Archives of Orthopaedic and Trauma Surgery

, Volume 113, Issue 5, pp 271–275 | Cite as

Comparison of the mechanical performance of three types of unilateral, dynamizable external fixators

An experimental study
  • R. A. Jaskulka
  • E. Egkher
  • B. Wielke
Original Article


Due to the increasing popularity of unilateral dynamizable external fixators for treating tibial shaft fractures, many new devices are being introduced onto the market. Especially in such half-frame fixators, the choice of any particular device depends above all on the stability of its construction. This study compares the biomechanical stability of three systems tested in axial compression, torsion, and both anterior-posterior and medial-lateral bending. In terms of the nondynamized phase, the AO/ASIF tubular fixator (as a one-plane, double-tube, unilateral frame) and the Martin Mono-Dynafix are, in general, less stable than the Orthofix fixator. After dynamization, the AO/ASIF system becomes particularly weak and offers low resistance especially to torque and any force that is perpendicular to the plane of assembly. The other two tested devices evinced much more stability; the Orthofix fixator seems superior to the Dynafix due to the different diameter of its screws.


Public Health Torque Mechanical Performance Axial Compression External Fixators 
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  1. 1.
    Aro HT, Kelly PJ, Lewallen DG, Chao EY (1990) The effects of physiologic dynamic compression on bone healing under external fixation. Clin Orthop Rel Res 256:260–273Google Scholar
  2. 2.
    Chao EY, Hein TJ (1988) Mechanical performance of the standard Orthofix external fixator. Orthopedics 11:1057–1069Google Scholar
  3. 3.
    Chao EYS, Aro HT, Lewallen DG, Kell PJ (1989) The effect of rigidity on fracture healing in external fixation. Clin Orthop Rel Res 241:24–35Google Scholar
  4. 4.
    De Bastiani G, Aldegheri R, Renzi Brivio L (1984) The treatment of fractures with a dynamic axial fixator. J Bone Joint Surg [Br] 66-B:538–545Google Scholar
  5. 5.
    Egkher E (1985) Theoretische und experimentelle Studien zur Technologie der externen Knochenbruchstabilisierung. Wien Klin Wochenschr 97 [Suppl 158]Google Scholar
  6. 6.
    Evans M, Spencer M, Wang Q, White SH, Cunningham JL (1990) Design and testing of external fixator bone screws. J Biomed Engl 2:457–462Google Scholar
  7. 7.
    Goodship AE, Kenwright J (1990) The influence of induced micromovement upon the healing of experimental tibial fractures. J Bone Joint Surg [Br] 67-B:650Google Scholar
  8. 8.
    Heitemeyer U, Claes L, Hierholzer G, Korber (1990) Significance of postoperative stability for bony reparation of comminuted fractures. An experimental study. Arch Orthop Trauma Surg 109:144–149Google Scholar
  9. 9.
    Huiskes R, Chao EY (1986) Guidelines for external fixation frame rigidity and stresses. J Orthop Res 4:68–75Google Scholar
  10. 10.
    Lewallen DG, Chao EY, Kasman RA, Kelly PJ (1984) Comparison of the effects of compression plates and external fixators on early bone healing. J Bone Joint Surg [Am] 66-A:1084–1091Google Scholar
  11. 11.
    Müller ME, Allgöwer M, Schneider R, Willenegger H (1991) Manual of internal fixation. Techniques recommended by the AO-ASIF group, 3rd edn. Springer, Berlin Heidelberg New YorkGoogle Scholar
  12. 12.
    Ralston JL, Brown TD, Nepola JV, Williams DR, Marsh JL (1990) Mechanical analysis of the factors affecting dynamization of the Orthofix dynamic axial fixator. J Orthop Trauma 4:449–457Google Scholar
  13. 13.
    Schatzker J, Horne JG, Sumner-Smith G (1977) The reaction of cortical bone to compression by screw threads. Clin Orthop Rel Res 111:248–252Google Scholar
  14. 14.
    Williams EA, Rand JA, An KN, Chao EY, Kelly PJ (1987) The early healing of tibial osteotomies stabilized by one-plane or two-plane external fixation. J Bone Joint Surg [Am] 69-A:355–365Google Scholar
  15. 15.
    Wu JJ, Shyr HS, Chao EY, Kelly PJ (1984) Comparison of osteotomy healing under external fixation devices with different stiffness characteristics. J Bone Joint Surg [Am] 66-A:1258–1264Google Scholar

Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • R. A. Jaskulka
    • 1
  • E. Egkher
    • 2
  • B. Wielke
    • 3
  1. 1.Department for Trauma SurgeryMedical Center EastViennaAustria
  2. 2.Clinic for Trauma SurgeryUniversity of ViennaAustria
  3. 3.Institute for Solid State PhysicUniversity of ViennaAustria

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