Balancing incompatible endoprosthetic design goals: A combined ingrowth and bone remodeling simulation

Abstract

In order to design a good cementless femoral implant many requirements need to be fulfilled. For instance, the range of micromotions at the bone-implant interface should not exceed a certain threshold and a good ratio between implant-bone stiffness that does not cause bone resorption, needs to be ensured. Stiff implants are known to evoke lower interface micromotions but at the same time they may cause extensive resorption of the surrounding bone. Composite stems with reduced stiffness give good remodeling results but implant flexibility is likely to evoke high micromotions proximally. Finding a good balance between these incompatible design goals is very challenging. The current study proposes a finite element methodology that employs subsequent ingrowth and remodeling simulations and can be of assistance when designing new implants. The results of our simulations for the Epoch stem were in a good agreement with the clinical data. The proposed implant design made of porous tantalum with an inner CoCrMo core performed slightly better with respect to the Epoch stem and considerably better with respect to a Ti alloy stem. Our combined ingrowth and remodeling simulation can be a useful tool when designing a new implant that well balances mentioned incompatible design goals.

On the optimal shape of hip implants

“…For different materials, results may differ, since it is known that the stem stability depend on material stiffness (Tarala et al, 2011). Also, the limited number of load cases, only Table 4 Bone mass variation (percentage variation is referred to the total amount of bone immediately after the surgery).…”

Numerical analysis of an osseointegrated prosthesis fixation with reduced bone failure risk and periprosthetic bone loss

“…To eliminate stress shielding around hip stems numerous shape and material modifications have been proposed and introduced to the designs throughout the past decades, i.e. proximally porous-coated stems (Rothman et al, 1996), composite implants (Glassman et al, 2001) or porous tantalum prostheses (Levine et al, 2006;Tarala et al, 2011a).…”

Activity intensity, assistive devices and joint replacement influence predicted remodelling in the proximal femur

“…In addition to remodelling, the cementless implant scenario involves the healing of surgical damage to the bone and surrounding soft tissues, transient responses to primary implant fixation, potentially external remodelling, and often the progressive osseointegration of implants through bioactive surface coatings for secondary fixation. Osseointegration has been simulated alone and combined with remodelling (Tarala et al 2011), and the effects of progressive implant-cement and implant-bone interface fixation and failure have been considered in hip resurfacing (Pal et al 2009;Caouette et al 2013). A simplification of the present study is the neglect of these effects.…”

“…This method has been applied to femoral implants in THR (Kerner et al 1999;Turner et al 2005), RHR (Gupta et al 2006;Pal et al 2009;Rothstock et al 2011;Dickinson et al 2012;Perez et al 2014), to acetabular cups (Ghosh et al 2013), and in other joints (van Lenthe et al 1997). Advanced approaches have combined strain adaptive bone remodelling with other associated mechanobiological processes, including cementless implant ingrowth (Tarala et al 2011) and periprosthetic defect healing (Dickinson et al 2012).…”