Knee Replacements

In the largest study of its kind, researchers from the Musculoskeletal Research Unit at the University of Bristol have identified the most important risk factors for developing severe infection after knee replacement. Patients who are under 60 years of age, males; so those with chronic pulmonary disease, diabetes, liver disease; also a higher body mass index are at increased risk of having the joint replacement redone due to infection.

The research, which follows their work on hip replacement publish last year [20 November 2018]; also show that some patients are at higher risk of early infection whilst others; so are more prone to late infection after knee replacement. The study analysed data from over 670,000 primary hip replacement patients; so with 3,659 requiring revision for infection.

Disability caused by osteoarthritis

Knee replacement, use mainly to treat pain and disability cause by osteoarthritis; hence is a common procedure with around 110,000 operations perform annually in the UK. A rare but serious complication affecting about one per cent of patients is deep infection. This causes considerable distress and often requires long; so protract treatments including revision surgery.

This study show the reason for surgery, the type of procedure perform and the type of prosthesis and its fixation; influence the risk of needing revision surgery for infection. Surgery perform following trauma, inflammatory arthropathy or a history of previous infection in the operate joint; hence were more likely to be revise for an infection. Cement total knee replacements were more likely to be revise for infection; so compare to patients with an uncemented implant.

Finally, the risk of revision was increase for patients with a posterior stabilised fixed bearing implant or a constrain condylar (CC) implant compare to those with an unconstrained (or cruciate retaining) fixed-bearing implant. The experience of the surgeon and the size of the orthopaedic centre had no or only small effects on the risk of revision for infection.

Post operative period

Uniquely, the research identify that these important factors have a different effect depending on the post operative period, with liver diseases or inflammatory arthropathy increasing the risk of revision for infection in the long-term but patients receiving a patellofemoral, unicondylar or uncement total knee replacement had a lower risk of late revision for infection.

This is an important factor to consider when conducting further research in this area as just considering overall risk or short-term risk may mean important effects are miss entirely. The researchers find the risk of revision for infection following primary knee replacement is affect by many different factors; but is mainly drive by patient and surgical factors. The possible issues identify in this study be consider; so by clinicians when preparing patients for knee replacement surgery.

It is equally important for clinicians to consider the issues that can’t be change and the factors that show time specific effects on the risk of prosthetic joint infection, to support patients appropriately in their decision making pre-operatively and after they have undergone knee replacement. The research team will analyse further data from the NJR to look at the treatment of infection when it does occur to see what treatment has the best outcomes for patients.