Conventional versus minimally-invasive cervical discectomy for treatment of severe degenerative disease at C5-C6: a biomechanical comparison using a model of the full cervical spine and finite element analysis

Abstract

The purpose of this study was to determine the dif-ferences in biomechanical responses of tissues in the cervical spine when pain and other problems secon-dary to severe disc degeneration disease are surgi-cally treated by conventional discectomy (CONDIS) compared to minimally-invasive discectomy (MIVDIS). A validated three-dimensional model of an intact, healthy, adult full cervical spine (C1-C7) (INT) was constructed. This model was then modified to create two models, one simulating each of the above-men-tioned two techniques for discectomy of the severely degenerated C5-C6 disc. For each of these three models, we used the finite element analysis method to obtain three biomechanical parameters at various tissues in the model, under seven different physio-logically relevant loadings. For each of the biome-chanical parameters, the results were expressed as relative change in its value when a specified combi-nation of simulated discectomy model and applied loading was used, with respect to the corresponding value in the intact model. We then computed the value of a composite biomechanical performance in-dex (CBPI) for CONDIS and MIVDIS models, with this value incorporating all of the aforementioned relative changes. We found that CBPI was marginally lower for MIVDIS model. This trend is the same as that reported for the relative complications rate and outcome measures following conventional and mini-mally-invasive discectomies in the lumbar spine. From a healthcare perspective, one implication of our finding is that minimally-invasive cervical discectomy should be considered an attractive option provided that detailed patient selection criteria are clearly de-fined and strictly followed.