Executive summary (across all report areas)

Part Four: Implant- and unit-level activity and outcomes 2014

OUTLIER UNITS FOR 90-DAY MORTALITY OR REVISION RATES FOR THE PERIOD 2003 TO 2014

The observed numbers of revisions of hip and knee replacements for each hospital were compared to the numbers expected given the unit’s case-mix in respect of age, gender and reason for primary.

Hospitals with a much higher than expected revision rate for hip and knee replacement have been identified (and can be found listed over the page). These hospitals had a revision rate that was above the upper of the 99.8% control limits (these limits approximate to +/-3 standard deviations). We would expect 0.2% (i.e. one in 500) to lie outside the control limits by chance with approximately half of these (one in 1,000) to be above the upper limit.

When examined over the life of the registry, a total of 22 hospitals reported higher than expected rates of revision for knee replacement and 39 hospitals had higher than expected rates of revision for hip surgery.

However, revisions taken only from the last five years of the registry show a drop to eight hospitals reporting higher than expected rates for knees, and six for hips.

The 90-day mortality for hip and knee replacement was calculated for all hospitals by plotting standardised mortality ratios for each hospital against the expected number of deaths. One hospital (closed in 2013) had a higher than expected mortality rate for knee replacement while none were identified for hip replacement.

Note: The case mix for mortality includes age, gender and ASA grade. Trauma cases and failed hemi-arthroplasties have been excluded from hip mortality analysis together with hips implanted for metastatic cancer since November 2014 (when recording of this latter reason began).

Note: Any units identified as potential outliers in Part Four have been notified. All units are provided with an Annual Clinical Report and additionally have access to an online NJR Management Feedback system.

Important note about the outlier hospitals listed below

In previous Annual Reports, the NJR have reported outlying hospitals based on all cases submitted to the NJR since 1 April 2003. To reflect changes in hospital practices and component use, the NJR now also reports outlying hospitals based on the last five years of data (21 February 2010 to 20 February 2015 inclusive, the latter date being when the dataset was ‘cut’).

Where an outlier hospital has deviated more markedly than the remainder of the outlier group, this is marked with an asterisk*. This reflects where the revision rate is the upper of the 99.99% control limits.

Outliers for hip mortality rate since 2003: None identified

Outliers for knee mortality rate since 2003: Redwood Diagnostic Treatment Centre (closed in 2013)

Outliers for hip revision rates since 2003 (note 1):

Nevill Hall Hospital *
The Royal London Hospital *
Sussex Orthopaedic NHS Treatment Centre *
Llandough Hospital *
Prince Charles Hospital *
Queen Elizabeth The Queen Mother Hospital
Basingstoke and North Hampshire Hospital *
Homerton University Hospital
The Tunbridge Wells Hospital
Medway Maritime Hospital *
Northampton General Hospital (Acute)
University Hospital Of Hartlepool *
University Hospital Of North Tees *
North Tyneside General Hospital *
St Michael's Hospital *
Salisbury District Hospital
Musgrove Park Hospital *
Rotherham District General Hospital *
Pilgrim Hospital *
Hospital Of St Cross
St Albans City Hospital *
Watford General Hospital *
York Hospital *
BMI Gisburne Park Hospital (Lancashire) *
BMI The Somerfield Hospital (Kent) *
Shepton Mallet Treatment Centre (Somerset) *
Nuffield Health Brighton Hospital (East Sussex) *
Nuffield Health Tees Hospital (Cleveland) *
Nuffield Health Wessex Hospital (Hampshire)
Nuffield Health York Hospital (North Yorkshire) *
Ashtead Hospital (Surrey) *
New Hall Hospital (Wiltshire) *
The Berkshire Independent Hospital (Berkshire)
Clifton Park Hospital (North Yorkshire) *
Dunedin Hospital (Berkshire)
Spire Alexandra Hospital (Kent)
Spire Cardiff Hospital (Glamorgan) *
Spire Gatwick Park Hospital (Surrey) *
Spire Tunbridge Wells Hospital (Kent)

Outliers for knee revision rates since 2003 (note 1): 

Part Four: Implant- and unit-level activity and outcomes 2014

Part Four of the annual report gives performance and data entry quality indicators for Trusts, Local Health Boards (many of whom comprise more than one hospital) and independent (private) providers in England, Wales and Northern Ireland for the 2014 calendar year. Outcomes analysis after hip and knee replacement surgery is also provided for the period 2003 to 2014. This year we have also included data for implant outliers.

Clinical activity

Overall in 2014, 151 NHS Trusts and Local Health Boards (comprising 245 separate hospitals) and 178 independent hospitals reported patient procedures to the NJR. The proportion of joint replacements entered into the NJR against those carried out (compliance) is only available by NHS Trust and Local Health Board. No data on this is currently available from private providers.

• 46% of NHS providers reported 95% or more of the joint replacements they undertook
• 37% of NHS providers reported between 80% and 95% and
• 17% of NHS providers reported less than 80%

Note: these figures exclude units in Northern Ireland as compliance is not available.

Of those hospitals submitting data, the proportion of patients who gave consent for their details to be entered into the NJR (consent) were:

NHS hospitals

• 51% of NHS hospitals achieved a consent rate of greater than 95%
• 35% achieved a consent rate of 80% to 95% and
• 14% recorded a consent rate of less than 80%

Independent hospitals

• 74% of independent hospitals achieved a consent rate greater than 95%
• 21% achieved a consent rate of 80% to 95% and
• 5% recorded a consent rate of less than 80%

Similarly, the proportion of entries in which there is significant data to enable the patient to be linked to an NHS number (linkability) are listed below:

NHS hospitals

• 87% achieved a proportion of patients with a linkable NHS number greater than 95%
• 12% achieved a proportion of 80% to 95% and
• 2% recorded a proportion of linkable records of less than 80%

Independent hospitals

• 61% achieved a proportion of patients with a linkable NHS number greater than 95%
• 33% achieved a proportion of 80% to 95% and
• 6% recorded a proportion of linkable records of less than 80%

Independent hospitals might be expected to have lower linkability rates than NHS hospitals, as a proportion of their patients may come from abroad and not have an NHS number.

Part Three: Outcomes after joint replacement 2003 to 2014

Part Three of the 12th Annual Report provides outcome data in relation to hip, knee, shoulder, elbow and ankle replacements. It describes activity between 1 April 2003 and 31 December 2014.

There were 1,837,781 procedures recorded in this period, though 11% of these were excluded because there were insufficient patient details to enable linkage. This relates predominantly to the early years of the registry and less so as data quality has improved. There were 708,311 primary total hip replacements, 772,818 knee replacements, 2,554 ankle replacements, 11,399 shoulder replacements and 1,079 elbow replacements.

Hip replacement procedures

The potential follow up for hip procedures was 11.75 years. Osteoarthritis was the predominant diagnosis in 93% of cases. A total of 60% of procedures were carried out on women and the median age at primary was 69 years. In terms of fixation there has been a trend away from cemented hip replacements which was 60.4% in 2003 and in 2014 represented just 31.8%. The most common form of fixation is uncemented but this has slightly declined from 2009 to 41.2% in 2014 with a slight rise of hybrid fixation which is now 23.1%. Hip resurfacing now represents less than 1%. When hips were cemented the most common articulation was metal-on-polyethylene and in uncemented procedures ceramic-on-ceramic was also favoured. With hybrid fixation there has been an increase in the use of ceramic-on-polyethylene.

The Kaplan-Meier cumulative revision risk estimates at eleven years were lowest in the cemented fixation group at 3.63% (95% Confidence Interval 3.43-3.83) and higher in the uncemented group at 8.25% (7.90- 8.62). However, the uncemented group contained the majority of metal-on-metal articulations and when uncemented fixation was used with ceramic-on-polyethylene bearing, the eleven-year revision estimate was 3.62% (3.24-4.05). Low revision risk was generally seen with the ceramic-on-polyethylene bearing, the revision probability being 2.98% with the cemented fixation and 2.15% with the hybrid fixation. It would appear that the articulation rather than the fixation has a major influence on survivorship.

The effect of gender and age are presented by fixation and bearing and once again there is a significant increase in revision risk in younger patients. For example, in male patients less than 55, the ten-year revision risk estimate was 7.26% (5.79-9.09) with the cemented hip replacement. In comparison this was just 2.83% (2.46-3.26) in patients over 75 years.

The common stem brand combinations are reported in terms of revision risk. Their numbers are large enough to be further sub-divided into bearing type. Several brands had low revision risk at ten years and were essentially comparable, for example the cemented Exeter V40 with a Contemporary cup with ceramic-on-polyethylene bearing had a ten-year revision estimate of 2.70% (1.72-4.21). The uncemented Corail Pinnacle with ceramic-on-polyethylene bearing had a ten-year revision risk of 2.19% (1.40-3.41). The ASR resurfacing had a revision estimate of 28.28% at ten years (26.21- 30.48). It is important to note that the figures at ten years in this paragraph are approximate as at this time point fewer than 250 cases remain at risk.

Revisions for different causes after primary hip replacement identified different trends with different methods of fixation and bearing. With a cemented metal-on-polythene hip replacement, for example, the incidence of aseptic loosening increased with time whereas dislocation and infection decreased. Revisions for adverse reaction to particulate debris were more common in metal-on-metal and the incidence increased with time.

This year the risk of dissociation of liner from the acetabular component was investigated as a reason for revision in uncemented cups with liners. This was generally a rare event with no particular trends between brands and articulation combinations.

The cumulative mortality was examined up to eleven years following primary surgery and as expected increased with age so for example this was low in men under 55 years of age, 5.48% (4.95-6.05) but rose to 86.20% (83.10-88.92) in men over 85 years.

Primary hip replacement for fractured neck of femur has been investigated in more detail with a cohort of 15,786 primary hip replacements identified. The revision risk was slightly higher than the non-fracture group and the mortality up to eleven years significantly higher approaching 50%, compared to just under 30% for the comparator group.

The revision total hip replacement has been studied. There were a total of 79,859 revisions of which 17,916 were revisions of primary operations identified in the registry and the remaining 52,780 related to unrecorded primaries, (either pre-dating 2003 or the primary had not been captured in the NJR). A total of 87.2% were single-stage revisions, 5.8% were stage one of two-stage procedures and 6.9% were stage two of two-stage procedures. The ten-year re-revision risk was 15.30% (14.72-15.89) which is nearly an order of magnitude greater than in the primary group. It was interesting that the ten-year re-revision risk estimate was 22.67% when the primary was recorded in the NJR compared to 13.9% when the primary was not recorded in the NJR. This probably relates to the fact that the revisions recorded in the NJR relate to infection, dislocation and adverse metal reaction compared to the other group.

Knee replacement procedures

Of the 772,818 primary knee replacements, osteoarthritis was the sole stated indication for surgery in 96% of cases. A total of 43% of primary knee replacement surgeries were performed on men and the median age for a male patient undergoing primary surgery was 70 years. Of all primary knee replacements, 84.3% were cemented total knee replacements, the majority of which were unconstrained fixed bearing knees, 4.7% were uncemented and 1.1% were hybrid. Unicondylar knee replacements were used in 8.7% of procedures and patellofemoral replacement made up 1.3% of all procedures.

In comparison to hip replacement there has been little temporal change between 2003 and 2014 in terms of implant selection. All cemented total knee replacement has risen from 85.1% of all recorded surgeries in 2003 to 87.5% in 2014 and there has been a decline in uncemented total knee replacements from 6.7% to 2.5% over the same time period. Unicondylar replacements have formed between 8% and 9% of all primaries each year over the eleven-year period and patellofemoral replacements have continued to form 1% to 1.5% of surgeries year on year. The Kaplan-Meier cumulative revision risk estimates at eleven years were 3.62% (3.51-3.75) for cemented total knee replacement, 4.91% (4.38-5.50) for uncemented total knee replacement and 3.57% (3.06-4.16) for hybrid total knee replacement.

As reported in previous years the corresponding eleven-year revision estimate for unicondylar replacements were higher than total knee replacements at 14.29% (13.44- 15.18) and for patellofemoral replacement the revision risk was 20.22% (18.05-22.61). Revision estimates have been broken down according to level of constraint, for example the eleven-year estimate for cemented total knee replacement with an unconstrained, fixed bearing was 3.35% (3.20-3.50) and the posterior-stabilised fixed bearing was 4.02% (3.77-4.27). Further detailed breakdown in relation to fixation, bearing, constraint, gender and age show marked differences in outcomes. For example, when a cemented, unconstrained, fixed bearing total knee replacement was used in women over 75 years of age, the risk of revision at eleven years after the primary was just 1.53% (1.36-1.71). In comparison, in women aged under 55, the revision risk estimate was 6.94% (6.09-7.90).

The detailed breakdown of brands with a sub-division of fixation, bearing and constraint within brand continues to show that the ten-year revision estimates are low (less than 4% for many brands). The chance of first revision at ten years after the primary surgery is similar across the majority of implant brands used in total knee replacements. For example, at ten years the revision estimate was 3.56% (3.33-3.81) for the Nexgen knee and the AGC had a comparable revision risk estimate of 3.55% (3.29-3.82).

Within the unicondylar brand group, the Zimmer unicompartmental implant shows a low revision estimate at seven years of 5.89% (4.93-7.07) compared to the Preservation at 14.38% (12.68-16.32). The cumulative mortality at eleven years after the primary knee replacement was similar to that observed in hip replacement and for men under 55 years of age this was 6.38% (5.40-7.54) but rose to 85.01% (81.51- 88.17) in men over 85.

Outcomes of revision knee replacement surgery are also reported. There were 47,829 revision operations recorded of which 17,649 were linked to a primary record. In 2014, 78% of revisions were single-stage; 11.2% were stage one of two-stage and 10.8% stage two of two-stage. The ten-year cumulative percentage probability of re-revision for the whole group was 14.32% (13.60-15.07) and, similar to hip replacement, the re-revision risks were higher when the primary was recorded in the NJR 17.06% (15.32-18.97), compared to 12.43% (11.64-13.27) when the primary was not recorded in the NJR.

A detailed analysis of pre- and post-operative Patient Reported Outcome Measures has been undertaken of a sample of patients who had an elective primary knee replacement in 2010 and had returned pre-operative and 6-month National PROMs. These patients were sent further PROMs at one and three years after their primary. Of the 32,147 invited participants, 20,721 and 17,485 respectively responded at one and three years.

The median pre-operative Oxford Knee Score (OKS) was 19, rising to 37 at six months, 38 at one year and 39 at three years after the primary. The corresponding median EQ-5D Index values at the same points in time were 0.587, 0.760, 0.760 and 0.796.
In relation to OKS, the pre-operative distribution was symmetrical but distributions were highly left skewed in post-operative periods. The EQ-5D Index distribution was bimodal in shape prior to the primary operation while all three post-operative EQ-5D Index distributions featured distinct clusters of Index values. Breakdowns of the OKS distribution are given by age, gender, area deprivation, ethnicity, BMI, ASA grade, living arrangements and co-existing diseases prior to surgery and prosthesis fixation.

Ankle replacement procedures

A total of 2,554 primary ankle replacements have been recorded on the NJR between 1 April 2010 and 31 December 2014. These were carried out by a total of 201 consultants in 217 hospitals. A total of 61% of consultants entered ten or more procedures and the maximum number carried out by any one hospital was 186. The median age at primary surgery was 68 years and 58% of procedures were carried out in men. A total of 98% of the procedures were uncemented.

The Mobility was the most commonly used brand of replacement until 2013. This has now been overtaken by the use of the Zenith. The Mobility was withdrawn from the market in 2014. There have been 49 revisions submitted to the NJR which may represent under-reporting. The four-year cumulative revision risk was 3.28% (2.37-4.55).

Shoulder replacement procedures

A total of 11,399 primary shoulder replacements were recorded on the NJR from 1 April 2012 until 31 December 2014. These were carried out by a total of 553 surgeons in 335 hospitals. The median age of primary surgery was 73 years and 71.6% of procedures were carried out in women.
Over the last two years there has been a slight decrease in the use of resurfacing arthroplasty and an increase of the reverse polarity total shoulder replacement which in 2014 represented nearly 40% of cases.

In terms of brand the market leader is the Delta Xtend. There were 165 shoulder revisions overall and the cumulative revision estimate at 2.5 years was 2.8% (2.35-3.42). The relatively small numbers and short follow-up did not allow for detailed breakdown of causes of revision or differences between the brands. The 90-day mortality following surgery, as expected, differed by indication for acute trauma and elective, 90- day mortality following trauma was 2.2% (1.4-3.4) and for elective surgery was 0.3% (0.2-0.4).

Part Two: Clinical activity 2014

Now to be found online at www.njrreports.org.uk, Part Two of the NJR 12th Annual Report presents data on clinical activity. This includes information on the volumes and surgical techniques in relation to procedures submitted to the NJR, with the most recent data being for the year 1 January 2014 to 31 December 2014. To be included in the report all procedures must have been entered into the NJR by 28 February 2015.

The information now includes historical data, going back to 2005 in most cases. Using the dedicated website, readers are able to use interactive, filterable graphs to identify the key information and trends associated with the following reports for hip, knee, ankle, elbow and shoulder data (where sufficient numbers are available):

• Total number of hospitals and treatment centres in England, Wales and Northern Ireland able to participate in the NJR and the proportion actually participating
• Number of participating hospitals, according to number of procedures performed
• Procedure details, according to type of provider
• Patient characteristics for primary replacement procedures, according to procedure type
• Age and gender for primary replacement patients
• ASA grades for primary replacement patients
• Body Mass Index (BMI) for primary replacement patients
• Indications for primary procedure based on age group
• Surgical technique for primary replacement patients
• Thromboprophylaxis regime for primary replacement patients, prescribed at time of operation
• Reported untoward intra-operative events for primary replacement patients, according to procedure type
• Patient characteristics for revision procedures, according to procedure type
• Indication for surgery for revision procedures
• Trends in use of the most commonly used brands and
• Patient characteristics and indications for surgery for revision procedures

For hips specifically

• Components removed during hip revision procedures
• Components used during single-stage hip revision procedures
• Trends in femoral head size and hip articulation
• Use of ODEP-rated implants

For knees specifically

• Implant constraint for primary procedures
• Bearing type for primary procedures

The interactive reports are new and users are encouraged to leave feedback using the links provided on the appropriate report page.

Part One: Annual progress 2014/15

The 12th Annual Report of the National Joint Registry ( NJR) is the formal public report for the period 1 April 2014 to 31 March 2015 and comprises distinct parts.

As part of the continued approach to sharing information about NJR progress, clinical activity and hospital and implant activity, the NJR has again refreshed and built upon its new, dedicated online annual report website ‘NJR Reports’ to showcase annual report data and information.

Some of these data can be found in the slimmer printed report – namely the executive summaries and the full detailed, statistical analysis of outcomes following joint replacement surgery.

A short summary of the NJR’s progress over 2014/15 is included below, with further detail available at www.njrreports.org.uk and in the Chairman’s introduction and Editorial Board Chairman’s foreword.

The total number of procedures recorded in the NJR now exceeds 1.8 million at 31 March 2015, with 2014/15 having the highest ever annual number of submissions at 226,871. This is against a backdrop of sustained data quality, although a high degree of monitoring and support to orthopaedic units is still required.

Overall key performance indicators demonstrated:

• Overall compliance (case ascertainment) was recorded as 96%
• Patient consent (to record their details in the NJR) was recorded as 93.8%
• Linkability (the ability to link a patient’s primary procedure to a revision procedure) was recorded as 92.8%

There have been changes in the NJR systems and processes that relate to these statistics and any comparison on the previous year will demonstrate variation – please see the data completeness and quality indicators section online for further detail.

The evolution of the NJR Steering Committee has continued, with a series of new appointments being made allowing for a number of long-standing members to conclude their final terms of office. In recognition of the great increase in scope and responsibilities of the NJR, the registry also continued the establishment of a revised governance, structure and operating model – seeing the new Medical Advisory and Executive Sub-committees take shape.

Another key achievement has been to continue the work in implementing a revised economic model. Launched from April 2014, the changes not only represented a significant cost saving to the NHS but meant a new, fair and proportionate cost contribution from orthopaedic device manufacturers for services provided through NJR Management Feedback to support post-market implant surveillance.

It should also be highlighted that the reports from the respective Chairman of the Implant Performance Sub-committee and the Surgeon Outlier Sub-committee are available online and outline how outlier analysis is undertaken. They also include the high-level outcomes of the monitoring process for 2014/15 with statistics provided in a new section on activity and outcomes, alongside hospital performance and outlier analyses.

Finally, the NJR remains committed to working for patients and driving forward quality in joint replacement surgery. Further progress and updates will be available at www.njrreports.org.uk and the main NJR website at www.njrcentre.org.uk.