Evaluation Of Screw Position By Computed Tomography After Lumbar Pedicle Screw Placement Guided By Lamina

Objective: It is rare to report the assurance of sagittal screw angle (SSA) in lumbar pedicle screw placement, and the SSA error is one of the factors which will seriously influence the results of operation and the clinical efficacy. For accurate insertion of screws into the lumbar pedicles and to avoid either pedicle cortex perforations, or neurological complication, more precise knowledge of lumbar pedicle anatomy is necessary. We found a new reference mark after the research of lumbar vertebrae anatomy: the lateral border of lamina. The lumbar pedicle screw were placed using this mark preoperatively, thin-cut computed tomography (CT) scans were available on the patients postoperatively. This study is to investigate the accuracy and feasibility of the lumbar pedicle screw placement guided by the lateral border of lamina.Methods: Between January 2008 and January 2010, 128 patients (86 men and 42 women) were analyzed. The age range of the patients was 25 to 67 years (mean, 48 years). 92 patients had lumber disc herniation (LDP), 23 patients had lumbar fracture, and 13 patients had lumbar spondylolisthesis. The angle (E') between axial line of lumbar pedicle and the lamina were measured by computed tomography preoperatively, and the pedicle screws were inserted using the new mark. Then evaluated the screw position by computed tomography and got the screw angle (θ) postoperatively. All angles were analyzed by SPSS 13.0.Results: A total of 584 pedicle screws were placed, all screws were scanned and evaluated by computed tomography after operation. No significant differences are showed between E' group and SSA' group. A total of 579 screws (99.1%) canals were placed in the cortical shell of the pedicle, only 5 screws (0.9%) were misplaced and violated the superior or inferior cortical shell but didn't injured the nerve. According to the Tang's classify: the excellent-and-fine rates is 95.37%.Conclusion: The CT evaluation shows that the screw position of lumbar pedicle screw placement guided by lamina is accurate. The lamina is a reliable reference mark, and this method is worth to generalizing for practical application.