The Development and Biomechanical Study of Novel Crosslink Device for Spinal Fusion- an Experimental Study in Porcine Model

This study aims to develop a novel crosslink device that can accommodate a variety of geometrical orientations of longitudinal spinal rods for multilevel spinal fusion. Biomechanical evaluation of short (functional segment unit) and long segment (six-level) posterior pedicle screw fixation constructs with and without the novel crosslink will be performed using porcine spines. Stiffness of the constructs will be compared Pedicle screw instrumentation has been widely used for stabilization of multiple-level spinal fusions. Due to a wide variety of factors, the paired longitudinal spinal rods are rarely geometrically aligned. Generally, the two rods have some convergence or divergence in the medial-lateral direction, and have not the same orientation with respect to the coronal plane. To solve these problems, surgeons need to bend the rods to accommodate a crosslink or bend the crosslink device to accommodate the rods, which makes the operation more difficult and enormously increases the operation time. Consequently, a novel crosslink accommodating a variety of geometrical orientations of the paired longitudinal rods is desired. This study is thus to develop a novel crosslink device that can be adjusted in universal angle and translation to accommodate the longitudinal spinal paired rods. Many clinical and biomechanical studies have been performed on pedicle screw instrumentation and their effects on the postoperative spinal constructs. Improved fusion rates have been demonstrated with increasingly rigid pedicle screw fixation. Although sagittal plane stiffness is significant improved with these devices, they are susceptible to instability under lateral bending and torsional loading condition. Generally, the torsion stiffness of bilateral rod constructs is augmented with the use of crosslink devices, and the crosslink configurations are commonly found include crosslink devices that directly connect the fixation rods at either one or two levels. Although the crosslink mechanisms provide increased resistance to both lateral bending and torsion loading, it remains controversial as to which crosslink configuration achieves the most stable construct. The relative mechanical benefit of different crosslink configurations is not known. Biomechanical performance of two-level and six-level posterior pedicle screw fixation constructs with and without the novel crosslink will be investigated. For two-level pedicle screw fixation construct, the effect of the presence of crosslink on pedicle screw fixation strength and construct stiffness will be evaluated in two ways: (1) screw pullout to failure (pullout force applied on 4 different directions; and (2) pure moment tests (flexion/extension, lateral bending and axial rotation). For six-level pedicle screw fixation constructs, spinal constructs of five different crosslink configurations (crosslink number and crosslink position) will be tested to measure the construct stiffness in flexion, extension, lateral bending and axial rotation. Construct stiffness for each loading mode will be compared among groups.

Project ID:PB10607-1404
External Project ID:MOST106-2221-E182-018