Fallibilities in the pedicular screwing

Introduction: The present study was designed by using variable-angle screws in a transpedicular fixation process on the mediolateral plane of lumbar vertebrae of cadavers in the Anatomy Departments of the Afyonkarahisar Kocatepe University and Isparta Süleyman Demirel University medical schools.Aim: The aim of the present study was to determine the degree of lateralization from the normal pedicular axis, which causes a defect in the pedicle on the mediolateral plane during transpedicular screwing in lumbar vertebrae, as well as to determine the consequences of continuing to screw despite the resistance experienced during screwing.Material and Method: The present study was performed on 100 pedicles of lumbar vertebrae of 10 cadavers. The pedicles were accessed in the prone position by posterior median incisions. Zero, 5, 10, and 15, and 0, 15, and 20 degree tunnels, through which 3 mm guide wires could pass, were created in each of the two wooden blocks we prepared, respectively. First, the access hole was accurately determined, and then the screwing process was performed based on the guide wires by making slopes with the blocks prepared laterally. Following the screwing process, a total laminectomy was performed on the lumbar vertebrae. Lumbar transpedicular screwing was performed by giving a slope of 10 and 15 degrees to the lateral side on the mediolateral plane by assuming the normal pedicle axis as 0 degrees. Forced 25 and free 25 transpedicular screwing processes were performed at a 10-degree slope to the lateral from the normal pedicular axis, as well as forced 25 and free 25 transpedicular processes at a 15-degree slope to the lateral from the normal axis.Results: Complications were more common in the 10- and 15-degree forced groups. There were no complications due to screw placement in the 10- and 15-degree free groups. Leaning against the medial wall was more common in the 15-degree free group, the mediolateral angle became corrected in the 10-degree free screwing while the screw was moving forward, and the completion of the screwing process was higher in the normal axis.Discussion: Neurologic damages are the most worrisome complications of transpedicular screwing. Pedicular screw applications with traditional methods are substantial due to personal clinical experience. Pedicular screw malpositions have been reported to occur at rates between 21.1% and 39.8% in the literature (26, 34-36). In a prospective study reported by Kotil et al. (41), medial wall perforation in the thoracolumbar area in 6 of 306 pedicle screws, where 2 of the perforations were radicular irritations. The present study demonstrated that additional propulsion to the rotating force of the screw should be avoided to prevent wall perforation after the accurate access site has been assessed during transpedicular screwing. In addition, the present study also demonstrated that perforation of the pedicle wall was lower with the blunt screw system compared to the sharp pointed screw system.Conclusion: During transpedicular screw application in lumbar vertebrae, assessing the access site and accuracy of the first cannulation of the pedicle performed consonant to the anatomic axis are of great importance. The angle error that would be performed according to the anatomic pedicle axis in normal human anatomy has been observed to vary within 0 to 15 degrees. As long as the access is performed accurately, the error has a tendency to be corrected even for errors up to 15 degrees of the normal pedicle axis due to the structure of the pedicle. When the progression of the screw has stopped in the course of the screwing process, removing the screw and controlling the direction of the screw is important for the protection from errors.