1. Introduction
Scoliosis is a three-dimensional complex deformity of the spine mainly characteristic in the frontal plane [
1]. In the current literature, several types of scoliosis are described, and the idiopathic form in adolescence (Adolescent idiopathic scoliosis: AIS) is the most prevalent, representing 80% of total cases [
2,
3]. AIS affects up to 2–3% of children around the world, and its occurrence is more likely in girls [
4]. AIS is characterized by a radiological spinal curve of at least 10° in the frontal plane (measured by the Cobb method), with different grades of vertebral axial rotation [
1]. Although radiographic image is the current gold standard for AIS diagnosis, several non-invasive devices and surface metrics have been validated to measure spinal curvatures and trunk shape in the last years [
5,
6,
7]. In particular, SpinalMouse
® and photogrammetry have been proposed like non-invasive and reliable methods for spinal analysis and postural evaluation in AIS [
8,
9]. Surgical and non-surgical interventions have been compared to manage prognosis in people with AIS and different treatments are recommended to improve physiological, functional, and psychological conditions [
1,
10,
11].
Even though AIS rarely causes any health problems during growth, the scoliosis progression can lead to a visible trunk deformity and elicit psychological disturbances [
5,
12]. Specifically, self-perceived body image and self-identity could be negatively affected and consequently reduce the AIS people Quality of Life (QoL) [
13]. For example, a recent review showed that participants with AIS reported dissatisfaction with physical appearance, which could lead to feelings of “embarrassment” and “inferiority” [
14]. Although approximately 40% of youth with AIS experienced some alterations in QoL, it is still unclear which are the most involved aspects [
15]. In recent years, an increased interest has been focused on self-perceived body image and some specific assessment tools have been developed. Among all, the Scoliosis Research Society Patient Questionnaire (SRS-22) and the Trunk Appearance Perception Scale (TAPS) are commonly used by clinicians and therapist during AIS evaluation [
16,
17]. SRS-22 is a five-domain questionnaire that consists of 22 items regarding function/activity, pain, self-perceived body image, mental health, and satisfaction of treatment. TAPS is a visual scale that allows evaluating self-perception of the trunk and deformity in scoliosis by three sets of body figures. However, previous studies reported different viewpoints on linear correlation between spinal curve magnitude and body image self-perception [
18,
19,
20]. Furthermore, whether mild scoliosis could impact AIS people self-perceived body image is still debated [
21,
22,
23].
The main purpose of the present study is to investigate whether the mild magnitude of the curve affects self-perceived body image measured by SRS-22 in people with diagnosis of AIS. In addition, we will compare SRS-22 self-image domain with others in order to understand the relation with different aspect of QoL. Finally, we will perform several regression models to analyze whether the self-perceived body image can be explained by the QoL, TAPS, SpinalMouse®, and photogrammetry measurements.
3. Results
Table 1 shows participants’ characteristics. Fifteen participants were recruited, with an age mean of 14.47 (±2.82) years old. The 31% was male and the 69% was female. The dorso-lumbar scoliosis (left or right) was the most common asymmetry observed (53.32%, equally distributed among left and right side).
Table 2 shows mean differences between female and male participants for each variable. Only ATSI means reported significant differences (
t13 = 2.9,
p = 0.01).
Figure 3 shows boxplots of all SRS domains. Each domain mean is displayed by a diamond within every box.
Table 2 shows the summary statistics for multivariate mean differences analysis.
Hotelling t2 = 70.29,
Hotelling F (3, 12) = 20.08, and the
p < 0.001. The post hoc analysis included six comparisons, and the significance level was settled at 0.0083 (0.05/6). Each comparison among domain three (self-perceived body image) and other domains reported statistically significant differences: domains three-one [−0.84 (95% C.I.: −1.07, −0.61);
t = −7.70;
p < 0.001]; domains three-two [−1.27 (95% C.I.: −1.63, −0.90);
t = −7.46;
p < 0.001]; domains three-four [−0.81 (95% C.I.: −1.14, −0.49);
t = −5.36;
p < 0.001]. All other comparisons are available on
Table 3. Only the difference between domain one (function/activity) and four (mental health) was not significant [−0.03 (95% C.I.: −0.34, 0.28);
t = −0.18;
p = 0.86].
Figure 4 shows boxplots of SRS domain three and the other domains mean (one, two and four), in which is displayed the relative mean difference (point distance among two diamonds). Its value equals to −0.97 (95% C.I.: −1.24; −0.70), the value of statistic
t is −7.79, and
p is <0.001.
Table 4 shows the coefficients correlation matrix in which all linear variable coefficients are reported. Totally twelve variables are included. The highest linear correlation coefficient value related to domain three is reported with the SRS domain one (
r = 0.66), whereas the lowest is with SpinalMouse value on antero-posterior axis (
r = 0.07).
Table 5 shows the stepwise regression model. At the beginning, seven predictor variables were selected (SpinalMouse on antero-posterior and lateral axis, and the curve degree; TAPS value; ATSI and POTSI; the mean of all SRS domains one, two and four). Although the model with five variables (with no POTSI and SpinalMouse on lateral axis) reported a discrete goodness of fit value (
R2 = 0.67,
adjusted-
R2 = 0.49), only two variables (the mean of all SRS domains and the mean of TAPS) met the inclusion criteria, and the final model explained the 27.5% (
adjusted R2) of the domain three variability (
p = 0.05).
Finally,
Table 6 displays each specific regression model for all instruments described [SRS-22 domains, TAPS, SpinalMouse
®, Photogrammetry (ATSI and POTSI)]. The model that better explains the domain three variability is represented by SRS-22 domains, which describes the 42% (
adjusted R2) of the response (D3). The better regressor seems to be the domain one (
t = 3.24,
p < 0.01). Differently, the photogrammetry model reports the lower goodness of fit value (
adjusted R2 = 0.012). However, neither TAPS (
F(4,10) = 1.82;
p = 0.2) or SpinalMouse (
F(4,10) = 1.09;
p = 0.39) models report a significant value of Fisher statistic, and both exhibit low goodness of fit values (
adjusted R2 = 0.05;
adjusted R2 = 0.02).
4. Discussion
The main purpose of this study was to investigate how fifteen participants with diagnosis of mild AIS perceived their body image, and how the mild magnitude of the curve impacted their QoL. We found a low mean value of SRS-22 domain three, which suggested that spinal asymmetry negatively affects self-perceived body image, even if severity of scoliosis is less than 25°. To our knowledge, no previous studies mainly investigated this outcome in patients with mild curves using SRS-22. Several authors focused on discriminative validity of this tool about curve severity and QoL, but body perception was the main topic especially in moderate and severe scoliosis [
20,
32,
33,
34]. Normative data for SRS-22 have been reported in healthy people from different countries [
35,
36]. In these studies, SRS-22 domains were analyzed and compared about age, gender, anthropometric measurement, ethnicity, and familiar status. Self-image scores were significantly lower in Southeast Asian people compared to US and Ghana, with mean values of 3.9, 4.2 and 4.2, respectively (
p < 0.0001) [
35]. In this study, self-image domain scores decreased ranging from 4.25 in age 10 to 3.76 in age 17, evidencing a negative correlation (r = −0.166,
p < 0.0001). Similarly, US people showed lower values in age 16–19 compared to 10–12, even if this difference was not significant (4.39 and 4.47, respectively). Berliner et al. evidenced good discriminative validity between small non-operative curves (<40° Cobb) and larger surgical curves (>40° Cobb) about pain, self-body image and SRS-22 total domain, with higher scores in non-operative curves compared to surgical curves [
33]. In this study, self-image domain mean values were 4.1 for 0°–19° and 4.0 for 20–40° curves, significantly different from severe curves scores (3.5 for 41°–50° and 3.3 for 51°–60° curves, respectively). Wang et al. reported that self-image SRS-22 scores correlates negatively with main Cobb angle, apical vertebral translation, and razor hump height, independently from type of scoliosis (single or double curves and spine localization). These authors reported a mean value of 3.08 for a sample’s mean curvature of 45° Cobb. In our study, the mean SRS self-image domain score was 3.2, smaller than the results evidenced by Berliner et al. for mild curves. Contrarily, the mean values for other SRS-22 domains in our sample were similar to previous authors (higher than 4.0). Furthermore, our result is close to SRS-22 self-image score reported by Makino [
37]. In this research, the authors investigated QoL and low back pain (LBP) in 111 female patients with nonsurgical scoliosis (mean Cobb angle range: 27.5°–36.1°). The SRS-22 self-image scores were 2.8 and 3.0 for LBP and No Pain groups, while other domains evidenced higher values (greater than 3.8 and 4.3 for LBP and No Pain groups, respectively). According to these findings, many studies underline that as greater is the curve magnitude as worser is the body-image perception [
13,
19,
20,
32]. Although in our study the participants Cobb angle was less than 25°, the results report a negative self-image perception and suggest the importance of proper assessment in mild scoliosis too. Despite SRS-22 have been commonly used for patient-outcome analysis, other specific questionnaire as the BIDQ-S (Body Image Disturbance Questionnaire-Scoliosis) could be selected [
38]. This tool was recently validated to measure the body image perception in AIS people and showed a strong correlation with SRS total score [
39]. In addition, Cheshire et al. reported that SRS-22 self-image domain has a weak strength of correlation with external measure of spine deformity (ISIS2 surface topography) and suggested the use of pictorial scale like TAPS [
34]. For this reason, we integrated SRS-22 with TAPS assessment in order to better understand body perception. However, the small sample size and the absence of a comparison group with Cobb angle greater than 25° must be considered as a limit.
The second intend of the current research was to analyze how participants with mild AIS perceived their quality of life and which SRS-22 domain could mostly influence the results. According with our expectations, domain three reported the lowest value when compared with each other domain and the total mean of the other domains, which suggests that the body-image perception could be the most critical factor that negatively affects the adolescent QoL when scoliosis is not severe. In agreement with this result, some researchers observed a significant linear correlation between poorer body image perception and poorer QoL, regardless of the Cobb angle magnitude [
13]. Additionally, Payne and colleagues found that adolescent with idiopathic scoliosis are more likely to be dissatisfied with their appearance than adolescents with no scoliosis, and this condition could impact their psychosocial growth [
40]. Consequently, greater relevance should be attributed to the body-image progression in adolescent with mild scoliosis and its effect on their quality of life. Recently, Kinel et al. suggested the use of ISYQOL (Italian Youth Quality of Life Questionnaire) for mild and moderate scoliosis [
41]. In this research, authors evidenced higher metric properties for ISYQOL compared to SRS-22 in 81 female patients with mean Cobb angle of 31°. In particular, the severity of scoliosis (10°–30° vs. >30°) demonstrated a direct statistically significant effect on QoL when evaluated with ISYQOL only. However, since ISYQOL is a unidimensional scale, it could not be possible to analyze which domain mostly impacts QoL as performed in SRS-22. The absence of a follow-up to evaluate the health-related quality of life progression and the use of SRS-22 alone must be considered. In addition, we could not draw conclusions on psychological factors due to the absence of psycho-social measurements.
Interestingly, we found that the SRS-22 perceived pain domain reported the highest mean value, which indicated that participants did not suffer of severe pain. The mean score presented in this study and the values evidenced by Berliner et al. for mild and moderate scoliosis are the same (SRS-22 pain domain: 4.6) [
33]. Our result agrees with authors who suggested that mild scoliosis rarely causes pain and impairments in adolescent, and recognized AIS as a spinal deformity without pain [
42,
43]. Despite several studies found that patients with AIS experienced pain more than control subjects with no scoliosis, further comparisons are needed among people with different curve magnitude (mild, moderate, and severe) [
44,
45]. However, many factors, such as radiographic parameters, psychological and mental distress, dissatisfaction, social influences, and hormonal status, could affect the perceived pain, and further investigations in this direction were beyond our aims.
The final purpose was to analyze whether the variability of the self-perceived body image could be explained by other SRS-22 domains (function/activity, pain, and mental health), self-perception of the trunk measured by TAPS, curvature and mobility of the spinal column in the frontal and sagittal planes evaluated by SpinalMouse
®, and the anterior and posterior asymmetries between left and right sides of the trunk measured by photogrammetry (ATSI, POTSI). To the authors’ knowledge, no previous study speculated on these relations and few comparisons were possible. However, our results show that the SRS-22’ domains one, two and four are good predictors of the domain three variability, explaining about 55% of it. Since health-related quality of life must be strongly considered for successful treatment of spinal deformities, we suppose that monitoring the QoL in people with mild idiopathic scoliosis is a primary necessity to prevent altered self-image perception during growth [
21,
41]. Further analysis and comparisons between specific QoL questionnaire and the SRS-22 are requested to correctly manage this severity of curvature too.
About TAPS, one study agrees with our results and reports a discrete linear correlation between the domain three and this pictorial scale (
r = 0.46), but no regression model was assessed [
22].
Differently, worse models are described by SpinalMouse
® and photogrammetry. These results suggest that the curvature and mobility of the spine and trunk asymmetries do not allow us to predict the self-image perception in our sample. Previously, Brewer et al. reported that volumetric asymmetries parameters measured by surface topography correlate better than Cobb angle with body perception and mental health, while Matamalas et al. demonstrated significant correlation between waistline asymmetry and body perception of deformity [
46,
47]. In addition, some questions about the role of shoulder balance using photogrammetry in trunk assessment for non-operated scoliosis have been posed [
47]. In this research, the authors underlined the importance to integrate surface topography with additional parameters like shoulder balance and waistline assessment. We suppose that low Cobb angle value, torso shape and poor trunk deformity evaluated by ATSI and POTSI could not correctly predict self-perceived body imagine in mild scoliosis. Despite this, the integration between specific QoL questionnaire (TAPS and SRS-22) and proper measurement (like photogrammetry and Spinal Mouse
®) is recommended to monitor scoliosis progression in non-invasive, quick, and scientific way.
The sample size, participants age and psychological characteristics, differences about type of curvature and phase of treatment represent a limit in our work. Future investigations are needed about the role of each evaluation tool in mild AIS compared with greater curvatures, in relation to specific scoliosis approach.