Outcome of lumbar fusion with template-guided cortical bone trajectory versus traditional pedicle screw trajectory – a prospective randomized trial

Abstract Purpose Traditional trajectory (TT) pedicle screw fixation remains the reference standard for lumbar fusion. Cortical bone trajectory (CBT) screw placement has been proposed as a less invasive alternative with potential biomechanical advantages, but the technique is demanding and its clinical value compared with freehand TT remains uncertain. Patient-specific, CT-based three-dimensional guides may improve CBT screw placement accuracy. The purpose of this randomized prospective trial was to compare fluoroscopy-guided freehand TT with patient-specific, template-guided CBT in lumbar fusion. The primary research question was whether template-guided CBT offers advantages in screw placement accuracy, functional outcomes, paraspinal muscle preservation, fusion status, or complications over 24 months. Methods Patients undergoing elective lumbar fusion for degenerative spinal disorders were prospectively enrolled and randomized to fluoroscopy-guided freehand TT or patient-specific, template-guided CBT screw placement. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and visual analog scale scores for back and leg pain. Screw position was assessed using postoperative CT scans and fusion status on 1-year CT scans, paraspinal muscle degeneration was evaluated on MRI. Complications and reoperations were recorded throughout follow-up. Results Sixty-seven patients were randomized to TT ( n = 34) or CBT ( n = 33). Most patients underwent single-level fusion (91% in TT vs. 97% in CBT). Instrumentation time was longer in the CBT group (25 vs. 18 min, p = 0.030), whereas total operative time and estimated blood loss were comparable. CBT was associated with shorter skin incisions in single-level fusions (9.5 vs. 12.0 cm, p = 0.002) and lower radiation exposure (416.0 vs. 734.5 mGy*cm2, p = 0.013). Intraoperative assessment showed fewer perfectly placed screws in the CBT group (90.3% vs. 100%, p < 0.001), and upper endplate perforation occurred more frequently with CBT (5 vs. 0 screws, p = 0.025). No significant between-group differences were observed in ODI, back or leg pain, pedicle fractures, infection, adjacent segment disease, pseudarthrosis or reoperation rates. At 6 months, maximum paraspinal muscle atrophy was lower in the CBT group (Goutallier grade 3 vs. grade 4, p = 0.037), while mean atrophy was comparable. No radiographic screw loosening was observed in either group at 24 months. Conclusion In this randomized prospective trial, freehand TT and patient-specific, template-guided CBT resulted in comparable clinical outcomes and overall complication rates at 24 months. CBT reduced radiation exposure, skin incision length, and maximum paraspinal muscle atrophy at 6 months, but these potential perioperative advantages must be balanced against longer instrumentation time, higher implant costs, and a higher rate of upper endplate perforation. Patient-specific, template-guided CBT appears feasible but was not clinically superior to freehand TT in this cohort. Comparisons of infrequent secondary outcomes should be interpreted cautiously because of the limited sample size.