Axial and para‑axial loading response evaluation on human cadaver‑harvested lumbar vertebral blocks: In vitro experiment with possible clinical implications for clinical practice

The aim of the present study conducted on the lumbar spine was to confirm that the pronounced decrease in resistance in the system is a phenomenon that can be eminently affected by the adaptive changes that occur at the level of the intervertebral disc at axial mechanical stresses. The biomechanical trial was carried out on 11 lumbar segments L1-L5, gathered from adult human cadavers. The dissection considered the complete keeping of all bone, disc, articulated and ligamentous components in their anatomical position. All 11 samples were frozen 24 h prior to the performance of the biomechanical measurement. The specimens were placed in the testing device, their placement being conditioned by the estimated dimensional values. Thus, to calculate the load and axial resistance, the models were placed vertically, central between the test machine ferries. The testing was carried out by applying variable forces and displacement supervision. The displacement interval was represented by a segment of 0-10 mm with surveillance every 2 mm. Mobility in the sagittal plane (flexion earlier in our case) was much higher than that in the frontal plane, obviously limiting mobility via the intervertebral disc and articular complex through the presence of arches. Statistical analysis demonstrated the lack of any correlation values between the two types of movements (R2=0.005507), underlining the absence of any prediction elements. A noteworthy aspect is that the correlations appeared low, statistically insignificant, even within the same movement in the sagittal plane between the two levels, L1-L3 and L3-L5 ([R.sup.2]=0.610427), which may lead to the possibility of the emergence of significant differences in mobility between respective levels. The behavior type of the monitored specimens and the results obtained allowed the mapping of objective parallelism between the values obtained and the behavior in vivo of the lumbar vertebral segment. Key words: lumbar spine, mechanical stresses, vertebral blocks, axial load, eccentric load