The information displayed in the charts shows how a hospital's performance compares to the national benchmark for a range of measures used to demonstrate quality in joint replacement surgery. The data is risk adjusted to take into account the fact that hospitals may undertake procedures on higher or lower-risk patients when compared to other hospitals. Patients at a high risk will generally have their operation carried out in an NHS hospital. The adjustment ensures a fair comparison between all hospitals.

   The vertical black line on the thermometer plots represents a national average ratio figure of 1. If a hospital plot is on the black line, then its performance is at exactly the average expected for that indicator.

If the plot is in the green band, then the hospital's performance is within the expected range.

If the plot is in the white area to the right of the green band, then the hospital's performance is outside of the expected range and, in this case, the data held by the Registry would indicate that the hospital's performance is worse than expected.

Likewise, if the plot is in the white area to the left of the green band, the hospital's performance is outside of the expected range. In this case, however, the plot indicates that the performance of the hospital is better than expected.

   Hover over the icon for a further definition of the quality measure and its source, including details about risk adjustment

Important note 1: These data are a snapshot in time of the relative performance of this hospital. A hospital’s results may fluctuate over time and get progressively better or worse, reflecting the types of procedures they carry out, implants used and/or the types of patients that they treat among other, local factors including whether the hospital is providing a full and accurate submission of data to the NJR.

Important note 2: This thermometer chart has been created to aid interpretation of the revision ratio and mortality ratio figures in the table (to the left of the thermometer). It is designed to show where hospitals perform better or worse than the national average and where their performance is within the expected range or outside the expected range.

For any given result (whether better or poorer), it also shows how likely it is that their performance has varied because of chance or because of actual practice. This depends on the how far the result is from the national average and the number of patients on which the analysis is based. The further the hospital indicator (red triangle) is from the centre, the less likely this is to be down to chance, especially if a large number of patient records have been analysed for the hospital. Where the number of patient records is low, this might indicate a less certain result.

Important note 3: The green band represents the range over which any performance away from the national average is not thought to be significant. However, it also worth noting that there is a less than one in a five hundred chance that the results for any individual hospital could fall outside the expected range by chance alone.

The results for Hospital A show that this hospital in with the expected range for mortality for the time period shown in the column 'Patient Outcomes Quality Measure'. For the ten-year indicator, this hospital has performed better than expected (red triangle in the white area to the left of the green band) and, for the five-year indicator, it has performed as expected (red triangle within the green band).

Click here to see the FAQ about hospitals showing worse than expected results FAQs