Poster Presentation 51st International Society for the Study of the Lumbar Spine Annual Meeting 2025

Introduction:
Chronic low back pain (CLBP) is a significant global health burden and research indicates a correlation between vertebral fractures (Vx) and CLBP [1]. Apart from key risk factors like osteoporosis, age, gender, genetics, or lifestyle, patients with a preceding vertebral fracture are at increased risk for subsequent fractures and accelerated intervertebral disc (IVD) degeneration [2].Vertebral fractures disrupt spinal integrity and biomechanics, causing chronic pain and functional impairments, but the detailed biomechanical mechanisms behind this resulting facture cascade remain poorly understood. The study aims to investigate the biomechanical effects of vertebral fractures on vertebral loading.

Methods:
We used our validated pipeline for automated generation of individualized models of the torso with detailed lumbar spine (Figure 1) [3] to assess the influence of prevalent vertebral fractures on spinal loading in 15 patients, which were diagnosed with single or multiple incidental vertebral fractures within a period of 4 to 7 years. For each patient two models were generated based on respective baseline and follow-up CT (Figure 2). Using a combination of inverse dynamics and static optimization, we simulated three static loading tasks: unloaded and loaded upright standing (while lifting 10kg with stretched arms) and 30° flexion. Subsequently, we compared compression and shear forces for baseline and follow-up conditions to evaluate the impact of additional fractures on spinal mechanics in each subject. 

Results:
Our results showed a moderate increase in compression forces of up to 50% in the area of the occurring fractures. However, in individual cases, there was even a reduction in the compression force of up to 40%. Regarding shear forces, a moderate to strong increase of up to 1400% was observed in all cases (Figure 3). While an increase in compression force could often be observed in the area of the occurring fracture, corresponding effects in shear load were observed in the area of the adjacent segments. However, loading patterns were highly individual and statistically relevant effects could not be derived from our results. 

Discussion:
Our results show that incidental fractures have a clear impact on spinal biomechanics. Especially regarding shear loading, the disruption of the mechanical conditions due to vertebral fractures can be one aspect leading to subsequent degenerative changes and even further fractures. To assess potentially statistically relevant effects, similar future study should consider large cohorts such as the German National Cohort (NAKO). However, our findings indicate, that the highly individual character of spinal loading patterns it challenging to derive generally valid insights. One major limitation of this study is the static simulation approach and implementation of generic postures. Individual characteristics such as compensatory postural adjustments during movement and muscle dynamics due to the prevalent pathologies need to be considered for a profound investigation of the relevance of biomechanics for subsequent fracture risk assessment.