Assessing mechanical integrity of spinal fusion by in situ endochondral osteoinduction in the murine model.
BACKGROUND
Historically, radiographs, micro-computed tomography (micro-CT) exams, palpation and histology have been used to assess fusions in a mouse spine. The objective of this study was to develop a faster, cheaper, reproducible test to directly quantify the mechanical integrity of spinal fusions in mice.


METHODS
Fusions were induced in ten mice spine using a previously described technique of in situ endochondral ossification, harvested with soft tissue, and cast in radiolucent alginate material for handling. Using a validated software package and a customized mechanical apparatus that flexed and extended the spinal column, the amount of intervertebral motion between adjacent vertebral discs was determined with static flexed and extended lateral spine radiographs. Micro-CT images of the same were also blindly reviewed for fusion.


RESULTS
Mean intervertebral motion between control, non-fused, spinal vertebral discs was 6.1 +/- 0.2 degrees during spine flexion/extension. In fusion samples, adjacent vertebrae with less than 3.5 degrees intervertebral motion had fusions documented by micro-CT inspection.


CONCLUSIONS
Measuring the amount of intervertebral rotation between vertebrae during spine flexion/extension is a relatively simple, cheap (<$100), clinically relevant, and fast test for assessing the mechanical success of spinal fusion in mice that compared favorably to the standard, micro-CT.
Dewan
Ashvin K
AK
Spine Research Lab, Baylor College of Medicine, Houston, TX USA. ashvin_dewan@yahoo.com.
Dewan
Rahul A
RA
Calderon
Nathan
N
Fuentes
Angie
A
Lazard
Zawaunyka
Z
Davis
Alan R
AR
Heggeness
Michael
M
Hipp
John A
JA
Olmsted-Davis
Elizabeth A
EA