Objective: Evaluate the accuracy of computer-assisted pedicle screw placement in patients with degenerative lumbrosacral spine using single-time, paired point registration alone technique in combination with the surgeon’s experience.

Material and Method: A computer-assisted pedicle screw insertion in lumbrosacral spine were performed in 62 consecutive patients (363 screws) using single-time, paired point registration without surface matching. After finding the entry point and trajectory of the pedicle under image guidance, the surgeon then inserted pedicle screws by his experience. Postoperative DynaCT scans were obtained and interpreted by two neuroradiologists. The Kappa statistic was used to measure the degree of interobserver agreement. The screw position was graded as follows: Grade A = entirely within the pedicle; B = medial or lateral pedicle wall breach less than 2 mm; C = medial or lateral pedicle wall breach equal to 2-4 mm; D = medial or lateral wall breach more than 4 mm. Clinical outcomes including a numeric pain score, neurologic symptoms, and complications were reviewed from all charts of patients. Additionally, the registration error, registration time, screwing time, and estimated blood loss were analyzed.

Results: A total of the 363 pedicle screws, the first neuroradiologist interpreted grade A in 95.6%, grade B in 4.1% and grade C in 0.3%, while the second neuroradiologist interpreted grade A in 95.3%, grade B in 3.6%, and grade C in 1.1%. There was no incidence of grade D in this present study. No neurologic or vascular injuries occurred from pedicle screw placement. The mean registration error was 1.54 + 1.28 (range, 0.9-2.5) mm with the mean time required for the registration process for each patient was 3.64 + 1.92 (range, 2-8) minutes. The mean screwing time for each patient was 20.29 + 9.44 (range, 13-40) minutes. The mean pain score improved from 6.45 + 1.74 points preoperatively to 3.04 + 0.82 points postoperatively. In the radiculopathy group, motor power gradually improved in all patients.

Conclusion: The use of single-time, paired point registration without surface mapping combined with surgeon’s perception for computer-assisted pedicle screw insertion has proven to be a safe and effective technique in degenerative lumbrosacral spine. The author’s technique did not rely solely on the image guidance. However, the navigation system would be very beneficial to improve decision-making, especially in surgery of patients with distorted spinal anatomy. Besides, this technique may decrease the overall operative time without compromise the accuracy of pedicle screw placement.

Keywords: Pedicle screw, Computer-assisted surgery, Navigation, Single-time registration, Lumbrosacral spine