[Accuracy of pedicle screw insertion in the thoracolumbar spine using image-guided navigation]

Design, application, and evaluation of a novel method for determining optimal trajectory of thoracic pedicle screws

Background

This is an experimental study performed on 15 adult cadavers. In this cadaveric study, we designed and evaluated a novel methodology for determining the optimal trajectory for the placement of thoracic pedicle screws. The accuracy of thoracic pedicle screw placement is critical to the spinal surgery. The concept, implement method, and significance of the optimal thoracic pedicle trajectory have not been reported.

Methods

The experimental study was performed on 15 adult cadavers. The Mimics software was used to design optimal trajectory through the pedicle central axis. Using three-dimensional (3D) printing, a navigation module with a locating facet and a stabilizing facet was developed. The thoracic pedicle screws were inserted with the help of the navigation module. The three-dimensional coordinates for the entry and the exit points of the screws were compared between the planned trajectories and the postoperative trajectories. The differences in coordinates were analyzed to evaluate the precision of the screw placement.

Results

The trajectories through the pedicle central axis showed an excellent symmetry between the single segments and for all thoracic vertebrae. Out of a total of 358 screws that were inserted, 15 (4.2%) screws breached the pedicle cortex with a breach distance of <2 mm. The qualifying rate was 98.6% (353/358) for the entry point precision of ≥3.2 mm, and 98.9% (354/358) for the exit point precision of ≥6.4 mm. In comparison to the designed qualified rate of 100% (358/358), the χ² was 3.22 and 2.26, respectively (P>0.05).

Conclusions

The optimal trajectory was obtained through the pedicle central axis, which significantly reduced the risk of cortex breach. A high degree of precision was obtained for the entry and the exit points of the screws when the postoperative trajectory was compared with the designed trajectory.

A Clinical Application Study of Mixed Reality Technology Assisted Lumbar Pedicle Screws Implantation

Background

This was a prospective comparative study of mixed reality (MR) technology assisted lumbar pedicle screws placement and traditional lumbar pedicle screws placement.

Material/Methods

Fifty cases of lumbar pedicle screws placement were randomly divided into 2 groups: 25 cases with MR technology in group A, and 25 cases without MR technology in group B. All patients had their scores on the Oswestry disability index (ODI) of low back pain and the visual analog scale (VAS) of the affected lower limb recorded at pre-operation. Blood loss, operative duration, success rate of first penetration by tap, and number of times C-arm fluoroscopy was performed were recorded at intraoperation. The postoperative drainage was recorded. The ODI of low back pain and VAS of the affected lower limb were recorded at 1, 3, and 6 months after operation.

Results

Group A had less bleeding, shorter operation time, higher success rate of first penetration by tap, and fewer times using C-arm fluoroscopy at intraoperation (P<0.05). There was significant difference in ODI scores and VAS scores at 1 mouth after operation (P<0.05). The postoperative drainage of group A was less than group B (P<0.05). The implantation accuracy of group A was higher than group B (P<0.05). The postoperative recovery rate of low back pain of group A was faster than group B (P<0.05).

Conclusions

The safety of spinal surgery and implantation accuracy of pedicle screw fixation system could be increased by MR technology.

Pediatric Lumbar Pedicle Screw Placement Using Navigation Templates: A Cadaveric Study

BACKGROUND

Pedicle screw technique is commonly used treatment of adult spinal trauma, tumor, degeneration. The application of pedicle screws is very challenging in children because children have a fast growing spine and spinal pedicle morphology of children and adult has large difference. 3 D reconstruction individual navigation templates improve the success rate of pediatric pedicle screw system. This study is aimed to provide a precise method for lumbar spine pedicle screw placement in children using computer-aided design and rapid prototyping technology.

MATERIALS AND METHODS

Computed tomography (CT) scans of cadaver specimens of 4 children were obtained, and the raw data were reconstructed using three-dimensional reconstruction software. Pedicle screws were placed using the conventional method or by using individually designed navigation templates based on the principles of reverse engineering and rapid prototyping technology.

RESULTS

We evaluated the accuracy of the pedicle screws placed using the two methods by CT scan. Ten navigation templates were designed for placement of 20 lumbar pedicle screws in the navigation group, and CT scan confirmed that all the screws were placed accurately in the corresponding pedicle. Conversely, of the 20 lumbar pedicle screws placed using the conventional method, 3 screws perforated the pedicle. The findings showed that lumbar pedicle screw placement was successful using navigation templates in children.

CONCLUSIONS

This technique is simple, easy to master, and allows personalized screw placement, thus providing a new and feasible method for lumbar pedicle screw placement in children.

A brief overview of 100 years of history of surgical treatment for adolescent idiopathic scoliosis

The history of surgical correction for adolescent idiopathic scoliosis reaches back about 100 years: the natural course of progressive, crippling and sometimes even life-threatening deformities which could not be controlled by external means called for effectual, invasive procedures. Hibbs 1911 aimed at halting progression by long, uninstrumented fusions. However, the lack of true correction, long rehabilitation times, high pseudarthrosis and infection rates, and a fusion mass which bent further once exposed to gravity again were not satisfying. The transition from slowing progression to halting progression and truly correcting the deformity lasted almost another half a century: Paul Harrington, confronted with many scoliotic polio patients, successfully introduced a hook-rod system for concave-distraction and convex-compression at the end of the 1950s. Many implant failures, a still-considerable pseudarthrosis rate, flattening of the sagittal profile and the lack of true three-dimensional (3D) correction were the shortcomings. In the 1970s the Frenchmen Cotrel and Dubousset took scoliosis surgery to the next level by introducing a versatile hook system and curve-pattern-adapted correction modes. The basics of the so-called derotation-manoeuvre consists in strategic distribution of the anchors along the curve, bending the rod accordingly, and rotating it back into the sagittal plane. The overall correction, stability and the fusion rates improved significantly. However, the effect on the sagittal and transverse plane were still limited. Lately, a better biomechanical understanding and bilateral, polysegmental strong three-column fixation with pedicle screw has become the benchmark method: in conjunction with posterior release techniques, osteotomies or even vertebral column resections for severe cases, it allows better 3D control (vertebral column manipulation), faster rehabilitation and better patient satisfaction.