An assessment of biomaterials for hip joint replacement

Hip replacement is a surgical process where natural hip joints are replaced by artificial hip joint that helps the human being for getting better lifestyle by reduction in the unavoidable pain and better leg movement. The selection of material and durability of the hip joint replacement are serious significance for the implantation, because it determines how load is transferred through the stem. In the selection of materials, various problems related to hip joint replacement are found like adverse tissue reaction, allergic reaction, wear and corrosion resistance etc. To overcome this problem one has to create different new biomaterial. This review gives brief description about the different biomaterial used for hip joint replacement.

Revision of a dual-modular stem in patients with adverse tissue reaction

Background: Dual-modular femoral components with exchangeable cobalt-chrome neck segments have had higher than expected failure rates due to corrosion and adverse local tissue reaction (ALTR). Complications, survival rates and early clinical outcomes of revision surgery for the treatment of corrosion and ALTR as a result of these implants are underreported. Methods: We identified 44 cases of revision THA for corrosion and ALTR resulting from the same dual modular stem. All revision procedures were performed using a modular tapered fluted titanium stem, ceramic heads and highly cross-linked polyethylene. Results: Complications included: dislocation, infection, reoperation, and chronic pain. Mean Harris Hip Score was 84 following revision surgery. Conclusions: Patients undergoing revision surgery for ALTR related to this prosthesis should be aware of the risk of postoperative dislocation and other complications and the potential long-term risk of some chronic pain.

Research: Design and Analysis of a Low-Stiffness Porous Hip Stem

Two major problems are associated with total hip replacement: 1) stress shielding and 2) the adverse tissue reaction to certain elements of the implant material. In this regard, a porous implant provides lower stiffness and vacancies for bone ingrowth, making it more suitable for the human bone compared with a solid stem. Moreover, second-generation titanium biomedical alloys, such as TNZT (Ti35Nb7Zr5Ta) and TMZF (Ti12Mo6Zr2Fe), have been introduced to prevent the adverse tissue reactions related to aluminum and vanadium elements of the popular Ti6Al4V alloy. In the current work, an analysis was performed based on uniaxial compression testing of cubic Ti6Al4V structures of different porosities to predict the governing equations that relate the relative density of the structure to the mechanical properties of the structure according to the Gibson-Ashby model. A numerical study was conducted to evaluate the change in stress distribution obtained by incorporating the new titanium alloys in porous hip stem implants. Implants modeled with the mechanical properties of TNZT and TMZF showed a minimum safety factor of 1.69 and 3.02, respectively, with respect to the yield strength. The results demonstrated an increase in the equivalent von Mises stresses and maximum principal elastic strain up to 7% and 15%, respectively, compared with the porous Ti6Al4V implant and up to 108% and 156%, respectively, compared with the solid Ti6Al4V implant.

Fabrication and Evaluation of a New Composite Composed of Tricalcium Phosphate, Gelatin and Chi-Li-Saan as a Bone Substitute

The purpose of this study was to prepare and evaluate the feasibility and biocompatibility of a new composite as a bone substitute. The new composite (GTGC) was mainly composed of tricalcium phosphate ceramics and gelatin to which Chi-Li-Saan, a Chinese medicinal remedy was added. The GTGC composite was manually packed into cylindrical Teflon molds, dried overnight in an oven and sterilized by γ-ray prior to use. Mature New Zealand rabbits, weighting 3–3.5 kg, underwent full-thickness excision of the parietal bone. In the experimental group, bone defects of 12 animals were filled with the GTGC composites and another 12 unreconstructed rabbits were considered as controls. Three rabbits were examined for each group in every time period at 2, 4, 8 and 12 weeks after operation. There was no evidence of adverse tissue reaction to the GTGC composite. In addition, examination with light and fluorescent microscopy revealed a significantly greater amount of new bone ingrowth in the GTGC group at the same implantion time as compared with the controls. Therefore, the GTGC composite could serve as a useful substitute when repairing bone defects.

Auditory Brainstem Prosthesis: Biocompatability of Stimulation

As part of a program to develop a central auditory system prosthesis, we have examined the reaction of tissue to different levels of stimulation from electrodes chronically implanted in the cochlear nucleus of the guinea pig. Tolerance and histologic reaction to 20 hours of periodic electrical stimulation of the cochlear nucleus were analyzed. Intraoperative and postoperative electrically evoked middle latency responses were monitored during stimulus trials. The threshold necessary to generate the middle latency responses was frequently below 50 μA. In the animals that received 50 and 100 μA of blphasic charge-balanced stimulation (corresponding to approximately 200 and 400 μC/cm2 phase), adverse tissue reaction was minimal, and glial proliferation along the electrode tract never exceeded 25 μm in width. Stimulation intensities of 150 and 200 μA (approximately 600 and 800 μC/cm2 phase) produced significant tissue response at the site of the electrode terminus, with necrosis, cell loss, and reactive cells present. Therefore neuronal damage was observed to occur at an intensity far greater than that required for eliciting an electrophysiologic response.

Adverse Tissue Reactions to Drugs: a Five-year Surveillance Study

Over a 5-year duration a total number of 57 881 tissue specimens from hospitalized patients were evaluated clinicopathologically for evidence of adverse tissue reactions to drugs. The incidence of alleged adverse tissue reactions was 3.7% of which 1.5% were definitely shown to be caused by a specific pharmacological agent. Regardless of the category of the adverse tissue reaction, the frequency of drug-related responses occurred most often in females, especially between the ages of 41 and 60 years. The target tissue affected adversely most often was endometrium where hyperplasia was the predominant response noted. An oestrogenic preparation was found most frequently to be implicated in the observed adverse tissue reaction. Evaluation of adverse drug reactions with the use of morphologic technique provides a rigorous and reliable mechanism to monitor deleterious effects in hospitalized patients.