Abstract
Funnel technique is a method used for the insertion of screw into thoracic pedicle. To evaluate the biomechanical characteristics of thoracic pedicle screw placement using the Funnel technique, trying to provide biomechanical basis for clinical application of this technology. 14 functional spinal units (T6 to T10) were selected from thoracic spine specimens of 14 fresh adult cadavers, and randomly divided into two groups, including Funnel technique group (n = 7) and Magerl technique group (n = 7). The displacement-stiffness and pull-out strength in all kinds of position were tested and compared. Two fixed groups were significantly higher than that of the intact state (P < 0.05) in the spinal central axial direction, compression, anterior flexion, posterior bending, lateral bending, axial torsion, but there were no significant differences between two fixed groups (P > 0.05). The mean pull-out strength in Funnel technique group (789.09 ± 27.33) was lower than that in Magerl technique group (P < 0.05). The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement. It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. Therefore, the funnel technique in the thoracic spine affords an alternative for the standard screw placement.
Highlights
Pedicle screw system has been widely used to support spine, maintain stability, and achieve solid bony fusion in patients with degeneration, fracture and scoliosis
Funnel technique is a method used for the screw insertion into thoracic pedicle, in which abrasion drill or bone nibbling forceps is used to increase the accuracy of screw insertion[5]
Independent sample t-test was used to analyze the two fixing groups, and the results showed that the maximum pull-out force in Funnel technique group (789.09±27.33) was lower than that in Magerl technique group (887.93±19.14) with a 11.1% difference and the difference was statistically significant (t=15.674,P=0.000)
Summary
Pedicle screw system has been widely used to support spine, maintain stability, and achieve solid bony fusion in patients with degeneration, fracture and scoliosis It has superior biomechanical and clinical data when compared with other methods of instrumentation[1]. Funnel technique is a method used for the screw insertion into thoracic pedicle, in which abrasion drill or bone nibbling forceps is used to increase the accuracy of screw insertion[5] This technology was firstly employed to make the specimen for thoracic vertebrae of cadavers in 2002, and the failure rate was reported to be only 6%1. Conclusions: The Funnel technique for the insertion point of posterior bone is a safe and accurate technique for pedicle screw placement It exhibited no effects on the stiffness of spinal column, but decreased the pull-out strength of pedicle screw. The funnel technique in the thoracic spine affords an alternative for the standard screw placement
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