Bone ingrowth around porous-coated acetabular implant: a three-dimensional finite element study using mechanoregulatory algorithm

Abstract

Fixation of uncemented implant is influenced by peri-prosthetic bone ingrowth, which is dependent on the mechanical environment of the implant-bone structure. The objective of the study is to gain an insight into the tissue differentiation around an acetabular component. A mapping framework has been developed to simulate appropriate mechanical environment in the three-dimensional microscale model, implement the mechanoregulatory tissue differentiation algorithm and subsequently assess spatial distribution of bone ingrowth around an acetabular component, quantitatively. The FE model of implanted pelvis subjected to eight static load cases during a normal walking cycle was first solved. Thereafter, a mapping algorithm has been employed to include the variations in implant-bone relative displacement and host bone material properties from the macroscale FE model of implanted pelvis to the microscale FE model of the beaded implant-bone interface. The evolutionary tissue differentiation was observed in each of the 13 microscale models corresponding to 13 acetabular regions. The total implant-bone relative displacements, averaged over each region of the acetabulum, were found to vary between 10 and 60 μm. Both the linear elastic and biphasic poroelastic models predicted similar mechanoregulatory peri-prosthetic tissue differentiation. Considerable variations in bone ingrowth (13-88%), interdigitation depth (0.2-0.82 mm) and average tissue Young's modulus (970-3430 MPa) were predicted around the acetabular cup. A progressive increase in the average Young's modulus, interdigitation depth and decrease in average radial strains of newly formed tissue layer were also observed. This scheme can be extended to investigate tissue differentiation for different surface texture designs on the implants.

Novel adaptive finite element algorithms to predict bone ingrowth in additive manufactured porous implants

“…Changes in bone density around an implant have been predicted for internal remodelling [16,22,23] and are associated with changes in bone density rather than changes in bone shape. Bone ingrowth in porous implants has been modelled to predict remodelling at equilibrium state [17,22,24], but yield little information on the progression of bone formation associated with adaptive shape changes, which has been observed clinically as extracortical bone formation adjacent to segmental prosthesis. Current algorithms based on SED are not able to predict the progression of bone ingrowth into substantially porous structures made by additive manufacturing.…”

Biomechanical behaviours of the bone–implant interface: a review

“…Moreover, histomorphometry is a destructive technique that cannot be used in clinical practice without having to carry out post-mortem experiments. Even if modelling and simulation allow powerful methods that take into account the effect of osseointegration at different scales to be implemented [31,[126][127][128][129], an important advantage of applying multi-modality experimental techniques is that they allow complementary information on the multi-scale properties of newly formed bone tissue to be retrieved.…”

The influence of loading configurations on numerical evaluation of failure mechanisms in an uncemented femoral prosthesis

“…13,37,38 Higher implant-bone relative displacements and inadequate peri-prosthetic bone ingrowth affect implant-bone primary fixation. [39][40][41][42] Bone resorption around the femoral implant cause a reduction in localised bone density and strength, which increases the risk of bone failure due to excessive bone strains. 2,3,5,43,44 In order to evaluate implant-bone failure, maximum principal strains (tensile and compressive), implant induced bone adaptation, bone interface failure and implant-bone relative displacements were considered as four major failure criteria.…”

“…The threshold level of dead zone used in this study was 75% of the physiological SED. The change in bone apparent density were computed as follows 38,42 :…”