Data Completeness and Quality

There are currently three types of organisation submitting details of hip, knee, ankle, shoulder and elbow joint replacement surgery to the NJR.

• NHS hospitals
• Independent sector hospitals
• Independent Sector Treatment Centres (ISTC)

There are no ISTCs in Wales, Northern Ireland, the Isle of Man or the States of Guernsey.

Table 1.3 below shows the number of reported procedures by type of provider from FY2014/15 to FY2019/20.

As at 31 March 2020, 3,068,085 hip, knee, ankle, shoulder, and elbow joint procedures had been submitted to the NJR and the NJR continues to be the largest registry of its kind in the world.

There were 258,943 procedure submissions in FY2019/20, which is a slight decrease from the figure reporting last year.  In March 2020, however, the number of reported procedures decreased significantly from the previous March due to the COVID-19 pandemic which meant that very few elective joint procedures took place.

Operation totals

Table 1.1 below shows, by country and joint type, the number of procedures reported to the NJR for the financial years 2014/15 to 2019/20.  Due to small numbers, data for the Isle of Man and the States of Guernsey are included with England. As for the previous five years, the number of knee replacement procedures (126,694) exceeded the number of hip replacement procedures (120,307) in FY2019/20 (48.9% and 46.5% as a proportion).  The number of hip and knee procedures submitted by hospitals in Northern Ireland has risen again in FY2019/20.

Operation types

Table 1.2, below, shows the number of procedures reported, by type, from 1 April 2014 to 31 March 2020.  Primary procedures make up 92.7% of all procedures reported during FY2019/20, the highest proportion since 2004.  The number of ankle, elbow, and shoulder revisions as a proportion of both primaries and revisions is higher than that for hips and knees.

The linkability rate for FY2019/20 was 96.35%, a slight increase from the figure reported last year for FY2018/19 (95.9%). The overall linkability for all records submitted to the NJR since 2003 is 92.9%, an increase on last year’s reported figure of 92.5%.

The linkability rate compares the number of records with the patient’s national identifier (NHS Number in England and Wales, and HCN in Northern Ireland) with the number of procedures recorded in the NJR.  National identifiers are validated or traced (if not originally submitted) via the national tracing services using the patient’s name, date of birth and postcode. For England, Wales and Isle of Man, the tracing is undertaken using NHS Digital’s Demographic Batch Service, whilst tracing of HCN numbers in Northern Ireland is carried out by the Health and Social Care of Northern Ireland.

A unique national identifier is required to link all primary and revision procedures relating to the same joint for a single patient. This linkage is essential to calculating clinical outcomes: without high rates of national identifier submission and tracing, the NJR’s ability to monitor clinical and implant performance is adversely affected.

Successful tracing of national identifiers is, however, dependent upon the correct submission of a patient’s name, date of birth, and postcode.

The informed consent rate for FY2019/20 was 94.78%, a slight increase from informed consent in FY2018/19 (93.98%)  Consent rates have remained steady for the past seven years.

The informed consent rate compares the number of records submitted where the patient has either agreed or refused to have their personal data (see note below) stored on the NJR database, with the number of procedures recorded on the NJR. If consent is refused then the details of the operation and implants are recorded but no patient details. It is a requirement that patients give voluntary, informed consent to have their personal data held on the NJR alongside their operation data. This personal information is essential to link patients’ primary and revision procedures together in order to monitor the outcomes of joint replacement surgery. Without high rates of consent, the NJR cannot achieve its goals.

Patients rarely decline consent and many units achieve consent rates of 100%. Lower consent rates in other units are generally caused by a lack of robust processes which mean that the completed consent form is not available to the person submitting the procedure details to the NJR.

Support under Section 251 of the NHS Act 2006 for English and Welsh Units

In England and Wales only, the NJR records consents in one of three ways: ‘Yes’, ‘No’, or ‘Not Recorded’. The support granted under Section 251 enables the NJR to collect patient details where ‘Not Recorded’ is indicated for consent. This is justified for reasons of patient safety as it enables the NJR to identify those patients who may have had a prosthesis implanted that is subsequently subject to either an MHRA Medical Device Alert or an MHRA Field Notice. The ‘Not recorded’ rate for FY2019/20 was approximately 5.22% which means that approximately 13,000 patients did not have their consent recorded and who, without Section 251 support, could not be identified in the event of either a Device Alert or Field Notice being issued that related to a device that they had had implanted.  However, this group of patients cannot be contacted for any follow-up audits or research projects.

The compliance rate from 1 April 2018 to 31 March 2019 for hip and knee submissions was 97% for NHS hospitals in England and Wales. The data for the year 1 April 2019 to 31 March 2020 is not yet available. 

Prior to 1 April 2014, the compliance rate was measured by comparing the number of levies raised for implant sales against the number of procedures submitted to the NJR.  With the adoption of a subscription model in April 2014, it is no longer possible to measure the compliance rate in this way.  It is not possible, therefore, to provide a chart showing annual compliance rates over the life of the NJR.

Compliance for hip, knee, ankle, elbow and shoulder procedures is compared to submissions made to the Hospital Episodes Statistics (HES) service in England and to the Patient Episode Database Wales (PEDW) service in Wales.  This comparison is based on a defined set of OPCS4 codes which can be obtained from the NJR Centre if required.

Whilst the use of HES and PEDW data enables the measurement of the rate of compliance for Trusts and Health Boards, it does not include those procedures undertaken in the independent sector.

Currently, there are issues when calculating compliance for NHS Trusts where those acute trusts have commissioned joint replacement procedures directly to independent sector hospitals.  In these cases, the procedure would appear in HES but not in the NJR as the independent hospital undertaking the procedure would submit the NJR record.  Whilst the NJR can determine that a procedure is NHS funded, it cannot determine which trust commissioned the procedure. Unfortunately, whilst a provider code is available within HES for outsourced procedures, this data field is often left incomplete.  This may result in published trust compliance rates that are lower than expected.  Communicating this issue widely has resulted in a reduction of the number of trusts querying low reported compliance rates.

The NJR has also commenced the pilot of an automated Data Quality Audit process which compares the records in hospital systems directly to the procedures submitted to the NJR.  This comparison identifies those procedures that have not been submitted to the NJR and which can then be entered retrospectively.  Once the automated process is rolled out to all hospitals and becomes fully embedded in hospital processes, compliance will be easier to monitor and is expected to increase.

About the key indicators of data quality and completeness

It is mandatory for the following providers of joint replacement surgery to collect and submit data to the NJR:

• All NHS Trusts and Foundation Trusts within NHS England
• All NHS Wales hospitals
• All hospitals in Northern Ireland performing Health and Social Care Northern Ireland (HSCNI) funded procedures
• All independent sector hospitals in England and Wales

Performance against the three key indicators of data quality (compliance, consent, and linkability) varies slightly throughout the year but has remained at the same levels as reported last year. Unit-level performance against these key indicators is available in the Downloads area.

The number of procedures submitted, with the corresponding consent rates, for each hospital are provided through the NJR StatsOnline service. Performance against all indicators is also included in an annual clinical report provided to Trust and Health Board chief executives and to independent healthcare companies.  Surgeons are also able to access annual clinical reports for those hospitals in which they practice.