Biomechanical evaluation of different asymmetrical posterior stabilization methods for minimally invasive transforaminal lumbar interbody fusion

Abstract

Beside several other advantages, the transforaminal approach for lumbar interbody fusion offers the possibility of reducing surgical trauma by limiting the approach to only 1 side. This requires posterior stabilization methods, which are applied without the need to damage contralateral muscles and soft tissues. The goal in this study was to compare different posterior stabilization methods for minimally invasive transforaminal lumbar interbody fusion (TLIF) biomechanically. Stiffness testing was performed in 8 fresh-frozen human cadaveric lumbar spine motion segments, including the following sequentially tested configurations: 1) native motion segment; 2) TLIF and bilateral pedicle screw (PS) construct; 3) TLIF and ipsilateral PS construct; 4) TLIF and ipsilateral PSs plus contralateral translaminar facet screws according to the Magerl technique; and 5) TLIF and ipsilateral PSs plus contralateral lumbar facet interference screw (LFIS). In extension, the unilateral range of motion (uROM) and elastic zone (EZ) were significantly lower than native motion segments for bilateral PS and LFIS. There were no significant differences among the different stabilization methods. In flexion, uROM and EZ were significantly lower than the native segment in the spines treated with bilateral PSs and translaminar facet screws. The LFIS differed from the native segment in EZ only. Again, there were no significant differences between the different posterior stabilization methods. In lateral bending, the EZ of spines treated with uni- and bilateral PS differed significantly. There were no additional significant differences. In rotation, the stiffness values of bilateral PS were significantly higher than native, unilateral PS, and LFIS. The comparison between ipsi- and bilateral PS showed a tendency, but not a significant difference for uROM and EZ. There was no statistically significant evidence that the TLIF method led to an asymmetrical motion behavior in our study. Bilateral PS augmentation offers significantly more stability than unilateral PSs in the majority of the test modes. There was no significant difference between the other tested methods. All tested stabilization methods could achieve at least the stability of the native segment.