The influence of pedicle screw placement on thoracic trabecular strain.

STUDY

DESIGN

Experimental study.

INTRODUCTION

Although pedicle screw loosening and fracture are not uncommon, there is little understanding of the loading relationship between the pedicle screw and surrounding bone. There is even less understanding of the trabecular bone mechanics one a pedicle screw has been removed.

OBJECTIVES

To investigate and understand the influence of the presence of pedicle screw placement and subsequent removal on vertebral trabecular strain under axial loading.

SETTING

Orthopaedic Research Laboratories, University of California, Davis, USA.

METHODS

Six cadaver spines were biomechanically loaded and the minimum principal and maximum shear strains were measured using texture correlation. The treatments were divided into three conditions as follows: (1) before screw placement, (2) during screw placement, and (3) after screw removal. The obtained data were statistically analyzed.

RESULTS

Trabecular strain adjacent to the pedicle screw was increased following pedicle screw placement and remained high following pedicle screw removal.

CONCLUSIONS

The current study demonstrates that pedicle screw placement greatly influences the trabecular bone and introduces weakness in the area following screw removal.