• Changfu Wu, Chun Chen, Weidong Wu, Weidong Zhao, Peidong Sun, Jihong Fan, Zhenyu Bi, Jinyuan Zhang, and Jun Ouyang.
• *Department of Anatomy, Southern Medical University and Guangdong Provincial Medical Biomechanical Key Laboratory and Academy of Orthopedics of Guangdong Province, Guangzhou, P.R. China †Department of Orthopedic Surgery, the Affiliated Hospital of Putian University, and the Affiliated Putian Hospital of Southern Medical University, Putian, Fujian, P.R. China ‡Department of Orthopedic Surgery, Navy General Hospital, Southern Medical University, Beijing, P.R. China; and §Shenzhen Digital Orthopedic Engineering Laboratory, Shenzhen, Guangdong, P.R. China.
• Spine. 2015 Jan 1;40(1):E1-8.

Study DesignBiomechanical in vitro study.ObjectiveTo determine whether the peak pull-out force (PPF) of cervical anterior transpedicular screw (ATPS) fixed in osteoporotic vertebrae positively influence screw stability or not before and after fatigue.Summary Of Background DataMultilevel cervical spine procedures with osteoporosis can challenge the stability of current screw-and-plate systems. A second surgical posterior approach is coupled with potential risks of increased morbidity and complications. Hence, anterior cervical instrumentation that increases primary construct stability, while avoiding the need for posterior augmentation, would be valuable.MethodsSixty formalin-fixed vertebrae at different levels were randomly selected. The vertebrae were divided into healthy controls (groups A1, A2), osteoporotic controls (B1, B2), healthy ATPS groups (C1, C2), osteoporotic ATPS groups (D1, D2), and osteoporotic restoration controls (E1, E2). The procedure of ATPS insertion was simulated with 2 pilot holes being drilled on each side of 20 vertebral bodies that were implanted with either vertebral screw or polymethylmethacrylate. Each side randomly received either instant PPF or PPF beyond fatigue (2.5 Hz; 20,000 times).ResultsThe prefatigue PPFs were significantly higher than the postfatigue PPFs in all groups (group A: 366.06 ± 58.78 vs. 248.93 ± 57.21 N; group B: 275.58 ± 23.18 vs. 142.79 ± 44.78 N; group C: 635.99 ± 185.28 vs. 542.57 ± 136.58 N; group D: 519.22 ± 122.12 vs. 393.16 ± 192.07 N, and group E: 431.78 ± 75.77 vs. 325.74 ± 95.10 N). The postfatigue PPFs were reduced by 32.00% (group A), 48.19% (group B), 14.69% (group C), 24.28% (group D), and 24.72% (group E). The acute and postfatigue PPFs of both control groups were significantly lower than that of ATPS groups (P < 0.05). The cyclic osteoporosis ATPS group achieved the same PPF compared with the vertebral restoration screw group.ConclusionThe findings of this study suggest that instant PPF and fatigue resistance capability of an ATPS fixation were significantly better than other control groups, especially in the osteoporotic vertebrae.

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