Shear and tensile strength of hydroxyapatite coating under loading conditions

An experimental study in dogs
  • R. T. Müller
  • T. Patsalis
Original Article


The shear and tensile strength of a hydroxyapatite (HA) coating on a femoral component was studied after physiological loading conditions in 8 German Shepherds. A proximal macrostructure on the stem was used to protect this region from shear stresses. Another four implantations with uncoated components were used as controls. In vitro testing of the HA layer demonstrated excellent tensile strength and stability to surface deformation. The loaded implants were tested at 6, 12, and 24 weeks. At 6 weeks the HA-coated components could easily be removed by axial loading, whereas the HA layer remained undamaged on the metal. However, pull out tests of implants older than 12 weeks showed complete debonding of the HA layer from the non-macrostructured surface due to shear forces in all cases. Debonding of the HA layer was also observed with microradiography. The macrostructured surface prevented dislodging of the component from this area at pull out test by distributing shear forces. Unlike in uncoated implants, considerable amounts of bone remained attached onto the HA macrostructure when the surrounding femur was pulled out. Shear forces cause debonding of the HA layer, while tensile stress affects failure within the bone. Physiological loading partially produces gaps at the interface so direct transmission of tensile forces onto the bone is lost, and the coating-metal interface becomes the weak point in the system.


Shear Stress Tensile Strength Tensile Stress Hydroxyapatite Shear Force 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Bobyn JD, Pilliar RM, Cameron HU, Weatherly CG, Kent GM (1989) The effect of porous surface configuration on the tensile strength of fixation of implants by bone ingrowth. Clin Orthop 149:291–298Google Scholar
  2. 2.
    Dhert WJ (1994) Retrieval studies on calcium phosphate-coated implants. Med Prog Technol 20:143–154Google Scholar
  3. 3.
    Filiaggi MJ, Coombs NA, Pilliar RM (1991) Characterization of an interface in the plasma sprayed HA coating/Ti-6A1-4V implant system. J Biomed Mater Res 25:1211–1229Google Scholar
  4. 4.
    Furlong RJ, Osborn JF (1991) Fixation of hip prosthesis by hydroxyapatite ceramic coatings. J Bone Joint Surg [Br] 73:741–745Google Scholar
  5. 5.
    Geesink RGT, Groot K de, Klein CPAT (1987) Chemical implant fixation using hydroxyl-apatite coatings. Clin Orthop 225 147–170Google Scholar
  6. 6.
    Hardy DCR, Frayssinet P, Guilhem A, Lafontaine MA, Delince PE (1991) Bonding of hydroxyapatite-coated femoral prostheses. J Bone Joint Surg [Br] 73:732–740Google Scholar
  7. 7.
    Hetherington VJ, Lord CE, Brown SA (1995) Mechanical and histological fixation of hydroxyapatite-coated pyrolytic carbon and titanium alloy implants: a report of short-term results. J Appl Biomater 6:243–248Google Scholar
  8. 8.
    Jasty M, Rubash HE, Paiement GD, Bragdon CR, Parr J, Harris WH (1992) Porous-coated uncemented components in experimental total hip arthroplasty in dog. Clin Orthop 280:300–309Google Scholar
  9. 9.
    Kroon PO, Freeman MAR (1992) Hydroxyapatite coating of hip prosthesis, effect on migration into the femur. J Bone Joint Surg [Br] 74:518–522Google Scholar
  10. 10.
    Meiss L, Mallinckrodt D v, Lindner HA, Pöllen P (1988) Zur Entwicklung hydroxyapatitbeschichteter Schäfte für Hüfttotal-endoprothesen. Med Orthop Tech 108:16–20Google Scholar
  11. 11.
    Osborn JF (1989) Physiologische Verankerung von belasteten Endoprothesen durch Verbundosteogenese — Ergebnisse humanhistologischer Auswertungen hydroxyapatitkeramikbeschichteter Titanschäfte. In: Willert HG, Heuck FHW (eds) Neure Ergebnisse in der Osteologie. Springer, Berlin Heidelberg New YorkGoogle Scholar
  12. 12.
    Shen WJ, Chung KCC, Wang GJ, McLaughlin RE (1992) Mechanical failure of hydroxyapatite- and polysulfone-coated titanium rods in a weight-bearing canine model. J Arthroplasty 7:43–49Google Scholar
  13. 13.
    Soballe K (1993) Hydroxyapatite ceramic coating for bone implant fixation — mechanical and histological studies in dogs. Acta Orthop Scand Suppl (255) 64:1–64Google Scholar
  14. 14.
    Spivak JM, Ricci JL, Blumenthal NC, Alexander H (1990) A new canine model to evaluate the biologic response of intramedullary bone to implant materials and surfaces. J Biomed Mater Res 24:1121–1149Google Scholar
  15. 15.
    Stephenson PK, Freeman MAR, Revell PA, Germain J, Tuke M, Pirie CJ (1991) The effect of hydroxyapatite coating on ingrowth of bone into cavities in an implant. J Arthroplasty 6:51–58Google Scholar
  16. 16.
    Thomas KA, Cook SD (1987) Hydroxylapatit-beschichtete metallische Implantate: Untersuchungen zu Verbindungsstärke und Histologie der Kontaktzone Knochen/Implantat. Phillip J 5:287–301Google Scholar
  17. 17.
    Willmann G, Richter H, Wimmer M (1993) Umlaufbiegeprüfung an mit Hydroxylapatit plasmabeschichteten Prüfkörpern aus TiA16V4. Biomed Tech 83:14–16Google Scholar

Copyright information

© Springer-Verlag 1997

Authors and Affiliations

  • R. T. Müller
    • 1
  • T. Patsalis
    • 1
  1. 1.Orthopädische UniversitätsklinikEssenGermany

Personalised recommendations