• 1. Lewis DD, Radasch RM, Beale BS, et alInitial clinical experience with the IMEX Circular External Skeletal Fixation System part I: use in fractures and arthrodeses. Vet Comp Orthop Traumatol 1999;12:108117.

    • Search Google Scholar
    • Export Citation
  • 2. Lewis DD, Radasch RM, Beale BS, et alInitial clinical experience with the IMEX Circular External Skeletal Fixation System part II: use in bone lengthening and correction of angular and rotational deformities. Vet Comp Orthop Traumatol 1999;12:118127.

    • Search Google Scholar
    • Export Citation
  • 3. Marcellin-Little DJ, Ferretti A, Roe SC, et alHinged Ilizarov external fixation for correction of antebrachial deformities. Vet Surg 1998;27:231245.

    • Search Google Scholar
    • Export Citation
  • 4. Marcellin-Little DJ. Fracture treatment with circular external fixation. Vet Clin North Am Small Anim Pract 1999;29:11531170.

  • 5. Anderson GM, Lewis DD, Radasch RM, et alCircular external skeletal fixation stabilization of antebrachial and crural fractures in 25 dogs. J Am Anim Hosp Assoc 2003;39:479498.

    • Search Google Scholar
    • Export Citation
  • 6. Jaeger GH, Wosar MA, Marcellin-Little DJ, et alUse of hinged transarticular external fixation for adjunctive joint stabilization in dogs and cats: 14 cases (1999–2003). J Am Vet Med Assoc 2005;227:586591.

    • Search Google Scholar
    • Export Citation
  • 7. Ehrhart N. Longitudinal bone transport for treatment of primary bone tumors in dogs: technique description and outcome in 9 dogs. Vet Surg 2005;34:2434.

    • Search Google Scholar
    • Export Citation
  • 8. Lotsikas PJ, Radasch RM. A clinical evaluation of pancarpal arthrodesis in nine dogs using circular external skeletal fixation. Vet Surg 2006;35:480485.

    • Search Google Scholar
    • Export Citation
  • 9. Farese JP, Lewis DD, Cross AR, et alUse of IMEX SK-circular external fixator hybrid constructs for fracture stabilization in dogs and cats. J Am Anim Hosp Assoc 2002;38:279289.

    • Search Google Scholar
    • Export Citation
  • 10. Rovesti GL, Bosio A, Marcellin-Little DJ. Management of 49 antebrachial and crural fractures in dogs using circular external fixators. J Small Anim Pract 2007;48:194200.

    • Search Google Scholar
    • Export Citation
  • 11. Kirkby KA, Lewis DD, Lafuente MP, et alManagement of humeral and femoral fractures in dogs and cats with linear-circular hybrid external skeletal fixators. J Am Anim Hosp Assoc 2008;44:180197.

    • Search Google Scholar
    • Export Citation
  • 12. Sereda CW, Lewis DD, Radasch RM, et alDescriptive report of antebrachial growth deformity correction in 17 dogs from 1999 to 2007, using hybrid linear-circular external fixator constructs. Can Vet J 2009;50:723732.

    • Search Google Scholar
    • Export Citation
  • 13. Ilizarov GA. Clinical application of the tension-stress effect for limb lengthening. Clin Orthop Relat Res 1990;250:826.

  • 14. Lewis DD, Bronson DG, Samchukov ML, et alBiomechanics of circular external skeletal fixation. Vet Surg 1998;27:454464.

  • 15. Lewis DD, Bronson DG, Cross AR, et alAxial characteristics of circular external skeletal fixator single ring constructs. Vet Surg 2001;30:386394.

    • Search Google Scholar
    • Export Citation
  • 16. Lewis DD, Cross AR, Carmichael S, et alRecent advances in external skeletal fixation. J Small Anim Pract 2001;42:103112.

  • 17. Marcellin-Little DJ. External skeletal fixation. In: Slatter D, ed. Textbook of small animal surgery. 3rd ed. Philadelphia: Saunders, 2003;18181834.

    • Search Google Scholar
    • Export Citation
  • 18. Cross AR, Lewis DD, Murphy ST, et alEffects of ring diameter and wire tension on the axial biomechanics of four-ring circular external skeletal fixator constructs. Am J Vet Res 2001;62:10251030.

    • Search Google Scholar
    • Export Citation
  • 19. Cross AR, Lewis DD, Rigaud S, et alEffect of various distal ring-block configurations on the biomechanical properties of circular external skeletal fixators for use in dogs and cats. Am J Vet Res 2004;65:393398.

    • Search Google Scholar
    • Export Citation
  • 20. Marcellin-Little DJ, Roe SC, Rovesti GL, et alAre circular external fixators weakened by the use of hemispheric washers? Vet Surg 2002;31:367374.

    • Search Google Scholar
    • Export Citation
  • 21. Ryan S, Ehrhart N, Zuehlsdorff K, et alComparison of alternate and simultaneous tensioning of wires in a single-ring fixator construct. Vet Surg 2009;38:96103.

    • Search Google Scholar
    • Export Citation
  • 22. Wosar MA, Marcellin-Little DJ, Roe SC. Influence of bolt tightening torque, wire size, and component reuse on wire fixation in circular external fixation. Vet Surg 2002;31:571576.

    • Search Google Scholar
    • Export Citation
  • 23. American Society for Testing and Materials. F 1541 standard specification and test methods for external skeletal fixation devices. In: Annual book of ASTM standards. West Conshohocken, Pa: American Society for Testing and Materials, 2002;131.

    • Search Google Scholar
    • Export Citation
  • 24. BronsonSamchukov ML, Birch JG, et alStability of external circular fixation: a multi-variable biomechanical analysis. Clin Biomech 1998;13:441448.

    • Search Google Scholar
    • Export Citation
  • 25. Podolsky A, Chao EY. Mechanical performance of Ilizarov circular external fixators in comparison with other external fixators. Clin Orthop Relat Res 1993;293:6170.

    • Search Google Scholar
    • Export Citation
  • 26. Fleming B, Paley D, Kristiansen T, et alA biomechanical analysis of the Ilizarov external fixator. Clin Orthop Relat Res 1989;241:95105.

    • Search Google Scholar
    • Export Citation
  • 27. Gasser B, Boman B, Wyder D, et alStiffness characteristics of the circular Ilizarov device as opposed to conventional external fixators. J Biomech Eng 1990;112:1521.

    • Search Google Scholar
    • Export Citation
  • 28. Kummer FJ. Biomechanics of the Ilizarov external fixator. Clin Orthop Relat Res 1992;280:1114.

  • 29. Goodship AE, Kenwright J. The influence of induced micromovement upon the healing of experimental tibial fractures. J Bone Joint Surg Br 1985;67:650655.

    • Search Google Scholar
    • Export Citation
  • 30. Kenwright J, Richardson JB, Cunningham JL, et alAxial movement and tibial fractures. A controlled randomised trial of treatment. J Bone Joint Surg Br 1991;73:654659.

    • Search Google Scholar
    • Export Citation
  • 31. Wolf S, Janousek A, Pfeil J, et alThe effects of external mechanical stimulation on the healing of diaphyseal osteotomies fixed by flexible external fixation. Clin Biomech 1998;13:359364.

    • Search Google Scholar
    • Export Citation
  • 32. Watson MA, Mathias KJ, Maffulli N. External ring fixators: an overview. Proc Inst Mech Eng H 2000;214:459470.

  • 33. Zhang G. Geometric and material nonlinearity in tensioned wires of an external fixator. Clin Biomech 2004;19:513518.

  • 34. Seibert RL, Lewis DD, Coomer AR, et alStabilisation of metacarpal or metatarsal fractures in three dogs, using circular external skeletal fixation. N Z Vet J 2011;59:96103.

    • Search Google Scholar
    • Export Citation
  • 35. Lewis DD, Farese JP. Circular external skeletal fixation. In: Bojrab JM, ed. Current techniques in small animal surgery. 5th ed. St Louis: Lippincott Williams & Wilkins, 2012;in press.

    • Search Google Scholar
    • Export Citation
  • 36. MicroScribe 3D desktop digitizing systems: user's guide and setup instructions. San Jose, Calif: Immersion Corp, 2000;19.

  • 37. Orbay GL, Frankel VH, Kummer FJ. The effect of wire configuration on the stability of the Ilizarov external fixator. Clin Orthop Relat Res 1992;279:299302.

    • Search Google Scholar
    • Export Citation

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Axial stiffness and ring deformation of complete and incomplete single ring circular external skeletal fixator constructs

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  • 1 Comparative Orthopaedic and Biomechanics Laboratory, University of Florida, Gainesville, FL 32610.
  • | 2 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.
  • | 3 Comparative Orthopaedic and Biomechanics Laboratory, University of Florida, Gainesville, FL 32610.
  • | 4 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.
  • | 5 Georgia Veterinary Specialists, 455 Abernathy Rd NE, Atlanta, GA 30328.
  • | 6 Comparative Orthopaedic and Biomechanics Laboratory, University of Florida, Gainesville, FL 32610.
  • | 7 Department of Orthopaedics and Rehabilitation, College of Medicine, University of Florida, Gainesville, FL 32610.
  • | 8 Comparative Orthopaedic and Biomechanics Laboratory, University of Florida, Gainesville, FL 32610.
  • | 9 Department of Mechanical and Aerospace Engineering, College of Engineering, University of Florida, Gainesville, FL 32610.
  • | 10 Comparative Orthopaedic and Biomechanics Laboratory, University of Florida, Gainesville, FL 32610.
  • | 11 Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

Abstract

Objective—To compare the axial stiffness, maximum axial displacement, and ring deformation during axial loading of single complete and incomplete circular (ring) external skeletal fixator constructs.

Sample—32 groups of single ring constructs (5 constructs/group).

Procedures—Single ring constructs assembled with 2 divergent 1.6-mm-diameter Kirschner wires were used to stabilize a 60-mm-long segment of 16-mm-diameter acetyl resin rod. Construct variables included ring type (complete or incomplete), ring diameter (50, 66, 84, or 118 mm), and fixation wire tension (0, 30, 60, or 90 kg). Axial loading was performed with a materials testing system. Construct secant stiffness and maximum displacement were calculated from the load-displacement curves generated for each construct. Ring deformation was calculated by comparing ring diameter during and after construct loading to ring diameter prior to testing.

Results—Complete ring constructs had greater axial stiffness than did the 66-, 84-, and 118-mm-diameter incomplete ring constructs. As fixation wire tension increased, construct stiffness increased in the 66-, 84-, and 118-mm-diameter incomplete ring constructs. Maximum axial displacement decreased with increasing fixation wire tension, and complete ring constructs allowed less displacement than did incomplete ring constructs. Incomplete rings were deformed by wire tensioning and construct loading.

Conclusions and Clinical Relevance—Mechanical performance of the 66-, 84-, and 118-mm-diameter incomplete ring constructs improved when wire tension was applied, but these constructs were not as stiff as and allowed greater displacement than did complete ring constructs of comparable diameter. For clinical practice, tensioning the wires placed on 84- and 118-mm-diameter incomplete rings to 60 kg is recommended.

Abstract

Objective—To compare the axial stiffness, maximum axial displacement, and ring deformation during axial loading of single complete and incomplete circular (ring) external skeletal fixator constructs.

Sample—32 groups of single ring constructs (5 constructs/group).

Procedures—Single ring constructs assembled with 2 divergent 1.6-mm-diameter Kirschner wires were used to stabilize a 60-mm-long segment of 16-mm-diameter acetyl resin rod. Construct variables included ring type (complete or incomplete), ring diameter (50, 66, 84, or 118 mm), and fixation wire tension (0, 30, 60, or 90 kg). Axial loading was performed with a materials testing system. Construct secant stiffness and maximum displacement were calculated from the load-displacement curves generated for each construct. Ring deformation was calculated by comparing ring diameter during and after construct loading to ring diameter prior to testing.

Results—Complete ring constructs had greater axial stiffness than did the 66-, 84-, and 118-mm-diameter incomplete ring constructs. As fixation wire tension increased, construct stiffness increased in the 66-, 84-, and 118-mm-diameter incomplete ring constructs. Maximum axial displacement decreased with increasing fixation wire tension, and complete ring constructs allowed less displacement than did incomplete ring constructs. Incomplete rings were deformed by wire tensioning and construct loading.

Conclusions and Clinical Relevance—Mechanical performance of the 66-, 84-, and 118-mm-diameter incomplete ring constructs improved when wire tension was applied, but these constructs were not as stiff as and allowed greater displacement than did complete ring constructs of comparable diameter. For clinical practice, tensioning the wires placed on 84- and 118-mm-diameter incomplete rings to 60 kg is recommended.

Contributor Notes

Some of the materials used in this study were provided by IMEX Veterinary Inc.

Presented as a podium presentation at the 38th Annual Conference of the Veterinary Orthopedic Society, Snowmass, Colo, March 2011.

None of the listed authors have a financial interest in any of the products or companies described in this manuscript.

Address correspondence to Dr. Hudson (HudsonC@ufl.edu).