Study on Accuracy of Pedicle Guide Wire Placement in the Lumbar Spine by MISS Robot with Manipulator Axial Position Guiding
|Keywords||Minimally invasive spine surgery robot (MISS robot) manipulator axial position lumbar pedicle precision|
BackgroundThere are many surgical methods in the treatment of spinal diseases, including traditional open surgery, as well as a variety of minimally invasive surgery which have developed in recent years, such as with open reduction and pedicle screw fixation for spinal fractures, posterior scoliosis surgery, spinal reconstruction with pedicle screw fixation after tumor resection, minimally invasive percutaneous pedicle screw osteosynthesis, percutaneous vertebropiasty (PVP), percutaneous kyphoplasty (PKP), percutaneous transpedicular biopsy, percutaneous anterior screw fixation for treatment of odontoid process fracture. As a result of these surgical procedures involving implantation of instrumentation, it will inevitably involve puncture accuracy and different path, especially transpedicular surgery which requests the highest puncture accuracy. Improper transpedicular puncture may lead to neurovascular damage or suboptimal biomechanical spinal stabilization. A number of studies have reported up to a 30% rate of screw misplacement. Currently there are several methods to monitor the process of pedicle screw placement, including X-ray, guide device, stimulus-evoked electromyography, computer-assisted image-guided technology and so on. However, these methods have some shortcomings. The accuracy and security is not high enough by X-ray guiding and guide device guiding, which depend on the clinical experience of the surgeon to a large extent; stimulus-evoked electromyography can not continue to monitor after the pedicle perforation; computer-assisted image-guided technology has been advanced to improve accuracy. However, these systems need expensive and special equipments with the disadvantage of cumbersome procedures. Some technical problems remain fully unresolved, such as dynamic monitoring, registration errors, unsatisfactory precision of screw implantation. Because of the suboptimal reliability and complexity, the frequency of use of the computer-assisted surgery technologies is relatively low. Therefore, to explore a more secure and reliable, simple and effective way to guide percutaneous pedicle puncture is urgent.PurposeTo evaluate the feasibility and accuracy of pedicle guide wire placement by MISS robot with manipulator axial position guiding, with a view to researching a method of minimally invasive pedicle guide wire implantation safely and reliably with high puncture precision.Methods1. Specimen selection.Six dry human cadaveric lumbar spines (L1 to L5) were used and inspected visually and radiographically to exclude abnormal morphology and bone defects.2. Preoperative determination.Spine specimens underwent pre-intervention CT scanning, and ideal transverse section angle (TSA) was measured according to the lateral cross-sectional image of each vertebral body.3. Operating methods and procedures.(1)The vertebral body specimen was fixed and C-arm was adjusted till the standard lateral image was obtained. The manipulator was lowered and its direction was adjusted, so that the guide wire could project through the center of the pedicle’s projection , and parallel upper endplate of the vertebral.(2)C-arm was adjusted till a standard posteroanterior image was obtained and the projection was in the center of the screen.(3) C-arm was rotated at a certain angle (design TSA) to obtain the projection of the target pedicle.(4) The robot manipulator was adjusted, so that the projection of the guide wire was at the projection center of target pedicle.(5) The manipulator was lowered. The robot set 0, when the guide wire reached the pedicle posterior cortex. The whole process was monitored to make sure the projection of the guide wire will not deviate from the center of pedicle projection until the guide wire was within the vertebral body.4. Measurement of indicators.(1) Sagital section angle (SSA) on standard lateral images;(2) Transverse section angle (the actual TSA) on post-procedural CT scans.(3) Deviation of the actual position from the center at the pedicle isthmus plane, and the distance between the guide wire track and medial cortical or lateral cortical on post-procedural CT scans.5. Statistical analysis.The results were expressed as (x|-)±s. Paired t test was used to analyze the difference between preoperative TSA and postoperative TSA with SPSS 10.0. Statistical significance was determined at the 0.05 Alpha level.ResultsA total of 60 guide wires were successfully inserted.(1) Sagital section angles (SSA) of L1-5 were -0.13±0.83°(range, -2-1°).(2) The designed transverse section angles of Ll-5 were 13.11±1.75°, 14.63±2.18°,16.79±2.38°,19.25±2.79°,29.67±4.58°, and the actual transverse section angles were 13.42±2.13°,14.83±1.72°,16.45±2.45°,19.70±3.19°,30.33±4.94°. There were no significant difference (P > 0.05) between actual TSA and designed TSA in all leves, no more than 2 degrees.(3) Deviation of the guide wire track from the center at the pedicle isthmus plane of Ll-5 was 0.17±0.16mm(0～0.5mm), 0.18±0.22mm(0～0.6mm), 0.16±0.17mm(0～0.5mm), 0.58±0.49mm(0～1.2mm), 0.86±0.68mm(0～1.7mm). The distance between the guide wire track and medial cortical was 1.85±0.47mm(1.0～ 2.6mm), 1.90±0.42mm(1.6～2.9mm), 2.12±0.36mm(1.6～2.6mm), 3.02±0.97mm(1.8～4.9mm), 4.67±1.40mm(2.2～6.9mm). The distance between the guide wire track and lateral cortical was 1.61±0.35mm(1.0～2.3mm), 1.80±0.29mm(1.6～2.5mm), 2.27±0.41mm(1.7～3.1mm), 3.09±0.83mm(1.7～4.2mm), 5.22±1.41mm(3.0～7.1mm).None of the guide wire track was found to have contracted or perforated the pedicle wall.ConclusionLumbar pedicle puncture is performed perfectly by MISS robot with manipulator axial position guiding, which can accurately guide the wire through the pedicle axis. This method can guide the pedicle wire plantation safely and reliably with the promotion of application value.