Authors’ reply to comment on: Physiotherapeutic scoliosis-specific exercises (PSSE-Schroth) can reduce the risk for progression during early growth in curves below 25°: prospective control study

We appreciate the feedback on our recently published study “Physiotherapeutic Scoliosis Specific Exercises (PSSE-Schroth) can reduce the risk for progression during early growth in curves below 25^ο: Prospective Control study”¹ by Kuru Colak et al.² We value your comments, and we are grateful for the opportunity to address all your concerns.

Firstly, the new PSSE-Schroth classification system is not closely aligned with the Rigo classification, as there are many significant differences on the criteria used for our curve types. For our classification we use clinical (trunk rotation, frontal plane asymmetry, pelvic tilt, significance of structural curves, rigidity), radiological (Cobb angle, axial rotation, vertebra deformity, growth stage, significance of structural curves, frontal plane asymmetry and in-brace correction for braced patients) and prognostic criteria (risk for progression, pain, cosmetic issues) to decide if overcorrection is allowed or not. Rigo’s Classification is based exclusively on two simple clinical criteria (structural thoracic curve and pelvic position in frontal plane) and it is mentioned in many previously published studies as Clinical Classification with a radiological correspondence.^{3, 4}

Lehnert-Schroth and Augmented Lehnert-Schroth does not have the same criteria and principles of correction with our classification system and PSSE-Schroth method, as the main decision from the beginning is whether thoracic or lumbar curve is the major.^3-5 We believe that in double balanced curves this is extremely challenging, thus we introduced a specific algorithm and different criteria for our classification system. Lenke classification is not related to non-operative treatment and our study, as it uses only radiological criteria mainly for surgical treatment.⁶ Therefore, we clarify that PSSE-Schroth classification is not a modified Rigo’s Classification, but a new accurate classification system, to fill the gaps from previous classifications and reduce dilemmas for therapists. The reliability study and validity study that we stated for our classification is in the review process for being published, so we could not use a reference for this.

Moreover, the role of a classification is not only to divide the curve types into some categories but to give the adequate information to the therapist on how to treat these curves. Rigo’s Classification and Barcelona Scoliosis Physical Therapy School (BSPTS) method are completely different to that point, because overcorrection is allowed only in A type (and is recommended in all A types, without lateral flexion to be permitted), but not allowed in B, C or E types, while in PSSE-Schroth classification we have for every curve type (3C, 4C, N3N4 and SL/STL) the (+) and (-) types, so every (+) curve type can do overcorrective exercises with lateral flexion, which is not allowed for Rigo’s classification and BSPTS method.⁷

Furthermore, for our classification and PSSE-Schroth method we have introduced the “Selective Overcorrection,” which means even in (+) curve types, the therapist can decide how much overcorrection is required, based on our criteria. The BSPTS method has some curve types that can be overcorrected without lateral flexion or not overcorrected in every exercise, and Schroth Best Practice and International Schroth Scoliosis Treatment (ISST) methods use lateral flexion as elementary correction for all curve types, so some overcorrection happens in every exercise.⁸ Instead, in PSSE-Schroth method we selectively use overcorrection and lateral flexion for specific curve types, having a different philosophy of what overcorrection is and how it can be used by our therapists. The above explanations confirm that PSSE-Schroth method is a unique approach with a new curve type classification, using innovative concepts of corrections.

For the statistical methods and comparison between groups, we analyzed Cobb angle and brace prescription rate that were available to us, because the control group was retrospectively analyzed so we could not retrieve data like trunk rotation or quality of life measurements from the past. All our data for the intervention group (PSSE-Schroth exercises) were prospectively collected from our prospective database and most of our subjects were followed up to the end of growth. The control group, as it is mentioned in the study, was retrospectively analyzed and had common baseline characteristics with the intervention group. This was a limitation that was already discussed in our study. Unfortunately, we could not have a prospective control group, because every patient that visits our clinic, with a potential to progress, is referred for scoliosis specific treatment and not only general or no exercises. So, we made a retrospective analysis of prospectively collected data.

Regarding figures 3 and 4, they are corrective techniques in PSSE-Schroth method to correct the thoracic concavity and shoulder block concavity. Especially, Thoracic Counter Traction is a new corrective strategy that was firstly introduced by PSSE-Schroth method, and it is described on the figure. This is another strong proof that PSSE-Schroth method is a unique approach and not a modified version of previously established methods. Surely, you are aware about the term Shoulder Counter Traction that was initially described by Katharina and Christa Schroth, and later implemented in BSPTS, Schroth Best Practice and ISST methods.⁹ Similarly, the description of body blocks, as you mentioned, was firstly described by Katharina and Christa Lehnert-Schroth and then implemented in BSPTS, Schroth Best Practice, ISST and now in PSSE-Schroth method.⁹

We clearly stated that our inclusion criteria were Cobb angle 15-25^ο for at least one curve, Risser sign 0-2 and trunk rotation more than 5^ο. This is the first ever study using so strict inclusion criteria for mild scoliosis treated only with scoliosis specific exercises, because we wanted our intervention group to have a real risk of progression. Other studies used 10-25^ο degrees without trunk rotation to be mentioned, so they had significantly higher chances of including patients with very low or even no potential to progress, having more functional than structural curves.¹⁰ Figures 5 and 6 were randomly selected from our whole group, and they both have some radiological axial rotation that can be easily seen from the pedicles position, and trunk rotation on the clinical photos. They were single structural thoracolumbar curves with a definite potential to progress.

However, here you can see two other patients that included in our study with double structural scoliosis and high risk of progression, that were significantly improved with PSSE-Schroth method as exclusive treatment, without bracing (Figure 1, 2). For our results, we also used a worst-case analysis, including all dropouts as failures, that was not done in most of the previous similar studies. We were also the first ever study using a clinical monitoring of patients as part of the treatment protocol, to early detect signs of progression and refer for an X-ray or bracing if needed. All these procedures are described in detail.

Figure 1.

—Double structural scoliosis, treated exclusively with PSSE-Schroth exercises, having significant clinical and radiological improvement.

Figure 2.

—Double structural scoliosis, treated exclusively with PSSE-Schroth exercises, having significant clinical and radiological improvement.

PSSE-Schroth classification is a newly developed curve type classification, using clinical, radiological and prognostic criteria. The strict inclusion criteria, the largest sample in published literature and the robust methodology that we used in our study strengthen our findings compared to previous studies that used lower thresholds for inclusion and did not measure the trunk rotation, which undoubtedly is an important prognostic factor for progression. Therefore, this study provided scientific evidence that PSSE-Schroth method was effective in mild adolescent idiopathic scoliosis treatment and can reduce the risk of progression and the need for bracing.