 ± 0.4 | 0.003a* |
| Correction | 0.6 ± 0.4 | -0.2 ± 0.4 | < 0.001a* | 0.5 ± 0.5 | -0.1 ± 0.4 | < 0.001a* | 0.6 ± 0.5 | -0.3 ± 0.5 | < 0.001a* |
| Satisfaction | |||||||||
| Pre | 3.6 ± 0.9 | 3.8 ± 0.9 | 0.403a | 3.5 ± 0.9 | 3.7 ± 0.9 | 0.472a | 3.8 ± 0.8 | 3.8 ± 0.8 | 0.761a |
| 2 year Post | 4.7 ± 0.4 | 4.1 ± 0.7 | < 0.001b* | 4.7 ± 0.3 | 4.2 ± 0.8 | 0.043a* | 4.7 ± 0.5 | 4.1 ± 0.6 | 0.006a* |
| Correction | 1.1 ± 0.8 | 0.4 ± 0.9 | < 0.001b* | 1.1 ± 0.8 | 0.4 ± 0.9 | 0.018b* | 1.0 ± 0.7 | 0.3 ± 0.8 | 0.005b* |
Yr: years, aMann-Whitney U test, bTwo Sample t-test, *p < 0.05
In the radiological analysis (Table 5), “I” group exhibited greater postoperative Cobb angle improvement compared to “NI” group (p = 0.003), despite having larger preoperative Cobb angles (p = 0.042). The “I” group demonstrated significantly better correction in the main Cobb angle compared to the “NI” group in both Lenke 1–4 (44.2 ± 8.6° vs. 37.9 ± 9.9°, p = 0.043) and Lenke 5–6 (44.9 ± 10.5° vs. 36.0 ± 11.4°, p = 0.047). Additionally, in Lenke 5–6, the “I” group showed significant improvements in RSH at the 2-year follow-up (4.6 ± 4.4 mm vs. 9.6 ± 5.0 mm, p = 0.013), CB (7.2 ± 4.0 mm vs. 13.4 ± 10.6 mm, p = 0.048), and AVT (10.5 ± 4.7 mm vs. 15.8 ± 5.4 mm, p = 0.011). No significant differences were observed in sagittal parameters (Supplemental Table 3).
Table 5.
Comparison of group ‘‘I’’ and group ‘‘NI’’
| Total | Lenke 1–4 | Lenke 5–6 | |||||||
|---|---|---|---|---|---|---|---|---|---|
| I (n = 32) | NI (n = 34) | p | I (n = 21) | NI (n = 18) | p | I (n = 11) | NI (n = 16) | p | |
| Radiological data | |||||||||
| Main Cobb, ° | |||||||||
| Pre | 56.0 ± 11.8 | 49.9 ± 12.0 | 0.042a | 57.6 ± 13.4 | 51.9 ± 12.5 | 0.181a | 53.1 ± 8.0 | 47.6 ± 11.6 | 0.160a |
| 2 year Post | 11.5 ± 9.5 | 12.8 ± 7.7 | 0.541a | 13.4 ± 10.6 | 14.0 ± 7.2 | 0.823a | 8.2 ± 6.2 | 11.6 ± 8.2 | 0.226a |
| Correction | 44.4 ± 9.1 | 37.0 ± 10.5 | 0.003a* | 44.2 ± 8.6 | 37.9 ± 9.9 | 0.043a | 44.9 ± 10.5 | 36.0 ± 11.4 | 0.047a |
| RSH, mm | |||||||||
| Pre | 10.0 ± 9.4 | 10.8 ± 8.2 | 0.439b | 10.7 ± 10.7 | 10.3 ± 7.6 | 0.680b | 8.7 ± 6.6 | 11.3 ± 9.0 | 0.436b |
| 2 year Post | 9.2 ± 6.2 | 8.9 ± 6.4 | 0.999b | 11.6 ± 5.7 | 8.3 ± 7.4 | 0.231b | 4.6 ± 4.4 | 9.6 ± 5.0 | 0.013b |
| Correction | 0.8 ± 12.1 | 2.0 ± 9.4 | 0.672a | -0.9 ± 13.8 | 2.1 ± 8.9 | 0.416a | 4.0 ± 7.7 | 1.7 ± 10.2 | 0.507a |
| ST, ° | |||||||||
| Pre | 2.2 ± 1.9 | 2.2 ± 1.5 | 0.991a | 2.4 ± 2.1 | 2.1 ± 1.3 | 0.678a | 2.0 ± 1.4 | 2.3 ± 1.8 | 0.546a |
| 2 year Post | 2.1 ± 1.3 | 2.0 ± 1.3 | 0.678a | 2.6 ± 1.2 | 2.0 ± 1.6 | 0.182a | 1.1 ± 0.9 | 1.9 ± 1.0 | 0.042a |
| Correction | 0.1 ± 2.5 | 0.3 ± 1.9 | 0.795b | -0.2 ± 2.8 | 0.2 ± 1.7 | 0.589a | 0.8 ± 1.6 | 0.4 ± 2.1 | 0.543a |
| CB, mm | |||||||||
| Pre | 16.5 ± 11.6 | 18.5 ± 11.4 | 0.457b | 15.3 ± 12.6 | 14.1 ± 9.5 | 0.878b | 19.0 ± 9.6 | 23.5 ± 11.6 | 0.368b |
| 2 year Post | 9.6 ± 7.2 | 10.6 ± 8.5 | 0.603b | 10.9 ± 8.2 | 8.1 ± 5.2 | 0.410b | 7.2 ± 4.0 | 13.4 ± 10.6 | 0.048b |
| Correction | 6.9 ± 14.1 | 8.0 ± 11.5 | 0.741a | 4.3 ± 15.5 | 6.1 ± 10.1 | 0.679a | 11.9 ± 9.7 | 10.1 ± 12.8 | 0.691a |
| AVT, mm | |||||||||
| Pre | 44.6 ± 13.0 | 43.3 ± 17.2 | 0.305b | 44.4 ± 15.0 | 41.6 ± 19.5 | 0.181b | 44.9 ± 8.6 | 45.2 ± 14.6 | 0.942b |
| 2 year Post | 10.7 ± 5.2 | 13.0 ± 5.7 | 0.089a | 10.8 ± 5.6 | 10.6 ± 4.9 | 0.868a | 10.5 ± 4.7 | 15.8 ± 5.4 | 0.011a |
| Correction | 33.9 ± 10.1 | 30.2 ± 16.3 | 0.059b | 33.5 ± 10.8 | 31.0 ± 18.0 | 0.112b | 34.5 ± 8.8 | 29.3 ± 14.7 | 0.294b |
AVT: Apical vertebral translation, CB: Coronal balance, ST: Shoulder tilt, RSH: Radiological shoulder height, LL: Lumbar lordosis (L1-S1), TK: Thoracic kyphosis, SVA: Sagittal vertical axis, SS: Sacral slope
aTwo Sample t-test, bMann-Whitney U test, *After Bonferroni correction p-value < 0.0033
In the multiple logistic regression analysis, factors with p-values < 0.05 were included, and correction of the main Cobb angle was found to be associated with the attainment of MCID (odds ratio = 1.086, 95% CI = 1.004–1.176, p = 0.040; Table 6).
Table 6.
Results of multiple logistic regression analysis
| Radiographic factor | P value | Odds ratio | 95% confidence interval |
|---|---|---|---|
| Main Cobb correction | 0.040* | 1.086 | 1.004–1.176 |
| Main Cobb pre | 0.899 | 0.996 | 0.936–1.060 |
*p < 0.05
Further grouping patients based on whether Cobb angle improvement exceeded 40° (Table 7) revealed that the number of patients achieving MCID was significantly higher in the ≥ 40° improvement group compared to the < 40° group (p = 0.007). Additionally, in terms of SRS-22r improvement, the total score (p = 0.004) and function score (p = 0.002) were higher in the ≥ 40° improvement group.
Table 7.
Comparison of patients with Cobb angle correction ≥ 40° vs. <40°
| Cobb angle correction ≥ 40° |
Cobb angle correction < 40° |
P value | |
|---|---|---|---|
| Total (n) | |||
| “I” group | 20 | 12 | 0.007a* |
| “NI” group | 10 | 24 | |
| SRS-22r Correct | |||
| Total | 0.5 ± 0.3 | 0.2 ± 0.4 | 0.004b* |
| Function | 0.2 ± 0.4 | -0.2 ± 0.7 | 0.002b* |
| Pain | 0.1 ± 0.5 | -0.1 ±0.5 | 0.118b |
| Self-image | 0.9 ± 0.7 | 0.6 ± 0.7 | 0.094b |
| Mental health | 0.3 ± 0.6 | 0.1 ± 0.6 | 0.205b |
| Satisfaction | 1.0 ± 0.7 | 0.6 ± 1.0 | 0.359c |
Yr: years, *p < 0.05, aChi-squared test, bTwo Sample t-test, cMann-Whitney U test, *p < 0.05
Discussion
This study shows that among patients with AIS undergoing posterior spinal fusion surgery, 32 of 66 (48.5%) patients experienced a clinically significant improvement in QoL within 2 years (based on an SRS-22r score Δ total ≥ 0.4). Postoperative MCID attainment in patients with AIS is influenced by both the preoperative Cobb angle and the degree of its surgical correction. While preoperative factor — the preoperative Cobb angle was patient-specific, the postoperative factor— the degree of improvement in the Cobb angle—might be affected by surgery.
Most studies assessing surgical outcomes in scoliosis treatment have relied on statistical significance, which may not reflect clinically meaningful improvement. To better assess surgical outcomes in AIS, our study used the MCID of the SRS-22r score as a grouping criterion, addressing the limitation of studies that focus solely on statistical differences. MCID represents the smallest change in treatment outcomes, which can guide clinical treatment decisions [15]. In recent years, MCID has been widely used to assess patient improvement and satisfaction following surgical treatment [16–18]. Wang et al. applied MCID concept to a study on minimally invasive spinal deformity surgery and analyzed 78 patients who did not reach MCID, identifying several factors influencing clinical outcomes [19]. Carreon et al. reported MCID thresholds of 0.20 for the SRS-22 pain domain and 0.98 for the appearance domain in patients with AIS [20]. Kelly et al. further set the MCID for the pain domain at 0.3 through the minimum detectable measurement difference, and proposed that the MCID for the activity domain should be at least 0.3 [21]. Crawford et al. suggested a total MCID score of 0.4 for SRS-22r in patients with spinal deformity [12]. Bennett et al. applied the MCID concept to the appearance domain of SRS-22r, analyzing factors influencing MCID achievement and found that greater Cobb angle correction was associated with higher likelihood of reaching the MCID [11]. Bastrom et al. reported that patients with AIS with major complications were less likely to achieve MCID improvements in the SRS-22 score, particularly in self-image and pain score [22]. Previous studies have highlighted the correlation between radiological improvements and patient satisfaction in AIS treatment. Ghandehari et al. reported that patients with AIS with more substantial spinal corrections experienced more pronounced improvements in their QoL, suggesting that the degree of deformity correction might be a pivotal factor in patient satisfaction and treatment success [23]. However, no research has discussed radiographic factors related to QoL based on MCID. This study further explored the specific impact of Cobb angle improvement on QoL, and the results indicated that the correction of Cobb angle might closely associated with improved QoL. This was particularly evident in all patients with AIS, regardless of whether they had a main thoracic curve (Lenke 1–4) or a main thoracolumbar/lumbar curve (Lenke 5–6).
More and more studies were focusing on the QoL of patients with AIS, with the SRS-22r questionnaire becoming an important aspect for doctors to understand AIS treatment outcomes. Our study found that 32 of 66 patients (48.5%) with AIS showed significant improvement in QoL. However, there is still controversy regarding the effect of surgery on pain improvement in patients with AIS. Mens et al. reported a mean SRS-22r total scores improvement of 0.4 in a 2-year study of Dutch patients with AIS, with preoperative total scores of 3.8 and postoperative total scores of 4.2. The pain scores were 3.8 before the surgery and 4.2 after the surgery [24]. Helenius et al. reported the 2-year follow-up QoL data of 52 patients with AIS, where the pain score improved from 4.0 to 4.3 [25]. However, a study by Alamrani et al. reported that, over the long term, pain decreased by 0.1 in patients with AIS [26]. A study by Kwan et al. found no significant improvement in pain domain over 2 years [27]. We compared SRS-22r scores for 66 surgical patients with AIS, revealing significant improvements in self-image, mental health, and satisfaction domains. Regarding the SF-36, improvements were noted in GH, MH, and HT, but not in PF and BP. Analyzing our results, we found no significant improvement in pain and functional scores, while self-image, mental health, and satisfaction significantly improved. Consistent with the findings of Carreon et al. [28], our study also found that patients with higher preoperative SRS-22r pain scores experienced no significant improvement in pain scores two years postoperatively. The lack of improvement in pain and function may be explained by increased scores among patients with substantial Cobb angle correction and decreased scores among those with minor correction. Although the subgroup size was limited, postoperative SRS-22r total score were more likely to reach the MCID when the Cobb angle correction was ≥ 40°, suggesting a potential association that warrants further investigation.
Surgery is an effective way for correcting spinal deformities, as demonstrated by radiographic improvements. Helenius et al. reported 5-year follow-up data for 49 patients with AIS, showing a reduction in Cobb angle from 53.2° preoperatively to 11.7° postoperatively [25]. Similarly, Zhou et al. reported outcomes in 70 patients with AIS, with Cobb angle decreasing from 53.4° to 7.3° [29]. In our cohort, the Cobb angle of patients with AIS changed from 52.9° preoperatively to 12.3° postoperatively. Compared to previous studies, our work provides a detailed description of the coronal and sagittal imaging data of patients before surgery, 1 week postoperatively, and at 2 years. Our results indicated improvements in coronal parameters except for RSH and ST, consistent with previous studies [27, 30]. Most radiological parameters remained stable between the 1-week and 2-year follow-ups, except for CB, TK, and SVA, which showed significant changes: CB decreased, TK increased, and SVA decreased. These findings suggest the need for long-term follow-up to monitor and manage potential postoperative changes in spinal alignment.
The main limitation of this study was its single-center design. However, we ensured standardized and consistent collection of patient information. While the MCID is a useful metric, it may not be optimal for evaluating all diseases. In this study, it was used to analyze the relationship between radiological parameters and improvements in QoL. Another limitation is the potential presence of ceiling effects, particularly in using the MCID as a criterion for categorizing patients. Although two patients were excluded due to high preoperative SRS-22r scores, the overall impact on the findings is small. Finally, this study focused solely on the total SRS-22r score; future research should investigate domain-specific MCIDs and their associated factors to prove a more comprehensive understanding of postoperative QoL improvements in patients with AIS.
Conclusion
Postoperative MCID attainment in patients with AIS is influenced by both the preoperative Cobb angle and the degree of its surgical correction.
Supplementary Information
Below is the link to the electronic supplementary material.
Acknowledgements
This research was funded in part by the National Key Research and Development Program of China (2023YFC2507700 to J.Z. and N.W.); National High Level Hospital Clinical Research Funding (2022-PUMCH-D-004 to J.Z. and N.W., 2022-PUMCH-C-033 to N.W.); National Natural Science Foundation of China (82172525); CAMS Innovation Fund for Medical Sciences (CIFMS, 2021-I2M-1-051 to J.Z. and N.W., 2023-I2M-C&T-A-003 to J.Z.); and the Non-profit Central Research Institute Fund of Chinese Academy of Medical Sciences (No. 2019PT320025).
Author contributions
Zhengye Zhao, Aoran Maheshati and Xueyi Zhang contributed equally to this work. Zhengye Zhao: Conceptualization, Visualization, Investigation, Methodology, Investigation, Formal analysis, Writing- Original draft. Aoran Mahesati: Conceptualization, Formal analysis, Writing- Original draft. Xueyi Zhang: Methodology, Software, Writing- Reviewing and Editing. Di Liu: Formal analysis, Writing- Original draft. Terry Jianguo Zhang: Writing − review & editing, Supervision, Resources, Funding acquisition. Nan Wu: Writing − review & editing, Validation, Supervision, Resources, Funding acquisition. All authors reviewed the manuscript.
Data availability
No datasets were generated or analysed during the current study.
Declarations
Competing interests
The authors declare no competing interests.
IRB statement
The local Medical Research Ethics Committee (Peking Union Medical College Hospital, Beijing, China) approved the study (No. I-24PJ0473).
Footnotes
Publisher’s note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Zhengye Zhao, Aoran Maheshati, Xueyi Zhang These authors contributed equally to this work.
Contributor Information
Terry Jianguo Zhang, Email: jgzhang_pumch@yahoo.com.
Nan Wu, Email: dr.wunan@pumch.cn.
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Data Availability Statement
No datasets were generated or analysed during the current study.