Feedback-Based Balance Training for Adolescents With Idiopathic Scoliosis

Background

Adolescent idiopathic scoliosis (AIS) is the most common pediatric spinal deformity, with a global prevalence of approximately 1-3% in adolescents aged 10-18 years. AIS is associated with paraspinal proprioceptive impairment, altered sensory reweighting, and biomechanical asymmetry of the trunk, all of which can disturb static and dynamic postural control. Conservative scoliosis-specific exercises are recommended by the 2016 SOSORT (International Society on Scoliosis Orthopaedic and Rehabilitation Treatment) guidelines as the first-line conservative treatment for mild-to-moderate AIS curves.

Recent randomized trials have suggested that adding sensorimotor or balance-focused training to scoliosis-specific exercises produces greater improvements in postural control and trunk symmetry than scoliosis-specific exercises alone. However, conventional balance training relies on therapist-mediated external feedback and does not provide quantitative real-time information on postural sway or weight distribution. Motor learning research indicates that augmented (device-based) visual feedback accelerates motor control acquisition, particularly when intrinsic proprioceptive feedback is impaired. The HUBER® 360 Evolution (LPG Systems, Valence, France) is a multi-axial neuromuscular training platform with force sensors in its handles and an integrated screen that delivers real-time visual biofeedback on applied force and weight distribution. Although its clinical efficacy has been demonstrated in chronic non-specific low back pain and other musculoskeletal populations, its effect in AIS has not previously been investigated in a controlled study.

Study Design

This is a prospective, two-arm, parallel-group, randomized controlled trial conducted at a single tertiary rehabilitation center.The a priori sample size required to detect a Group × Time interaction in the primary outcome at α = 0.05 and 80% power was calculated using G*Power as 50 participants (25 per arm); 72 participants are enrolled to allow for attrition during follow-up.

Interventions

The intervention protocol consists of 12 clinic-based sessions delivered over 4 weeks, three sessions per week. Each session comprises 40 minutes of individualized conservative scoliosis exercises (identical between arms) followed by a 30-minute balance training component that differs between arms.

The individualized conservative scoliosis exercise program is informed by the general principles outlined in the 2016 SOSORT guidelines (three-dimensional auto-correction, adaptation to activities of daily living, stabilization of the corrected posture, and patient education) and is tailored to each patient based on curve pattern, apex location, and clinical examination findings. The program is delivered by physiotherapists experienced in scoliosis rehabilitation but who are not formally certified in any specific Physiotherapeutic Scoliosis-Specific Exercise (PSSE) school.

Intervention arm: 40 minutes of individualized conservative scoliosis exercises followed by 30 minutes of HUBER® 360-based feedback balance training, both delivered under physiotherapist supervision in the clinic.

Active comparator arm: 40 minutes of individualized conservative scoliosis exercises delivered in the clinic under physiotherapist supervision, plus a 30-minute structured home-based balance exercise program performed by the participant independently after detailed instruction by a physiotherapist. The home-based balance program is performed three times per week for 4 weeks (matching the frequency and total exposure of the intervention arm) and includes bilateral and unilateral stance exercises, balance tasks with eyes open and closed, exercises on different surfaces, and controlled weight-shifting tasks, organized according to a progressive difficulty principle. No device-based or real-time biofeedback is used.

Outcome Assessment

Outcomes are assessed at three pre-specified time points: T0 (baseline, week 0), T1 (immediately after the 4-week intervention, week 4), and T2 (12-week follow-up, week 16 from baseline). All assessments use validated, device-based, automated measurement systems where applicable, minimizing observer bias.

The primary outcome is the change in the Stability Index, a measure of overall postural control performance during a multi-axial dynamic balance task on the TecnoBody ProKin PK252 stabilometric platform (TecnoBody S.r.l., Dalmine, Italy), where lower values indicate better postural stability. This parameter is conceptually comparable to the Overall Stability Index (OSI) reported by the Biodex Balance System, which was used as the reference source for the a priori sample size calculation.

Pre-specified key secondary outcomes are: change in mediolateral standard deviation of the center of pressure; change in Romberg area ratio (eyes-closed to eyes-open sway area); change in Limits of Stability (LOS); change in the Scoliosis Research Society-22 Patient Questionnaire (SRS-22) total score; and change in single-leg stance time.

Pre-specified exploratory outcomes include the remaining TecnoBody ProKin static, dynamic, and proprioceptive parameters; postural and spinal alignment parameters measured by the DIERS Formetric 4D rasterstereographic surface topography system (DIERS International GmbH, Wiesbaden, Germany); and SRS-22 subdomain scores (function/activity, pain, self-image, mental health).