Influence of thread design on pedicle screw fixation. Laboratory investigation.

Object: The authors conducted a study to determine the thread properties that provide optimal screw fixation in cancellous bone, when screws of the same external screw diameter are used.

Methods: Three compliance engineering-certified screws in clinical use, all of the same external diameter and length, were compared in an axial pullout experiment with respect to advantageous thread properties. As test material, standardized Sawbone blocks with 3 different densities (0.