Total hip arthroplasty (THA) in cases of large acetabular defects and in patients with osteoporotic bone can be difficult. Furthermore, achieving a long-term stable fixation of the acetabular cup is challenging [1–4].
Cement usage for acetabular cup fixation in primary THA has fallen out of favor in recent decades mostly due to increased risk of aseptic loosening in mid and long-term follow-up [5–8]. Biological fixation of highly porous biomaterials in THA plays an important role in long term survivorship of acetabular implants. A long-term stable fixation of these implants depends largely on the osseointegration of bone tissue into them .
Following acetabular component placement osseointegration depends on both the quality of bone tissue, and the properties of the implant surface [10–12]. New highly porous biomaterials were developed to enhance osseointegration and survivorship of acetabular reconstruction . Current, highly porous biomaterials for THA are made of tantalum and titanium (partial use alloy Ti6Al4V) . The advantages of porous tantalum are: high thermal conductivity, biocompatibility [15, 16], and they have been shown to have good survivorship in long term follow-up [17, 18]. However according to the Swedish Hip Arthroplasty Registry and the Australian Orthopaedic Association National Joint Replacement Registry data, Trabecular Metal acetabular components in primary THA showed a higher risk for revision compared with other uncemented acetabular cups [19, 20].
Current research focuses on porous titanium materials characteristics, as well as their comparison with tantalum implants [21, 22]. Titanium porous implants have low thermal conductivity, high yield strength, low weight, have been shown to have high survival  and lower cost compared to tantalum implants . In a 10-year clinical randomized trial of primary THA porous tantalum monoblock cups exhibited greater stability and 100% survivorship compared to porous-coated titanium monoblock cup . In another study using multivariate logistic regression, the authors compared the survival of porous tantalum and porous titanium acetabular components with primary THA at an average of 44.4 months the authors found no difference in outcomes .
Bone changes in osteoporosis may cause additional difficulty in acetabular reconstruction as well as increasing the risk of aseptic failure and loosening. Under these conditions, the requirements for implant materials become even more important. In order to study osseointegration and fixation properties animal models were established for material evaluation . It has been established that osteoporosis can affect the fixation and osseointegration of implants [25, 26], in particular, giving the different response of osteoporotic cortical and trabecular bone to material implantation . Therefore, establishing the structural features of bone tissue around porous implant materials is important for selecting a particular material for use in patients with low bone mineral density.
In an early study, we compared the osseointegration of a tantalum material with titanium in an ovariectomy model, revealing the highest rate of osseointegration with the tantalum material, while the overall rates of osseointegration in animals with osteoporosis were lower than non-osteoporotic animals . As a result of this, we decided to study several available titanium materials on the market, as well as one novel material in a similar experiment to understand the formation and osseointegration of bone around these materials in an osteoporosis model in comparison with a normal bone model.
The aim of this study was to compare structural features of femoral bone in ovariectomized and non-ovariectomized rats after implantation of different porous materials.