Application of a Novel Attachable Magnetic Nerve Stimulating Probe in Intraoperative Lumbar Pedicle Screw Placement: A Porcine Model Study

Pedicle screw instrumentation is a fundamental technique in lumbar spine surgery. However, several complications could occur when placing a pedicle screw, the most serious being damage to the neural structures. We developed an attachable magnetic nerve stimulating probe used for triggered electromyography (t-EMG) to avoid these. This study aimed to investigate the efficacy of this probe for intraoperative neuromonitoring (ION) during lumbar pedicle screw placement in a porcine model. Forty pedicle screws were inserted bilaterally into the pedicles of the fourth and fifth lumbar vertebrae of five pigs; 20 were inserted typically into the pedicle without nerve damage (Group A), and the other 20 were inserted through the broken medial wall of the pedicle to permit contact with the neural structures (Group B). We measured the triggered threshold for pedicle screw placement through the conventional nerve probe and our newly developed magnetic probe. There was no significant difference in the triggered threshold between the two instruments (p = 0.828). Our newly developed magnetic stimulating probe can be attached to a screwdriver, thus preventing real-time screw malpositioning and making it practical and equally safe. This probe could become indispensable in revision spine surgeries with severe adhesions or endoscopic spine surgeries.

Neurological events due to pedicle screw malpositioning with lateral fluoroscopy–guided pedicle screw insertion

OBJECTIVEThe risk of novel postoperative neurological events due to pedicle screw malpositioning in lumbar fusion surgery is minimized by using one of the several image-guided techniques for pedicle screw insertion. These techniques for guided screw insertion range from intraoperative fluoroscopy to intraoperative navigation. A practical technique consists of anatomical identification of the screw entry point followed by lateral fluoroscopy used for guidance during insertion of the screw. This technique is available in most clinics and is less expensive than intraoperative navigation. However, the safety of lateral fluoroscopy–guided pedicle screw placement with regard to novel postoperative neurological events due to screw malposition has been addressed only rarely in the literature. In this study the authors aimed to determine the rate of novel postoperative neurological events due to intraoperative and postoperatively established screw malpositioning during lateral fluoroscopy–assisted screw insertion.METHODSIncluded patients underwent lateral fluoroscopy–assisted lumbosacral screw insertion between January 2012 and August 2017. The occurrence of novel postoperative neurological events was analyzed from patient files. In case of an event, surgical reports were screened for the occurrence of intraoperative screw malposition. Furthermore, postoperative CT scans were analyzed to identify and describe possible screw malposition.RESULTSIn total, 246 patients with 1079 screws were included. Novel postoperative neurological events were present in 36 patients (14.6%). In 8 of these 36 patients (3.25% of the total study population), the neurological events could be directly attributed to screw malposition. Screw malpositioning was caused either by problematic screw insertion with immediate screw correction (4 patients) or by malpositioned screws for which the malposition was established postoperatively using CT scans (4 patients). Three patients with screw malposition underwent revision surgery without subsequent symptom relief.CONCLUSIONSLateral fluoroscopy–assisted lumbosacral screw placement results in low rates of novel postoperative neurological events caused by screw malposition. In the majority of patients suffering from novel postoperative neurological events, these events could not be attributed to screw malpositioning, but rather were due to postoperative neurapraxia of peripheral nerves, neuropathy, or intraoperative traction of nerve roots.

Comparison of posterior open screw fixation with percutaneous fixation among traumatic thoracolumbar fracture patients.

Objectives: To compare outcome and adverse events of open posterior pedicle screw fixation with percutaneous posterior pedicle screw fixation among patients suffering traumatic thoracolumbar fractures in our population. Study Design: Retrospectively Analyzed. Setting: Department of Neurosurgery, DHQ Teaching hospital, Gujranwala. Period: June 2015 to May 2019. Material & Methods: The patients who underwent open pedicle screw fixation (group 1) and percutaneous fixation (group 2) for traumatic thoracolumbar fractures information’s collected included patient’s age, gender, operation time, intra-operative blood loss, duration of radiation exposure during surgery, hospital stay duration, non-union at 6months and post-operative screw malpositioning and infection. Statistical analysis was done using SPSS version 25. Independent sample T test and Chi-square test for independence were used for quantitative and qualitative variables respectively to determine their significant association with type of surgery. The p values were statistically significant if < 0.05. Results: Out of 82 patients, 60.9 (n=50) underwent open pedicle screw surgery and 39.1% (n=32) underwent percutaneous fixation. Both cohorts had similar preoperative data including age (p=0.54) and gender (p=0.505). In comparison to open surgery group, the patients who underwent percutaneous fixation had significantly lesser operation time (46.63 + 6.25 minutes vs 89.88 + 9.05 minutes, p<0.01), lesser intraoperative blood loss (78.75 + 23.93 ml vs 330.40 + 101.87ml, p<0.01), greater intraoperative fluoroscopic exposure time (400.19 + 31.22 seconds vs 190.06 + 30.28 seconds, p<0.01), and lesser hospital stay time (3.13 + 0.871 days vs 5.08 + 1.209days, p<0.01). The incidence of post-surgery complications like screw malpositioning (p=0.621) and infection (p=0.733) was similar in both cohorts. The fracture union rates were also comparable in both cohorts (p=0.664). Conclusion: Minimally inavsive percutaneous posterior pedicle screw fixation had lesser operation time, blood loss, and hospital stay duration and greater fluoroscopic exposure than conventional open posterior pedicle screw fixation among patients with traumatic thoracolumbar fractures in our studied population. It also had a similar radilogic outcome and post-operative adverse events like screw malpositioning and local infection, showing the non-inferiority as compared to conventional open instrumentation. Prospective trials with large sample size are required to find superiority if any of one modality over other exists in our people.

Three Dimensional Fluoroscan is More Accurate and Repeatable Than Two Dimensional Fluoroscan for Measuring Central Scaphoid Screw Placement in a Cadaver Model

A commonly accepted treatment method for scaphoid fractures is dorsal percutaneous fixation [1, 2]. This has been shown to decrease the need for cast immobilization and allow faster recovery [3, 4]. For this approach a central screw placement is critical as it provides greater stiffness and load to failure, and allows a longer screw to be inserted which increases screw compression. All of these factors aid in fracture union [5]. However, the complex shape of the scaphoid bone makes central screw placement difficult, as the main axis cannot be easily visualized. Currently, scaphoid screws are placed using K wires guided under 2D fluoroscopy; however, intra-operative 3D fluoroscopy, which can create a CT reconstruction, is becoming more readily available. The goals of this study are to see if there is a significant difference between 2D and 3D fluoroscopic imaging in measuring screw malpositioning (distance off-center) and if there is a difference in repeatability.

Accuracy of pedicle screw insertion in the cervical spine for internal fixation using frameless stereotactic guidance

Object Although transpedicular fixation is a biomechanically superior technique, it is not routinely used in the cervical spine. The risk of neurovascular injury in this region is considered high because the diameter of cervical pedicles is very small and their angle of insertion into the vertebral body varies. This study was conducted to analyze the clinical accuracy of stereotactically guided transpedicular screw insertion into the cervical spine. Methods Twenty-seven patients underwent posterior stabilization of the cervical spine for degenerative instability resulting from myelopathy, fracture/dislocation, tumor, rheumatoid arthritis, and pyogenic spondylitis. Fixation included 1–6 motion segments (mean 2.2 segments). Transpedicular screws (3.5-mm diameter) were placed using 1 of 2 computer-assisted guidance systems and lateral fluoroscopic control. The intraoperative mean deviation of frameless stereotaxy was < 1.9 mm for all procedures. Results No neurovascular complications resulted from screw insertion. Postoperative computed tomography (CT) scans revealed satisfactory positioning in 104 (90%) of 116 cervical pedicles and in all 12 thoracic pedicles. A noncritical lateral or inferior cortical breach was seen with 7 screws (6%). Critical malplacement (4%) was always lateral: 5 screws encroached into the vertebral artery foramen by 40–60% of its diameter; Doppler sonographic controls revealed no vascular compromise. Screw malplacement was mostly due to a small pedicle diameter that required a steep trajectory angle, which could not be achieved because of anatomical limitation in the exposure of the surgical field. Conclusions Despite the use of frameless stereotaxy, there remains some risk of critical transpedicular screw malpositioning in the subaxial cervical spine. Results may be improved by the use of intraoperative CT scanning and navigated percutaneous screw insertion, which allow optimization of the transpedicular trajectory.