Biomechanical comparison of same size transfacet screws versus pedicle screws across the L5-S1 native disc
Objective: There is resurgence in facet screw use; however, there is a paucity of data comparing the stability of transfacet pedicle screws (TFPS) to standard pedicle screw-rod constructs at L5-S1. The authors aim to compare the stabilizing potential of TFPS compared to pedicle screws of the same length and diameter at L5-S1 with an intact native disc. Methods: Flexibility of human cadaveric lumbar spine segments was biomechanically tested in vitro to provide a comparison of two types of posterior stabilization across L5-S1. Fourteen cadaveric spine specimens (T12-S1) were tested in intact condition, then after, surgical procedures performed at L5-S1 using 5.0 × 40 mm transfacet pedicle screws (Group #1) and same sized pedicle screw-rod construct (Group #2). Specimens were studied using standard non-destructive pure moment flexibility tests. Results: Transfacet pedicle screws (TFPS) allowed less motion in all loading modes than bilateral pedicle screw-rod (BPSR) construct, with a significantly smaller range of motion allowed during extension and axial rotation (p < 0.05). Transfacet pedicle screws allow less lateral bending than BPSR compared to the intact specimen, although the magnitude of the difference was less than during flexion or extension. Conclusion: Bilateral transfacet screws provided better immediate postoperative stability in vitro intact posterior element facets without osteophytes than equivalent-sized unilateral or a bilateral standard pedicle screw at L5-S1. These are limited to a biomechanical application as larger sized pedicle screws are used in the clinical setting. Further biomechanical and clinically relevant studies are warranted to verify these points.
West Indian Medical Journal
Digital Object Identifier (DOI)
Chin, K. R.; Pencle, F. J.R.; Newcomb, A. G.U.; Reis, M. T.; Reyes, P. M.; Malhotra, D.; Yu, W. D.; Bruce, C. A.; and Crawford, N. R., "Biomechanical comparison of same size transfacet screws versus pedicle screws across the L5-S1 native disc" (2017). Neurobiology. 736.