The researchers subjected the cadavers’ spines to 20º of flexion and 15º of extension, then measured intradiscal pressures, along with segmental motion, at the intact C4-C5 and C6-C7 vertebrae of their specimens respectively. Subsequently, they measured these variables on the C5-C6 vertebrae following anterior cervical plating. By performing a paired measures t-test on their measurements of changes in intradiscal pressure and segmental motion, the authors arrived at their results.
The research findings demonstrated that intradiscal pressures (the dependent variable) increased considerably during the flexion (the independent variable) imposed upon them. Pressures at the C4-C5 vertebrae increased by roughly 73.2% during the course of this flexion, and at the C4-C5, an increase in pressure of approximately 45.3% was observed. Although intradiscal pressures at adjacent levels increased during pressure, this effect failed to reach significance. Both during extension and flexion, the researchers’ measurements of segmental motion during flexion increased at these adjacent levels. Based on these results, the authors cite substantial intensification of intradiscal pressure and segmental motion at levels adjacent to fusion as primary causes of early disc degeneration and pathology. In part, these measured effects account for one mechanism of early disc degeneration at levels adjacent to cervical spine fusion, which is in line with the author’s hypothesis.
Issues relating to a criticism of Eck et al. (2002) fall generally between two categories: (a) potential confounding variables in the design of the experiment, and (b) methodological limitations that may prevent more accurate results. One potential confound in the experiment is the possibility of inconsistency between the cadaver specimens. In the Materials and Methods section, no mention is made of how the cervical spines of these