Professor Mike Reed, Chairman, Editorial Board
Mr Tim Wilton, NJR Medical Director
The NJR Editorial Board develops the strategy and style of the report and all members take responsibility for producing a report that is rigorously edited, taking almost a full year to write and review. The Board brings together experts on data collection and reporting as well as generous input from patients, clinicians from specialist societies and members of the NJR management team.
Each year the Editorial Board aims to make progress in reporting on our rich data resource, making data easily accessible to improve patient outcomes.
Specific additions to this year’s report have been:
• Dual mobility hip replacement
• Knee replacement and resurfacing of the patella by brand
• Survival of unicompartmental knee replacement
• Separation of cemented and uncemented prostheses at brand level
• Multicompartmental knee replacement
• Construct based knee analysis
In addition there has been considerable work to elaborate and refine the characterisation and classification of implants so that clearer definition of sub-groups can be now used throughout the elbow and shoulder sections.
This report is based on data up to the end of 2019 and thus outcomes are not affected by the COVID-19 pandemic. The NJR and its committees have continued to be visible at both national and international meetings with a presence at the specialist society conferences, many of which have been held virtually this year. The NJR has always been pleased to support the British Orthopaedic Association (BOA), British Elbow and Shoulder Society (BESS), British Hip Society (BHS), British Association for Surgery of the Knee (BASK), British Orthopaedic Foot and Ankle Society (BOFAS), European Hip Society (EHS), European Orthopaedic Research Society (EORS) and the European Federation of National Associations of Orthopaedics and Traumatology (EFORT).
The 17th Annual Report will be formally launched at the BOA Online Congress in September 2020. There will be no printed copy this year.
There is considerable additional information available online and we would encourage you to explore the NJR’s dedicated annual report website at reports.njrcentre.org.uk. The website offers a helpful interactive platform for the descriptive NJR data, with supporting appendices; and, when published, the latest NJR Patient Guides.
Commentary on findings
This year NJR’s Annual Report is based on 3,016,279 records and the NJR maintains its position as the largest orthopaedic registry in the world. The report presents joint replacement up to 16 years of follow-up, with data on hips, knees, shoulders, elbows and ankle replacements. A further quarter of a million records were added this year.
The following numbers of linkable primary joint replacements are available for analysis: 1,191,253 hips, 1,300,897 knees, 6,589 ankles, 45,784 shoulders and 4,373 elbow replacements. There are further linkable revisions for each joint.
Many brand combinations are reporting cumulative probability of revision up to 15 years, and in Table 3.H6 the overall success of hip replacement survival at 15 years is:
• 12.95% revision in female patients aged under 55 (males: 10.68%)
• 9.41% revision in female patients aged 55 to 64 (males: 9.36%)
• 5.74% revision in female patients aged 65 to 74 (males: 7.29%)
• 3.63% revision in female patients aged 75 and over (males: 5.07%)
Hybrid hips continue to take ground from both cemented and uncemented hip replacement and these are now as common as uncemented hip replacement. With respect to implant bearing choice in cemented hip replacement, the use of metal-on-polyethylene dominates, but in uncemented and hybrid hip replacements ceramic-on-polyethylene is becoming more dominant.
Across all of hip replacement, use of the 28mm head is decreasing, with 32mm heads becoming more common. In cemented hip replacement 28mm and 32mm heads are chosen at similar rates after years of 28mm predominating.
In Table 3.H5, revision of dual mobility bearings, predominantly metal-on-polyethylene-on-metal, is presented. With the available follow-up, revision rates are generally higher than non-dual mobility bearings.
The median number of primary total hip replacements per surgeon is around 21 per year.
Many brand combinations are reporting out to 15 years, and in Table 3.K6 the overall success of knee replacement survival at 15 years is:
• 15.74% revision in female patients aged under 55 (males: 16.21%)
• 8.44% revision in female patients aged 55 to 64 (males: 9.01%)
• 4.66% revision in female patients aged 65 to 74 (males: 5.27%)
• 2.67% revision in female patients aged 75 and over (males: 2.84%)
Broadly speaking, unconstrained knee replacements appear to be outperforming posterior stabilised (PS) knee replacements at 15 years. The degree to which this higher rate is seen in PS knees varies between brands, so surgeons would be well-advised to check the precise results for their chosen implant against the details in Table 3.K9 (b). Monobloc tibias perform particularly well at 15 years but this is based on low numbers.
Table 3.K7 (b) reports cumulative revision by brand with and without patella resurfacing, and there are differences between these brands. Although there is, in general, a higher revision rate for those knees where the patella was not resurfaced primarily, there is a wide variation in this respect between brands and types of total knee replacement and this is important information for the practising knee surgeon. There are, in fact, one or two constructs where this general rule is reversed so surgeons should neither assume that primary resurfacing makes no difference to the revision rate nor should they assume it necessarily lessens the revision rate. Surgeons are encouraged to check the results for their favoured implants.
ODEP ratings for knees take into consideration the different revision rates according to the sub-division within brands so it is important that surgeons check the exact sub-type they are using or some surgeons may get a shock when they see their own published ODEP rating usage.
Results for multicompartmental replacements are presented and show broadly similar revision rates to patellofemoral replacement at five years. These rates are generally higher than those seen with other types of knee replacement although it is not yet possible to say whether that trend will persist at longer follow-up.
The median number of primary total knee replacements per surgeon is around 40 per year, whereas for unicompartmental knees the median number per surgeon is approximately seven per year. This issue has been the subject of formal advice from BASK, that for better results and lower revision rates, surgeons should be performing at least ten unicondylar replacements per year, if they do the operation at all.
The early re-revision rate is marginally lower in cruciate retaining (CR) and posterior stabilised (PS) knees if the patella was not resurfaced at the primary operation. This presumably reflects the fact that some of the first revisions in those knees were to perform a secondary resurfacing, and might indicate that those secondary resurfacing procedures were therefore associated with a lower risk of subsequent re-revision, than revisions where other components are replaced.
A total of 6,589 ankle replacements have been analysed for this report which although a tiny proportion of the hip and knee procedures does nevertheless represent a huge collection of total ankle replacements.
In 2019, the median number of cases per consultant (5) and per unit (3) remains very low in comparison with hips and knees and only a small proportion (3.2%) of surgeons perform more than 20 cases per annum. It seems unlikely that these small volumes of ankle replacement performed by many surgeons represent the best way to ensure improved outcomes for the patients. Guidance from BOFAS about this issue can be seen in section 3.4.4.
About a quarter of revision operations gave infection as the indication, but only a small number of these suggested that there was a high suspicion of infection at the time of revision surgery. Overall, revision of ankle replacement is running at around 10% at nine years, which is a similar rate to that for unicondylar knees. Relatively few of these ankle revisions are for something comparatively “minor” such as “bearing exchange”, so if the actual overall revision rate remains similar to that for unicondylar knees that will not be a reason for us to be complacent.
Under-reporting of amputation and perhaps of arthrodesis following failed ankle replacement remains a problem, and this may need to be addressed on a wider front than through the foot and ankle surgery community, as some of these procedures may be done by a wide variety of surgeons.
There are quite large differences shown between revision rates for different ankle replacement brands but the data about this should be interpreted with some caution. There are some surgeons who perform much larger numbers than average so that if they have particularly good (or particularly poor) revision rates those surgeons could introduce disproportionate influence to the implant results.
Due to the withdrawal of the high-selling Mobility implant from the market five years ago and almost simultaneous introduction of the Infinity implant, which immediately became the best-seller, it will be several more years before meaningful longer-term comparisons will be possible between revision rates of some of the most popular ankle implants.
This report relates to 45,784 primary and 5,087 revision shoulder replacements. The numbers of cases continue to increase year on year, but analysis of the outcomes remains challenging due to a number of conflicting issues relating to shoulder arthroplasty specifically. The categorisation of the implants has not been clear in the past for a number of reasons:
1) The constructs have rapidly evolved and are complex and variable;
2) the devices are not necessarily used as an entire joint construct in every case;
3) some manufacturers have many shoulder implant brands and surgeons are able to mix components from these different brands to make a shoulder construct; and
4) there has been confusion in the past over precisely how some cases would properly be classified due to partly missing implant descriptors.
This year, a new revised classification framework will enable extensive revision of the categories and re-classification of some implants which will greatly enhance the future analysis of these operations.
Reverse polarity total shoulder replacement continues to increase in proportion to humeral hemiarthroplasty and conventional total shoulder replacement, so that of all fully classified procedures this has increased from 26.8% to 52.2% from 2012 to 2019. In addition, there remain another 13.3% which are not yet fully confirmed in the new classification and many of these are also reverse polarity shoulders.
The median number of cases performed by a surgeon each year remains low compared to hips or knees, and despite this the number of surgeons performing these operations has increased significantly in seven years.
In comparing revision rates for different types of shoulder replacement, higher rates of revision for all types of humeral hemiarthroplasty can be seen compared to reverse polarity or stemmed conventional total shoulder replacements. It is very difficult to identify the degree to which such differences might be due to intrinsic differences in the success of the implants, differences in indication and potential differences in the ease of revision (and consequently willingness to perform revision surgery). The reader is therefore advised to interpret these revision results with caution.
Revision rate is regarded by shoulder surgeons as a relatively poor indicator of the success of the procedure as there may be a significant proportion of patients with poor function and ongoing symptoms who have not had revision surgery. Other outcomes are therefore vital and the PROMs programme seeks to provide such additional evidence. The completeness of the PROMs data is not good at present however and so it should again be interpreted with great caution. This is illustrated in Figure 3.S5, which shows that the revision rate in those returning valid PROMs is better than that for the rest of the shoulder patients.
Despite this drawback, the shoulder PROMs cohort is one of the largest in the world and it is interesting to see that the limited data available suggests that the PROMs gain after humeral hemiarthroplasty is less than after either reverse polarity or conventional total shoulder procedures. Since humeral hemiarthroplasty also has higher revision rates this implies that the revision rate is truly worse, rather than reflecting a lower threshold for revision surgery, however more in-depth analysis of other confounders is needed to clarify this.
Considerable variation is seen in the revision rates for individual implant brands, but at present for most shoulder brands these are not available for more than a few years. Nevertheless, that some reverse shoulders show higher rates of revision after just one year than some others show at six years is of concern, even with relatively small numbers of cases available for analysis.
This report relates to 4,373 primary elbow replacements performed for trauma and elective indications, over 2,000 of which have been implanted in the last three years. Although this represents a very large collection of elbow replacements, the procedures are varied, as are the indications, so that the categorisation into sub-groups still leaves relatively small groups which are currently difficult to analyse in terms of outcome.
The extensive re-classification work has enabled much more clarity, for example, whether the procedure has included a radial head implant and whether the distal humeral implant has been used as a hemiarthroplasty.
Although similar for the first three years, the revision rate for acute trauma cases is better than for elective cases thereafter. The numbers for trauma cases are relatively small and the indications for acute surgery are somewhat different. The difference between acute and elective outcomes will therefore need further elaboration when larger numbers are available.
The very small numbers of elbow replacements performed by surgeons, and by each unit, continue and have not changed significantly in the last three years. This is the subject of a discussion process with Getting It Right First Time (GIRFT) and the British Elbow and Shoulder Society (BESS) to decide whether regional rationalisation of these procedures can be introduced.
The NJR continues to work collaboratively with many stakeholders; the most important, of course, are the patients we serve, and whom we would like to thank for allowing the NJR to use their data.
The NJR is a huge team effort. Many thanks also to the following without which the NJR could not function:
All members of the NJR Steering Committee
Members of the NJR sub-committees:
Regional Clinical Coordinators
Members of the Data Access Review Group
Members of the NJR Patient Network
Medicines and Healthcare products Regulatory Agency (MHRA)
Care Quality Commission (CQC)
Getting It Right First Time (GIRFT)
British Orthopaedic Association (BOA)
British Hip Society (BHS)
British Association for Surgery of the Knee (BASK)
British Elbow and Shoulder Society (BESS)
British Orthopaedic Foot and Ankle Society (BOFAS)
European Orthopaedic Research Society (EORS)
Healthcare Quality Improvement Partnership (HQIP)
Northgate Public Services (UK) Ltd
University of Bristol
University of Oxford
Confidentiality Advisory Group
Association of British HealthTech Industries (ABHI)
On a personal note, we would particularly like to thank Laurel Powers-Freeling, Chairman of the NJR and Elaine Young, NJR Director of Operations.
Northgate Public Services, University of Bristol and University of Oxford teams have done a first-class job, as always.
Particular personal thanks to Vicky McCormack and Deirdra Taylor for getting the final report into shape.