Asymmetrical intrapleural pressure distribution: a cause for scoliosis? A computational analysis.

PURPOSE

The mechanical link between the pleural physiology and the development of scoliosis is still unresolved. The intrapleural pressure (IPP) which is distributed across the inner chest wall has yet been widely neglected in etiology debates. With this study, we attempted to investigate the mechanical influence of the IPP distribution on the shape of the spinal curvature.

METHODS

A finite element model of pleura, chest and spine was created based on CT data of a patient with no visual deformities. Different IPP distributions at a static end of expiration condition were investigated, such as the influence of an asymmetry in the IPP distribution between the left and right hemithorax. The results were then compared to clinical data.

RESULTS

The application of the IPP resulted in a compressive force of 22.3 N and a flexion moment of 2.8 N m at S1. An asymmetrical pressure between the left and right hemithorax resulted in lateral deviation of the spine towards the side of the reduced negative pressure. In particular, the pressure within the dorsal section of the rib cage had a strong influence on the vertebral rotation, while the pressure in medial and ventral region affected the lateral displacement.

CONCLUSIONS

An asymmetrical IPP caused spinal deformation patterns which were comparable to deformation patterns seen in scoliotic spines. The calculated reaction forces suggest that the IPP contributes in counterbalancing the weight of the intrathoracic organs. The study confirms the potential relevance of the IPP for spinal biomechanics and pathologies, such as adolescent idiopathic scoliosis.