[Biomechanical evaluation of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion with transfacetopedicular screws].

Objective: To assess the biomechanical stability of asymmetrical posterior internal fixation for transforaminal lumbar interbody fusion (TLIF) with transfacetopedicular screws (TFPS).

Methods: Range of motion (ROM) testing was performed in 7 fresh-frozen human cadaveric lumbar spine motion segments in flexion/extension, lateral bending, and axial rotation using 10.0 Nm torques at the L3-4 motion segment. The sequential test configurations included intact motion segment, TLIF and ipsilateral pedicle screw (PS), TLIF and ipsilateral PS plus contralateral TFPS according to Boucher technique, and TLIF and bilateral PS. The ROM was determined to assess the construct stability.

Results: In flexion/extension, lateral bending, and axial rotation, no measureable difference was found in the ROM between the standard bilateral pedicle screw and the novel asymmetric posterior internal fixation after TLIF. After TLIF, the ipsilateral PS construct provided less segment stability than the novel asymmetric construct with TFPS in flexion, left bending and left rotation. In rotation, the novel asymmetric construct allowed for significant off-axial rotation motions detrimental to the stability and fusion.

Conclusion: Ipsilateral PS placement plus contralateral TFPS provides stability comparable to that of TLIF with bilateral PS, and can be an alternative in minimal invasive surgery.