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J. Bredow [1; 2] and L. Löhrer [1] and J. Oppermann [2] and M. J. Scheyerer [2] and R. Sobottke [3] and P. Eysel [2] and J. Siewe [2]

Academic Editor: Panagiotis Korovessis

1, Center for Spinal Surgery, Schön Klinik Düsseldorf SE & Co. KG, Am Heerdter Krankenhaus 2, 40549 Düsseldorf, Germany

2, Department of Orthopedic and Trauma Surgery, University Hospital of Cologne, Cologne, Germany, uhc-international.com

3, Department of Orthopedics, Medical Center City Aachen GmBH, Wuerselen, Germany, mz-ac.de

Received Nov 21, 2016; Accepted Jul 4, 2017

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

Fusion surgery is a standard operative treatment for various pathologies of the lumbar spine, with good clinical results [1]. Overall, however, this procedure is still judged otherwise, even in the literature [2]. Conditions related to the fusion lead to postoperative changes in the biomechanics of the spine. Thus, the initially good clinical results after fusion can be mitigated by degeneration of the adjacent segment [3]. The risk of a clinically relevant adjacent segment disease (ASDi) has been estimated at 0.6–3.9% annually [4, 5]. ASDi are emerging degenerative changes at a spinal level adjacent to a surgically treated level or levels in spine, accompanied by related symptoms like instability, radiculopathy, or myelopathy [6]. Adjacent segment degeneration (ASD) represents radiographic changes without the symptomatology [6].

Risk factors include age at time of surgery (>60 years) and preexisting damage of the facet joints or intervertebral discs in the adjacent segment. Also, multiple segment fusions bordering but not including the L5/S1 segment are more frequently associated with adjacent segment instability. Other operation-specific factors are laminectomy adjacent to a fusion as well as sagittal imbalance [4, 5, 7].

Previous innovations developed to counter the risk of adjacent instability include disc replacement, dynamic stabilization, and percutaneous instrumentation [8]. Posterior dynamic stabilization (PDS) is a rapidly growing field of spine surgery. To simplify the discussion of PDS implants, Khoueir et al. classified these into interspinous spacer, pedicle screw-based, and total facet joint replacement systems [9]. The concept includes conservation and restoration of intervertebral motion in a controlled manner, either through restriction of extreme motion...

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