Patients with adolescent idiopathic scoliosis perceive positive improvements regardless of change in the Cobb angle – Results from a randomized controlled trial comparing a 6-month Schroth intervention added to standard care and standard care alone. SOSORT 2018 Award winner

The Cobb angle is the most frequently used “disease process” outcome used to monitor the status of adolescent idiopathic scoliosis (AIS) because the primary goal of treatment is to stop progression or correct the curves thereby preventing or attenuating possible health effects in adulthood [1]. The Scoliosis Research Society (SRS) recommendations standardizing the reports of non-operative research identifies the Cobb angle as the primary outcome [2]. The Society on Scoliosis Orthopaedic and Rehabilitation Treatment (SOSORT) consensus also recognizes the importance of monitoring the Cobb angle change in the conservative treatment. However, among treatment priorities, SOSORT ranks it behind aesthetics, quality of life, disability, back pain, psychosocial well-being, progression in adulthood and pulmonary function [3, 4].

The success of conservative treatments is most commonly defined by a curve progression of 5° or less in the Cobb angle at the end of the treatment [2]. This threshold recommendation between two radiographs comes from studies investigating the reliability of Cobb angle measurements where 5° was the standard error of measurement (SEM) reported for manual Cobb angle measurements and often interpreted as the smallest difference that could be reliably attibuted to true change rather than measurement error [5]. However, semi-automatic methods produce smaller SEM than the manual method [6]. In their systematic review of literature, Langensiepen and colleagues looked at the reproducibility of the new techniques of Cobb angle measurement, including, semi-automatic, automatic and using smart phone device, and found that the SEM for intra-rater reliability ranged from 0.74° to 3.4°, and for inter-rater reliability ranged from 1.2° to 5.1° [6]. Despite the common use of the Cobb angle, there is no conclusive evidence to suggest that the improved radiological outcomes also relate to other long-term improvements in those with scoliosis, such as function, quality of life, self-image and pain [7]. Moreover, Cobb angle is poorly related to the overal quality of life [8]. According to the Cochrane Collaboration, patient-related outcomes are important to collect and monitor in research in order to represent what is most important to patients about a condition and its treatment, and therefore should be studied in addition to disease process measurements [9].

Schroth physiotherapeutic scoliosis specific exercises (PSSE) consists of sensorimotor, postural and corrective breathing exercises individualized to the patient’s specific scoliosis curve pattern leading to correction of asymmetric posture in daily activities [10]. The main goals of the Schroth exercises is the recalibration of normal postural alignment through static/dynamic postural control to achieve the overall corrected postural stabilization [10]. The key component of the Schroth method is auto-correction, defined as the patient’s ability to reduce spinal deformity through active postural realignment of the spine in three dimensions [11]. Auto-correction is achieved through self-elongation and specific segmental corrections adapted to each curve pattern. SOSORT considers auto-correction to be the most important element of a scoliosis-specific exercise treatment [11]. Supervised Schroth exercises have been shown, in short term studies, to improve curve severity [12], pain [13], muscle endurance [12‐15], self-image [13] and surface topography characteristics [16].

Patients undergo many changes during the course of AIS treatment. Some are small and some are large, but not all are valued or even perceived by patients. Many definitions have been proposed for clinically meaningful changes in the context of an intervention. Clinically significant effect has been defined as “the extent to which therapy moves someone outside the range of the dysfunctional population or within the range of the functional population.” [17]. Other suggest that clinically important changes refer to changes in a patient’s functioning that are meaningful for the individuals receiving a medical intervention [18]. The minimal important difference (MID) “denotes the smallest score or change in score that would likely be important from the patient’s or clinician’s perspective” [19].

When it comes to research on scoliosis, little is known about what changes patients perceive as important, including their perceptions and interpretations of changes in the Cobb angle.

Therefore, in a sample of patients undergoing 6-months of conservative treatment for AIS, we sought to determine the minimal change in the Cobb angle associated with perceived improvement in back status. As our sample consisted of participants receiving standard of care (observation and bracing) or standard of care plus exercises, our secondary objective was to determine if there was difference in the perceived change reported in each of the two groups.

This is a secondary analysis of a previously published RCT [12]. The anchor method was used to determine the MID in the largest Cobb angle in response to 6 months of conservative treatment [20]. The anchor is an external indicator of change used to interpret the observed change in a target outcome [21]. In the present study, the global rating of change was used as anchor and the change in the largest Cobb angles was used as target outcome. To undergo MID estimation, the target and the anchor must be appreciably correlated for accurate prediction [19]. This is because the change in the target must reflect the change in the anchor [22].

Of the 50 subjects enrolled in the trial, six did not complete the study and radiographs were missing for four, resulting in a total sample size of 40. The mean age and LC at baseline were 13.4 ± 1.6 years and 28.5 ± 8.8 °s, respectively for the overall sample. Age, sex, number of braced participants, height and weight were similar between the two trial groups but those in the Schroth group presented slightly larger LC at baseline [29.1 (25.4–32.8) vs 27.9 (24.3–31.5), respectively] (Table 1).

Our study aim was to determine the change in Cobb angle required for AIS patients undergoing a 6-month Schroth RCT program to observe a positive change in their backs. In our sample 60% of the participants perceived improvement in their backs, which was associated with as little as 1° improvement in the Cobb angle over a 6-month treatment period. The MID based on changes in LC in participants reporting a GRC ≥2 (who rated their change as “a little bit better” to “a great deal better”) was an improvement of 1.3°. The ROC curve analysis revealed a similar MID estimate, a 1° improvement in the LC, by selecting the cutoff best predicting patients perceiving an improvement. Both of these estimates are smaller than the SEM of manual Cobb measurements (5°) or computer-based measurements (2.5°) [24].

The Schroth approach primarily aims to improve the postural awareness to correct the misalignments imposed by the scoliosis. Schroth uses specific corrective breathing, auto-correction [11] consisting of self-elongation and postural corrections specific for each curve pattern which is eventually integrated in daily activities. Much of the Schroth corrections target aspects other than the coronal plane deformity. Bracing and observation do not solely focus on improving the Cobb angle. Bracing aims to stop progression and observation reassures patient that they do not need more aggressive treatment yet. Therefore, the participants’ perceived positive change could arise in response to other effects of these conservative interventions regardless of the improvement in the Cobb angle. Research suggests that Schroth exercises improve posture in all three planes as measured by surface topography [16]. With the conservative interventions, the participant’s postural awareness and the overall body and trunk balance might have improved after the intervention and, some participants might have perceived improvement unrelated to the changes in the Cobb angle.

Some participants with AIS experience back pain and discomfort [34‐37], as well as decreased function [35, 36], self-esteem, [38] and mental health concerns [39, 40]. The severity of these changes is only weakly related to the Cobb angle especially in curves severities treated conservatively [8, 41]. It may be that these outcomes, which are not routinely monitored in scoliosis research are being positively affected under the influence of the Schroth therapy [16, 42]. Other impairments, signs and symptoms of scoliosis could be affected by the conservative intervention, which in turn may be determinants of the perceived clinically important changes. This topic could be the focus of future research.

Although SOSORT suggests esthetics, quality of life, disability, and back pain as the most important outcomes to monitor in the treatment of patients with scoliosis, the Cobb angle remains the most widely used and accepted outcome in scoliosis care [43]. Tracking Cobb angle change makes most sense in surgery, where the primary goal is curve correction/stopping curve progression [44]. In contrast, the main objective of conservative treatments, including bracing and PSSE, is preventing progression in order to avoid further deterioration of signs and symptoms of scoliosis as well as directly addressing those signs and symptoms, with an ultimate goal to prevent surgery [4, 43]. In conservative care it is therefore logical to supplement the Cobb disease process outcomes with patients centered outcomes [45]. Patients undergoing conservative treatments constitute different populations with different specific characteristics and needs [46]. Patients under observation and surgical candidates could be perceived as two extremes along a continuum of treatment, where patients under observation may present with little to no concerns about scoliosis depending on individuals. Patients undergoing surgery are on the other side of the spectrum presenting with severe consequences due to scoliosis. In-between are the patients treated conservatively with obvious signs and symptoms of scoliosis but not as severe as to require surgery [47]. Outcomes deemed clinically important may vary along the continuum of treatment.

The current study was designed to determine whether the patients with Schroth PSSE added to the standard of care and those receiving standard care alone perceive important change beyond the simple two-dimensional Cobb angle change. Twelve participants in the Schroth and none in the Control group were classified as truly improved, while 15 participants in the Control and one in the Schroth group were classified as truly deteriorated. In our study, 17 patients in each group wore a brace which shows that the randomization was successful. Given above mentioned, and the fact that the brace did not have a significant main effect, as shown previously, [12] we concluded that the effect on the outcome was from the added treatment, i.e. Schroth PSSE.

Our results suggest that adolescents with AIS in our study who were undergoing conservative treatment, experience a positive change in the state of their backs even if the Cobb angle has not improved beyond the conventionally accepted threshold of 5° or the 2.5° SEM of our Cobb measurement approach [2]. Future studies are needed to determine if this observation is generalizable. The purpose of using a Cobb angle in this study was to show that while it is generally reliable and most commonly used to assess the effectiveness of a treatment, it does not appear to be what drives the patient perception of their back improvement. Patients often perceive changes in their bodies, their self-image and their sense of control related to their medical condition that is not reflected in the most commonly used clinical indicators such as Cobb angles. This paper supports this by finding that patients report improvement despite little or no change in their radiographs. Therefore, our understanding of what participants consider important when undergoing a conservative management of scoliosis should be improved.

Key limitations of this study are the relatively small sample size, intermediate follow-up duration and there is still a need for a validation of the MID estimates. Only 40 of 50 enrolled patients were analyzed because six dropped out and did not provide a GRC and four additional radiographs were missing. One control relocated and another control travelled for 3 months. Four Schroth participants dropped out because of time constraints. The radiographs were missing because the treating clinician did not order them, or they were acquired too late. The reasons for missing were unrelated to outcomes. Therefore, we believe that the sample was representative of the full dataset.

Generally, 6-month follow-up is considered a short follow-up in intervention trials [48]. However, the Cochrane Back and Neck review group distinguishes the following follow-up terms in exercise trials: short-term (closest to 4 weeks), intermediate (between 4 weeks and 1 year) and long-term (closest to 1 year). For surgery trials relating to back and neck, however, they suggest 2- or 5-year follow-up. [49]. This suggests that exercise and surgery trials for scoliosis should interpret the outcome timepoints differently, because the purpose and nature of these two interventions is clearly different. Patients with AIS are typically monitored routinely until 1–2 years after reaching skeletal maturity [48]. What is perceived as clinically important by patients over this intermediate interval may be different than what is considered important over the full follow-up duration until maturity. Nevertheless, we argue that this 6-month duration is important for adolescents who are either attending regular exercise sessions, wearing a rigid brace full time or waiting for the next exam while under observation wondering if their condition progressed. Future research may be needed to demonstrate whether perceiving important short and intermediate terms improvements has long term implications on motivation and compliance with treatments and final outcomes.

There still is controversy concerning what is the best methods to estimate the MID. It is therefore, recommended to use different methods and triangulate results to arrive at a MID range or weighted estimate based on multiple methods. It is also recommended to obtain validation of estimation provided by original estimation attempts and to verify whether estimates in one context can generalize to others (anchor choice, different conservative treatments, follow-up duration, sample characteristics). Estimates presented in the present study should be validated in future research. Further, patients receiving a brace and under observation at our institution are usually told that stabilization not improvement is the goal of the care they receive. Therefore, it is possible that some patients in the study perceived positive outcome event when the Cobb angles showed little to no change. Future studies could examine effect of using different GRC cut-offs to estimate the MID.

This was a secondary analysis of a randomized controlled trial that investigated the effect of the Schroth exercises added to standard of care on curve severity, muscle endurance and quality of life as compared to standard of care alone consisting of observation or bracing. In the RCT, ethically, we could not withhold bracing if indicated for a patient. The present study did not focus on the effectiveness of the conservative treatments compared, only on determining MID using the combined sample. Our RCT study was not powered to allow subgroup analysis of the effect of different conservative treatments. The continuing multicenter SETS trial should allow for these comparisons (ClinicalTrials.​gov, NCT01610908).

Participants undergoing Schroth treatment added to the standard of care or standard care alone over 6 months perceived a positive change in the state of their backs even if the Cobb angle did not improve beyond the accepted threshold of 5°. The perceived improvement in the overall back status appears to be due to improvements in outcomes other than the two-dimensional Cobb angle. This study warrants investigating further outcomes that might be more relevant in determining what the patients with AIS perceive as important to monitor during the conservative treatment.