The purpose of this study was to compare the cross-sectional area of the sciatic nerve in different positions of spinal manipulation using flexion-distraction technique.

Thirty healthy participants were assessed in 6 different flexion-distraction technique positions of varying lumbar, knee, and ankle positions. Participants stood in the following 3 positions with the lumbar in the neutral position: (A) with knee extended, (B) with knee flexed, and (C) with the knee extended and ankle dorsiflexion. Participants then stood in the following 3 positions with the lumbar flexed: (D) with the knee extended, (E) with the knee flexed, and (F) with knee extended and ankle dorsiflexion. The cross-sectional area (CSA) of the sciatic nerve was measured with ultrasound imaging in transverse sections in the posterior medial region of the left thigh. The CSA values measured at each position were compared.

We analyzed 180 ultrasound images. The cross-sectional area of the sciatic nerve (in mm²) in position B (mean; standard deviation) (59.71-17.41) presented a higher mean cross-sectional area value compared with position D (51.18-13.81; P =.005), position F (48.71-15.16; P = .004), and position C (48.37-16.35; P = .009).

The combination of knee extension and ankle dorsiflexion reduced the CSA of the sciatic nerve, and flexing the knee and keeping the ankle in the neutral position increased it.