Biomechanical study of lumbar spinal arthroplasty with a semi-constrained artificial disc (activ L) in the human cadaveric spine.
OBJECTIVE
The goal of this study was to evaluate the biomechanical features of human cadaveric spines implanted with the Activ L prosthesis.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Department of Neurosurgery, Korea University Medical Center, Seoul, Korea.
Sung-Kon
SK
Ha
Se-Hoon
SH
Kim
Daniel H
DH
Kim
Jung-Yul
JY
Park
Dong-Jun
DJ
Lim
Sang-Kook
SK
Lee