Purpose
Minimally invasive technique in spinal surgery have evolved including cortical bone trajectory (CBT) screw technique which is s new lumbar pedicle screw path, as an alternative fixation technique for lumbar spine. Theoretical advantage is that it provides enhanced screw torque and has biomechanical characteristics, also it minimizes approach-related damages. Midline lumbar fusion (MIDLF) has appeared with CBT screw technique. Many studies of CBT screw reported the effectiveness of MIDLF. We adopted this technique for lumbar degenerative spondylolisthesis and evaluated early radiological outcomes.
Materials and Methods
From May 2014 to March 2015, 17 patients (mean age 65.6±7.5 years; 4 males, 13 females) underwent MIDLF procedures for the treatment of single level lumbar spondylolisthesis. Average follow-up period was 8.8±2.7 months. Initial and last follow-up X-ray and computed tomography (CT) were evaluated for screw malposition, detection of peri-screw halo, loosening of the construct, or signs of spinal instability.
Results
The average bone mineral density (BMD) was -1.9±0.8. Eleven patients were fused at L4-5, 5 were at L3-4, and 1 was at L2-3. Five CBT screws were converted into pedicle screws due to intraoperative misposition of screws, so total 63 CBT screws were evaluated for peri-screw halo and malposition. There were no findings of screw pull-out or breakage in all screws. Four out of 63 (6.3%) screws were judged as peri-screw halo, and 20 (41.2%) screws were judged as malposition (1 medial; 2 superior; 17 lateral pedicle violation). But, there were no screw related nerve root injury. In all cases, interbody bony mass were identified. Four out of 17 (23.6%) patients were detected more than 2 degrees motions on flexion-extension lateral X-rays at final follow-up, and 1 out of these 4 patients was identified loss of reduction. There was no operation related complication.
Conclusion
There is no doubt that MIDLF with CBT screw is the minimally invasive method. Many numbers of screw malposition identified in our series were thought to be due to our earlier experience of trying free hands technique. We recommend the use of intraoperative fluoroscopy, which achieve accuracy. Although MIDLF with CBT has theoretical strengths, we must evaluate further long-term clinical follow-up and measure outcome.

Variable posterior surgical techniques for atlantoaxial (C1-2) joint instability (AAI) have been introduced and advanced steadily during the past century. Many surgical techniques using wire or clamp were introduced before 1980s and these surgical approaches provided low biomechanical strength and low fusion rate. After then, screwbased techniques (trans-articular or segmental fixation) were introduced and popularized as an alternative or “gold standard” method. Screw-based methods have recently gained popularity and modified according to their targeted anatomical regions (pedicle, posterior arch, C1 lateral mass, pars inter-articularis and laminar). Each surgical technique has own strength and weaknesses, and their usefulness has been proved through many biomechanical analysis and clinical applications. Advantage and limitation of each surgical technique will be reviewed.

Objective
Peridural fibrosis may cause failed back syndrome and the presence of fibrosis renders reoperations risky. Therefore, preventing the adhesion of scar tissue to the dura and nerve root is one of the issues in spinal surgery. Thus, the purpose of this study is to evaluate and compare the efficacy and the safety between two anti-adhesive agents, BNCH-202 (Korea BNC Inc, Daegu, Korea) and Guardix-SOL (Hanmi, Seoul, Korea).
Methods
Sixty eight patients were enrolled in this study. To evaluate and compare the efficacy in preventing epidural adhesion formation and the safety in human laminotomy models, the two barriers tested were either BNCH-202 or Guardix-SOL (gel/film combination). Clinical evaluation was performed at 0, 6 and 12 weeks to assess pain and functional outcome. The patients were also assessed radiographically with postoperative magnetic resonance imaging (MRI) to evaluate the presence of perinueral scar and adhesion.
Results
There was no statistically significant difference between two biologic barriers in terms of the safety issue, clinical and radiological efficacy. There were no significant differences between the BNCH-202 group and the control group on the preoperative ODI and VAS scores. In general, the ODI and VAS scores decreased in both groups at all the time points. At the 6 week and 12 week time point, the VAS scores for back pain/ leg pain and the ODI scores in both groups were lower than the preoperative score in each group (P<0.01). And at the 12-week time point, the peridural scar scores were assessed in both groups. The mean value of the peridural scar score in BNCH-202 group was not inferior to the mean value of that in Guardix-SOL group.
Conclusion
The results demonstrated that BNCH-202 gel is as effective as Guardix-SOL in reducing posterior dural adhesions in the spine with no apparent safety issues. It can improve patients’ postoperative clinical outcome.