Biomechanical Study of Lumbar Spinal Arthroplasty with a Semi-Constrained Artificial Disc (Activ L) in the Human Cadaveric Spine

Department of Neurosurgery, Korea University Medical Center, Seoul, Korea.
Journal of Korean Neurosurgical Society (Impact Factor: 0.64). 04/2009; 45(3):169-75. DOI: 10.3340/jkns.2009.45.3.169
Source: PubMed


The goal of this study was to evaluate the biomechanical features of human cadaveric spines implanted with the Activ L prosthesis.
Five cadaveric human lumbosacral spines (L2-S2) were tested for different motion modes, i.e. extension and flexion, right and left lateral bending and rotation. Baseline measurements of the range of motion (ROM), disc pressure (DP), and facet strain (FS) were performed in six modes of motion by applying loads up to 8 Nm, with a loading rate of 0.3 Nm/second. A constant 400 N axial follower preload was applied throughout the loading. After the Activ L was implanted at the L4-L5 disc space, measurements were repeated in the same manner.
The Activ L arthroplasty showed statistically significant decrease of ROM during rotation, increase of ROM during flexion and lateral bending at the operative segment and increase of ROM at the inferior segment during flexion. The DP of the superior disc of the operative site was comparable to those of intact spine and the DP of the inferior disc decreased in all motion modes, but these were not statistically significant. For FS, statistically significant decrease was detected at the operative facet during flexion and at the inferior facet during rotation.
In vitro physiologic preload setting, the Activ L arthroplasty showed less restoration of ROM at the operative and adjacent levels as compared with intact spine. However, results of this study revealed that there are several possible theoretical useful results to reduce the incidence of adjacent segment disease.

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    • "The current design of non-constrained artificial discs (NADs) may be improved by constructing semi-constrained disc prostheses, wherein a fiber structure is added to simulate the fiber-connecting properties of the physiological disc and to constrain its activity. This modification may decrease the stress on the zygapophysial joints and improve the clinical therapeutic effects of lumbar disc replacement (5). The present study investigated a newly designed semi-constrained integrated artificial disc (SIAD; Weigao Orthopaedic Device Co., Ltd., Weihai, China) with a titanium plate in its framework, polyethylene glycol terephthalate elastic ligaments that simulate the annulus fibrosus of the physiological discs and a polyetheretherketone (PEEK) core that simulates the nucleus pulposus. "
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    • "Ha et al. [62] conducted a study on five L2-S2 spines in which range of motion, facet strains and intradiscal pressures were monitored. A 400 N compressive load and 8 Nm moments in all three planes were applied to compare the intact, postimplantation of Semiconstrained Activ-L device at L4-L5 level. "
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