Biomechanical comparison of interspinous distraction device and facet screw fixation system on the motion of lumbar spine: a finite element analysis

Background A large amount of biomechanical and clinical evidence from previous studies suggest the efficiency of the two different posterior lumber non-fusion methods, interspinous distraction device (ISDD) and facet screw fixation system (FSS), but the biomechanical comparison of ISDD and FSS has not been thoroughly clarified.

Methods In the current study, finite element methods were used to investigate the biomechanical comparison of ISDD and FSS. The range of motion (ROM), intradiscal pressure (IDP) and the protective effects gained by maintaining disc heights were evaluated.

Results The ROM was similar between the two non-fusion methods under static standing, flexion and lateral bending. The FSS appeared to be more effective in resisting extension. At the implanted level L3/4, FSS displayed better results for maintaining and increasing posterior disc heights. At the L4/5 level in extension and lateral bending, FSS was better than ISDD, with comparable results observed in other motions. Comparing the posterior and lateral disc heights, FSS appeared to be more effective than ISDD. FSS also had a minor effect on the inferior adjacent segment than ISDD. FSS was more effective in reducing IDP than ISDD in extension.

Conclusion Through the finite element analysis study, it can be seen that FSS demonstrates more beneficial biomechanical outcomes than does ISDD, such as being more effective in resisting extension, maintaining and increasing lumbar disc heights and reducing the inferior adjacent IDP in extension.