Analysis of patients awaiting hip replacement
An analysis of patients awaiting hip replacement was performed in order to identify indicators for surgery. From these data, fast- track selection criteria were generated and investigated in a study of a second cohort of patients attending a traditional orthopaedic clinic.
These criteria correctly predicted the outcome of the orthopaedic consultation in 38 patients out of a total of 52. During the pilot stage, positive fast track selection criteria were shown to have a positive predictive value of 92% for joint replacement being carried out and a negative predictive value of 46%.
These results have enabled patients to be selected for a fast track clinic reducing the number of hospital visits, cost to primary care trusts and delay between referral and treatment.
Evaluation of the safety and efficacy of an acetabular cup
A clinical study was undertaken to evaluate the safety and efficacy of an anatomically shaped, flexible acetabular cup. Clinical results achieved were satisfactory, although some deficiencies in the model were identified.
Design changes to the original model have since been implemented to improve both initial stability and long term biological fixation. This was achieved through modifications made to the anchoring mechanism and by the application of an appropriate backing surface layer promoting bone growth. In addition, changes to the articulation have also been introduced to improve implant durability and bearing performance, utilising a carbon fibre reinforced polyetheretherketone-alumina couple.
Simulated loading, in both models, was performed using Finite Element Analysis. Mechanical and tribological tests were also performed to ensure the robustness of the new optimised design. Bio-compatibility of the articulation couple was demonstrated using an animal model.
Implantation of the device has been extensively tested and re-validated in vitro to achieve a favourable polar contact between cup and femoral head and establish a reproducible operative technique.
This preliminary work is undertaken prior to commencing a post market surveillance study of the CE marked implant.
