Optimisation du choix des vertèbres limites (UIV/LIV) dans la scoliose idiopathique de l’adolescent : Traction axiale face au test de Bending.

Details

Supervisors

Mahaudens, Philippe

Faculty

Faculté des sciences de la motricité

Degree label

Master [60] en kinésithérapie et réadaptation

Abstract

enIntroduction The surgical treatment of Adolescent Idiopathic Scoliosis (AIS) poses a major biomechanical challenge: maximizing deformity correction while fusing as few segments as possible. The strategic selection of the upper instrumented vertebra (UIV) and lowest instrumented vertebra (LIV) is crucial to prevent severe complications such as the distal adding-on phenomenon or proximal junctional kyphosis (PJK). This study evaluates the respective efficacy of dynamic radiographic side-bending and axial traction tests to anticipate the behavior of these vertebrae and guide surgical decision-making. Methods A retrospective observational study was conducted on 31 surgical patients. Coronal radiographic parameters (angulation and translation) were measured on static and dynamic preoperative radiographs, and then compared to postoperative results at 1 and 6 months. A dual metrological filter was applied: the Minimal Detectable Change (MDC95) and the Minimal Clinically Important Difference (MCID), calculated following a double-blind evaluation. These thresholds allow for isolating true spinal mobility from the mere "measurement noise" inherent to imaging software. Results The analysis demonstrates that longitudinal traction is the most reliable and accurate predictor of the postoperative spatial (translation) and angular (tilt) position of the LIV and UIV. Conversely, the side-bending test presents an asymmetrical bias (overestimation or underestimation) that limits its reliability in predicting the final horizontalization of the LIV. However, it remains relevant for evaluating the flexibility reserve of non-instrumented discs. Finally, the 6-month follow-up confirms the excellent stability of the surgical constructs, with no significant degradation or adding-on phenomenon. Conclusion Axial traction establishes itself as the reference tool for dictating the safety and final position of the surgical construct, while the side-bending test objectifies the flexibility reserve required to achieve it. The use of traction, supported by robust statistical thresholds (MDC/MCID), provides the surgeon with an objective rationale to validate vertebral-sparing strategies. This allows for the preservation of valuable lumbar discs while ensuring the long-term durability of the correction. These results practically redefine the hierarchy and interpretation of dynamic examinations in the surgical planning of scoliosis.