Abstract
Introduction
Early-stage pullout is a common problem for surgeons during the fixation of osteoporotic bones. Poor bone quality limits the use of pedicle screws for patients with osteoporosis. In this study, the researchers investigated the effects of hole and gap position and type on the pullout strength of cannulated screws.
Methods
Seven different designs were tested, including a control group. All cannula diameters were 2 mm and holes were drilled with a diameter of 1.5 mm. Gaps were milled with a 2-mm-diameter tool with 2-mm displacement proximally. All holes and gaps were drilled or opened unilaterally and bilaterally. Grade 40 and 10 polyurethane foam was used to simulate healthy and osteoporotic bones, respectively. For pullout tests, insertion depth was 30 mm and 2-mm-diameter pilot holes were drilled into blocks before screws were inserted. The cross-head speed was 2 mm/min. For torsion tests, 1 side of the screw was fixed and other was twisted clockwise.
Results
For torsion tests, the maximum torque value exhibited by the control group (non-cannulated) was 14.94 Nm. The highest torsional strength among tested cannulated screws was 13.54 Nm for Single side two holes including design (S2H) (p <.0001). The minimum torsional strength was 9.45 Nm with a breaking angle of 39° (p <.005). Comparing results for samples pulled out from grade 40 polyurethane foam, single side slot including design (SS) samples exhibited the highest pullout strength with a maximum force of 3,104 N.
Conclusions
The unilateral, sequential, 3-radial hole, drilled, cannulated screw was the optimal alternative when considering pullout and torsional strength as criteria.
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References
Kim YY, Choi WS, Rhyu KW. Assessment of pedicle screw pullout strength based on various screw designs and bone densities—an ex vivo biomechanical study. Spine J 2012;12:164–8.
Evans SL, Hunt CM, Ahuja S. Bone cement or bone substitute augmentation of pedicle screws improves pull-out strength in posterior spinal fixation. Mater Med 2002;13:1143–5.
Halvorson TL, Kelley LA, Thomas KA, et al. Effects of bone mineral density on pedicle screw fixation. Spine (Phila Pa 1976) 1994;19:2415–20.
Becker S, Chavanne A, Spitaler R, et al. Assessment of different screw augmentation techniques and screw designs in osteoporotic spines. Eur Spine J 2008;17:1462–9.
Jacob AT, Ingalhalikar AV, Morgan JH, et al. Biomechanical comparison of single- and dual-lead pedicle screws in cadaveric spine. J Neurosurg Spine 2008;8:52–7.
Lill CA, Schneider E, Goldhahn J, et al. Mechanical performance of cylindrical and dual core pedicle screws in calf and human vertebrae. Arch Orthop Trauma Surg 2006;126:686–94.
Hsu CC, Chao CK, Wang JL, et al. Increase of pullout strength of spinal pedicle screws with conical core: biomechanical tests and finite element analyses. J Orthop Res 2005;23:788–94.
Abshire BB, McLain RF, Valdevit A, Kambic HE. Characteristics of pullout failure in conical and cylindrical pedicle screws after full insertion and back-out. Spine J 2001;1:408–14.
Demir T, Camuscu N, Türeyen K. Design and biomechanical testing of pedicle screw for osteoporotic incidents. Proceedings of Institution of Mechanical Engineers: Part H: Engineering in Medicine 2012;226:256–62.
Krenn MH, Piotrowski WP, Penzkofer R, Augat P. Influence of thread design on pedicle screw fixation. J Neurosurg Spine 2008;9:90–5.
Mehta H, Santos E, Ledonio C, et al. Biomechanical analysis of pedicle screw thread differential design in an osteoporotic cadaver model. Clin Biomech 2012;27:234–40.
Gao M, Lei W, Wu Z, et al. Biomechanical evaluation of fixation strength of conventional and expansive pedicle screws with or without calcium based cement augmentation. Clin Biomech 2011;26:238–44.
Vishnubhotla S, McGarry WB, Mahar AT, Gelb DE. A titanium expandable pedicle screw improves initial pullout strength as compared with standard pedicle screws. Spine J 2011;11:777–81.
Wan S, Lei W, Wu Z, et al. Biomechanical and histological evaluation of an expandable pedicle screw in osteoporotic spine in sheep. Eur Spine J 2010;19:2122–9.
Bostan B, Esenkaya I, Gunes T, et al. A biomechanical comparison of polymethylmethacrylate-reinforced and expansive pedicle screws in pedicle-screw revisions. Acta Orthop Traumatol Turc 2009;43:272–6.
Lei W, Wu Z. Biomechanical evaluation of an expansive pedicle screw in calf vertebrae. Eur Spine J 2006;15:321–6.
Cook SD, Barbera J, Rubi M, et al. Lumbosacral fixation using expandable pedicle screws: an alternative in reoperation and osteoporosis. Spine J 2001;1:109–14.
Rohmiller MT, Schwalm D, Glattes RC, et al. Evaluation of calcium sulfate paste for augmentation of lumbar pedicle screw pullout strength. Spine J 2002;2:255–60.
Burval DJ, McLain RF, Milks R, Inceoglu S. Primary pedicle screw augmentation in osteoporotic lumbar vertebrae: biomechanical analysis of pedicle fixation strength. Spine (Phila Pa 1976) 2007;32:1077–83.
Hashemi A, Bednar D, Ziada S. Pullout strength of pedicle screws augmented with particulate calcium phosphate: an experimental study. Spine J 2009;9:404–10.
Yazu M, Kin A, Kosaka R, et al. Efficacy of novel-concept pedicle screw fixation augmented with calcium phosphate cement in the osteoporotic spine. J Orthop Sci 2005;10:56–61.
Taniwaki Y, Takemasa R, Tani T, et al. Enhancement of pedicle screw stability using calcium phosphate cement in osteoporotic vertebrae: in vivo biomechanical study. J Orthop Sci 2003;8:408–14.
Milcan A, Ayan I, Zeren A, et al. Evaluation of cyanoacrylate augmentation of transpedicular screw pullout strength. J Spinal Disord Tech 2005;186:511–4.
McKoy BE, An YH. An injectable cementing screw for fixation in osteoporotic bone. J Biomed Mater Res Appi Biomater 2000;53:216–20.
Yi X, Wang Y, Lu H, et al. Augmentation of pedicle screw fixation strength using an injectable calcium sulfate cement: an in vivo study. Spine (Phila Pa 1976) 2008;33:2503–9.
Kang SH, Kim KT, Park SW, Kim YB. A case of pedicle screw loosening treated by modified transpedicular screw augmentation with polymethylmethacrylate. J Korean Neurosurg Soc 2011;49:75–8.
Cho W, Wu C, Zheng X, et al. Is it safe to back out pedicle screws after augmentation with polymethyl methacrylate or calcium phosphate cement? A biomechanical study. J Spinal Disord Tech 2011;24:276–9.
Wu Z, Gao M, Sang H, et al. Surgical treatment of osteoporotic thoracolumbar compressive fractures with open vertebral cement augmentation of expandable pedicle screw fixation: a biomechanical study and a 2-year follow-up of 20 patients. J Surg Res 2012;173:91–8.
Yamana K, Tanaka M, Sugimoto Y, et al. Clinical application of a pedicle nail system with polymethylmethacrylate for osteoporotic vertebral fracture. Eur Spine J 2010;19:1643–50.
Sugimoto Y, Tanaka M, Konishi H, et al. Posterior spinal fusion using a pedicle nail system with polymethylmethacrylate in a paraplegic patient after vertebral collapse caused by osteoporosis. Spine J 2009;9:e5–8.
Johnson AE, Keller TS. Mechanical properties of open-cell foam synthetic thoracic vertebrae. J Mater Sci Mater Med 2008; 19: 1317–23.
Zdero R, Schemitsch EH. The effect of screw pullout rate on screw purchase in synthetic cancellous bone. J Biomech Eng 2009;131: 024501.
Chen LH, Tai CL, Lai PL, et al. Pullout strength for cannulated pedicle screws with bone cement augmentation in severely osteoporotic bone: influences of radial hole and pilot hole tapping. Clin Biomech 2009;24:613–8.
ASTM F1839-08. Standard specification for rigid polyurethane foam for use as a standard material for testing orthopaedic devices and instruments. 2012. West Conshohocken, PA: ASTM.
ASTM F543-13e1. Standard specification and test methods for metallic medical bone screws. 2013. West Conshohocken, PA: ASTM.
Choma TJ, Pfeiffer FM, Swope RW, Hirner JR Pedicle screw design and cement augmentation in osteoporotic vertebrae: effects of fenestrations and cement viscosity on fixation and extraction. Spine (Phila Pa 1976) 2012;37:E1628–32.
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Author disclosures: TT (none); AK (none); YO (none); DS (none); DT (none).
This study was supported by Osimplant (Bone Implant) and TUBI-TAK, Project 111M583.
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Tolunay, T., Arslan, K., Yaman, O. et al. Biomechanical Performance of Various Cement-Augmented Cannulated Pedicle Screw Designs for Osteoporotic Bones. Spine Deform 3, 205–210 (2015). https://doi.org/10.1016/j.jspd.2014.09.055
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DOI: https://doi.org/10.1016/j.jspd.2014.09.055