Preventing cortical breaches with impact analysis during spinal instrumentation surgery

Abstract

Patient integrity and implant primary stability can be jeopardized when cortical breaches caused by either the pedicle finder (PF) or the implant occur during pedicle screw placement. The aim of this study was to evaluate the potential of impact analysis performed on the PF and on the surgical screwdriver (SS) as a method to detect bone perforations during spinal instrumentation surgery. An indicator was derived from the temporal variation of the impact force signal recorded by an instrumented hammer (IH) impacting the surgical instruments. This indicator depends on the impacted system rigidity. Its sensitivity to the perforation of the interface between trabecular and cortical bone mimicking phantoms has been investigated. Five typical variations of the indicator were identified. A reproducibility analysis performed on all perforations showed that the PF impulse behavior is sensitive to insertion depth, cortical bone entry and cortical bone fracture and the SS impulse behavior could assess optimal screw anchorage.