Pedicle screw‐based posterior dynamic stabilizers for degenerative spine: In vitro biomechanical testing and clinical outcomes

Abstract

Dynamic stabilization in a degenerate symptomatic spine may be advantageous compared with conventional fusion procedures, as it helps preserve motion and minimizes redistribution of loads at instrumented and adjacent segments. This article presents a systematic review of biomechanical and clinical evidence available on some of the pedicle screw based posterior dynamic stabilization (PDS) devices. Using Medline, Embase, and Scopus online databases, we identified four pedicle-screw-PDS devices for which both, biomechanical testing and clinical follow-up data are available: Graf artificial ligaments, Isobar TTL, Polyetheretherketone rods, and Dynesys. The current state-of-the-art of pedicle-screw-PDS devices is far from achieving its desired biomechanical efficacy, which has resulted in a weak support for the posited clinical benefits. Although pedicle-screw-PDS devices are useful in salvaging a moderately degenerate functionally suboptimal disc, for severe disc degeneration cases fusion is still the preferred choice. We conclude that a pedicle-screw-PDS device should aim at restoring load sharing amongst spinal elements while preserving the qualitative and quantitative nature of spinal motion, especially minimize posterior shift of the helical axis of motion. More precise and objective assessment techniques need to be standardized for in vivo evaluation of intervertebral motion and load sharing amongst spinal elements across different pedicle-screw-PDS devices.

Dual pitch titanium-coated pedicle screws improve initial and early fixation in a polyetheretherketone rod semi-rigid fixation system in sheep

“…These systems are designed to maintain physiological intervertebral motion, stabilize abnormal segments, remove stress from lumbar discs, decrease interface stress of implants, improve load-sharing, and sustain segmental balance. [3]…”

Non-fusion procedure using PEEK rod systems for lumbar degenerative diseases: clinical experience with a 2-year follow-up

“…To eliminate or minimize these adverse outcomes, less rigid constructs have recently been introduced for the treatment of lumbar degenerative diseases [ 5 , 6 ]. These systems are defined as dynamic or semi-rigid stabilization systems.…”

“…A similar biomechanical effect between PEEK rod systems and Dynesys was reported earlier [ 5 ]. To the best of our knowledge, Dynesys is designed to stabilize the treated segment without fusion [ 6 , 17 ]. Therefore, theoretically PEEK rod systems might also be effective if used in non-fusion operations.…”

Numerical analysis of spinal stabiliser in spondylolisthesis treatment with pedicle screws

“…The way of treating is decided by a doctor based on a patient observation, rating of radiographic examination and an advancement of a disease. The aim of treatment is to get a spinal stability and protect from neurobiological disorders [3,[13][14][15] One of the general methods is setting special constructions of stabilisers -pedicle screws ( fig. 4).…”