Skip to main content
SpringerLink
Log in

Pullout strength of thoracic pedicle screws improved with cortical bone ratio: a cadaveric study

  • Original Article
  • Published:
Journal of Orthopaedic Science

Abstract

Background

The application of pedicle screw constructs for the osteoporotic vertebrae remains a serious clinical challenge for spinal surgeons and has been intensely studied recently. However, the exact role of the pedicular cortical bone composition and the screw-bone gap on the screw fixation failure has yet to be quantitatively documented. The current study aims to address this gap in our knowledge and elucidate possible relationships.

Methods

Twelve fresh-frozen human cadaveric thoracic spine vertebrae (T9–T12) were harvested from six human cadavers (five males; one female; 63.5 ± 17 years). A three-dimensional reconstruction of the individual vertebrae was firstly rendered from computed tomography (CT) scan images to allow calculation of the cortical bone ratio. Specimens were then subdivided into three groups: Intact, 1-mm screw-bone gap, and 2-mm screw-bone gap. The gap groups were subjected to a standard cyclic fatigue-loading protocol. The pullout strength of the pedicle screws for all specimens were then determined.

Results

The pullout strength of the 1-mm and 2-mm groups were significantly reduced when compared with the intact group. A moderate to excellent positive correlation was identified between the cortical bone area ratio and pullout strength for all groups (r > 0.55). A cortical shell ratio of 0.73 or higher was also found to be a safe cut-off index for screw fixation failure, even with an observable 1-mm screw-bone gap.

Conclusions

The current in vitro cadaveric spine study identified a significant correlation between cortical bone area ratio and the thoracic pedicle screw pullout strength. The presented results also demonstrate that the fatigue-loading-induced screw-bone gap of 1-mm was sufficient to cause a significant decrease in the pullout strength. However, a cortical bone area ratio of 0.73 or higher in this group was able to preserve most of the screw-bone interfacial strength, and subsequently may prevent a complete implant failure.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Log in via an institution

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3
Fig. 4
Fig. 5
Fig. 6

Similar content being viewed by others

References

  1. Johnell O, Kanis JA. An estimate of the worldwide prevalence and disability associated with osteoporotic fractures. Osteoporos Int. 2006;17(12):1726–33.

    Article  CAS  PubMed  Google Scholar 

  2. Esses SI, Sachs BL, Dreyzin V. Complications associated with the technique of pedicle screw fixation. A selected survey of ABS members. Spine (Phila Pa 1976). 1993;18(15):2231–8 (discussion 8–9).

    Article  CAS  Google Scholar 

  3. Okuyama K, Abe E, Suzuki T, Tamura Y, Chiba M, Sato K. Influence of bone mineral density on pedicle screw fixation: a study of pedicle screw fixation augmenting posterior lumbar interbody fusion in elderly patients. Spine J. 2001;1(6):402–7.

    Article  CAS  PubMed  Google Scholar 

  4. Higashino K, Kim JH, Horton WC, Hutton WC. A biomechanical study of two different pedicle screw methods for fixation in osteoporotic and nonosteoporotic vertebrae. J Surg Orthop Adv. 2012;21(4):198–203.

    Article  PubMed  Google Scholar 

  5. Shea TM, Laun J, Gonzalez-Blohm SA, Doulgeris JJ, Lee WE 3rd, Aghayev K, Vrionis FD. Designs and techniques that improve the pullout strength of pedicle screws in osteoporotic vertebrae: current status. Biomed Res Int. 2014;2014:748393.

    Article  PubMed Central  PubMed  Google Scholar 

  6. Krenn MH, Piotrowski WP, Penzkofer R, Augat P. Influence of thread design on pedicle screw fixation. Laboratory investigation. J Neurosurg Spine. 2008;9(1):90–5.

    Article  PubMed  Google Scholar 

  7. Patel PS, Shepherd DE, Hukins DW. The effect of screw insertion angle and thread type on the pullout strength of bone screws in normal and osteoporotic cancellous bone models. Med Eng Phys. 2010;32(8):822–8.

    Article  PubMed  Google Scholar 

  8. Hirano T, Hasegawa K, Takahashi HE, Uchiyama S, Hara T, Washio T, Sugiura T, Yokaichiya M, Ikeda M. Structural characteristics of the pedicle and its role in screw stability. Spine (Phila Pa 1976). 1997;22(21):2504–9 (discussion 10).

    Article  CAS  Google Scholar 

  9. Weinstein JN, Rydevik BL, Rauschning W. Anatomic and technical considerations of pedicle screw fixation. Clin Orthop Relat Res. 1992;284:34–46.

    PubMed  Google Scholar 

  10. Ricci WM, Tornetta P 3rd, Petteys T, Gerlach D, Cartner J, Walker Z, Russell TA. A comparison of screw insertion torque and pullout strength. J Orthop Trauma. 2010;24(6):374–8.

    Article  PubMed  Google Scholar 

  11. Shah AH, Behrents RG, Kim KB, Kyung HM, Buschang PH. Effects of screw and host factors on insertion torque and pullout strength. Angle Orthod. 2012;82(4):603–10.

    Article  PubMed  Google Scholar 

  12. 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(10):1077–83.

    Article  Google Scholar 

  13. Helgeson MD, Kang DG, Lehman RA Jr, Dmitriev AE, Luhmann SJ. Tapping insertional torque allows prediction for better pedicle screw fixation and optimal screw size selection. Spine J. 2013;13(8):957–65.

    Article  PubMed  Google Scholar 

  14. Wilke HJ, Jungkunz B, Wenger K, Claes LE. Spinal segment range of motion as a function of in vitro test conditions: effects of exposure period, accumulated cycles, angular-deformation rate, and moisture condition. Anat Rec. 1998;251(1):15–9.

    Article  CAS  PubMed  Google Scholar 

  15. Krag MH, Weaver DL, Beynnon BD, Haugh LD. Morphometry of the thoracic and lumbar spine related to transpedicular screw placement for surgical spinal fixation. Spine (Phila Pa 1976). 1988;13(1):27–32.

    Article  CAS  Google Scholar 

  16. Misenhimer GR, Peek RD, Wiltse LL, Rothman SL, Widell EH Jr. Anatomic analysis of pedicle cortical and cancellous diameter as related to screw size. Spine (Phila Pa 1976). 1989;14(4):367–72.

    Article  CAS  Google Scholar 

  17. Kothe R, O’Holleran JD, Liu W, Panjabi MM. Internal architecture of the thoracic pedicle. An anatomic study. Spine (Phila Pa 1976). 1996;21(3):264–70.

    Article  CAS  Google Scholar 

  18. Panjabi MM, Takata K, Goel V, Federico D, Oxland T, Duranceau J, Krag M. Thoracic human vertebrae. Quantitative three-dimensional anatomy. Spine (Phila Pa 1976). 1991;16(8):888–901.

    Article  CAS  Google Scholar 

  19. Lill CA, Schneider E, Goldhahn J, Haslemann A, Zeifang F. Mechanical performance of cylindrical and dual core pedicle screws in calf and human vertebrae. Arch Orthop Trauma Surg. 2006;126(10):686–94.

    Article  CAS  PubMed  Google Scholar 

  20. Koller H, Fierlbeck J, Auffarth A, Niederberger A, Stephan D, Hitzl W, Augat P, Zenner J, Blocher M, Blocher M, Resch H, Mayer M. Impact of constrained dual-screw anchorage on holding strength and the resistance to cyclic loading in anterior spinal deformity surgery: a comparative biomechanical study. Spine (Phila Pa 1976). 2014;39(6):E390–8.

    Article  Google Scholar 

  21. Hsu CC, Chao CK, Wang JL, Hou SM, Tsai YT, Lin J. Increase of pullout strength of spinal pedicle screws with conical core: biomechanical tests and finite element analyses. J Orthop Res. 2005;23(4):788–94.

    Article  PubMed  Google Scholar 

  22. Tsai KJ, Murakami H, Horton WC, Fei Q, Hutton WC. Pedicle screw fixation strength: a biomechanical comparison between 4.5-mm and 5.5-mm diameter screws in osteoporotic upper thoracic vertebrae. J Surg Orthop Adv. 2009;18(1):23–7.

    PubMed  Google Scholar 

  23. 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(2):164–8.

    Article  PubMed  Google Scholar 

  24. Pare PE, Chappuis JL, Rampersaud R, Agarwala AO, Perra JH, Erkan S, Wu C. Biomechanical evaluation of a novel fenestrated pedicle screw augmented with bone cement in osteoporotic spines. Spine (Phila Pa 1976). 2011 Aug;36(18):E1210-4.

  25. Wu Z, Nassar SA, Yang X. Pullout performance of self-tapping medical screws. J Biomech Eng. 2011;133(11):111002.

    Article  PubMed  Google Scholar 

  26. Saraf SK, Singh RP, Singh V, Varma A. Pullout strength of misplaced pedicle screws in the thoracic and lumbar vertebrae—A cadaveric study. Indian J Orthop. 2013;47(3):238–43.

    Article  PubMed Central  PubMed  Google Scholar 

  27. Koller H, Zenner J, Hitzl W, Resch H, Stephan D, Augat P, Penzkofer R, Korn G, Kendell A, Meier O, Mayer M. The impact of a distal expansion mechanism added to a standard pedicle screw on pullout resistance. A biomechanical study. Spine J. 2013;13(5):532–41.

    Article  PubMed  Google Scholar 

  28. Brasiliense LB, Lazaro BC, Reyes PM, Newcomb AG, Turner JL, Crandall DG, Crawford NR. Characteristics of immediate and fatigue strength of a dual-threaded pedicle screw in cadaveric spines. Spine J. 2013;13(8):947–56.

    Article  PubMed  Google Scholar 

  29. Yuksel KZ, Adams MS, Chamberlain RH, Potocnjak M, Park SC, Sonntag VK, Crawford NR. Pullout resistance of thoracic extrapedicular screws used as a salvage procedure. Spine J. 2007;7(3):286–91.

    Article  PubMed  Google Scholar 

Download references

Acknowledgments

This study was supported by a research grant from The National Science Council (NSC 102-2622-B-002-003-CC2, NSC 102-2221-E-002-060-MY3) and National Health Research Institutes (NHRI-EX103-10333EI).

The authors would like to acknowledge the contributions of Dr. Jwo-Luen Pao to clinical consultation and Sheng-Yuan Cheng to data collection.

Conflict of interest

None of the authors have any personal or institutional financial interest in the drugs, materials, or devices described in this manuscript submission.

Author information

Authors and Affiliations

  1. Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, 602 Jen-Shu Tower, 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan, ROC

    Wen-Kai Chou, Andy Chien & Jaw-Lin Wang

  2. Department of Mechanical Engineering, College of Engineering, National Taiwan University, 602 Jen-Shu Tower, 1, Section 4, Roosevelt Road, Taipei, 10617, Taiwan, ROC

    Jaw-Lin Wang

Authors
  1. Wen-Kai Chou
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Andy Chien
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Jaw-Lin Wang
    View author publications

    You can also search for this author in PubMed Google Scholar

Corresponding author

Correspondence to Jaw-Lin Wang.

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Chou, WK., Chien, A. & Wang, JL. Pullout strength of thoracic pedicle screws improved with cortical bone ratio: a cadaveric study. J Orthop Sci 19, 900–906 (2014). https://doi.org/10.1007/s00776-014-0614-3

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s00776-014-0614-3

Keywords

Search

Navigation