Vol. 10, Issue 4 (2024)

Background: There have been many studies that have analyzed the diagnostic validity of SLRT and Bragard test so far. However, few studies have analysed the strain of lumber nerve root in vivo. 
Objective: We aimed to elucidate the strain rate of the L5 and S1 nerve roots in Thiel-embalmed specimens using the SLRT and Bragard tests in hip flexion of 0°, 30°, 60°, and 90° to confirm in vivo scientific validation.
Materials and Methods: Four Thiel-embedded specimens were used. The strain rate data of the nerve root were obtained using a displacement sensor under the following conditions: hip joint flexed to 0°/30°/60°/90° with knee flexion of 0° (SLRT) and hip joint flexed to 0°, 30°, 60°, and 90° in conjunction with knee extension/flexion of 0° and 20° of ankle dorsiflexion (Bragard test). 
Results: Both the L5 and S1 nerve roots had significantly greater strain at 60° and 90° of hip flexion than at 0° and 30° of hip flexion. both the L5 and S1 nerve roots had significantly greater strain at 30°, 60°, and 90° of hip flexion than at 0° of hip flexion. No significant differences were found for 30°, 60°, and 90° of hip flexion. The straining ratio of the SLRT to Bragard test in both the L5 and S1 nerve roots was greatest at 30° of hip flexion.
Conclusion: We were able to confirm the in vivo scientific validation of the increasing hip flexion angle during the SLRT. The results of this study also suggested that reducing the hip flexion angle to 30° and dorsiflexing the ankle joint may increase the efficacy of the Bragard test with the straining ratio or the SLRT to Bragard test in patients with positive SLRT.