Introduction: Over the past decade, a new technique called cortical screw fixation has been developed, which allows for medialized screw placement through stronger cortical bone. Several studies have shown biomechanical equivalence or superiority of cortical screws, but only one other study has looked at clinical outcomes.

Methods: We prospectively looked at the senior author’s patients who underwent cortical versus pedicle lumbar screw fixation between 2013 and 2015 for lumbar degenerative disease. Eighteen patients underwent cortical screw fixation and 15 patients underwent pedicle screw fixation. We looked at pain and functional outcomes using a visual analog scale from 1 to 10 for pain and the Oswestry Disability Index (ODI) for function. Mann-Whitney and Fisher Exact tests were used to analyze the data.

Results: The cortical screw cohort showed a trend towards having less peak postoperative pain (p = 0.09). The average postoperative pain was similar between the two cohorts (p = 0.93). There was also no difference in pain 6 to 12 weeks after surgery (p = 0.8). However, at 6 to 8 months, the cortical screw cohort showed a trend towards worsening pain compared to the pedicle screw cohort (p = 0.02). Both the cortical and pedicle screw groups had reductions in ODI compared to before surgery, with an 8.9 reduction in the cortical group (P=0.04) and 9.2 reduction in the pedicle group (P=0.03). There was no difference in ODI outcomes between the groups.

Conclusions: The cortical screw patients showed a trend towards less pain in the short term (1-3 days post-surgery) and more pain in the long term (4-8 months post-surgery) compared to pedicle screw patients. There was no difference in functional outcome between the groups, though both groups had statistically significant reductions in pain and ODI at follow-up.

Patient Care: Cortical screws are a brand new technique to place a more medialized screw with less lateral dissection required. There are several studies that look at biochemical outcomes for cortical screws, but few that look at clinical outcomes.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) describe the differences in technique for traditional pedicle versus cortical screws; 2) describe the pain and functional outcomes between the two cohorts.

References: 1. Santoni BG, Hynes RA, McGilvray KC, Rodriguez-Canessa G, Lyons AS, Henson MAW, Womack WJ, Puttlitz CM: Cortical bone trajectory for lumbar pedicle screws. Spine J. 2009, 9:366-373. doi:10.1016/j.spinee.2008.07.008 2. Wray S, Mimran R, Vadapalli S, Shetye SS, McGilvray KC, Puttlitz CM: Pedicle screw placement in the lumbar spine: effect of trajectory and screw design on acute biomechanical purchase. J Neurosurg Spine. 2015, 22:503-510. doi:10.3171/2014.10.spine14205 3. Ueno M, Sakai R, Tanaka K, Inoue G, Uchida K, Imura T, Saito W, Nakazawa T, Takahira N, Mabuchi K, Takaso M: Should we use cortical bone screws for cortical bone trajectory? J Neurosurg Spine. 2015, 22:416-421. doi:10.3171/2014.9.spine1484