Biomechanical Comparison of a Novel Percutaneous Transfacet Device and a Traditional Posterior System for Single Level Fusion

Abstract

Posterior spinal fusions are indicated for a variety of spinal disorders. Transfacet fixation minimizes soft tissue disruption and preserves the adjacent facet joint. This technique is uncommon due to concerns with biomechanical stability and proper implant placement. For these reasons, a length adjustable implant may obviate the clinical concerns but necessitates biomechanical study. This study evaluated the in vitro biomechanical stability between a novel transfacet fixation device compared with standard pedicle screws during cyclic physiologic loading in a human cadaveric model. Cadaveric L4-L5 lumbar motion segments from 16 human spines were tested in cyclic flexion/extension, lateral bending, and torsion after insertion of either transfacet fixation devices or 5.5 mm pedicle screw instrumentation. A load cell was used to measure the compressive forces on the anterior column during testing. Motion segment stiffness and anterior column compression were analyzed with a 1-way analysis of variance (P<0.05). The transfacet device demonstrated a statistically similar stiffness when compared with the pedicle screw system for each test direction. For anterior column loading during physiologic testing, there were no biomechanical differences between stabilization systems. Percutaneous transfacet fixation is an attractive surgical option for single-level spinal fusions. A biomechanical evaluation of a novel device for this application demonstrated similar stability to a pedicle screw system. The length adjustability of the device may alleviate concerns for precise device placement and the biomechanical stability may produce similar rates and quality of posterior spinal fusions.

Ipsilateral pedicle screw placement with contralateral percutaneous facet screws: Early results with an alternative in lumbar arthrodesis

“…This analysis has shown this confi guration of instrumentation to be equivalent to traditional methods with respect to stiffness, range of motion, and extension. [2][3][4] Ferrera and colleagues reached this same conclusion and observed a decrease in fl exion potential in systems reliant upon transfacet fi xation, a possible benefi t for inter-body arthrodesis. 5 Various authors have assessed similar fusion constructs for bony fusion at 6 to 24 months.…”

Unilateral and Bilateral Sacropelvic Fixation Result in Similar Construct Biomechanics

“…Methods similar to this have been used to report stiffness in the past. 19,20,21 The total range of motion (°) of L6 to S1 rotation was also calculated using the data from the motion capture system. These data were analyzed using a 2-way analysis of variance (P Ͻ 0.05) to test the effects of the independent variables of anterior interbody graft and iliac fixation.…”

Managing Design Excellence Tools During the Development of New Orthopaedic Implants

“…The Viper F2 system was found to be equivalent to the existing Viper 2 system in all ranges of motion (flexion extension, lateral bending, and axial rotation), and analysis details available in separate publications [11][12][13][14][15][16][17][18][19][20]21]. This technique is expensive, requires expertise in tissue testing, and only provides comparative in vitro performance in a model not fully representative of the real clinical environment.…”

“…The new Viper 2 system relies on directly fixing the spine using the vertebral facets via only one screw and washer per side. Simple facet screws have been used several decades ago with mixed clinical success [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Due to the popularity of minimally-invasive-surgery (MIS) in recent years, there is a renewed interest in more sophisticated MIS facet screw systems coupled with washers, expected to provide clinical performance equivalent to pedicle screws and rods, while minimizing operating room time, blood loss, cost and surgical trauma.…”