Changes to NJR alarm surgeon identification and notification procedures for knee

The NJR surgeon performance outcome monitoring function can identify surgeons as potential outliers (alarm level) for revision rates of their primary knee replacements using the overall data for their entire knee practice.  This involves the NJR calculating the surgeon’s revision rate in relation to the average revision rate for all knees but does not involve any adjustment for the proportion of unicompartmental knees (UKR) compared to total knees (TKR) performed. This parameter has been the measure used to decide whether a surgeon is a potential outlier and also to decide whether that possibility needs to be notified to the medical director of their hospital for investigation.

This has meant that some surgeons could possibly be identified as a potential outlier when they are not an outlier for either their TKR or  UKR practice when those are assessed in isolation. Similarly, some surgeons are not identified as potential outliers when their UKR practice or TKR practice in isolation does reveal outlier status but their overall practice does not.

There is clear evidence that in most surgeons’ practice the revision rate for UKRs is higher than that for TKR which means that using a composite revision rate without reference to the proportion of the two operations performed can lead to considerable uncertainty for some knee surgeons.  Furthermore there is evidence that other outcomes are often better for UKR than for TKR and are not taken into consideration by this assessment. The recent National Institute for Health and Care Excellence (NICE) guidance ( has acknowledged this variation in relative outcome measures and has recommended that patients suitable for a medial UKR should be offered one.

One of the NJR’s key stakeholders, the British Association for Surgery of the Knee (BASK), recently proposed that that the alarm process should be amended to be triggered for surgeons who were identified as potential outliers for their TKR practice data and/or their UKR practice data, but not for surgeons whose revision rate data for their overall practice was outlying. Following extensive discussion between the NJR and the BASK executive, a modification to the potential outlier process for alarm level surgeons will be implemented from the second 2022 review of surgeon performance data (November 2022):

1) The unit medical director will not be routinely notified of outlier status in one of their unit surgeons based solely on the data from their entire knee practice (TKR and UKR combined), although the data point for that surgeon will still appear on the unit Annual Clinical Report (ACR).

2) A surgeon whose 5 and/or 10-year data shows outlier status either for their TKR practice alone or for their UKR practice alone will be notified of that status.  The unit medical director will be notified of that surgeon’s status 6 weeks later.

3) The surgeon Consultant Level Report (CLR) will continue to contain the funnel plot information about overall knee practice as well as the data about TKR and UKR practice separately, to assist the surgeon in monitoring their own practice.

4) In order to address the possibility that the overall knee practice data for a surgeon might indicate an imminent outlier status in the subgroups, for every surgeon whose overall 5 and/or 10 year knee practice data demonstrates outlier status the NJR Surgical Performance Committee Chair will examine that surgeon’s results individually and assess whether there is a “case to answer”. If there are no concerns then the surgeon will be notified as an ‘alert’. If it is felt that there is a potential problem then the surgeon and the medical director would be notified in the same way as has happened up to the introduction of these changes.

Examples of such a scenario might be:

a) The surgeon’s overall knee practice data show that outlier status has developed;

b1) while the individual plots for TKR and UKR  do not yet show outlier status one or both of these is extremely close to the line

b2) one or both of the individual plots may be clearly heading upwards towards the outlier status on serial 6-monthly plots.

The NJR and the BASK executive believe this change will maintain the safety of the patients.

The NJR will review the changed procedure after a year, to enable a subsequent decision to be made on whether the change will be maintained.

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