Primary lumbosacral stability after open posterior and endoscopic anteriorfusion with interbody implants - A roentgen stereophotogrammetric analysis

Study Design. After posterior stabilization of the spondylolytic lumbosacra l level, mobility of the fused vertebrae could be studied before and after an additional anterior endoscopic interbody fusion using roentgen stereopho togrammetric analysis. Objective. To determine the in vivo primary lumbosacral stability of additi onal anterior interbody fusion after transpedicular screw fixation. Summary of Background Data. In vitro studies indicate a significant decreas e in segmental motion after pedicle screw fixation and additional anterior fusion. Roentgen stereophotogrammetric studies demonstrate the adequacy of transpedicular lumbar instrumentation in posterolateral fusions. There are no studies examining the effect of additional anterior interbody fusion aft er posterior instrumentation in vivo. Methods. In this study, 15 patients with low-grade spondylolisthesis at L5- S1 underwent a two-stage open posterior and endoscopic anterior lumbar fusi on using carbon fiber (Brantigan I/F) cages. At surgery, tantalum markers w ere implanted into the fifth lumbar (L5) and the first sacral (S1) vertebra . All the patients were examined by roentgen stereophotogrammetric analysis after the first and second surgical procedures. Results. After implantation of the posterior pedicle system only, the mean intervertebral mobility determined by roentgen stereophotogrammetric analys is was 0.23 mm in the transverse (x), 0.54 mm in the vertical (y), and 1.2 mm in the sagittal (z) axes. After additional anterior endoscopic fusion wi th carbon cages, the remaining translation between the fused segment L5/S1 decreased to 0.17 mm in the x, 0.16 mm in the y, and 0.44 mm in the z axes. Conclusion. Anterior endoscopic lumbosacral fusion significantly increases the primary stability of the posterior fusion with a pedicle system in two axes of motion.