Titanium as a metal for implantation. Part 1: physical properties

The scientific basis for the use of titanium and its alloys in implant surgery is reviewed, including the structural metallurgy, mechanical properties, corrosion resistance and biocompatibility. The clinical application are discussed in relation to orthopaedic, oral, plastic and reconstructive and cardiovascular surgery.

Biomaterials and biocompatibility

This review attempts to assess the present status of biomaterials, especially in relation to their interaction with tissue. The terms biomaterial and biocompatibility are defined and both the present areas of clinical application and the requirements of biomaterials for these applications discussed. The types of biomaterials in clinical use and those under development are briefly described. Problems associated with implant functionality are covered, dealing with fatigue, wear and membrane permeability. Of more importance are the problems relating to biocompatibility and metallic corrosion, polymer and ceramic degradation, local tissue changes, systemic effects, infection, implant loosening, blood compatibility and the assessment of biocompatibility.

A histochemical method for the determination of titanium in tissues surrounding implants

Images

Hair sampling for chromium content following Charnley hip arthroplasty

The chromium content of hair has been studied by neutron activation analysis of samples from 62 patients following a Charnley unilateral or bilateral hip arthroplasty by an artificial joint of stainless steel against polyethylene, inserted three to five years previously. The patients lived in the North Wales area of the British Isles. Hair chromium content was also studied in 51 control subjects of similar age to that of the patients, from the same geographical area and often from the patients' own households. Chromium content was recorded as parts per million (ppm) of hair weighed and analyzed in the state received, without preliminary ashing or chemical "washing" of the samples in the laboratory. Fifty of the 51 control subjects showed less than 2 ppm chromium in hair; one showed 2-5 ppm; none showed more than 5 ppm. Fifty-nine of the 62 patients showed less than 2 ppm chromium in hair; three showed 2-5 ppm; none showed more than 5 ppm. Attention is drawn to certain practical aspects when collecting hair samples for chromium analysis. The use and validity of hair sampling as one method of screening for systemic chromium accumulation following implant surgery is discussed. The method may be a useful adjunct to monitoring of chromium levels in blood samples. In this preliminary study, hair sampling has given no evidence of any major risk of systemic chromium accumulation in patients using a Charnley arthroplasty for periods of up to five years; no conclusion can be made concerning periods longer than this. The findings do not exclude systemic reactions of the hypersensitivity type, since this type of reaction could develop to only small amounts of chromium.

The effect of metal clips on the tensile properties of healing skin wounds

The effects of nylon sutures and metal skin clips on the tensile properties of healing skin wounds have been studied in the pig. Wounds closed with clips have significantly poorer mechanical properties at 5, 7 and 14 days after wounding than similar wounds in the same animal closed with interrupted nylon sutures. This difference increased progressively with the period of retention of the clips. It is also shown that in equivalent groups of 14-day wounds, those in which clips were retained after the seventh day had a lower tensile strength, poorer ability to absorb energy and a lower elastic modulus than similar wounds where clips had been removed early. No such adverse effect was noted with nylon sutures.

Future prospects for biomaterials

Biomaterials have many uses in medicine and surgery but success in their use is often difficult to achieve. In this paper some of the deatures that contribute to the success or failure of biomaterials are discussed in relation to a hypothetical implant situation. The phenomena of biomaterial-tissue interfacial reactions, wear, prosthesis instability, infection, hypersensitivity and carcinogenesis are considered. Emphasis is given both to the causes and clinical significance of these phenomena and interpreted in terms of the furture prospects for the biomaterials.

Effect of Solute–Solute Interaction on Molecular Luminescence in Rigid Glasses: Anomalous Thioxanthenone Phosphorescence and Anthracene Fluorescence

The phosphorescence spectra and lifetimes of thioxanthenone in a number of rigid matrices at 77°K was found to be dependent on the concentration, rate of cooling of the glass, and on the wavelength of excitation. At 77°K and at concentrations greater than ~5 × 10−5 M, aggregates of thioxanthenone are believed to be responsible for a new phosphorescence band at 472 nm, and a corresponding absorption band at 390–395 nm.The formation of aggregates is also believed to be responsible for the variations, with excitation wavelength, of the fluorescence lifetime of anthracene in polymethacrylate at ambient temperatures.

Proton conductance of copper sulfate pentahydrate crystals

It has been demonstrated that protons are injected into single crystals of copper sulfate pentahydrate by using saturated aqueous solutions of copper sulfate as electrodes. The resulting proton current is space-charge limited and follows Child's law, from which a proton mobility of 10−5 cm2 V−1 s−1 was deduced. The injected proton current was verified by tracer experiments with tritium.