62. Impaction grafting of the pedicle: a biomechanical analysis

Abstract

BACKGROUND CONTEXT Current options for revising screw failure includes larger diameter revisions and/or injecting cement into the vertebral body for secondary screw fixation. An alternative revision method is impaction grafting (pedicoplasty) of the failed pedicle screw track. This technique utilizes impaction of allograft bone into the pedicle and vertebral body through a series of funnels in an attempt to reconstitute a new pedicle. PURPOSE Evaluate the feasibility of a new revision technique (pedicoplasty) compared to conventional clinical options. STUDY DESIGN/SETTING In vitro biomechanical pullout testing. METHODS Investigators utilized 10 vertebral bodies (L1–L5) free of metastatic disease or primary bone disease. Following primary screw insertion, each screw was subjected to a pullout force that was applied axially along the screw trajectory at 5 mm per minute until failure. Each specimen was instrumented with a pedicoplasty (P) revision utilizing the original screw size and on the contralateral side either a fenestrated screw with cement augmentation (CA) or a screw upsized by 1 mm (UP) in a semi-randomized fashion; these revisions were then pulled out using the previously mentioned methods. RESULTS There were no significant differences in initial pullout values between all groups (p 0.05). Primary pullout values for the paired CA and P were 396 ±227N and 308 ±114N, respectively (n=5). Revised pullout values for the paired CA and P were 960 ±227N and 598 ±114N, respectively (p CONCLUSIONS This biomechanical investigation demonstrated no significant differences between pedicoplasty and upsized revision screws. There was significantly higher pullout strength for cement augmented revisions compared to both pedicoplasty and upsized revisions. Consideration should be given to this novel pedicoplasty technique when maintenance of pedicle dimensions is required or further screw diameter increases are not possible. FDA DEVICE/DRUG STATUS Pedicle Screws (Approved for this indication), Bone Cement (Approved for this indication).