[Artificial Disc Replacement] Facet Joint Biomechanics at the Treated and Adjacent Levels After Total Disc Replacement

[Justin]

Spine. Volume 36(1), 1 January 2011, p E27–E32

Facet Joint Biomechanics at the Treated and Adjacent Levels After Total Disc Replacement

Botolin, Sergiu MD, PhD*; Puttlitz, Christian PhD†; Baldini, Todd MS*; Petrella, Anthony PhD†; Burger, Evalina MD*; Abjornson, Celeste PhD§; Patel, Vikas MD*. Author Information: *University of Colorado at Denver, Aurora, CO; †Colorado State University, Fort Collins, CO; ‡Colorado School of Mines. Golden, CO; §Synthes Spine, West Chester, PA. © 2011 Lippincott Williams & Wilkins, Inc.

Study Design. Biomechanical study using human cadaveric lumbar spines.

Objective. To evaluate effects of total disc replacement (TDR) on spine biomechanics at the treated and adjacent levels.

Summary of Background Data. Previous studies on spine biomechanics after TDR were focused on facet forces and range of motion and report contradictory results. Characterization of contact pressure, peak contact pressure, force, and peak force before and after TDR may lead to a better understanding of facet joint function and may aid in prediction of long-term outcomes after TDR.

Methods. Seven fresh-frozen human cadaveric lumbar spines were potted at T12 and L5 and installed in a 6 degrees of freedom displacement-controlled testing system. Displacements of 15° flexion/extension, 10° right/left bending, and 10° right/left axial rotation were applied. Contact pressure, peak contact pressure, force, peak force, and contact area for each facet joint were recorded at L2–L3 and L3–L4 both before and after TDR at L3–L4. The data were analyzed with analysis of variance and t tests.

Results. Axial rotation had the most impact on contact pressure, peak contact pressure, force, peak force, and contact area in intact spines. During lateral bending and axial rotation, TDR resulted in a significant increase in facet forces at the level of treatment and a decrease in contact pressure, peak contact pressure, and peak force at the level superior to the TDR. With flexion/extension, there was a decrease in peak contact pressure and peak contact force at the superior level.

Conclusion. Our study demonstrates that rotation is the most demanding motion for the spine. We also found an increase in facet forces at the treated level after TDR. We are the first to show a decrease in several biomechanical parameters after TDR at the adjacent superior level. In general, our findings suggest there is an increase in loading of the facet joints at the level of disc implantation and an overall unloading effect at the level above.

[Gilbert P]

Hi Justin

Thanks for this information

Gil

[ajj1001]

does it say which disc was used in the study?

[Justin]

Hi Justin

Thanks for this information

Gil

No problem!

does it say which disc was used in the study?

"Intra-articular pressure was measured in real time in both left and right facet joints at L3–L4 (Treated), and L2–L3 (Adjacent) level with a Tekscan 6900 Sensor (Tekscan Corp, Boston, MA)."

[Hooch]

That abstract is missing a sentence for some reason.

Contact pressure, peak contact
pressure, force, peak force and contact area for each facet joint were recorded
at L2-L3 and L3-L4 both before and afterTDRat L3-L4 (ProDisc-L, Synthes

Spine). The data were analyzed with ANOVAs and t-tests.

[Justin]

Methods. Seven fresh-frozen human cadaveric lumbar spines were potted at T12 and L5 and installed in a 6 degrees of freedom displacement-controlled testing system. Displacements of 15° flexion/extension, 10° right/left bending, and 10° right/left axial rotation were applied. Contact pressure, peak contact pressure, force, peak force, and contact area for each facet joint were recorded at L2–L3 and L3–L4 both before and after TDR at L3–L4. The data were analyzed with analysis of variance and t tests.

Bolded sentence is from abstract and my post above.

That abstract is missing a sentence for some reason.

Contact pressure, peak contact
pressure, force, peak force and contact area for each facet joint were recorded
at L2-L3 and L3-L4 both before and afterTDRat L3-L4 (ProDisc-L, Synthes
Spine). The data were analyzed with ANOVAs and t-tests.

Chris, your quote as written above is not found in the full-text publication.

[Hooch]

You have the full publication and they do not specify the disc? Unusual.

The quote is from an abstract from the 25th NASS, in a supplement provided by the 10th volume of The Spine Journal.

This later publication in Spine does not detail the disc in the abstract, but credits Synthes Spine, which should provide a bit of a clue.

Chris.

[Justin]

You have the full publication and they do not specify the disc? Unusual.

The quote is from an abstract from the 25th NASS, in a supplement provided by the 10th volume of The Spine Journal.

This later publication in Spine does not detail the disc in the abstract, but credits Synthes Spine, which should provide a bit of a clue.

Chris.

Interesting. The ProDisc is mentioned in the full-text, but not the abstract. I was just confused about your post--I thought I was missing something when I read the abstract. Thanks.