Elsevier

World Neurosurgery

Volume 120, December 2018, Pages e745-e751
World Neurosurgery

Original Article
Robot-Assisted Versus Fluoroscopy-Assisted Cortical Bone Trajectory Screw Instrumentation in Lumbar Spinal Surgery: A Matched-Cohort Comparison

https://doi.org/10.1016/j.wneu.2018.08.157Get rights and content

Highlights

  • The CBT technique for screw placement is a better alternative option for lumbar fixation than the PS technique.

  • Some potential risks exists with CBT screw insertion.

  • The TiRobot system could maximize the potential of the CBT technique by alleviating its shortcomings.

Objective

The aim of the present study was to compare the accuracy and safety of TiRobot system-assisted with those of fluoroscopy-assisted cortical bone trajectory screw placement in lumbar spinal surgery.

Methods

We included 58 patients who required instrumentation in a retrospective matched-cohort study. The primary outcome measures were the accuracy of screw placement using the modified Gertzbein-Robbins scale and the incidence of proximal facet joint violation. Secondary outcome measures included operative time, intraoperative blood loss, postoperative hospital stay, radiation exposure, and complications.

Results

A total of 231 screws were placed (TiRobot group [RG], 86 screws; fluoroscopy group [FG], 145 screws). In the RG, 87.2% of the screws had perfect positions (grade A). The remaining screws were grade B (8.1%) and C (4.7%). In the FG, 66.9% of the screws had perfect positions (grade A). The remaining screws were grade B (20.0%), C (9.0%), and D (4.1%). The proportion of clinically acceptable screws (grade A or B) was greater in the RG than in the FG. In the RG, the most common direction of screw deviation was cephalad endplate and was the vertebral cortex in FG. No difference was found in facet joint violation between the 2 groups. The operative time and blood loss were slightly greater in the RG than in the FG. No statistically significant difference was found in the postoperative hospital stay between the 2 groups. The mean cumulative radiation time was greater for the RG than for the FG, but the radiation exposure to the surgeon was significantly lower in the RG than in the FG.

Conclusions

Robot-assisted screw placement is more accurate and safe compared with fluoroscopy-assisted placement for lumbar spinal cortical bone trajectory instrumentation.

Introduction

In 2009, Santoni et al.1 reported a new trajectory for pedicle screw insertion for lumbar fixation, the cortical bone trajectory (CBT), from medially to laterally and from cranially to caudally. Their study demonstrated that a 30% increase in failure load of the CBT screw in uniaxial pullout compared with the traditional pedicle screw (PS).1 Recently, both cadaveric2, 3 and clinical4, 5 studies have shown that the CBT technique is a better alternative option for lumbar fixation, especially for patients with osteoporosis and obesity.6 Generally, the indications for CBT and PS were similar in most studies. Therefore, the novel technique was expected to replace traditional lumbar fixation strategies. However, during CBT screw insertion, several risks should be considered,7, 8 including the occurrence of insertion point or pedicle fractures owing to an immoderate screw diameter; nerve root injury due to an insufficient cephalad trajectory; and greater radiation exposure due to intraoperative multiplanar fluoroscopy. Hence, a thorough understanding of the anatomy, accurate surgical procedures, and reliable protection are essential to decrease these risks.

A new commercially available robotic system called TiRobot (TINAVI Medical Technologies Co., Ltd., Beijing, China) was developed to assist surgeons with spinal screw placement. This system could help doctors to plan the screw trajectories, optimal positioning, and the dimensions of implants. Subsequently, the surgeon will be able to perform the drilling and screw insertion manually.

The introduction of robots into spinal surgery could maximize the potential of the CBT approach by overcoming the shortcomings of fluoroscopy-assisted instrumentation. To the best of our knowledge, no studies have yet compared the robot-assisted approach with the conventional technique. The aim of the present study was to compare the accuracy and safety of robot-assisted versus fluoroscopy-assisted CBT screw instrumentation.

Section snippets

Patients

The present retrospective medical record review included patients who had undergone CBT screw instrumentation after developing spinal disease from June 2015 to March 2018. During the study period, 20 patients had undergone surgery with the aid of the TiRobot system and 38 patients with the fluoroscopy-assisted technique. All patients underwent cortical bone trajectory surgery performed by the same team of experienced surgeons. The decision to operate using robotic assistance or the conventional

Baseline Characteristics

We organized and used a total of 86 CBT screws for the RG and 145 screws for the fluoroscopy group (FG). The mean patient age and BMI in the RG were significantly greater than those in the FG (P < 0.01). The other baseline characteristics did not differ between the 2 groups (Table 1).

Primary Outcome

A detailed listing of the CBT screw accuracy grades is provided in Table 2. Overall, in the RG, a perfect trajectory (grade A) was observed in 87.2% of 86 screws. The remaining screws were graded B (n = 7; 8.1%)

Advances in CBT Screw Technique and Orthopedic Surgical Robots

The CBT screw technique is a novel lumbar fixation method. Several biomechanical studies2, 4, 5 have demonstrated favorable mechanical properties compared with PS because CBT screws are inserted in a region of high bone density. In clinical studies,11 the CBT was considered to be more minimally invasive than PS placement. CBT screw insertion through a caudomedial insertion point enables less-invasive posterior lumbar fixation by limiting dissection of the facet joints and reducing muscle

Conclusions

Robot-assisted screw placement is a more accurate and safe alternative to the fluoroscopy-assisted approach for lumbar spinal cortical bone trajectory instrumentation.

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    Conflict of interest statement: The present study was supported by the National Key Development Program of Digital Medical Equipment Research and Development Special Funding (grant 2016YFC0105800) and the National High Technology Research and Development Program of China (grant 2015AA043201).

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