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Biomechanical testing of anterior and posterior thoracolumbar instrumentation in the cadaveric spine

Invited submission from the Joint Section Meeting on Disorders of the Spine and Peripheral Nerves, March 2004

Kurt M. Eichholz, Patrick W. Hitchon, Aaron From, Paige Rubenbauer, Satoshi Nakamura, Tae Hong Lim and James Torner

of posterior implants. The spines were irrigated with normal saline (0.9% NaCl) throughout the experiments to prevent the specimens from drying out. Three retroreflective markers were placed strategically on each vertebra: one on each transverse process and one on the spinous process. The intact spine was then mounted on a biomechanical testing frame. 15 The angular rotation at L2–4 was measured using the Motion Analysis Neuroscience Real Time 3D System (Motion Analysis Corp., Santa Rosa, CA), which uses three high-resolution digital video cameras to determine

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Denis J. DiAngelo and Kevin T. Foley

Object

An experimental study was performed to determine the biomechanical end-mounting configurations that replicate in vivo physiological motion of the cervical spine in a multiple-level human cadaveric model. The vertebral motion response for the modified testing protocol was compared to in vivo motion data and traditional pure-moment testing methods.

Methods

Biomechanical tests were performed on fresh human cadaveric cervical spines (C2–T1) mounted in a programmable testing apparatus. Three different end-mounting conditions were studied: pinned–pinned, pinned–fixed, and translational/pinned–fixed. The motion response of the individual segmental vertebral rotations was statistically compared using one-way analysis of variance and Student-Newman-Keuls tests (p < 0.05 unless otherwise stated) to determine differences in the motion responses for different testing methods.

Conclusions

A translational/pinned–fixed mounting configuration induced a bending-moment distribution across the cervical spine, resulting in a motion response that closely matched the in vivo case. In contrast, application of pure-moment loading did not reproduce the physiological response and is less suitable for studying disc arthroplasty and nonfusion devices.

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Gabriel C. Tender, Scott Kutz, Richard Baratta and Rand M. Voorhies

. Spine 20: 421–430, 1995 14. Kip PC , Esses SI , Doherty BI , Alexander JW , Crawford MJ : Biomechanical testing of pars defect repairs. Spine 19 : 2692 – 2697 , 1994 Kip PC, Esses SI, Doherty BI, Alexander JW, Crawford MJ: Biomechanical testing of pars defect repairs. Spine 19: 2692–2697, 1994 15. McFadden KD , Taylor JR : Axial rotation in the lumbar spine and gaping of the zygapophyseal joints. Spine 15 : 295 – 299 , 1990 McFadden KD, Taylor JR: Axial rotation in

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Seoung Woo Park, T. Jesse Lim and Jon Park

, and biomechanical testing was repeated. Biomechanical Testing The specimens were tested in 6 different modes of motion: flexion, extension, right and left lateral bending, and right and left axial rotation ( Fig. 2A–D ). For each mode of motion, a moment up to 8.0 Nm was used with a rate of 0.5 Nm/second. In addition, during each mode of loading, a constant compression follower preload of 400N was applied through 2 loading cables passing through the center of rotation in the sagittal plane on both the left and right sides of the spine. To minimize the

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Nader S. Dahdaleh, Satoshi Nakamura, James C. Torner, Tae-Hong Lim and Patrick W. Hitchon

put into the freezer again until 8 hours prior to the motion analysis testing, when they were placed at room temperature for thawing. Motion Analysis Three noncolinear retroreflective markers were secured to the transverse and spinous processes of C-3 and C-7. Specimens were mounted on a biomechanical testing frame. Angular rotation of C-3 relative to C-7 was measured using the Real-Time 3D Motion Analysis System ( Fig. 1 ) (Motion Analysis Corp.), which uses 3 high-resolution analog video cameras. 6 , 12 , 13 Three video cameras track the coordinates of the

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Roger Härtl, Robert H. Chamberlain, Mary S. Fifield, Dean Chou, Volker K. H. Sonntag and Neil R. Crawford

testing apparatus. Biomechanical Testing Nonconstraining, nondestructive pure moment loading was applied to each specimen through a system of cables and pulleys in conjunction with a standard servohydraulic test system (MTS, Minneapolis, MN), as described previously. 1 Loads were applied about the appropriate anatomical axes to induce six different motions: flexion, extension, left lateral bending, right lateral bending, left axial rotation, and right axial rotation. Before data were recorded in any of the loading tests, specimens were preconditioned three times

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Prashant Chittiboina, Esther Wylen, Alan Ogden, Debi P. Mukherjee, Prasad Vannemreddy and Anil Nanda

dorsocaudal part is formed by the posterior element of the axis and C-3. Transfixation of C1–2 did not alter the relationship of the ventrocranial and dorsocaudal parts (see Fig. 7 ). Another unrelated but somewhat more important reason for C1–2 transfixation was to isolate the C2–3 level for biomechanical testing. The transfixation was performed between C-1 and the anterior fracture fragment of C-2 and did not affect the stability at the C2–3 disc space. Aluminum rods 9.6 mm in diameter were cut to custom length and attached to the C-1 facets by using Bondo. To allow the

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Philipp Schleicher, Paavo Beth, Andreas Ottenbacher, Robert Pflugmacher, Matti Scholz, Klaus John Schnake, Norbert P. Haas and Frank Kandziora

intact. After removing disc material, preparation of the endplates was performed with curved curettes and rasps. Finally, the TLIF spacer was inserted using a curved implant holder, according to the manufacturer's surgical technique. Biomechanical Testing Eight cadaveric lumbar spine specimens were harvested. The average donor age (3 female, 5 male) was 67.25 ± 7.91 years (range 55–80 years). The medical history was checked to exclude traumatic, neoplastic, or metabolic disorders of the spine. Every specimen was evaluated radiographically to exclude significant

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Sung-Min Kim, T. Jesse Lim, Josemaria Paterno and Daniel H. Kim

) were used. Materials and Methods Cadaveric Specimen Preparation Twenty-four human cadaveric lumbosacral spines (L2—S1) were obtained from Science Care Anatomical (Phoenix, AZ). The mean age of the seven male and nine female donors was 71 ± 10 years (± SD) with a range between 54 and 90 years. Anteroposterior and lateral radiographs of the specimens were obtained to exclude bone abnormalities, and BMD measurements were made using dual-energy x-ray absorptiometry (DEXA, Hologic QDR 4500A; Hologic, Inc., Waltham, MA). En bloc specimens for biomechanical testing

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Lisa A. Ferrara, Illya Gordon, Madeline Coquillette, Ryan Milks, Aaron J. Fleischman, Shuvo Roy, Vijay K. Goel and Edward C. Benzel

each measurement parameter * Measurements Condition Description Condition No. Group Name Pressure (MPa) † Load (N) ‡ intact disc 1 Disc no no bone graft only 2 Graft yes no bone graft w/ ventral plate 3 Plate yes yes graft, plate, & PMMA added to graft site 4 PMMA yes yes removal of plate 5 Removal yes no * Pressures at the bone graft–endplate mortise interfaces and loads along a ventral cervical plate were measured during biomechanical testing of each cervical