Fig. 1

Experimental steps chronologically from A to H: (A) Preparation of single vertebral body; (B) Embedding of caudal side of vertebral body; (C) Pre-drilling with 2.5 mm; (D) Image of instrumented screwdriver used to implant the pedicle screws and measure insertion torque; (E) Implantation of the pedicle screws starting with left pedicle; (F) Example for X-ray control; (G) Embedding of the cranial side of vertebral body leaving enough space for subsequent biomechanical testing; (H) Distraction test in materials testing machine simulating distraction in cranio-caudal direction during surgery