ABSTRACT
PURPOSE: The biomechanical responses of degenerative porcine intervertebral disc were compared with those MATERIALS AND METHODS: Two groups were set; Group A (44.0+/-2.8 months old, female) and Group B (6.2 +/-1.3 months old, female). Histological (H&E stain) observations were carried out to see the degeneration for both groups. Then biomechanical responses were investigated by measuring height changes in disc, intradiscal pressure values and relaxation time for each specimen under axial compressive loads. RESULTS: Degenerative changes were confirmed through H&E staining in Group A. The ratios of the nucleus pulposus area to total area were 14.7+/-4.5% and 29.2+/-6.0% in Group A and B, respectively (p=0.000). The decrease rates in disc height were 12.1+/-3.3% and 21.6+/-7.6%, in Group A and B, respectively under the axial compression of 740 N (p=0.000). No significant difference in intradiscal pressure measured in anterior zone between-groups except at axial load of 740N (p> 0.05). However, significant difference in pressure was found in posterolateral zone when the load was 542 N and higher (542 N: p=0.015, 740 N: p=0.010). The average relaxation time for Group A was significantly longer than that for Group B at 740N, i.e., at maximum load (anterior: p=0.010, posterolateral: p=0.014). CONCLUSION: Different biomechanical responses in degenerative disc were confirmed. They are 1) less flexible, 2) slower in energy relaxation under axial loading, and 3) larger portion of the external load were taken up at posterior part of annulus fibrous, especially in degenerative disc.