Systemic alterations in somatosensory function in adolescent idiopathic scoliosis: a quantitative sensory testing study of pressure pain thresholds

Abstract Background Adolescent Idiopathic Scoliosis (AIS) predominantly affects females. Orthotic treatment is the most common management, yet the prescription of corrective force lacks objective, physiological guidance. The patient’s perception of this force as pressure is crucial for tolerance and compliance, but the characteristics of back pressure-pain perception in AIS remain unexplored. Objective This study aimed to systematically quantify the back Pressure Pain Threshold (PPT) in female AIS patients, compare it with healthy controls (HC), and investigate its relationship with spinal curve types and other factors. Methods 28 female AIS patients and 104 age-matched HC group were enrolled. PPT was assessed at the Hegu point and 36 back sites using a pressure algometer. Data analysis utilized Kruskal-Wallis tests for group comparisons, Wilcoxon signed-rank tests and Bonferroni correction for pairwise testing, and linear mixed-effects models (LMM) to evaluate systemic and local influences. Results AIS patients demonstrated systemic hypoalgesia, with significantly higher PPT across sites compared to HC group. HC group showed distinct topographic specificity (proximal > distal PPT), which was absent in AIS groups. LMM revealed that while the median HC PPT at the corresponding site (HC_PPT) was related to the right Hegu point PPT (H_R), body side, muscle type, and spinal position, AIS models were simplified indicating a loss of wide-scale topographic features and a primary association with H_R and the average HC_PPT. Conclusion Female AIS patients exhibit systemic alterations in pain modulation and a loss of topographic specificity. These findings provide a physiological objective basis for assessing mechanical pressure sensitivity and offer potential somatosensory evidence for the future development of individualized orthotic force-setting protocols.