A cross-sectional comparative design was used for this study.

All the study participants completed the KIDSCREEN-27 once and the additional category ‘Self-Perception’ from the KIDSCREEN-52, along with questions about the intensity of their physical activity and the school category or educational track they were in. Participants in the scoliosis group also answered questions regarding the wearing time of the brace, the Cobb angle and the intensity of their therapy.

The KIDSCREEN instrument was developed within the project ‘Screening and Promotion for Health-related QoL in Children and Adolescents – A European Public Health Perspective’ to evaluate and standardise the general QoL of healthy and chronically ill children and adolescents. The questionnaire aims to detect children at risk of health-related QoL restriction (Ravens-Sieberer 2006).

KIDSCREEN-27 includes the following five dimensions: ‘Physical Well-being’, ‘Psychological Well-being’, ‘Autonomy and Parent Relation’, ‘Social Support and Peers’ and ‘School Environment’. It takes 10 min to 15 min to complete the whole questionnaire. The higher the score, the better the QoL. The internal consistency was reported to be good to excellent in all the dimensions (ranging from 0.80 to 0.84) (Ravens-Sieberer 2006).

The supplementing question ‘Self-Perception’ was chosen because we hypothesise that adolescents with scoliosis could have reduced values in ‘Self-Perception’ (Rusovs et al. 2013; Wang et al. 2021).

The returned questionnaires were anonymised, and all subsequent data processing was conducted in an anonymised manner.

For all continuous data, the mean, the median and the s.d. were calculated for the group of adolescents with and without scoliosis.

Statistical analysis was done using R Version 4.3.3. Through Rasch analysis, the raw data, initially ordinal in nature, were transformed into interval-scaled T-values, allowing mathematical calculations. The raw data of each study participant were converted into Rasch person parameters P, and then the KIDSCREEN T-values were calculated using the following formula (Equation 1):

μ = mean person parameter of the standard population, σ = standard deviation of the person parameters in the standard population.

The person parameter P for each subcategory of KIDSCREEN, as well as μ and σ, was taken from the KIDSCREEN manual. A value ± ½ s.d. of the mean T-values of the norm data can be defined as ‘high or low’ QoL. The mean ± ½ s.d. range is categorised as the ‘normal’ range (Ravens-Sieberer 2006).

The a priori hypothesis: H0: µ1 = µ2, H1: µ1 ≠µ2, was analysed with the t-test between the groups with or without scoliosis.

In the scoliosis group, Spearman’s correlation coefficient was calculated between the T-scores and the data about Cobb angle, age, brace, therapy duration, sport and school. A correlation was classified as significant when p < 0.05 (Doi et al. 2021).

The Ethics Committee of Zurich (Switzerland) accepted the study (Ref. Nr. KEK-ZH-Nr. 2013-0402). The caregivers and the participants provided written informed consent before the start of the study. All adolescents participated voluntarily.

To collect questionnaires from 30 adolescents with scoliosis, we invited 61 individuals. Similarly, to achieve 30 responses from adolescents without scoliosis, we approached 85 individuals to participate in our study.

The study included 60 participants, comprising 30 individuals with scoliosis and 30 healthy adolescents as a comparison group.

Table 1 presents descriptive data from the two study groups. The complete data frame is available on request.

In none of the categories were the mean T-scores of adolescents with scoliosis significantly lower than those of the comparison group or the norm data of Swiss girls (see Table 2) (Ravens-Sieberer 2006). In the comparison group, the mean of the category ‘Self-Perception’ was just below the range of ‘normal’ T-scores and therefore defined as low. In this category, the mean T-score of adolescents without scoliosis was lower than that of adolescents with scoliosis.

Against our hypothesis, the female adolescents with scoliosis reached very similar QoL mean values in comparison to our healthy comparison group or to the norm data.

In the category ‘Psychological Well-being’, the adolescents with a Cobb angle ≥ 45° scored notably lower in T-scores for QoL than patients with a Cobb angle < 45°.

33% (n = 10) of the adolescents with scoliosis had reduced QoL in the categories ‘Psychological Well-being’ and/or ‘Physical Well-being’. Six per cent (n = 2) of the adolescents with scoliosis had ‘low’ T-scores in all categories. In the comparison group, no adolescent had ‘low’ scores in all categories.

It is widely recognised that scoliosis is a risk factor for reduced QoL (Kaya et al. 2022; Torén & Diarbakerli 2022). This is contrary to our findings. We recognised participants with scoliosis with reduced QoL, but in general, the adolescents with scoliosis did not have lower scores than the healthy comparison group. There are few studies that have also obtained such results. One study detected even better results in almost every category of KIDSCREEN-52 in participants in the scoliosis group. They included only newly diagnosed patients; therefore, it is unknown whether the QoL would have changed after treatment began (Kontodimopoulos et al. 2018). In a study of 1205 learners with scoliosis, the deformity did not impact the adolescents greatly until a diagnosis was made and treatment was planned or contact with specialists established (Rainoldi et al. 2015). In most studies, QoL is observed during treatment. Therefore, it is difficult to determine whether the reduced QoL is because of scoliosis or the treatment.

The QoL in adolescents with scoliosis is mostly measured with scoliosis-specific questionnaires. However, a generic questionnaire like KIDSCREEN may be insufficient for detecting a reduced QoL in patients with scoliosis. Kontodimopoulos et al. (2018) combined KIDSCREEN-52 with SRS 22 (very often used to measure QoL in patients with scoliosis) for their measures of QoL in patients with scoliosis. In their analysis, the category ‘Physical Well-being’ (identical to the category in KIDSCREEN-27) was a significant predictor for all four dimensions in the SRS 22 Questionnaire. The authors concluded that the generic instrument KIDSCREEN-52 is detecting disease-specific QoL aspects (Kontodimopoulos 2018).

It seems like the QoL of the patients with scoliosis is influenced by more complex constructs than scoliosis.

A large body of research acknowledges influencing factors for QoL in adolescents with scoliosis (Anwer et al. 2015; Kaya et al. 2022; Parent et al. 2010; Salah et al. 2023; Schreiber et al. 2013; Tavernaro et al. 2012; Wang et al. 2021), which seems important when studying this construct. In our study, we additionally performed correlation analysis between the categories of KIDSCREEN 27 and the category ‘Self-Perception’ from KIDSCREEN-52 and different characteristics around the individual patient to seek more insight into our data.

The most mentioned associations to low QoL in conservative treatment were the brace treatment and the Cobb angle (Salah et al. 2023; Wang et al. 2021). Our results may not support the finding that brace treatment correlated to QoL, as only 8 (26%) participants in the scoliosis group wore a brace, which is an insufficient number to detect a true correlation. But other findings strengthen this relationship. Ugwonali et al. (2004) compared 78 braced patients to 136 non-braced in the comparison group. They showed the surprising result that the QoL of the braced patients was not below the not braced or the norm data. There the QoL was measured by evaluation of the parents’ perspective, which might have biased the degree of QoL and hindered a true comparison. Further research found that the QoL of adolescents with scoliosis treated with a brace was similar to the adolescents with scoliosis without a brace (observation treatment) or to healthy children. They found decreased QoL in patients who did not participate in their treatment decisions, regardless of whether they were undergoing brace or observation treatment (Schwieger et al. 2016).

Quality of life during brace treatment may also be influenced by the Cobb angle correction during treatment. Researchers hypothesised that a decreasing Cobb angle supported the patients’ feeling of experiencing an effective treatment, which reduced their stress levels of wearing a brace (Khoshhal et al. 2019). In another study, patients experienced decreasing QoL in the first period of brace treatment, but afterwards, this effect vanishes (Di Maria et al. 2023). In our study, we did not ask the braced patients at what time they started the treatment or how their Cobb angle changed. Factors that could have influenced our results remain, therefore, unknown.

We did see a difference in QoL in all KIDSCREEN 27 categories and in the category ‘Self-Perception’ from KIDSCREEN-52. We recognised a significant difference (p = 0.01) in ‘Psychological Well-being’ when we performed a subgrouping of the participants in the scoliosis group into one group with Cobb angles of ≥ 45° and one group with Cobb angles < 45°. The participants with Cobb angles of ≥ 45° had lower scores in the mentioned categories than the participants with smaller curves. This is in accordance with the recognised association between severity of the deformity and QoL. Quality of life remains steady until the curve reaches a critical Cobb angle of about 45 degrees (surgical threshold), beyond which QoL begins to decline linearly as deformity worsens. The relationship between QoL and scoliosis severity is more accurately represented by segmented models than by linear ones (Parent et al. 2010). The question is whether the deformity decreases the QoL or whether the recommended treatment for the deformity does. This is challenging to analyse, as guidelines suggest informing patients with a Cobb angle of 45° or more about the option for surgery. Interestingly, if patients were compliant with the treatment, they had remarkably better QoL scores than patients who were non-compliant (Rivett, Stewart & Potterton 2014). In our study, we did not ask about the initial Cobb angle and about the compliance. So, it remains unclear whether patients with Cobb angles ≥ 45° experienced deformity progression because of non-compliance. Hence, we do not know if the Cobb angle ≥ 45° was the cause or the consequence of the low scores.

Sport might be another influencing factor for QoL in patients with scoliosis. Research findings indicated that adolescents with scoliosis are less likely to participate in sports or exercises compared to healthy adolescents. And their QoL, as measured by EQ-5D-5L, was lower (Torén & Diarbakerli 2022). This is in line with a described relationship between movement and improved satisfaction in adolescents with scoliosis (Tones, Moss & Polly 2006). And with the observation that physical activity reduced mental distress in adolescents with scoliosis (Leszczewska et al. 2012). It is therefore possible that the physical activity of our patient group – which did not differ from the comparison group – had a positive influence on their QoL. As exercises in physical therapy may impact QoL positively (Anwer et al. 2015; Schreiber et al. 2013), it could have influenced the QoL of our study groups too.

Potentially, a treatment team of doctors, orthotists and physical therapists working hand in hand with the patient who undergoes a scoliosis treatment could influence the QoL as a main factor. The management of the patients, often overlooked, emerges as a pivotal determinant of QoL (Tavernaro et al. 2012). In this study, the management of the participants with scoliosis was not evaluated because the participants were from different clinics, and a treatment team like that described in the study of Tavernaro et al. (2012) did not exist.

There are many factors that can influence the complex construct of QoL in patients with scoliosis. Research indicates that QoL and supporting mental health in scoliosis patients during treatment need more attention (Wang et al. 2021). However, this is still not part of the standard assessment or therapy goals in Switzerland. We therefore recommend implementing the QoL in the standard assessment.

Hypothetically, our results were influenced by a selection bias because only every second participant in the scoliosis group was willing to participate, and the less compliant might have rejected their inclusion.

This study provides interesting insight into the QoL in adolescents with scoliosis but is limited in its external validity. The sample size was calculated for a comparison analysis between two groups and is too small to draw conclusions about the general scoliotic population. Especially when examining correlations with patient characteristics or factors influencing QoL, our data are too limited.

In general, it is known that good QoL in adolescents is crucial for a healthy transition to adulthood, and it is the foundation for health in life (Inchley et al. 2020; Ravens-Sieberer et al. 2012). Therefore, it seems important to be aware of the QoL in this period. To seek insight into an adolescent’s perspective during scoliosis treatment seems challenging. Adolescents with scoliosis tend to be introverted (D’Agata, Sánchez-Raya & Bagó 2017), and a high percentage of parents of adolescents with scoliosis are unaware of their children’s emotional and behavioural problems (Sanders et al. 2018). If parents struggle with this, healthcare providers might face similar challenges. On the other hand, patients with scoliosis desire more often a conversation about mental health than healthcare providers are offering (Zeck & Glahn Castille 2023). But there is a growing emphasis on recognising the child’s perspective as equally or more relevant than the one of experts or the findings of literature reviews (Ravens-Sieberer 2006).

Physical therapists play an important role in the treatment team for patients with scoliosis and often see these patients more frequently than other disciplines involved (Tavernaro et al. 2012). Thus, it is important that physical therapists know how to detect and observe reduced QoL in patients with scoliosis efficiently. If it is recognised early, physical therapists can offer possible solutions and interact with other disciplines to improve the situation for the patient.

The KIDSCREEN-27 could be a valuable tool for clinical practice, offering a practical way to assess the QoL of patients with scoliosis compared to healthy adolescents. It provides a basis for offering interventions or adapting treatment procedures to improve QoL.

Assessing QoL is important throughout the entire treatment process. However, there are times when monitoring the QoL should be emphasised, such as the beginning of brace treatment, which is a particularly challenging period for patients with scoliosis (Di Maria et al. 2023). It is also known that physical therapy and physical activity can improve QoL (Anwer et al. 2015; Leszczewska et al. 2012; Schreiber et al. 2013). So this could be highlighted during the difficult initial phase of brace treatment, or psychological support can be offered.

Quality of life is connected with compliance, and compliance is connected to treatment success of objective measurements like the Cobb angle (Rivett et al. 2014). To be able to offer patients tailored therapy, the recording of QoL in a way that can be integrated into everyday practice should be included.

Methodologically, we suggest for future studies to integrate the questionnaire into the clinical setting where all participants with scoliosis answer the questionnaire as part of their assessment to avoid potential selection bias because of non-compliance.

Future research should seek to integrate the point of view of the adolescent patients, their mental well-being and their input about treatment success. Qualitative studies might explore these elements more deeply and could strengthen a patient-oriented treatment approach (Essex et al. 2021; Joarder et al. 2023).