Cross-links in posterior pedicle screw-rod instrumentation of the spine: a systematic review on mechanical, biomechanica
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REVIEW ARTICLE
Cross‑links in posterior pedicle screw‑rod instrumentation of the spine: a systematic review on mechanical, biomechanical, numerical and clinical studies Frédéric Cornaz1,2 · Jonas Widmer1,2 · Jess Gerrit Snedeker1,2 · José Miguel Spirig1 · Mazda Farshad1 Received: 13 May 2020 / Revised: 13 May 2020 / Accepted: 5 September 2020 © The Author(s) 2020
Abstract Purpose Dorsal screw-rod instrumentations are used for a variety of spinal disorders. Cross-links (CL) can be added to such constructs, however, no clear recommendations exist. This study aims to provide an overview of the available evidence on the effectiveness of CL, potentially allowing to formulate recommendations on their use. Methods A systematic literature review was performed on PubMed and 37 original articles were included and grouped into mechanical, biomechanical, finite element and clinical studies. The change in range of motion (ROM) was analyzed in mechanical and biomechanical studies, ROM, stiffness and stress distribution were evaluated in finite element studies and clinical outcome parameters were analyzed in clinical studies. Results A relative consistent reduction in ROM in axial rotation with CL-augmentation was reported, while minor and less consistent effects were observed in flexion–extension and lateral bending. The use of CLs was clinical beneficial in C1/2 fusion, while the limited clinical studies on other anatomic regions show no significant benefit for CL-augmentation. Conclusion While CL provides some additional axial rotation stability in most situations, lateral bending and flexion–extension are less affected. Based on clinical data, CL-augmentation can only be recommended for C1/2 instrumentations, while for other cases, further clinical studies are needed to allow for evidence-based recommendations. Keyword Cross-link · Transfixation · Transverse connector · Dorsal instrumentation · Spine · Systematic review Abbreviations AR Axial rotation CL Cross-link dS-S CL Diagonal screw-screw cross-links FE Flexion–extension hR-R CL Horizontal rod-rod cross-links hS-S CL Horizontal screw-screw cross-links LB Lateral bending ROM Range of motion
Frédéric Cornaz, Jonas Widmer these authors contributed equally. * Frédéric Cornaz [email protected] 1
Department of Orthopaedics, Balgrist University Hospital, University of Zurich, Zurich, Switzerland
Institute for Biomechanics, Balgrist Campus, ETH Zurich, Lengghalde 5, CH‑8008 Zurich, Switzerland
2
Introduction Dorsal instrumentation is an effective tool in the surgical treatment of various spinal disorders. It is generally based on a screw-rod construct composed of pedicle or lateral mass screws combined with vertically oriented connecting rods. It has been shown that the rigidity of instrumentations correlates with fusion rate [1] and consequently, high rigidity in all loading directions is aspired. A large plethora of implants like plates, hooks, cerclages, cross-links and interbody devices were developed to be added to a dorsal screwrod con
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