The effect of bone ingrowth depth on the tensile and shear strength of the implant–bone e-beam produced interface
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New technologies, such as selective electron beam melting, allow to create complex interface structures to enhance bone ingrowth in cementless implants. The efficacy of such structures can be tested in animal experiments. Although animal studies provide insight into the biological response of new structures, it remains unclear how ingrowth depth is related to interface strength. Theoretically, there could be a threshold of ingrowth, above which the interface strength does not further increase. To test the relationship between depth and strength we performed a finite element study on micro models with simulated uncoated and hydroxyapatite (HA) coated surfaces. We examined whether complete ingrowth is necessary to obtain a maximal interface strength. An increase in bone ingrowth depth did not always enhance the bone–implant interface strength. For the uncoated specimens a plateau was reached at 1,500 μm of ingrowth depth. For the specimens with a simulated HA coating, a bone ingrowth depth of 500 μm already yielded a substantial interface strength, and deeper ingrowth did not enhance the interface strength considerably. These findings may assist in optimizing interface morphology (its depth) and in judging the effect of bone ingrowth depth on interface strength.
KeywordsShear Strength Interface Strength Bone Ingrowth Finite Element Method Model Coated Specimen
This study was partly sponsored by Eurocoating SpA (Trento, Italy) and “Provincia Autonoma di Trento” under the project called “E-Ortho”. The authors would like to thank Pierfrancesco Robotti and Emanuele Magalini (Eurocoating, Trento, Italy), who actively participated in this study and provided the CT scan of the EBM produced structures.
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