Accuracy of patient-specific template-guided vs. free-hand fluoroscopically controlled pedicle screw placement in the thoracic and lumbar spine: a randomized cadaveric study.

Abstract

Dorsal spinal instrumentation with pedicle screw constructs is considered the gold standard for numerous spinal pathologies. Screw misplacement is biomechanically disadvantageous and may create severe complications. The aim of this study was to assess the accuracy of patient-specific template-guided pedicle screw placement in the thoracic and lumbar spine compared to the free-hand technique with fluoroscopy. Patient-specific targeting guides were used for pedicle screw placement from Th2-L5 in three cadaveric specimens by three surgeons with different experience levels. Instrumentation for each side and level was randomized (template-guided vs. free-hand). Accuracy was assessed by computed tomography (CT), considering perforations of <2mm as acceptable (safe zone). Time efficiency, radiation exposure and dependencies on surgical experience were compared between the two techniques. 96 screws were inserted with an equal distribution of 48 screws (50%) in each group. 58% (n=28) of template-guided (without fluoroscopy) vs. 44% (n=21) of free-hand screws (with fluoroscopy) were fully contained within the pedicle (p=0.153). 97.9% (n=47) of template-guided vs. 81.3% (n=39) of free-hand screws were within the 2mm safe zone (p=0.008). The mean time for instrumentation per level was 01:14±00:37 for the template-guided vs. 01:40±00:59min for the free-hand technique (p=0.013), respectively. Increased radiation exposure was highly associated with lesser experience of the surgeon with the free-hand technique. In a cadaver model, template-guided pedicle screw placement is faster considering intraoperative instrumentation time, has a higher accuracy particularly in the thoracic spine and creates less intraoperative radiation exposure compared to the free-hand technique.