Pelvic alignment and plantar pressure asymmetry in adolescents with idiopathic scoliosis: a cross-sectional observational study

Abstract

Background

Pelvic alignment plays a central role in maintaining postural stability, and asymmetries in pelvic orientation may alter plantar pressure distribution. In adolescents with idiopathic scoliosis (AIS), compensatory adaptations of the pelvis and lower limbs may contribute to imbalance and asymmetrical weight bearing. The aim of this study is to investigate the association between pelvic torsion, rotation, and tilt with static and dynamic plantar pressure asymmetries in adolescents with idiopathic scoliosis.

Methods

This study included 60 adolescents with AIS aged 10–18 years. Pelvic parameters were obtained using the DIERS Formetric 4D surface topography system, and static and dynamic plantar pressure distributions were measured with the GaitScan system. Side-to-side differences in forefoot and rearfoot loading were compared using paired t-tests, and correlations between pelvic parameters and plantar pressure asymmetries were analyzed with Spearman’s Correlation test (p < 0.05).

Results

Significant plantar pressure differences were found between the convex and concave side of curve. Forefoot loading was lower on the convex side (28.8% vs. 33.9%), whereas rearfoot loading was higher (71.6% vs. 66.6%, exact p = 0.002, effect size r = 0.48). Dynamic loading also favored the convex side (55.4% vs. 45.6%, exact p < 0.001, effect size r = 0.61). Correlations between pelvic torsion, rotation, and tilt with pressure asymmetries were weak and not significant.

Conclusion

Adolescents with idiopathic scoliosis exhibit marked plantar pressure asymmetries, particularly under dynamic conditions.

Introduction

Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformity characterized by lateral curvature and vertebral rotation, affecting approximately 2–3% of adolescents [1, 2]. While its etiology remains unclear, biomechanical factors—including pelvic alignment and foot pressure distribution—have been suggested to play a role in the postural adaptations observed in AIS patients [3]. The pelvis functions as a biomechanical bridge between the spine and lower extremities, and asymmetries in pelvic torsion, rotation, or tilt may influence overall postural balance and weight-bearing patterns [4].

Previous research has investigated pelvic alignment and plantar pressure separately in AIS populations. For instance, systematic reviews have shown that individuals with AIS exhibit increased sway and mediolateral instability during quiet standing, indicating deficits in postural control [5]. It has also been reported that foot posture and gait mechanics are significantly altered in patients with AIS, particularly in association with curve severity and pelvic asymmetries [5–7]. However, few studies have examined the direct relationship between pelvic alignment parameters and both static and dynamic plantar pressure distribution in this population.

This represents a meaningful gap in the literature, as the combined assessment of pelvic parameters and plantar pressure asymmetries may provide insights into compensatory postural strategies adopted by AIS patients. Such information is clinically relevant, as it could help guide physiotherapeutic scoliosis-specific exercise (PSSE) planning and orthotic interventions by addressing not only spinal deformity but also the secondary biomechanical imbalances contributing to postural instability [3].

Therefore, this study aims to evaluate the relationship between pelvic torsion, rotation, and tilt values and static and dynamic foot pressure distributions in individuals with AIS, using advanced technologies such as DIERS Formetric 4D and GaitScan to provide a comprehensive analysis of postural adaptations in this population.

Materials and methods

Study design

This retrospective cross-sectional study was conducted between September 2024 and January 2025.

Participants

Adolescent idiopathic scoliosis cases between the ages of 10–18 were evaluated. Inclusion criteria: not having any acute injury related to the musculoskeletal system in the last 6 months before the evaluation, being diagnosed with C thoracic scoliosis. Exclusion criteria: individuals with missing data in pelvic parameters or base pressure values, and cases with neurological or musculoskeletal pathology other than Adolescent Idiopathic Scoliosis were not be included in the study.

The study consists of male and female adolescent idiopathic scoliosis cases between the ages of 10–18. The sample size of the study was determined as 60 people with 80% power and a 95% confidence interval in the G-Power (Heinrich Heine Universität Düsseldorf) program based on the study conducted by Zhu et al. [7].

Scoliosis severity was classified according to Cobb angle measurements as mild (10–24°), moderate (25–40°), and severe (> 40°). None of the participants had received brace treatment prior to assessment. All participants were undergoing physiotherapeutic scoliosis-specific exercise (PSSE) interventions; however, treatment protocols were not standardized across participants.

Measurements

Pelvic parameters of the cases (rotation, torsion, tilt) were evaluated using the DIERS Formmetric 4D Imaging Method. The method allows photogrammetric video recording of the posterior surface using raster stereography. Based on the data obtained, a precise three-dimensional model of the posterior surface is created. Considering the anatomical and biomechanical assumptions of the model, it is possible to calculate fixed anatomical points, spinal curvatures, and spatial form parameters of the trunk as a result of these calculations [8].

Static-dynamic foot pressure analyses of the subjects were evaluated using the GaitScan foot pressure system (Orthotic Group, Markham, Ontario, Canada). GaitScan consists of a 578 × 418 × 12 mm force floor mat containing 4,096 pressure sensors with a sampling frequency of approximately 125 Hz. For static foot pressure, participants are asked to stand comfortably and without contraction on the platform [9]. Values are obtained after waiting a few seconds. For dynamic pressure analysis, participants completed three walking trials at a self-selected comfortable walking speed. The mean values obtained across the trials were used for statistical analyses. During the test, participants walk barefoot at a comfortable pace of their choosing, with their eyes looking straight ahead, and perform an average of three trials from which data are obtained for analysis.

Statistical analysis

Data were analysed using SPSS 21.0 (IBM Corp, Armonk, NY, USA). The normality of the data was checked with the Shapiro-Wilk test. Descriptive data are given as mean and standard deviation. The Wilcoxon signed-rank test was used to compare the values of the convex and concave sides. The relationship between pelvic parameters and static dynamic foot pressure analysis parameters was examined with the Spearman’s Correlation Test. The significance value was accepted as 0.05.

Results

Participants characteristics

Descriptive statistics of the participants are shown in Table 1. The major curve pointed to the right in 39 cases and to the left in 21 cases.

Table 1.

Descriptive characteristics of the participants (n = 60)

	Mean ± SD / n (%)
Age	12.33 ± 4.43
Gender	22 Male (36.66%) 38 Female (63.33%)
Height (cm)	150.81 ± 17.63
Weight	44.3 ± 17.72
Body Mass Index	18.6 ± 4.25
Cobb Angles (°)	20.22 ± 9.96 (12°-42°)
Severity of scoliosis
Mild (10°-24°)	42 (%70)
Moderate (25°-40°)	14 (%23,4)
Severe (> 40°)	4 (%6,6)

Plantar pressure and weight distribution values

Table 2 presents the plantar pressure and weight distribution values according to the convex and concave curve sides. The mean forefoot weight% was lower on the convex side than on the concave side (28.8% vs. 33.9%), whereas the mean rearfoot weight% was higher on the convex curve side (71.6% vs. 66.6%). Accordingly, the mean difference between rearfoot and forefoot weight percentages was 42.4% points on the convex curve side and 31.2% points on the concave curve side. On both sides, the differences between forefoot and rearfoot weight distribution were statistically significant (exact p = 0.001, effect size r = 0.52 on the convex side, and exact p = 0.003, effect size r = 0.45 on the concave side). Static total weight distribution was nearly symmetrical between the convex and concave sides (49.9% and 50.1%, respectively; p = 0.894). In contrast, dynamic weight distribution was significantly greater on the convex side than on the concave side (55.4% vs. 45.6%, exact p < 0.001), demonstrating a remarkably strong magnitude of asymmetry (effect size r = 0.61), which firmly reinforces the clinical relevance of dynamic loading shifts.

Table 2.

Comparison of plantar pressure weight percentages according to convex and concave side of the curve

	Convex Side (%)	Concave Side (%)	p-value*	Effect size (r)
Mean Forefoot Weight%	28.8	33.9	0.002	0.48
Mean Rearfoot Weight%	71.6	66.6	0.002	0.48
Forefoot vs. Rearfoot Mean Difference	42.4	31.2	0.001	0.52
Static Total Weight Distribution	49.9	50.1	0.894	0.02
Dynamic Weight Distribution	55.4	45.6	0.001	0.61

Wilcoxon signed-rank test was used for side-to-side comparisons; p < 0.05 considered statistically significant

Partial correlations between pelvic parameters

Table 3 presents the partial correlations between pelvic obliquity (PO), pelvic torsion (PT), and pelvic rotation (PR) on the convex side. A weak correlation was observed between PO and PT (r = 0.084), which was not statistically significant (p = 0.525). Similarly, the correlations between PR and PO (r = 0.141, p = 0.282) and PR and PT (r = 0.121, p = 0.357) were also weak and not statistically significant.

Table 3.

Inter-correlation matrix of three-dimensional pelvic alignment parameters on the convex side of the scoliotic curve

		PT	PR
PO	Correlation*	0.084	0.141
	P value	0.525	0.282
PT	Correlation*	-	0.121
	P value	-	0.357

* Spearman Correlation Analysis, PO Pelvic Obliquity, PT Pelvic Torsion, PR Pelvic Rotation

Discussion

This study investigated the relationships between pelvic torsion (PT), pelvic rotation (PR), and pelvic tilt (PO) and their associations with static and dynamic plantar pressure characteristics in adolescents with idiopathic scoliosis (AIS). Two principal findings emerged from the present study. First, significant asymmetries in plantar pressure distribution were observed between the convex and concave sides of the scoliotic curve, particularly under dynamic loading conditions. Second, despite these asymmetrical loading patterns, no significant correlations were identified between static pelvic alignment parameters and plantar pressure variables.

The coexistence of dynamic plantar pressure asymmetries and weak associations with static pelvic alignment suggests that structural deformities alone may not adequately explain functional loading behavior in AIS. Rather, this finding may reflect a biomechanical mismatch between static posture and dynamic movement, whereby neuromuscular compensation mechanisms and adaptive gait strategies help maintain functional balance despite underlying structural asymmetries. Consequently, static pelvic alterations may not directly translate into predictable changes in dynamic weight-bearing patterns.

These findings should be interpreted within the context of previous literature. Several studies have reported that pelvic alignment influences postural control, gait characteristics, and weight distribution in adolescents with idiopathic scoliosis [10, 11]. However, evidence regarding the specific contributions of pelvic torsion, pelvic rotation, and pelvic tilt to plantar pressure asymmetries remains limited and inconsistent.

Gait analysis studies have demonstrated that AIS can affect spine mobility and gait mechanisms. Specifically, kinematic differences in the spine, pelvis, and lower limbs may contribute to the causation and progression of idiopathic scoliosis [12]. Luo et al. (2021) reported that pelvic tilt exhibited a positive correlation with baropodometric parameters, except for forefoot weight% [5]. Similarly, Liu et al. (2022) found that sagittal pelvic tilt and axial rotation influenced balance and gait parameters, which aligns with our findings that pelvic alterations contribute to dynamic plantar pressure shifts [4]. Additionally, Zhu et al. (2021) observed that patients with AIS exhibited altered foot posture and walking performance, which further supports our results indicating asymmetrical weight-bearing strategies in response to pelvic misalignment [7].

Another noteworthy finding of this study was the distinct regional loading patterns observed between the convex and concave sides during walking. Our results demonstrated that while forefoot loading was significantly lower on the convex side, rearfoot loading was remarkably higher (71.6% vs. 66.6%, p = 0.002) with a moderate-to-large effect size (r = 0.48). This systematic shift suggests a sagittal plane compensatory mechanism coupled with the three-dimensional spinal deformity. In adolescents with AIS, the posterior displacement of the center of mass or structural alterations in pelvic torsion on the major curve side may lead to an increased heel-strike impact and prolonged rearfoot contact on the convex side. Conversely, the contralateral concave side appears to facilitate a compensatory forward progression strategy, manifesting as increased forefoot propulsion (33.9% vs. 28.8%). These findings highlight that scoliosis-related structural asymmetries do not merely affect global weight-bearing but also alter regional foot biomechanics. Consequently, clinical interventions, including customized orthotic management and physiotherapeutic scoliosis-specific exercises (PSSE), should not only target coronal plane alignment but also address these specific regional hindfoot and forefoot loading discrepancies across the kinetic chain.

Neurophysiological studies have identified significant evidence of impaired standing balance in individuals with AIS, who rely heavily on visual and proprioceptive information to maintain upright posture. Additionally, increased activity on the convex side of the intrinsic spinal muscles has been frequently reported [13]. Prior studies have also emphasized the impact of pelvic asymmetries on plantar pressure in scoliosis patients. Kim et al. (2019) demonstrated significant differences in foot pressure distribution based on spinal deformity severity, suggesting that pelvic positioning may influence postural stability [14]. Furthermore, Catan et al. (2020) highlighted the role of plantar pressure distribution in evaluating postural imbalances in AIS, reinforcing the need for a comprehensive assessment of pelvic parameters [6]. Our findings extend these observations by demonstrating that pelvic torsion and rotation contribute to weight distribution asymmetries, particularly in dynamic conditions. One important methodological consideration is the discrepancy between the measurement conditions of the study variables: while pelvic parameters (pelvic torsion, rotation, and tilt) were assessed under static conditions using the DIERS Formetric 4D system, dynamic plantar pressure data were collected during gait via the GaitScan platform. This mismatch in measurement modalities may partly explain the weak and non-significant correlations observed between the variables. From a biomechanical standpoint, static pelvic alignment may not directly predict dynamic foot loading patterns due to neuromuscular compensations and altered kinematics during gait. Nevertheless, we chose to explore these correlations based on the hypothesis that static pelvic asymmetries could predispose individuals to consistent dynamic compensations, even if not directly proportional. Acknowledging this conceptual limitation is crucial in interpreting the study’s findings and highlights the need for future research integrating synchronized dynamic pelvic and plantar data using motion capture or wearable sensor technology.

One notable limitation of the present study is the absence of an age- and sex-matched healthy control group. Without a normative comparison, it is difficult to determine whether the observed plantar pressure asymmetries and pelvic parameter values are unique to AIS patients or fall within the spectrum of normal developmental variation. While our findings demonstrate statistically significant differences between the convex and concave sides of the curve, the degree to which these asymmetries deviate from typical adolescent biomechanics remain unclear. Some studies have reported that typically developing adolescents exhibit relatively symmetrical foot loading patterns and minimal pelvic asymmetries under static and dynamic conditions [5, 15, 16]. Therefore, future research should incorporate a matched control group to strengthen the interpretation of scoliosis-specific biomechanical adaptations.

The clinical significance of our findings lies in providing preliminary insights into dynamic weight-bearing asymmetries in adolescents with idiopathic scoliosis. Although correlations between pelvic parameters and plantar pressures were not statistically significant, asymmetrical loading patterns were consistently observed, particularly under dynamic conditions. However, in the absence of a healthy control group, it cannot be determined whether these asymmetries are specific to AIS or represent variations within normal adolescent biomechanics. Therefore, these findings should be interpreted with caution. Importantly, the lack of significant associations between static pelvic alignment parameters and plantar pressure variables suggests that structural deformities alone may not adequately explain dynamic loading behavior. This finding may reflect the influence of neuromuscular compensation mechanisms and adaptive gait strategies that help maintain functional balance despite postural asymmetries. From a clinical perspective, these results highlight the importance of complementing static postural assessment with dynamic functional evaluation. Rehabilitation approaches may benefit from considering dynamic balance, proprioceptive function, and sensorimotor control in addition to conventional postural correction strategies. Furthermore, the combined use of DIERS Formetric 4D and GaitScan technologies may provide complementary information regarding structural and functional adaptations in adolescents with idiopathic scoliosis. Future clinical protocols may also benefit from incorporating plantar pressure assessment as an additional tool for identifying functional asymmetries and compensatory gait patterns [6, 16].

Recent advancements have explored the use of gait patterns as biomarkers for scoliosis classification. A video-based novel, non-invasive method utilizing deep learning algorithms has shown promise in diagnosing scoliosis through gait analysis, offering the potential for early detection and monitoring without radiation exposure [17].

Physiotherapeutic scoliosis-specific exercises (PSSE) have been recommended as a first-line conservative treatment approach for adolescents with idiopathic scoliosis. While the present study did not evaluate treatment outcomes, the observed discrepancy between static pelvic alignment and dynamic plantar loading suggests that both structural and functional components should be considered during clinical assessment and rehabilitation. Future studies should investigate whether interventions targeting dynamic balance and sensorimotor control can influence plantar pressure asymmetries and functional performance in AIS.

Study limitations and future directions

While this study provides valuable insights, several limitations must be considered. The sample size, though sufficient for detecting significant differences, may not fully capture the variability in pelvic parameter influences on plantar pressure. Additionally, while our analysis focused on weight distribution and correlations with PT, PR, and PO, other biomechanical factors, such as muscle activation patterns and neuromuscular coordination, were not assessed. Future research should incorporate electromyographic and kinematic analyses to provide a more comprehensive understanding of the interplay between pelvic alignment and plantar pressure.

Another important limitation is the biomechanical mismatch between the measurement contexts of pelvic parameters (static) and plantar pressures (dynamic). This discrepancy may have reduced the ability to detect meaningful associations and should be considered when interpreting the findings. Future research should incorporate real-time dynamic pelvic tracking during gait analysis to better characterize postural interactions during movement.

The absence of an age- and sex-matched healthy control group further limits the interpretation of the results. Consequently, it remains unclear whether the observed plantar pressure asymmetries and pelvic alignment characteristics are specific to adolescents with idiopathic scoliosis or represent normal developmental variability. Therefore, disease-specific or causal inferences should be made with caution.

Although all participants were receiving physiotherapeutic scoliosis-specific exercise (PSSE), treatment protocols were not standardized with respect to exercise type, frequency, duration, or treatment history. As a result, the potential influence of PSSE on plantar pressure distribution and gait characteristics could not be evaluated. Furthermore, none of the participants had a history of brace treatment, precluding any assessment of orthotic effects on the measured outcomes.

Future longitudinal studies involving matched healthy controls, standardized treatment protocols, and dynamic biomechanical assessments are warranted to clarify the evolution of plantar pressure adaptations and pelvic asymmetries in AIS. Such investigations may also help clarify the mechanisms underlying plantar pressure asymmetries and determine whether interventions targeting balance, gait adaptations, and neuromuscular control can improve functional outcomes in adolescents with idiopathic scoliosis [3, 18].

Conclusion

This study is among the first to comprehensively examine the relationship between pelvic alignment parameters (torsion, rotation, and tilt) and both static and dynamic plantar pressure asymmetries in adolescents with idiopathic scoliosis using advanced three-dimensional imaging and high-resolution pressure analysis systems. Although the correlations between pelvic parameters and plantar pressure asymmetries were weak and not statistically significant, the presence of consistent side-to-side differences in plantar pressure, especially under dynamic conditions, highlights underlying postural adaptations associated with scoliosis.

These findings provide preliminary evidence regarding the relationship between pelvic alignment parameters and plantar pressure asymmetries in adolescents with idiopathic scoliosis. However, due to the absence of a healthy control group, the findings should be interpreted cautiously and cannot be considered specific to AIS. Further studies, including matched control participants are required to confirm and extend these observations. Recognizing these asymmetry patterns may help shape future research aimed at refining diagnostic assessments and developing targeted rehabilitation strategies. Further longitudinal studies incorporating larger sample sizes, control groups, and dynamic pelvic tracking methods are warranted to validate and expand upon these preliminary observations.

Authors’ contributions

GA, OS, and ESA made substantial contributions to the conception and design of the study. GA and OS were involved in the acquisition of data, and GA, OS, and ESA contributed to data analysis and interpretation. GA drafted the manuscript, while OS and ESA critically revised it for intellectual content. All authors have approved the submitted version, agree to be personally accountable for their contributions, and will ensure that any questions regarding the integrity or accuracy of the work are appropriately addressed and resolved.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Data availability

The datasets generated and/or analysed during the current study are not publicly available, but are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

The study was approved by the University of Health Sciences Gulhane Scientific Research Ethics Committee on May 28, 2024, with approval number 2024 − 270/ 46418926) and adhered to the Declaration of Helsinki. Informed consent forms were obtained from the patients.

Competing interests

The authors declare no competing interests.