Four-point bending as a method for quantitatively evaluating spinal arthrodesis in a rat model.
The most common method of evaluating the success (or failure) of rat spinal fusion procedures is manual palpation testing. Whereas manual palpation provides only a subjective binary answer (fused or not fused) regarding the success of a fusion surgery, mechanical testing can provide more quantitative data by assessing variations in strength among treatment groups. We here describe a mechanical testing method to quantitatively assess single-level spinal fusion in a rat model, to improve on the binary and subjective nature of manual palpation as an end point for fusion-related studies. We tested explanted lumbar segments from Sprague-Dawley rat spines after single-level posterolateral fusion procedures at L4-L5. Segments were classified as 'not fused,' 'restricted motion,' or 'fused' by using manual palpation testing. After thorough dissection and potting of the spine, 4-point bending in flexion then was applied to the L4-L5 motion segment, and stiffness was measured as the slope of the moment-displacement curve. Results demonstrated statistically significant differences in stiffness among all groups, which were consistent with preliminary grading according to manual palpation. In addition, the 4-point bending results provided quantitative information regarding the quality of the bony union formed and therefore enabled the comparison of fused specimens. Our results demonstrate that 4-point bending is a simple, reliable, and effective way to describe and compare results among rat spines after fusion surgery.
Biomechanics Laboratory, Spine Center, Department of Surgery, Cedars Sinai Medical Center, Los Angeles, California, USA.
Samuel T
ST
Robinson
Biomechanics Laboratory, Cedars Sinai Medical Center, Los Angeles, California, USA.
Mark T
MT
Svet
Spine Tissue Engineering Laboratory, Spine Center, Department of Surgery, Cedars Sinai Medical Center, Los Angeles, California, USA.
Linda A
LA
Kanim
Biomechanics Laboratory, Spine Center, Department of Surgery, Cedars Sinai Medical Center, Los Angeles, California, USA. Melodie.Metzger@cshs.org.
Melodie F
MF
Metzger
D000818:Animals; D001696:Biomechanical Phenomena; D008159:Lumbar Vertebrae / Q000601:surgery*; D018583:Pliability; D016059:Range of Motion, Articular / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013123:Spinal Fusion / Q000379:methods* / Q000592:standards*; D016896:Treatment Outcome