gms | German Medical Science

Objective: In order to develop a single port procedure for lumbar stabilization a technical requirement exists to create another kind of internal fixation. Vector-LIF, first described in 2011 (DE102011119646A1), is a novel construct consisting of dorsoventral pedicle screws ipsilaterally, a translaminar screw below and a horizontal converging upper screw contralaterally.

Method: After informed consent six patients were operated using the Vector-LIF because of different pathologies. Preoperative biokinemetric simulation software was used to determine the optimal height of the device regarding the sagittal balance. Vector-LIF uses conventional microsurgical decompression through the standard dorsal midline approach from one side with undercutting. Reaching the contralateral recess the contralateral facet joint has to be opened using a high speed drill to achieve a good release Vector-LIF preserves the anatomical structures of the facet joints for segment's conduct stability and fast ossification of the facet joints as a natural fixateur. Vector-LIF is using vertical dorsally converging dorsoventral pedicle screws ipsilaterally. Contralaterally it is using a translaminar vector for the screw below and a horizontal dorsally-converging vector for the upper screw intending to reach the lamina pedicle complex.

Results: For determining the optimal height of the cage, a biokinemetric analysis of the lumbar spine was done based on a preoperative x-ray. In all cases the software suggested height of the cage was used. Postoperative CT-scans showed a correct placement of the implants. Pre- and postoperative clinical status was documented using the International Spine Registry – Spine Tango. Mean surgery time was 129 minutes, average blood loss 200 ml. All seven patients showed considerable postoperative improvement in clinical scores (VAS, ODI, SF-36). After documented bony fusion in the CT scan, the fixation system was removed in three cases in a small surgical procedure.

Conclusions: Zhe Intraoperative challenge was to connect the four screws with one rod. Another disadvantage of this procedure is the fact that the cage has to be implanted first and then the reposition is done with the help of the rod, because after implanted rod it is not possible to get access to the disc-space. So it is not a useful procedure in high grade spondylolisthesis. In order to develop this promising procedure, we are prototyping a template for the punctual connection and for reposition first.