Asymmetric load transmission induces facet joint subchondral sclerosis and hypertrophy in patients with idiopathic adolescent scoliosis: Evaluation using finite element model and surgical specimen

Abstract Background Physiological and ideal spinal alignment is critical for efficient load transfer to support and maintain our body. However, in patients with adolescent idiopathic scoliosis (AIS), imbalanced load transfer occurs due to abnormal twisting and rotation of the spinal column. This study aimed to investigate the asymmetric stress overload and distribution on the facet joints of AIS patients using finite element (FE) analysis and surgical specimens. Methods FE models of the thoracic spine were created from a total of 13 female AIS patients (Lenke type 1, n = 4: Lenke type 2 n = 5; Lenke type 3, n = 4). A load of 200 N on the T3 vertebra and 30 N each on the bilateral superior articular processes were applied in the vertical direction to quantify the contact force on the facet joints from T3 to T11. In addition, morphological and histological analyses were performed on the inferior articular processes taken during surgery. Results Contact forces of the facet joint progressively increased from the mid to lower thoracic spine of the concave side, reaching a maximum around the apex. More than 90% of the load was transmitted by the facet joints at the concave side, resulting in facet joint subchondral sclerosis and hypertrophy. Conclusions FE models revealed the asymmetric stress overload and distribution on the facet joints of AIS. The asymmetric load transmission could be responsible for degeneration, such as hypertrophy and subchondral sclerosis of the facet joint of AIS.