Researchers from the Musculoskeletal Research Unit at the University of Bristol have recently published their findings from a study which shows that hip and knee replacements last longer than previously believed.

There are two types of knee replacement surgery currently performed in the UK: total knee replacement (TKR) and unicondylar (partial) knee replacement (UKR). The latter replaces only the damaged part, leaving the functioning section of the knee. Hip replacement surgery involves two components: a prosthetic ball and socket. Surgeons use different methods and materials in order to fix the components to the bone.

The most common reason for both hip and knee replacement surgery is osteoarthritis, but other conditions that can cause damage and lead to the need for replacement surgery include rheumatoid arthritis, fracture and injury. Replacement surgery is usually only recommended if other conservative treatments, for example physiotherapy and steroid injections, have been used and have not helped with pain and mobility.

The study highlighted the most common factors causing replacements to fail, including infection, fracture, wear and tear, and reaction to ‘wear particles’ (debris which sloughs off the prosthesis with normal wear and tear). Once a replacement has failed, revision surgery is required, which carries with it higher risks and lower success rates.

Case studies from over 25 years, which included more than 500,000 patients, were analysed in the study. The findings were as follows:

  • of all hip replacements analysed, 89% were found to last 15 years; 70% lasted 20 years; and 58% lasted 25 years;
  • of all total knee replacements analysed, 93% lasted 15 years, 90% lasted 20 years, and 82% lasted 25 years;
  • of all partial knee replacements, 77% lasted 15 years; 72% lasted 20 years and 70% lasted 25 years.

Dr Jonathan Edwards, one of the lead authors of the study, commented in a BBC report: "At best, the NHS has only been able to say how long replacements are designed to last, rather than referring to actual evidence from multiple patients' experiences of joint replacement surgery. Given the improvement in technology and techniques in the last 25 years, we expect that hip or knee replacements put in today may last even longer."

Rosie Nelson, an associate in Penningtons Manches’ clinical negligence team, said: “This study offers positive news to patients facing replacement surgery, showing that of the cases analysed, an average of 8 out of 10 knee replacements and 6 out of 10 hip replacements lasted for 25 years. With more tangible data on the longevity of replacements than previously existed, surgeons and patients can make better, more informed decisions as to whether replacement surgery should be carried out in a specific case, and if so, when this should be done.”