The biomechanical effects of graded upper articular process arthroplasty on lumbar spine: A finite element study

Superior articular process arthroplasty is important for intervertebral foramen microscopy but may lead to spinal instability. Currently, there has been no relevant study in relation to the biomechanical analysis of superior articular process arthroplasty. Hence, this study is intended to verify biomechanical effects after unilateral S1 superior articular process arthroplasty.

Eight finite element (FE) models of lumbosacral vertebrae (L4-S) were constructed, and the superior articular process formation was simulated with the help of Geomagic studio. Then, the models were imported into Nastran software after optimization. Normal load and appropriate torque were applied to simulate forward flexion, back extension, lateral flexion and lateral rotation. In the end, changes of lumbar range of motion (ROM) and structural stress were compared with those of normal model.

Compared with the normal model, formed from ventral to dorsal (Longitudinal), the larger motion of lumbar spine and the greater larger stress of articular process showed statistical significance (P < 0.05) in most of directions when the forming range was greater than 3/5. Formed from the apex to the base (transverse), the larger motion of lumbar spine and the greater stress of articular process showed statistical significance (P < 0.05) in most of directions when the forming range was great than 1/5.

When conducting unilateral S1 articular process arthroplasty from ventral to dorsal, the forming range is recommended to be less than 3/5 of the superior articular process. Notably, it is not advisable to form from the apex to the base.