Transcortical or intracondylar? Which model is accurate for predicting biomaterial attachment in total joint replacement?

Abstract

Despite four decades of research on material and porous coatings intended for cementless fixation in total joint replacement (TJR), aseptic mechanical loosening unrelated to particulate disease remains a concern. One main question asked is how translational are the animal models used to screen material and porous coatings intended for TJR fixation? Another question is how specific are the translational models at targeting the cementless TJR components that have the highest loosening rates? The hypothesis tested was that the bone response would be different between the two bone types-cortical and cancellous-used in translational animal modeling. The osteoblastic jumping distance (OJD), percent ingrowth, and appositional bone response were measured to assess the response between cancellous and cortical bone at two different anatomical locations, within the same limb. With 500 µm inset, titanium porous coated implants and negative control dinosaur (coprolite) implants were investigated. The data demonstrated that cortical bone had 7 times OJD than cancellous bone. The bone ingrowth data demonstrated 16 times higher bone ingrowth than the cancellous bone. Light microscopy showed predominately fibrous tissue attachment (98%) in cancellous bone. Screening of materials intended for TJR require a translational model predictive of the clinical condition. The results demonstrated that the transcortical model rendered false-positive data. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 578-588, 2018.

Bone ingrowth comparison of irregular titanium and cobalt‐chromium coatings in a translational cancellous bone model

“…The biological healing zone only appeared to influence 100–200 μm of bone in the periprosthetic region of the porous‐coated plugs, suggesting the host tissue was relatively unaffected by the porous‐coated plug placement. This coincides with Bloebaum et al, which reported that the osteoblastic jumping distance of cancellous bone from the surgically prepared surface was ~169 μm in a similar translational cancellous bone model (Bloebaum et al, ). The observed unaltered host bone was confirmed with light microscopy analysis which reveled healthy bone marrow in the adjacent host trabeculae as well as osteoblast activity within both porous coating types.…”

“…The radiography demonstrated well‐placed plugs with good bone‐implant contact for both porous coating types at Time = 0 with the exception to a single CoCr plug that only achieved ~50% ABI due to surgical error. This observation emphasizes the need for precision operative placement of porous‐coated devices to achieve initial bone implant‐contact to avoid gaps that can lead to fibrous tissue being interposed between the coating and host trabeculae (Bloebaum et al, ). The lower ABI in this lone plug was shown to be due to over drilling at the time of surgical placement and was not indicative of the porous coating material.…”

“…Recently, Bloebaum et al suggested that using the wrong translational animal model may be responsible for the failure thus far to achieve reproducible cementless skeletal attachment clinically. The authors demonstrated that screening a potential material intended for cementless fixation in the transcortical model could result in false positive data compared to the more sensitive weight‐bearing cancellous bone model, thus, contributing to early clinical failure due to a lack of bone fixation in various implant systems in addition to other major design flaws (Bloebaum et al, ; de Steiger, Hang, Miller, Graves, & Davidson, ).…”

Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone

“…New bone was observed in the cancellous gap sites in the Ti HA group that could be attributed to the presence of the calcium phosphate coating and local biological benefits [8,36]. This effect was particularly apparent at the early (4 week [7, 8, 12-14, 25-28, 37, 38] and dogs [11,15,[39][40][41] as well as cancellous sites as performed in this study [12,13,26,28] and intercondylar sites [37,38,42]. Care should always be taken when making Titanium alloy coated with plasma sprayed titanium.…”

Bone ongrowth and mechanical fixation of implants in cortical and cancellous bone

“…Preclinical studies have limitations but allow for tighter control of variables such as animal age, implant geometry, and implantation conditions that can help identify the advantages as well as disadvantages of different technologies. A variety of large animal preclinical models have been used to examine the bone- implant interface with cylindrical dowels to evaluate bone ingrowth and ongrowth to different materials and surface coatings in cortical sites in sheep [7, 8, 12-14, 25-28, 37, 38] and dogs [11,15,[39][40][41] as well as cancellous sites as performed in this study [12,13,26,28] and intercondylar sites [37,38,42]. Care should always be taken when making the jump to the human clinical scenario.…”