Pre-Operative Assessment of Fusion-Related Bone Failure

Of the overpatients undergoing instrumented spinal fusion surgery each year in the United Statesoverultimately require a revision surgerythe majority of which are secondary to insufficient bone qualityBiomechanical problems associated with insufficient bone quality include pseudarthrosisinsufficiency fractures of the proximal adjacent vertebrasubsidence of any intervertebral implant graft constructand loosening of an implanted pedicle screwNo objective clinical test is currently available for surgeons to reliably identify a patientandapos s risk of these adverse outcomesA bone mineral density test is not enoughas andquot normalandquotbone may still have insufficient quality for high stresses near the implantThe overall goal of this Phase II SBIR project is to clinically validate our virtual stress testVSTtechnology for pre operatively identifying spinal fusion patients who are at high risk of a failed surgeryVST utilizes the CT scan already acquired for the patient s pre operative assessment to construct a virtualthree dimensional model of the fusion construct in order to investigate its mechanical response to loadingOur proposed pre operative spinal fusion evaluationbased on VSThas three elementsaPerform VST to assess pedicle screw looseningendplate subsidenceand vertebral failureall specificto the patient s vertebrae and spinal fusion surgical planFrom that informationidentify patients at highrisk of a failed fusion surgery due to insufficient bone qualitybFor each vertebral levelspecify optimal screw sizing and placement for each pedicleand measurebone mineral densityBMDand vertebral strengthcProvide a comprehensive assessment of risk of a future vertebral fracture due to osteoporosisHaving developed the VST technology in our Phase I studythis Phase II study seeks to validate its use in the largest ever biomechanics study of spinal fusion patientsThis case cohort study will includewomen and men who underwent spinal fusion surgery at Kaiser Permanente Southern California fromhave a pre surgical CT scan and at leastdays of follow upCasesnwill be patients with an adverse surgical outcome that required re operation after the index procedureHalf of this cohort will be used to optimize the virtual stress tests for pedicle screw looseningendplate subsidenceand vertebral failureUsing the remainder of the cohortVST will be performed blinded to surgical outcomes in order to test the hypothesis that VST predicts failed surgeryindependent of BMD and other clinical risk factorsIf successfulthis study would result in a biomechanics based clinical tool for pre operatively evaluating a patientandapos s risk of spinal fusion failure due to insufficient bone qualityGiven the options that now exist for addressing such issuessuch as use of anabolic bone forming agents or prophylactic bone cement injectionsuch a tool could lead to a reduction in adverse surgical outcomes and thus fewer re operations and revisions Statement of Relevance Of the overpatients undergoing instrumented spine fusion surgery each year in the United Statesoverultimately require a revision surgeryThis project will produce a biomechanics based tool to identify pre operatively patients at risk of spine fusion failure secondary to insufficient bone qualityGiven the options that now exist for addressing such issuessuch as use of anabolic bone forming agents or prophylactic bone cement injectionsuch a tool could lead to a reduction in adverse surgical outcomes and thus fewer reoperations and revisions