Biomechanical testing of a PEEK-based dynamic instrumentation device in a lumbar spine model.
BACKGROUND
The purpose of this study was to investigate the range-of-motion after posterior polyetheretherketone-based rod stabilisation combined with a dynamic silicone hinge in order to compare it with titanium rigid stabilisation.


METHODS
Five human cadaveric lumbar spines with four vertebra each (L2 to L5) were tested in a temperature adjustable spine-testing set-up in four trials: (1) native measurement; (2) kinematics after rigid monosegmental titanium rod instrumentation with anterior intervertebral bracing of the segment L4/5; (3) kinematics after hybrid posterior polyetheretherketone rod instrumentation combined with a silicone hinge within the adjacent level (L3/4) and (4) kinematics after additional decompression with laminectomy of L4 and bilateral resection of the inferior articular processes (L3). During all steps, the specimens were loaded quasi-statically with 1°/s with pure moment up to 7.5Nm in flexion/extension, lateral bending and axial rotation.


RESULTS
In comparison to the native cadaveric spine, both the titanium device and polyetheretherketone-based device reduce the range-of-motion within the level L4/5 significantly (flexion/extension: reduction of 77%, p<0.001; lateral bending: reduction of 62%, p<0.001; axial rotation: reduction of 71%, p<0.001). There was a clear stabilisation effect after hybrid-instrumentation within the level L3/4, especially in flexion/extension (64%, p<0.001) and lateral bending (62%, p<0.001) but without any effect on the axial rotation. Any temperature dependency has not been observed.


CONCLUSIONS
Surprisingly, the hybrid device compensates for laminectomy L4 and destabilising procedure within the level L3/4 in comparison to other implants. Further studies must be performed to show its effectiveness regarding the adjacent segment instability.
Department for Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30, 52074 Aachen, Germany. Electronic address: cherren@ukaachen.de.
Christian
C
Herren
Institute of General Mechanics, RWTH Aachen, Templergraben 64, 52062 Aachen, Germany.
Agnes
A
Beckmann
Department for Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30, 52074 Aachen, Germany.
Sabine
S
Meyer
Department for Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30, 52074 Aachen, Germany.
Miguel
M
Pishnamaz
Institute of General Mechanics, RWTH Aachen, Templergraben 64, 52062 Aachen, Germany.
Marion
M
Mundt
Department of Orthopaedic and Trauma Surgery, Medizinisches Zentrum StädteRegion Aachen GmbH, Mauerfeldchen 25, 52146 Aachen, Germany; Department of Orthopaedic and Trauma Surgery, University of Cologne, Joseph-Stelzmann-Straße 9, 50924 Cologne, Germany.
Rolf
R
Sobottke
Institute of Molecular and Cellular Anatomy, University Hospital RWTH Aachen, Wendlingweg 2, 52070 Aachen, Germany.
Andreas
A
Prescher
Institute of General Mechanics, RWTH Aachen, Templergraben 64, 52062 Aachen, Germany.
Marcus
M
Stoffel
Institute of General Mechanics, RWTH Aachen, Templergraben 64, 52062 Aachen, Germany.
Bernd
B
Markert
Department for Trauma and Reconstructive Surgery, University Hospital RWTH Aachen, Pauwelsstraße 30, 52074 Aachen, Germany.
Philipp
P
Kobbe
Department of Trauma, University Hospital Zurich, Raemistr, 100, 8091 Zurich, Switzerland.
Hans-Christoph
HC
Pape
Department of Orthopaedic and Trauma Surgery, University of Cologne, Joseph-Stelzmann-Straße 9, 50924 Cologne, Germany.
Peer
P
Eysel
Department of Orthopaedic and Trauma Surgery, University of Cologne, Joseph-Stelzmann-Straße 9, 50924 Cologne, Germany.
Jan
J
Siewe
D000368:Aged; D000369:Aged, 80 and over; D001577:Benzophenones; D001696:Biomechanical Phenomena; D002102:Cadaver; D019299:Decompression, Surgical; D005260:Female; D006801:Humans; D007659:Ketones; D007796:Laminectomy; D008159:Lumbar Vertebrae / Q000503:physiopathology* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009984:Orthopedic Fixation Devices; D011092:Polyethylene Glycols; D011108:Polymers; D016059:Range of Motion, Articular / Q000502:physiology*; D012399:Rotation; D013123:Spinal Fusion / Q000295:instrumentation*; D013130:Spinal Stenosis / Q000503:physiopathology* / Q000601:surgery; D014025:Titanium
D001577:Benzophenones; D007659:Ketones; D011108:Polymers; C063834:polyetheretherketone; D011092:Polyethylene Glycols; D014025:Titanium
Biomechanics; Hybrid Instrumentation; PEEK; Temperature dependency; Topping off