The effect of hydroxyapatite on titanium pedicle screw resistance: an electrical model.

Background Context: Intraoperative detection of a pedicle wall breach implicitly reduces surgical risk, but the reliability of intraoperative neuromonitoring has been contested. Hydroxyapatite (HA) has been promulgated to increase pedicle screw resistance and negatively influence the accuracy of electromyography.

Purpose: The primary purpose of this experiment is to evaluate the effect of HA on pedicle screw electrical resistance using a controlled laboratory model.

Pedicle morphometry in the upper thoracic spine: limits to safe screw placement in older patients.

Study Design: An anatomic study of pedicle dimensions and orientation was performed for upper thoracic vertebrae from elderly human subjects.

Objectives: To quantify dimensions of thoracic pedicles, and to determine the potential for safe transpedicular screw fixation in the upper thoracic spine.

Summary Of Background Data: Clinical and anatomic reports support thoracic pedicle fixation as a safe, effective alternative to hook fixation in both normal and osteoporotic bone.