A finite element study of posteroanterior lumbar mobilization on elderly vertebra geometry

The applying posteroanterior (PA) load through the spinous process of the vertebral bone is one of the methods for assessment and treatment for back pain in physical therapy. Central PA mobilization is crucial to be investigated the harmful effect on osteoporotic vertebral bone. Therefore, the objective of our study was to investigate the effect of PA load on elderly L1 lumbar vertebra geometry with different bone properties. The finite element model of L1 vertebra was generated from elderly computed tomography images. A 100 N PA load was applied at posterior aspect of spinous process of L1 vertebra in two different homogeneous material properties; (1) healthy L1, (2) osteoporotic L1. The distribution of von Mises stresses and minimum principal strains in mid-transverse sections of L1 vertebra was determined. The results revealed that PA load caused higher values of stresses and strains at pedicles and laminae in transverse section of L1 vertebra. Moreover, changing the elastic modulus influenced stresses and strains distributions in transverse sections of L1 vertebra. In conclusion, applying PA force through spinous process tends to cause a crack initiation at pedicles and laminae in L1 elderly vertebra.