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Knee replacement surgery is a major operation that involves removing all or part of the knee joint and replacing it with a prosthetic implant. As it is a major surgery, it is usually only offered after other treatments, such as steroids or physiotherapy, have been tried and failed.

Patients who suffer from conditions such as osteoarthritis, rheumatoid arthritis, gout, haemophilia, bone dysplasia or avascular necrosis may experience pain and discomfort in the knee to a level where surgery is recommended, or it may be necessary due to deformity or injury. Some more information about types of knee replacement surgery can be found in the PDF attachment to this post.

There are several different designs of prosthetic knee replacements that are currently in use. A study of the long-term outcomes with each type of prosthesis was conducted at St George’s Hospital in London and Scarborough General Hospital, with results published by Ali Ghoz, Alice Dawson, Bassel El-Osta and Mark Andrews. This is one of many Ali Ghoz publications relating to his specialism of arthroplasty. The study compared outcomes for 1,635 patients over a ten-year period.

Knee Replacement Implants

There are many different types of knee replacement implants. The type recommended for each patient depends on several factors. These include the medical history, general health and fitness, and specific knee anatomy and issues of the patient. The performance record and cost of the implant will also be a factor, as will the familiarity and experience of the operating surgeon with the particular device. Implants can be made of a combination of strong plastics, ceramic materials and metal alloys. Metal parts are always bordered with plastic to ensure movement is smoother for less wear and tear. In the UK, there are currently more than 50 different knee prosthesis models that can be used.

Choosing the Optimal Prosthesis

The sheer volume of prosthesis options alone makes is difficult for doctors to assess which is the optimum choice for each patient. Designs of prosthesis that are used infrequently can be linked to prosthesis failure, which can be due to the operating surgeon being unfamiliar with the design. The difficulties with choice are compounded due to a lack of long-term studies comparing outcomes across patient groups with a wide variety of the available options. The recent study published explored outcomes across a large group of patients over a ten-year period and included 15 different knee prosthesis models, using the OKS (Oxford Knee Score) as an assessment tool. The embedded short video explains what the OKS is and how it is used to evaluate outcomes post-arthroplasty.

The Oxford Knee Score from Ali Ghoz on Vimeo.

Study Results

The results of the retrospective study demonstrated that there is no significant difference in patient outcomes for any of the 15 knee prosthesis designs involved in the study. The average scores of all patient groups showed significant improvement at three months following the operation, going from a mean score of 15.8 pre-operatively to a mean score of 39.4 post-operatively. In the long-term the functional outcomes for each group of patients were also not significantly different.

The study concludes that there is no convincing evidence that any of the knee prosthesis designs and models that are currently in use have an advantage over any another. Prospective randomised studies for further research would be beneficial, using lower rates of attrition and larger numbers of patients. The more information a surgeon has available, the more likely they are to be able to make an informed choice for each individual patient as to the best option for prosthesis.

The infographic attachment gives an overview of knee replacement statistics in the UK.