Evaluation of the influences of various force magnitudes and configurations on scoliotic curve correction using finite element analysis

Optimization of in-brace corrective force in adolescents with Lenke type 5 curve using finite element model

BACKGROUND

Pelvic parameters have been taken into consideration for the evaluation of the outcomes of bracing in AIS. To discuss the stress required to correct the pelvic deformity related to Lenke5 adolescent idiopathic scoliosis (AIS) by finite element analysis, and provide a reference for the shaping of the pelvic region of the brace.

METHODS

An three-dimensional (3D) corrective force on the pelvic area was defined. Computed tomography images were used to reconstruct a 3D model of Lenke5 AIS. Computer-aided engineering software Abaqus was used to implement finite element analysis. By adjusting the magnitude and position of corrective forces, coronal pelvic coronal plane rotation (PCPR) and Cobb angle (CA) of lumbar curve in the coronal plane, horizontal pelvic axial plane rotation, and apical vertebra rotation (AVR) were minimized to achieve the best effect on the spine and pelvic deformity correction. The proposed corrective conditions were divided into three groups: (1) forces applied on X-axis; (2) forces applied both in the X- and Y-axis; and (3) forces applied along the X-, Y-, and Z-axis at the same time.

RESULTS

In three groups, CA correction reduced by 31.5%, 42.5%, and 59.8%, and the PCPR changed to 12°, 13°, and 1° from 6.5°, respectively. The best groups of correction forces should simultaneously locate on the sagittal, transverse, and coronal planes of the pelvis.

CONCLUSIONS

For Lenke5 AIS, 3D correction forces can sufficiently reduce scoliosis and pelvic asymmetrical state. Force applied along the Z-axis is vital to correct the pelvic coronal pelvic tilt associated with Lenke5 AIS.

Optimized scheme for paired transverse corrective forces in S-shaped scoliosis via ultrasound and application in Chêneau brace: a pilot study

BACKGROUND

There is currently no consensus on the optimal positions of the transverse corrective forces (TCFs) for scoliosis braces.

OBJECTIVES

This study aimed to explore an optimal scheme of placing paired TCF for S-shaped adolescent idiopathic scoliosis and its feasibility in Chêneau brace (CB) treatment.

STUDY DESIGN

Cross-over feasibility pilot trial.

METHODS

Ten S-shaped adolescent idiopathic scoliosis participants were invited to receive four tests with different paired TCF positions under ultrasound. The positions of the paired TCF were test 1: thoracic apical vertebra (AV), lumbar AV; test 2: 2 cm inferior to thoracic AV, lumbar AV; test 3: thoracic AV, 2 cm superior to lumbar AV; and test 4: 2 cm inferior to thoracic AV, 2 cm superior to lumbar AV. The test scheme with the highest mean in-force correction rate (IFCR) for the thoracic spinous process angle (SPA) was further applied in the CB fabrication of 4 additional participants.

RESULTS

A significant higher mean IFCR of the thoracic SPA of 63.6% was found in test 2 (P < 0.001), which also contributed to its higher overall IFCR of the SPA of 64.6% (P = 0.001). Moreover, the mean in-brace correction rates for the thoracic and overall curves in CB were 46.4% and 51.8%, respectively. No adverse events were reported.

CONCLUSIONS

Placing paired TCF at the lumbar AV and 2 cm inferior to the thoracic AV achieved better treatment efficacy than other schemes. The practical application of this scheme on the CB was feasible.

Evaluation of the efficiency of various force configurations on scoliotic, lordotic and kyphotic curves in the subjects with scoliosis

BACKGROUND

The efficiency of the braces designed for scoliotic subjects depends on configurations and also magnitudes of the forces used to stabilize and correct scoliotic curve. However, the effects of various force configurations on the spinal curves in sagittal plane should also be considered. The aim of this study was to determine the efficiency of various force configurations on scoliotic, lordotic and kyphotic curves.

METHOD

A 3d model of spine was developed based on CT scan images of spine obtained from a scoliotic girl. The model was exported to Abaqus software to check the effects of various force configurations and magnitudes on spinal curves. The spinal curves in thoracic and lumbar, lordotic and kyphotic curves were evaluated in this study. Transverse forces, vertical forces and combination of transverse and vertical forces were selected in this study.

RESULTS

The results of this study showed that use of transverse forces did not influence the scoliotic curve significantly. Vertical directed forces not only decreased scoliotic curves but also decreased lordotic and kyphotic curves. It seems that a combination of both transverse and vertical directed forces decreased scoliotic curves but did not influence spinal curves in sagittal plane.

CONCLUSION

It is recommended to use a combination of transverse and vertical forces to decrease scoliotic curve without significant side effects on the spinal curves in sagittal plane. As this is a case study the outputs of the study should be used with caution.