Objective: To explore the best surgical fusion level for adolescent idiopathic scoliosis (AIS) of PUMC II d(2) with finite element model (FEM).
Methods: FEM (T(5)-S) of PUMC II d(2) idiopathic scoliosis was used to simulate upper thoracic curve, lower lumbar curve and double curve fusion manners. The pedicle of concave vertebral arch received 50, 100 and 150 N load respectively. Displacement of T(5) and T(11) on upper sagittal plane (displacement of Z axis positive value on upper sagittal plane, displacement of negative value on lower sagittal plane) and their different values were compared. T(5) displacement represented the outcomes of double curve orthopedics. T(11) displacement represented the outcomes of lower lumbar curve orthopedics. Their difference (T(5)-T(11)) represented the outcomes of upper thoracic curve orthopedics. Different fusion segments and displacement of T(5) and T(11) under different orthopedic forces were measured.
Results: In PUMC II d(2) lateral curvature, T(5) displacement on Z axis: fusion displacement of double curve was greater than the upper or lower curve alone (F = 8, P < 0.01). Difference of T(5)-T(11) displacement: double curve orthopedics > upper thoracic curve orthopedics alone > lower lumbar curve orthopedics alone (F = 8, P < 0.01). Displacement of T(11) on Z axis: double curve orthopedics > lower lumbar curve orthopedics alone > upper thoracic curve orthopedics alone (F = 8, P < 0.01).
Conclusion: Fusing two curves achieves the best effect on the AIS of PUMC II d(2) in comparison with upper or lower curve fusion alone. Effects of 3 kinds of load on correction of upper thoracic curve: double curve orthopedics > upper thoracic curve orthopedics alone > lower lumbar curve orthopedics alone. Effect of 3 kinds of load on correction of lower lumbar curve orthopedics alone: double curve orthopedics > lower lumbar curve orthopedics alone > upper thoracic curve orthopedics alone. Three-dimensional finite element analysis is an effective method to analyze the biomechanics of scoliosis deformity correction and provides a virtually non-invasive verification manner. And it may optimize the surgical protocol.