Pedicle screws with modular head vs. preassembled head used in cortical bone trajectory: Can pars and pedicle fractures be prevented in osteoporotic bone?. (January 2018)

• Record Type: Journal Article
• Authors: Cheng, Wayne K.; Akpolat, Yusuf T.; İnceoğlu, Serkan; Danisa, Olumide A.
• Is Part Of: Journal of clinical neuroscience. Volume 47(2018)
• Page Start: 304
• Page End: 310
• Publication Date: 2018-01
• Subjects: Pedicle screw instrumentation -- Cortical bone trajectory -- Complication -- Pedicle fracture -- pars fracture -- Screw loosening -- Modular head screw -- Preassembled head screw; Brain -- Surgery -- Periodicals; Neurosciences -- Periodicals; Nervous system -- Surgery -- Periodicals; Brain -- surgery -- Periodicals; Neurosurgical Procedures -- Periodicals; Neurosciences -- Periodicals; Electronic journals; 616.8
• DOI: 10.1016/j.jocn.2017.09.012
• Languages: English
• ISSNs: 0967-5868

Abstract

Highlights: Pars/pedicle fractures as a result of cortical bone trajectory have been reported. Modular head screw (n = 24) and pre-assembled head screws (n = 24) were compared. There were 6 fractures occurred with pre-assembled head screws vs 1 in the modular head screws (p = 0.04). Modular head screw had significantly lower fracture rate for cortical bone trajectory in osteoporotic bone. There was no clear anatomic variable to predict potential fracture risk in CBT. Abstract: Pars and pedicle fractures as a result of CBT (cortical bone trajectory) during pedicle screw placement have been reported. The primary aim of the study is to compare the fracture rate between screws with modular heads to screws with standard pre-assembled tulip heads. The secondary aim of the study is to determine the potential variables that can be identified prior to instrumentation in order to predict risk of fractures. Twenty-four fresh frozen lumbar vertebrae were obtained from five different cadavers. Anatomical landmark measurements were obtained. Right and left pedicles of each vertebra were randomly instrumented with the preassembled head screws (n = 24) and modular head screws (n = 24) under video recording. X-ray images were obtained for measuring relative angle deviations between tapped and final screw trajectories. Finally, pullout tests were performed. Seventeen out of twenty-four (70.8%) of the spinous processes had to be excised in order to obtain proper trajectories. Six fractures occurred with pre-assembled head screws versus one in the modular head screws (p = 0.04). Distances from the midline to the medial wall of the pedicle were marginally significant as a predictor for fracture (p = 0.08). The pullout loads between both types of screws were not statistically different (p = 0.38). Age was better correlated with pullout load than absolute bone density value (p < 0.001). In conclusion, modular head screws had a significantly lower fracture rate than pre-assembled head screws for cortical bone trajectory in osteoporotic bone. There was no clear anatomic variable that could be measured pre-operatively to predict potential fracture risk in CBT.