Boston brace correction in idiopathic scoliosis: a biomechanical study.

STUDY DESIGN

To analyze Boston brace biomechanics, pressure measurements and finite element simulations were done on 12 adolescent idiopathic scoliosis patients.

OBJECTIVES

The aim was to analyze the Boston brace effectiveness using a finite element model and experimental measurements.

SUMMARY OF BACKGROUND DATA

There are not very many biomechanical studies of Boston brace effectiveness, and its biomechanical action is not completely understood.

METHODS

This study was performed on 12 girls with scoliosis treated with the Boston brace system. The experimental protocol was composed of the acquisition of two sets of multiplanar radiographs with and without brace followed by the pressure acquisition at the brace-torso interface. A personalized finite element modeling of the trunk was generated from the 3D reconstruction of the patient's geometry. The brace treatment was simulated by the application of equivalent forces calculated from the pressure measurements.

RESULTS

Two Boston brace force patterns were defined from the pressure measurements. The first one consisted of high right thoracic forces of 31-113 N, lumbar forces less than 47 N, and included a left thoracic extension working as a counter pad. The second one consisted of low thoracic forces less than 20 N, lumbar forces up to 70 N, without left thoracic extension. The simulations showed that the passive forces only produced a coronal Cobb angle correction up to 9 degrees, whereas real correction was up to 16 degrees.

CONCLUSION

High thoracic pads reduced more effectively both thoracic and lumbar scoliotic curves than lumbar pads only. The study suggests that mechanisms other than brace pads produce correction and contribute to the force equilibrium within the brace.