BIOMECHANICAL EVALUATION OF INTERSPINOUS DEVICE, MIDFIX IN DESTABILIZED SPINE

Objective:The purpose of this study was to evaluate the stability and loosening of the Midfix device under complex cyclic loading with the resection of interspinous and supraspinous ligaments.Materials and Methods: A biomechanical study of motion analysis and cyclic loading on six fresh-frozen lamb spines was conducted.Specimens were divided into three groups: control, destabilized, and midfix groups.The excision of interspinous and supraspinous ligaments was performed in the destabilized and Midfix groups.Axial loads of 400 N were applied to the spine, and an increased moment of up to 8400 N-mm was generated through the axial movement to achieve the flexion-extension (FE) and right-left bending (LB) motions.During testing, the extensometer recorded the intervertebral displacement at decompression levels L4-5.According to the analysis, the value for which p<0.05 was considered statistically significant.Results: Implantation of the ISD (Interspinous Device) to strengthen segment stabilization resulted in a significant decrease in the range of motion of 43.2% in extension, 57.8% in flexion, and 25.6% in LB, yet an increase in right bending by 25.6%.A comparison between the intact spine and Midfix groups revealed significant differences in the range of motion in FE and LB.However, there were no statistically significant differences in right bending. Conclusion:The Midfix device stabilized the segments after resecting the interspinous and supraspinous ligaments.In addition, Midfix was more effective in flexion and extension than the other loading modes.Therefore, the lack of a stabilizing effect in bending should be carefully considered.