Biomechanic analysis of the stability and vertebra strain distribution of asymmetrical posterior internal fixation in minimally invasive transforaminal lumbar interbody fusion / 局解手术学杂志

ABSTRACT

Objective To assess the biomechanical stability and vertebra strain distribution of asymmetrical posterior internal fixation for minimally invasive transforaminal lumbar interbody fusion ( MI-TLIF) . Methods Range of motion ( ROM) and strain distribution testing were performed in 8 fresh-frozen calf lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 5. 0 Nm torques at the L4-5 motion segment. The sequential test configurations included intact motion segment, TLIF with unilateral pedicle screw ( UPS) , TLIF with UPS plus transfacet pedicle screws ( UPS+TFPS) , and TLIF with bilateral pedicle screw ( BPS) . The ROM was deter-mined to assess the construct stability. Strain distribution was recorded along with flexion and lateral bending configurations. Results In flexion/extension, lateral bending, and axial rotation, there was no significant difference in the ROM between BPS and UPS+TFPS fixation after TLIF. After TLIF, the UPS construct provided less segment stability than BPS and UPS+TFPS fixation in flexion, lateral bending. Strain distribution under UPS+TFPS fixation was respectively 21. 8% and 24. 2% higher than that under BPS fixation along with flexion and lateral bending. Conclusion UPS+TFPS fixation provides stability comparable to that of MI-TLIF with bilateral PS, with better load share with the vertebrae body.