In radiotherapy planning, computed tomography (CT) images are used to calculate the dose in the patient. However, a high density hip prosthesis can cause streaking artefacts in CT images, which make dose calculations for nearby organs inaccurate. This study aim to quantify the impact of a hip prosthesis on 6 MV photon beam dose distribution using the Monte Carlo (MC) simulation. To quantify the radiation dose at the hip prosthesis accurately, image processing techniques were used to generate CT images free from streak artefacts. MATLAB software was used to produce computer-generated phantoms consisting of bone, titanium, stainless steel and CoCrMo. Percentage depth dose (PDD) and beam profile were used to analyse the impact of the hip prosthesis on the dose distribution of the photon beam. PDD showed that the absorbed dose was reduced as the density of the material increased, and the dose was reduced by as much as 49% when the photon beam struck the highest density material (CoCrMo, 8·2g/cm3). However, dose was increased at the tissue-hip prosthesis interface (depths of 4 and 19cm). As the depth increased, the absorbed dose decreased due to attenuation of photons by the tissue and the metal.

Many new hip prostheses are now available for use in total hip replacement. The majority remain untested relative to standard prostheses; however, many new prostheses are substantially more costly. We examine how much more effective new prostheses must be, in terms of reducing the need for revision operations, in order to justify this increased cost.

Objective: To evaluate the appropriateness of the use of hip joint replacements (HJRs) using explicit criteria developed by an expert panel.

Methods: Observational study. Nine hundred ninety-seven patients from five hospitals with a diagnosis of osteoarthritis, avascular necrosis, hip fracture, or revision who were undergoing HJR were consecutively included in the study during a 1-year period. The appropriateness of the indication was judged by explicit criteria. Complications were recorded at the time of the intervention and 3 months postoperatively.

Results: Of the 1,030 interventions, 604 were for osteoarthritis, 31 avascular necrosis, 191 fractures, and 204 revisions. No differences were found among the hospitals for the main clinical and patient variables. Indications for surgery were considered appropriate in 59% of cases, uncertain in 32%, and inappropriate in 8%, mainly in the osteoarthritis group. Differences were found in the rates of appropriateness among some centers. The complication rate did not differ among the groups based on the level of appropriateness of the procedure.

Conclusions: The appropriate use of HJR, as measured by the criteria established by the panel, identified a moderate percentage of inappropriate indications. Those equivocal and inappropriate cases demand further studies to identify patients with an adequate risk-to-benefit ratio from this procedure.