Technical Report of Free Hand Pedicle Screw Placement using the Entry Points with Junction of Proximal Edge of Transverse Process and Lamina in Lumbar Spine: Analysis of 2601 Consecutive Screws

OBJECTIVE A variety of different pedicle screws entry point techniques are used for the lumbar pedicle screws placement. This study reported Kim's entry point of lumbar pedicle screws with free hand technique and the accuracy of this technique. METHODS We retrospectively reviewed the 584 cases with free hand placed lumbar pedicle screw placement. The diagnosis included 491 cases with degenerative spine, 59 cases with trauma, 29 cases with metastatic disease, and 5 cases with scoliosis. A total of 2601 lumbar pedicle screws were placed, and the entry points of lumbar pedicle screws were the junction of proximal edge of transverse process and lamina. Incidence and extent of cortical breach by misplaced pedicle screw was determined by review of intra-operative and post-operative radiographs and/or computed tomography. RESULTS Among the total 2601 lumbar free hand placed pedicle screws, 114 screws (4.4%) in 79 patients (13.5%) were repositioned screws with suspected screw malposition during operation, and 37 screws (1.4%) in 31 patients (5.3%) were identified as moderate to severe breaching the pedicle after post-operative imaging studies. Among the patient with malpositioned screws, 3 patients showed nerve irritation sign of the lesion, and 2 cases were symptom improved after nerve block and conservative management, and 1 case was removed the screw after the failure of the treatment. CONCLUSION Free hand pedicle screw placement based on external landmark with the junction of proximal edge of transverse process and lamina showed acceptable safety and accuracy and avoidance of radiation exposure.