Biomechanical changes in disc pressure and facet strain after lumbar spinal arthroplasty with charité™ in the human cadaveric spine under physiologic compressive follower preload

Aim: Arthroplasty maintains the biomechanical features of a healthy disc, decreases the adjacent segment disease rate, and decreases the accelerated degeneration rate of the neighboring discs in traditional fusion procedures. However, there are only a few reports on adjacent disc pressure (DP) and facet strain (FS) after lumbar arthroplasty under a physiologic compressive preload. Material and Methods: Baseline DP and FS measurements were obtained from five intact cadaveric human lumbosacral spines for different modes of motion. DP was measured by inserting pressure transducer needle tips into the L3-L4 and L5-S1 discs. FS gauges were fixed on both sides of the laminae near the L3-L4, L4-L5, and L5-S1 facet joints. After SB Charité™ III implantation at the L4-L5 level, the measurements were repeated at preload and compared with those of the intact spine. Results: Under the preload condition, the central DP of the upper disc was decreased during extension and bending, and it significantly increased during rotation (p < 0.05). In the lower disc, the central DP insignificantly decreased during bending and increased during extension and flexion. A statistically significant increase in FS was observed during rotation at the operative facet (p < 0.05). Compared to the intact spine, all FS values were insignificantly decreased during lateral bending but increased during axial rotation. Conclusion: In an ex-vivo physiologic preload setting, the SB Charité™ III provided relatively inconsistent and sometimes increased DP or FS at the operative and adjacent levels after arthroplasty.