Acta Neurochirurgica

, Volume 160, Issue 2, pp 405–411 | Cite as

Regional Hounsfield unit measurement of screw trajectory for predicting pedicle screw fixation using cortical bone trajectory: a retrospective cohort study

  • Keitaro Matsukawa
  • Yuichiro Abe
  • Yoshihide Yanai
  • Yoshiyuki Yato
Original Article - Spine



The sufficiency of screw anchoring is a critical factor for achieving successful spinal fusion; however, no reliable method for predicting pedicle screw fixation has been established. Recently, Hounsfield units (HU) obtained from computed tomography (CT) was developed as a new reliable tool to determine the bone quality. The purpose of the present study was to demonstrate the utility of regional HU measurement of the screw trajectory to predict the primary and long-term fixation strength of pedicle screws.


The insertional torque of pedicle screws using the cortical bone trajectory technique was measured intraoperatively in 92 consecutive patients who underwent single-level posterior lumbar interbody fusion. The cylindrical area of each screw was plotted on the preoperative CT image by precisely confirming the screw position, and the screw trajectory was measured in HU. First, three parameters: the bone mineral density (BMD) of the femoral neck and lumbar vertebrae, and regional HU values of the screw trajectory, were correlated with the insertional torque and compared among three groups. Next, pedicle screw loosening was evaluated by postoperative CT obtained 12 months after surgery, and clinical and imaging data were analyzed to assess whether regional HU values could be used as a predictor of screw loosening.


Regional HU values of the screw trajectory (r = 0.75, p < 0.001) had stronger correlation with the insertional torque than the femoral BMD (r = 0.59, p < 0.001) and lumbar BMD (r = 0.55, p < 0.001). The incidence of screw loosening was 4.6% (16/351). Multivariate logistic regression analysis revealed that regional HU value (odds ratio = 0.70; 95% confidence interval = 0.56-0.84; p = 0.018) was an independent risk factor significantly affected screw loosening.


Regional HU values of the screw trajectory could be a strong predictor of both primary and long-term screw fixation in vivo.


Hounsfield units Pedicle screw fixation Screw loosening Insertional torque Bone density Simulation analysis Cortical bone trajectory 



We thank Akio Seitoku for helpful advice on measuring HU.


No funds were received in support of this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript.

Compliance with ethical standards

Conflict of interest


Ethical approval

All procedures performed in studies involving human participants were in accordance with the ethical standards of our institutional (National Hospital Organization, Murayama Medical Center) and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.

Informed consent

Informed consent was obtained from all individual participants included in the study.


  1. 1.
    Aichmair A, Moser M, Bauer MR, Bachmann E, Snedeker JG, Betz M, Farshad M (2017) Pull-out strength of patient-specific template-guided vs. free-hand fluoroscopically controlled thoracolumbar pedicle screws: a biomechanical analysis of a randomized cadaveric study. Eur Spine J 26:2865–2872CrossRefPubMedGoogle Scholar
  2. 2.
    Brantley AG, Mayfield JK, Koeneman JB, Clark KR (1994) The effects of pedicle screw fit: an in vitro study. Spine (Phila Pa 1976) 19:1752–1758CrossRefGoogle Scholar
  3. 3.
    Bredow J, Boese CK, Werner CML, Siewe J, Löhrer L, Zarghooni K, Eysel P, Scheyerer MJ (2016) Predictive validity of preoperative CT scans and the risk of pedicle screw loosening in spine surgery. Arch Orthop Trauma Surg 136:1063–1067CrossRefPubMedGoogle Scholar
  4. 4.
    Bühler DW, Berlemann U, Oxland TR, Nolte LP (1998) Moments and forces during pedicle screw insertion: in vitro and in vivo measurements. Spine (Phila Pa 1976) 23:1220–1228CrossRefGoogle Scholar
  5. 5.
    Cho W, Cho SK, Wu C (2010) The biomechanics of pedicle screw-based instrumentation. J Bone Joint Surg (Br) 92:1061–1065CrossRefGoogle Scholar
  6. 6.
    Coe JD, Warden KE, Herzig MA, McAfee PC (1990) Influence of bone mineral density on the fixation of thoracolumbar implants: a comparative study of transpedicular screws, laminar hooks, and spinous process wires. Spine (Phila Pa 1976) 15:902–907CrossRefGoogle Scholar
  7. 7.
    DeWald CJ, Stanley T (2006) Instrumentation-related complications of multilevel fusions for adult deformity patients over age 65: surgical considerations and treatment options in patients with poor bone quality. Spine (Phila Pa 1976) 31:S144–S151CrossRefGoogle Scholar
  8. 8.
    Halvorson TL, Kelly LA, Thomas KA, Whitecloud TS, Cook SD (1994) Effects of bone mineral density on pedicle screw fixation. Spine (Phila Pa 1976) 19:2415–2420CrossRefGoogle Scholar
  9. 9.
    Hu SS (1997) Internal fixation in the osteoporotic spine. Spine (Phila Pa 1976) 22:S43–S48CrossRefGoogle Scholar
  10. 10.
    Kim JB, Park SW, Lee YS, Nam TK, Park YS, Kim YB (2015) The effects of spinopelvic parameters and paraspinal muscle degeneration on S1 screw loosening. J Korean Neurosurg Soc 58:357–362CrossRefPubMedPubMedCentralGoogle Scholar
  11. 11.
    Law M, Tencer AF, Anderson PA (1993) Caudo-cephalad loading of pedicle screws: biomechanisms of loosening and methods of augmentation. Spine (Phila Pa 1976) 18:2438–2443CrossRefGoogle Scholar
  12. 12.
    Lee JH, J-H LE, Park JW, Shin YH (2012) The insertional torque of a pedicle screw has a positive correlation with bone mineral density in posterior lumbar pedicle screw fixation. J Bone Joint Surg (Br) 94:93–97CrossRefGoogle Scholar
  13. 13.
    Matsukawa K, Taguchi E, Yato Y, Imabayashi H, Hosogane N, Asazuma T, Nemoto K (2015) Evaluation of the fixation strength of pedicle screws using cortical bone trajectory: what is the ideal trajectory for optimal fixation? Spine (Phila Pa 1976) 40:E873–E878CrossRefGoogle Scholar
  14. 14.
    Matsukawa K, Yato Y, Hynes RA, Imabayashi H, Hosogane N, Yoshihara Y, Asazuma T, Nemoto K (2017) Comparison of pedicle screw fixation strength among different transpedicular trajectories: a finite element study. Clin Spine Surg 30:301–307PubMedGoogle Scholar
  15. 15.
    Matsukawa K, Yato Y, Imabayashi H, Hosogane N, Abe Y, Asazuma T, Chiba K (2016) Biomechanical evaluation of fixation strength among different sizes of pedicle screws using the cortical bone trajectory: what is the ideal screw size for optimal fixation? Acta Neurochir 158:465–471CrossRefPubMedGoogle Scholar
  16. 16.
    Matsukawa K, Yato Y, Kato T, Imabayashi H, Asazuma T, Nemoto K (2014) In vivo analysis of insertional torque during pedicle screwing using cortical bone trajectory technique. Spine (Phila Pa 1976) 39:E240–E245CrossRefGoogle Scholar
  17. 17.
    Meredith DS, Schreiber JJ, Taher F, Cammisa FP Jr, Girardi FP (2013) Lower preoperative Hounsfield unit measurements are associated with adjacent segment fracture after spinal fusion. Spine (Phila Pa 1976) 38:415–418CrossRefGoogle Scholar
  18. 18.
    Mi J, Li K, Zhao X, Zhao CQ, Li H, Zhao J (2017) Vertebral body Hounsfield units are associated with cage subsidence after transforaminal lumbar interbody fusion with unilateral pedicle screw fixation. Clin Spine Surg 30:E1130–E1136PubMedGoogle Scholar
  19. 19.
    Myers BS, Belmont PJ, Richardson WJ, Yu JR, Harper KD, Nightingale RW (1996) The role of imaging and in situ biomechanical testing in assessing pedicle screw pull-out strength. Spine (Phila Pa 1976) 21:1962–1968CrossRefGoogle Scholar
  20. 20.
    Schreiber JJ, Anderson PA, Rosas HG, Buchholz AL, Au AG (2011) Hounsfield units for assessing bone mineral density and strength: a tool for osteoporosis management. J Bone Joint Surg Am 93:1057–1063CrossRefPubMedGoogle Scholar
  21. 21.
    Schreiber JJ, Hughes AP, Taher F, Girardi FP (2014) An association can be found between Hounsfield units and success of lumbar spine fusion. HSS J 10:25–29CrossRefPubMedGoogle Scholar
  22. 22.
    Turkyilmaz I, Sennerby L, McGlumphy EA, Tözüm TF (2009) Biomechanical aspects of primary implant stability: a human cadaver study. Clin Implant Dent Relat Res 11:113–119CrossRefPubMedGoogle Scholar
  23. 23.
    Turkyilmaz I, Tumer C, Ozbek EN, Tözüm TF (2007) Relations between the bone density values from computed tomography, and implant stability parameters: a clinical study of 230 regular platform implants. J Clin Periodontol 34:716–722CrossRefPubMedGoogle Scholar
  24. 24.
    Yamagata M, Kitahara H, Minami S, Takahashi K, Isobe K, Moriya H, Tamaki T (1992) Mechanical stability of the pedicle screw fixation systems for the lumbar spine. Spine (Phila Pa 1976) 17:S51–S54CrossRefGoogle Scholar
  25. 25.
    Zdeblick TA, Kunz DN, Cooke ME, McCabe R (1993) Pedicle screw pullout strength: correlation with insertional torque. Spine (Phila Pa 1976) 18:1673–1676CrossRefGoogle Scholar

Copyright information

© Springer-Verlag GmbH Austria, part of Springer Nature 2017

Authors and Affiliations

  • Keitaro Matsukawa
    • 1
  • Yuichiro Abe
    • 2
  • Yoshihide Yanai
    • 1
  • Yoshiyuki Yato
    • 1
  1. 1.Department of Orthopaedic Surgery, National Hospital OrganizationMurayama Medical CenterTokyoJapan
  2. 2.Department of Orthopaedic SurgeryWajokai Eniwa HospitalEniwaJapan

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