Minimum volumes for total knee replacement (TKR): Higher case volumes result in better quality of treatment

The more frequently surgeons and hospitals perform TKR, the less frequently complications and revisions occur. Quality of life is also better and fewer patients undergoing surgery die.

In a series of commissions awarded by the Federal Joint Committee (G-BA) to the Institute for Quality and Efficiency in Health Care (IQWiG), the question is whether for certain surgical procedures, a correlation can be shown between the volume of services provided per hospital and the quality of treatment results. IQWiG's rapid report on total knee replacement (TKR), also called total knee arthroplasty (TKA), is now available.

According to the findings, there are positive correlations between the volume of services and the quality of treatment with regard to numerous outcomes, both at the hospital and surgeon level: The higher the case volumes for TKR, the less frequently severe complications occur. Hospital stays are shorter and fewer readmissions and renewed surgical procedures of the knee are required.

In addition, health-related quality of life and survival probabilities are better when more than 50 TKRs are performed per year in a hospital. In addition, a study on the specific health care situation in Germany provides indications that, after the introduction of minimum case volumes for TKR, fewer wound infections or postoperative bleeding events occur, at least in the short term.

Number of TKRs increases and age of patients decreases

A common cause for TKR is a severe degeneration of the joint (gonarthrosis), which is often accompanied by pain and limited mobility.

With more than 193,000 cases in Germany in 2019, TKR is one of the 20 most common inpatient surgical procedures, albeit with strong regional fluctuations. The number of patients under the age of 60 is growing continuously, and with it the number of renewed surgical procedures (revisions), especially after initial implants in patients under 50.

The currently valid annual minimum volume for TKRs per hospital is 50. For this rapid report, IQWiG only considers the initial TKR. The Institute addresses the correlation between volume of services and quality of treatment for partial TKR (unicondylar sled prosthesis) and for revisions in separate reports.

Relatively many studies, but with limited data quality

A total of 18 studies provided data on the correlation between the volume of services at the hospital or surgeon level and the quality of treatment for TKR. The study results are of limited informative value, mainly because the studies are largely retrospective observational studies based on routine and/or registry data. However, compared with previous IQWiG reports on minimum volumes for different surgical procedures, there are more studies on TKR investigating and showing a correlation between the volume of services and quality of treatment not only at the hospital, but also at the surgeon level. In addition, three studies provide usable data on health-related quality of life.

Higher case volumes lead to better treatment results

At both levels, hospital and surgeon, there is a correlation between the volume of services and quality of treatment for several outcomes in the studies: With increasing case volumes, for example, complications occur less frequently during or immediately after surgery and also in the longer term (after six months). Wound infections and pneumonia also occur less frequently. In addition, health-related quality of life (e.g., mobility and independence) is better the more frequently TKRs are performed. Hospital stays are then also shorter and there are fewer readmissions and renewed procedures such as amputation, joint stiffening (arthrodesis) or removal of the TKR (excision) with subsequent replacement of the implanted knee joint (revision).

In three studies, health-related quality of life was investigated with validated measurement instruments and a positive correlation between the case volume and the quality of treatment was found for single aspects of quality of life (e.g., joint function, mobility), both at the hospital and at the surgeon level.

Effects of a minimum case volume in health care

In contrast to previous IQWiG reports on minimum volumes for different surgical procedures, for TKR there is a study summarizing the effects of a minimum case volume on the quality of treatment in real-life care in German hospitals: After introduction of the minimum case volume of 50 procedures per hospital and year, the number of patients with postoperative bleeding or haematoma in the surgical wound of the knee decreased. There was also a correlation for wound infections, although a temporal effect (period effect) cannot be ruled out here, as an improvement had already become apparent before the introduction of the minimum case volume.

Process of report production

In March 2021, the G-BA commissioned IQWiG to prepare the report on the correlation between the volume of services and the quality of treatment results for TKR as a so-called rapid report. Interim products were therefore not made available for a hearing. This rapid report was sent to the contracting agency, the G-BA, on 3 February 2022 and has now been published.

An extract of the final report will be soon be published in English. If you would like to be informed when it is published, please contact info@iqwig.de.