OBJECTIVES: To evaluate the safety and efficacy of a novel bone cement-injectable cannulated pedicle screw augmented with polymethylmethacrylate in osteoporotic spinal surgery. METHODS: This study included 128 patients with osteoporosis (BMD T-score –3.2±1.9; range, –5.4 to –2.5) who underwent spinal decompression and instrumentation with a polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screw. Postoperative Visual Analogue Scale scores and the Oswestry Disability Index were compared with preoperative values. Postoperative plain radiographs and computed tomography (CT) scans were performed immediately after surgery; at 1, 3, 6, and 12 months; and annually thereafter. RESULTS: The mean follow-up time was 42.4±13.4 months (range, 23 to 71 months). A total of 418 polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screws were used. Cement extravasations were detected in 27 bone cement-injectable cannulated pedicle screws (6.46%), mainly in cases of vertebral fracture, without any clinical sequela. The postoperative low back and lower limb Visual Analogue Scale scores were significantly reduced compared with the preoperative scores (<0.01), and similar results were noted for the Oswestry Disability Index score ( p <0.01). No significant screw migration was noted at the final follow-up relative to immediately after surgery ( p <0.01). All cases achieved successful bone fusion, and no case required revision. No infection or blood clots occurred after surgery. CONCLUSIONS: The polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screw is safe and effective for use in osteoporotic patients who require spinal instrumentation.
The objectives of this study were to investigate the safety and biomechanical stability of a polymethylmethacrylate (PMMA)-augmented bone cement-injectable cannulated pedicle screw (CICPS) in cancellous bone model, and to analyze the stress distribution at the screw-cement-bone interface. The OMEGA cannulated pedicle screw (OPS) and conventional pedicle screw (CPS) were used as control groups. Safety of the CICPS was evaluated by the static bending and bending fatigue tests. Biomechanical stability was analyzed by the maximum axial pullout strength and maximum torque tests. Stress distribution at the screw-cement-bone interface was analyzed by the finite element (FE) method. The CICPS and CPS produced statistically similar values for bending stiffness, bending structural stiffness, and bending yield moment. The maximum pullout force was 53.47 ± 8.65 N in CPS group, compared to 130.82 ± 7.32 N and 175.45 ± 43.01 N in the PMMA-augmented OPS and CICPS groups, respectively (p < 0.05). The CICPS had a significantly greater torque than the OPS and CPS. The FE model did not reveal excessive stress at the screw-cement-bone interface in the CICPS group. In conclusion, PMMA-augmentation with CICPS may be a potentially useful method to increase the stability of pedicle screws in patients with osteoporosis. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 104B: 960-967, 2016.
Ankylosing spondylitis cervical spine fractures (ASCFs) are particularly unstable and need special consideration when selecting appropriate internal fixation technology. However, there is a lack of related biomechanical studies. This study aimed to investigate the biomechanical influence of the pattern, length, and density of instrumentation for the treatment of ASCF. Posterior, anterior, and various combined fixation approaches were constructed using the finite element model (FEM) to mimic the surgical treatment of ASCFs at C5/6. The rate of motion change (RMC) at the fractured level and the internal stress distribution (ISD) were observed. The results showed that longer segments of fixation and combined fixation approaches provided better stability and lowered the maximal stress. The RMC decreased more significantly when the length increased from 1 to 3 levels (302% decrease under flexion, 134% decrease under extension) than from 3 to 5 levels (22% decrease under flexion, 23% decrease under extension). Longer fixation seems to be more stable with the anterior/posterior approach alone, but 3-level posterior fixation may be the most cost-effective option. It is recommended to perform surgery with combined approaches, which provide the best stability. Long skipped-screwing posterior fixation is an alternative technique for use in ASCF patients.
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