Computer tomography assessment of pedicle screw insertion in percutaneous posterior transpedicular stabilization

Abstract

Percutaneous insertion of cannulated pedicle screws has been recently developed as a minimally invasive alternative to the open technique during instrumented fusion procedures. Given the reported rate of screw misplacement using open techniques (up to 40%), we considered it important to analyze possible side effects of this new technique. Placement of 60 pedicle screws in 15 consecutive patients undergoing lumbar or lumbosacral fusion, mainly for spondylolisthesis, were analyzed. Axial, coronal, and sagittal reformatted computer tomography images were examined by three observers. Individual and consensus interpretation was obtained for each screw position. Along with frank penetration, we also looked at cortical encroachment of the pedicular wall by the screw. Thirteen percent of the patients (2/15) had severe frank penetration from the screws, while 80% of them (12/15) had some perforation. On axial images the incidence of severe frank pedicle penetration was 3.3% while the overall rate of screw perforation was 23%. In coronal images the overall screw perforation rate rose to 30% while the rate of severe frank pedicle penetration remained unchanged. One patient (6.6%) suffered S1 root symptoms due to a frankly medially misplaced screw, requiring re-operation. This study has shown that percutaneous insertion of cannulated pedicle screws in the lumbar spine is an acceptable procedure. The overall rate of perforation in axial images is below the higher rates reported in the literature but does remain important. Frank penetration of the pedicle was nevertheless low. It remains a demanding technique and has to be performed with extreme care to detail.

Factors affecting the accurate placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion

“…However, the accurate placement of pedicle screws in the clinical setting remains challenging due to variabilities of the pedicle structure and the insertion technique. The incidence of pedicle screw misplacement ranges from 4.9 to 55% under intraoperative fluoroscope guidance [4,5] and up to 11% with navigation assistance [6,7].…”

Benefit and accuracy of intraoperative 3D-imaging after pedicle screw placement: a prospective study in stabilizing thoracolumbar fractures

“…The main problem of the procedure is the false positioning of the pedicle screws, which affects up to 40% of the screws [7]. This results in revision rates from 2.8 to 6.6% [16,24]. Lateral malpositions affect the stability and can cause loosening of the fixateur.…”

Robot-assisted and fluoroscopy-guided pedicle screw placement: a systematic review

“…Lastly, all included studies involved independent blinded investigators to assess pedicle screw position using post-operative fine-cut CT. Unfortunately the metric tools used to satisfactorily determine screw placement varied widely including the Gertzbein and Robbins scale, Rampersaud scale, and Wiesner and Schizas scale [6,15,19,28]. In the instance when the same scale was shared, criteria for a satisfactory position varied; for example, while the Schizas et al and Lieberman et al studies both adopted the Rampersaud scale, the former considered positions A and B adequate (completely in pedicle, or \2 mm breach), while the latter considered only position A acceptable (completely in pedicle only).…”