Artigo joelho

Prévia do material em texto

www.thelancet.com Vol 393 February 16, 2019 655
Articles
How long does a knee replacement last? A systematic review 
and meta-analysis of case series and national registry reports 
with more than 15 years of follow-up
Jonathan T Evans, Robert W Walker, Jonathan P Evans, Ashley W Blom, Adrian Sayers*, Michael R Whitehouse*
Summary
Background Knee replacements are the mainstay of treatment for end-stage osteoarthritis and are effective. Given 
time, all knee replacements will fail and knowing when this failure might happen is important. We aimed to establish 
how long a knee replacement lasts.
Methods In this systematic review and meta-analysis, we searched MEDLINE and Embase for case series and cohort 
studies published from database inception until July 21, 2018. Articles reporting 15 year or greater survival of primary 
total knee replacement (TKR), unicondylar knee replacement (UKR), and patellofemoral replacements in patients 
with osteoarthritis were included. Articles that reviewed specifically complex primary surgeries or revisions were 
excluded. Survival and implant data were extracted, with all-cause survival of the knee replacement construct being 
the primary outcome. We also reviewed national joint replacement registry reports and extracted the data to be 
analysed separately. In the meta-analysis, we weighted each series and calculated a pooled survival estimate for each 
data source at 15 years, 20 years, and 25 years, using a fixed-effects model. This study is registered with PROSPERO, 
number CRD42018105188.
Findings From 4363 references found by our initial search, we identified 33 case series in 30 eligible articles, which 
reported all-cause survival for 6490 TKRs (26 case series) and 742 UKRs (seven case series). No case series reporting on 
patellofemoral replacements met our inclusion criteria, and no case series reported 25 year survival for TKR. The 
estimated 25 year survival for UKR (based on one case series) was 72·0% (95% CI 58·0–95·0). Registries contributed 
299 291 TKRs (47 series) and 7714 UKRs (five series). The pooled registry 25 year survival of TKRs (14 registries) was 
82·3% (95% CI 81·3–83·2) and of UKRs (four registries) was 69·8% (67·6–72·1). 
Interpretation Our pooled registry data, which we believe to be more accurate than the case series data, shows that 
approximately 82% of TKRs last 25 years and 70% of UKRs last 25 years. These findings will be of use to patients and 
health-care providers; further information is required to predict exactly how long specific knee replacements will last. 
Funding The National Institute for Health Research, the National Joint Registry for England, Wales, Northern Ireland, 
and Isle of Man, and the Royal College of Surgeons of England. 
Copyright © 2019 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.
Introduction
Osteoarthritis of the knee is a common and potentially 
debilitating condition. The mainstay of treatment for end-
stage disease is knee replacement, and this procedure has 
been shown to be effective in most cases.1 Depending 
upon the extent of disease, replacement surgery can take 
the form of total knee replacement (TKR), unicondylar 
knee replacement (UKR), or patellofemoral replacement 
(PFR). In TKR, all the articular surfaces of the tibiofemoral 
joint are replaced (with or without the articulating surface 
of the patella). UKR and PFR are suitable for disease 
confined to one compartment and only that compartment 
is replaced. TKR, UKR, and PFR are now some of the 
most common surgical procedures worldwide with a 
marked secular increase.
The aim of knee replacement surgery is the long-term 
relief of pain and restoration of function. Unfortunately, 
knee replacements fail for a variety of reasons, including 
loosening, infection, persistent pain, and instability,2 and 
might require revision within the lifetime of the recipient. 
Knowing what the long-term failure rates are is important 
to facilitate resource planning, medicolegal assessment, 
benchmarking of different implants, and the provision of 
informed consent to patients. Given enough time, all knee 
replacements will fail and need to be revised. Revision is 
expensive3,4 and results in worse outcomes than primary 
surgery.
The National Institute of Health and Care Excellence 
set a UK benchmark in 2014, which stated that individual 
hip replacement components are only recommended if 
5% or fewer need revision at 10 years,5 but no equivalent 
benchmark exists for knee replacement in either the 
medium (10 years) or long term.
In the UK, in 2016, the typical patient requiring knee 
replacement was aged 69 years with a body-mass index 
of 31 kg/m². Almost all (99%) knee replacements were 
Lancet 2019; 393: 655–63
*Joint senior authors
This online publication has been 
corrected. The corrected version 
first appeared at thelancet.com 
on February 20, 2019
Musculoskeletal Research Unit, 
Translational Health Sciences, 
Bristol Medical School, 
University of Bristol, 
Southmead Hospital, Bristol, 
UK (J T Evans MRCS, 
Prof A W Blom PhD, 
A Sayers MSc, 
M R Whitehouse PhD); 
Department of Trauma and 
Orthopaedics, Torbay and 
South Devon NHS Foundation 
Trust, Torquay, UK 
(R W Walker MRCS); Health and 
Policy Research Group, 
University of Exeter, Exeter, UK 
(J P Evans MSc); and National 
Institute for Health Research 
Bristol Biomedical Research 
Centre, University Hospitals, 
Bristol NHS Foundation Trust, 
University of Bristol, Bristol, 
UK (Prof A W Blom, 
M R Whitehouse)
Correspondence to: 
Mr Jonathan T Evans, 
Musculoskeletal Research Unit, 
Translational Health Sciences, 
Bristol Medical School, University 
of Bristol, Southmead Hospital, 
Bristol BS10 5NB, UK 
j.t.evans@bristol.ac.uk
http://crossmark.crossref.org/dialog/?doi=10.1016/S0140-6736(18)32531-5&domain=pdf
Articles
656 www.thelancet.com Vol 393 February 16, 2019
done in patients with osteoarthritis and 56% of patients 
were women.3 In 2016, 108 713 knee replacement 
procedures were done in England, Wales, Northern 
Ireland, and the Isle of Man.3 60 different implants were 
used for primary TKR, comprising 90·1% of all knee 
replacement pro cedures; 18 different UKR implants and 
nine different PFR implants were used.6
In this study, we wish to answer a simple question that 
is posed to us by our patients, multiple times per day—
how long does a knee replacement last?
Methods
Search strategy and selection criteria
This systematic review and meta-analysis followed 
a predefined protocol registered with PROSPERO 
(CRD42018105188) and adhered to PRISMA guidelines.7 
We did one systematic review and meta-analysis of case 
series and cohort studies reporting survival outcomes of 
knee replacements and a second meta-analysis of 
national joint replacement registries with more than 
15 years of follow-up.
We systematically searched MEDLINE and Embase for 
case series and cohort studies that reported survival 
outcomes of knee replacements, published between com-
mencement of each database and July 21, 2018. 
The search was done through the Ovid SilverPlatter 
platform and contained keywords relating to knee 
replacement, survival, and medical subject heading terms 
(see appendix for details of exact search terms used). 
Bibliographies of all included articles, as well as review 
articles, were manually screened for additional citations 
(JTE). Nine studies were excluded because they were 
not written in English. Studies were included if they 
involved patients undergoing any type of knee replacement 
(TKR, UKR, or PFR) for osteoarthritis or a predominantly 
unselected patient group (eg, studies that investigated 
only one or two indications, such as rheumatoid arthritis, 
were excluded). Survival reports of specific implants with 
a mean or median follow-up of more than 15 years were 
required. Articles that reviewed specifically complex 
primary surgeries or revisions were excluded, because 
thesetypes of procedures have different survivorship of 
the implants. Some articles reported sur vivorship from 
Research in context
Evidence before this study
We searched MEDLINE and Embase for systematic reviews and 
meta-analyses published in English. Our search identified 
34 systematic reviews, but none of these articles produced a 
combined survival estimate with more than 15 years follow-up, 
and although many reviews compared subgroups (eg, 
cemented vs cementless), we believe these studies to be prone 
to selection bias. Before the advent of national joint 
replacement registers, case series were the only sources of 
survival estimates for knee replacements. A previous analysis 
of the Finnish Arthroplasty Registry provided an estimate of 
the survival of total knee replacement at 15 years of 88·7% 
(95% CI 88·5–88·9) for total knee replacement (TKR) and 
69·6% (68·2–70·9) for unicondylar knee replacement (UKR). 
An analysis that used the UK Clinical Practice Research Datalink 
(CPRD) database was published in 2017, and estimated survival 
of TKR to be 89·7% (95% CI 87·5–91·5) at 20 years.
Added value of this study
To our knowledge, we have provided the first simple and 
generalisable estimate of the survival of knee replacements at 
25 years, providing an answer to the question—how long does a 
knee replacement last? Our findings showed that approximately 
82% of TKRs and 70% of UKRs last for 25 years.
Implications of all the available evidence
Our findings, combined with those of previous registry analyses 
and the analysis of the CPRD data by Bayliss and colleagues, are 
of use to patients, people providing and commissioning 
health-care services, and those needing an estimate of knee 
replacement survival for medicolegal purposes. 
Figure 1: Flow chart of case series and cohort study selection
TKR=total knee replacement. UKR=unicondylar knee replacement. PKR=patellofemoral replacement.
4363 potentially eligible case series or cohort studies 
 identified by search of database
1481 duplicates identified
2 additional articles identified from 
 manual search of references
26 series reporting TKR survival 
 included in quantitative 
 synthesis (meta-analysis)
7 series reporting UKR survival 
 included in quantitative 
 synthesis (meta-analysis)
0 series reporting PFR survival 
 included in quantitative 
 synthesis (meta-analysis)
2882 non-duplicate citations
2670 excluded after screening
 1072 insufficient follow-up
 787 not primary TKRs
 471 no survival analysis
 316 disease-specific indication other than osteoarthritis
 24 duplicates that were not identified previously 
212 full-text articles reviewed
30 articles included (33 unique case series)
184 excluded
 83 insufficient follow-up or no survival analysis 
 34 systematic reviews 
 11 articles based on registry data
 10 no CIs provided 
 46 other 
See Online for appendix
Articles
www.thelancet.com Vol 393 February 16, 2019 657
registry data; we excluded these studies because their 
inclusion would lead to duplication of data identified from 
the second data source. Systematic reviews were retrieved, 
and citations searched, but pooled data from the reviews 
themselves were not included because their inclusion 
would result in duplication.
The first national joint replacement registry was 
founded in Sweden in 1975; at the time of writing, 
six registries have more than 15 years of potential follow-
up for knee replacement (those in Australia, Denmark, 
Finland, New Zealand, Norway, and Sweden). For the 
analysis of data from national joint replacement registries, 
we reviewed websites and the most recent annual reports 
of national joint replacement registries with 15 years of 
follow-up at the time of data collection (July 21, 2018) for 
15 year or longer survival data on TKR, UKR, or PFR 
constructs. These national registries collect data on all 
patients undergoing knee replacements in both public 
and private hospitals and aim to include all joint 
replacements in their cohort.
Abstract screening and data extraction
The abstracts of journal articles were screened by three 
reviewers (JTE, RWW, and JPE) using the web application 
Rayyan,8 and in cases of disagreement were included for 
full review. Data were extracted twice on publication 
date, implant type, fixation technique, number of knee 
replacements, age and sex of recipient, indication for 
knee replacement, loss to follow-up, and summary 
survivorship estimates (including CIs), when available. 
Data were not extracted from figures to prevent potential 
inaccuracy, particularly in the case of older, low-reso-
lution figures. Any discrepancy between the twice-
extracted data was rectified by review of the full text by 
all reviewers, after which there were no cases of 
disagreement.
Data analysis
Our primary exposure was the make and model of the 
knee replacement construct and our primary outcome 
was all-cause revision of any part of this construct. We 
required estimates of survival for specific constructs 
because we believe that this make and model of the 
construct fundamental to the outcome of surgery. Aggre-
gated data from multiple constructs would not allow this 
level of detail and would thus hide the variability in 
performance between constructs. Statistical analysis 
was done with Stata 15 (release 15). Knee replacement 
construct survival estimates at 15 years, 20 years, and 
25 years, assuming survivorship approximated risk, were 
pooled with meta-analysis. Each series was weighted 
according to its standard error (calculated from published 
CIs). A fixed-effects model was used. Variability between 
studies and publication bias were assessed using visual 
representation of the data. 
Data from registries were analysed in the same way 
as data from the case series to produce equivalent 
forest plots. The contribution each implant series made 
was weighted according to the standard error of that 
individual estimate.
Study quality was assessed using the non-summative 
four-point system (consecutive cases, multicentre, under 
20% loss to follow-up, and using multivariable analysis) 
developed by Wylde and co-workers.9 This system was 
preferred over the summative MINORS score because of 
the high loss to follow-up in joint replacement case series 
and because some of the scoring criteria were not 
relevant to joint replacement.10
Individual case series articles Australian Orthopaedic 
Association National Joint 
Replacement Registry annual 
report, 2017
Finnish Arthroplasty Report, 
November, 2017
TKR UKR TKR UKR TKR UKR
Study-level characteristics
Location 26 articles in 
ten countries
Seven articles in 
four countries
Australia Australia Finland Finland
Number of unique implant series included 26 7 24 0 23 5
Year of publication 1999–2018 1999–2013 2017 NA 2017 2017
Participant-level characteristics
Total joint replacements included 6490 742 209 435 0 89 856 7714
Mean age (years) 67·3* 68·7* 68·5† NA 65–74‡§ 65–74‡§
Proportion of female patients 55·4%¶ 65·0%¶ 56·8%† NA 68·4%†§ 68·4%†§
Proportion of arthroplasties implanted for 
osteoarthritis
87·5%|| 93·7%|| 97·6%† NA 88·9%†§ 88·9%†§
TKR=total knee replacement. UKR=unicondylar knee replacement. NA=not applicable. *Weighted mean for age by number of arthroplasties in series. †All primary knee 
operations in the report (not just those included in study). ‡Exact value not reported, median within this age range. §Note that these values are the same in the TKR and UKR 
columns because the Finnish Arthroplasty Registry does not differentiate between TKR and UKR. ¶Weighted proportion of female patients by number in study if the 
proportion of women was reported. ||Weighted proportion by number of arthroplasties in series if reported. 
Table 1: Study-level and participant-level characteristics of contributing data sources
Articles
658 www.thelancet.com Vol 393 February 16, 2019
This study is registered with PROSPERO, number 
CRD42018105188.
Role of thefunding source
The funder of the study had no role in study design, data 
collection, data analysis, data interpretation, or writing of 
the report. The corresponding author had full access to 
all the data in the study and had final responsibility for 
the decision to submit for publication.
Results
The search of published case series produced 4363 articles. 
1481 duplicates were removed, leaving 2882 articles 
for screening (figure 1). After screening, 212 full-text 
articles remained for review, with two additional citations 
identified through manual search of references and 
reviews (appendix). Nine articles that were not written 
in English were excluded. Following review of full-text 
articles, 30 journal articles reporting 33 unique case 
series were included; these articles reported 7232 knee 
replacements (range 50–1000). 26 case series reported 
survival of TKRs and seven reported survival of UKRs; no 
case series reporting on PFR met our inclusion criteria. 
A full list of included articles and survival estimates can 
be found in the appendix. A summary of study-level and 
patient-level characteristics of each data source is provided 
(table 1).
Quality assessment of the case series revealed that 
22 (67%) of 33 were consecutive, 1 (3%) of 33 were 
multicentre, all 33 (100%) had less than 20% loss to 
follow-up, and only 4 (12%) of 33 included multivariable 
analyses. These proportions reflect the fact that, in 
general, the quality of published case series is low.
26 unique case series reported survival for 6490 TKRs, 
with follow-up ranging from 15 years to 23 years. 14 series 
reported survival at 15 years (4137 TKRs) and five at 
20 years (763 TKRs). Not all series reported survival at 
exactly 15 years or 20 years and some series reported 
survival at more than one timepoint. Pooled analysis of 
data derived from case series reported at exactly 15 years 
or 20 years showed an all-cause construct survivorship 
of 96·3% (95% CI 95·7–96·9) at 15 years and 94·8% 
Figure 2: Forest plot of estimates for reported survival of knee replacements from case series11–32
(A) Total knee replacements at 15 years and 20 years. (B) Unicondylar knee replacements at 15 years, 20 years, 
and 25 years. The CIs for individual point estimates are shown with horizontal lines. The surrounding box shows the 
contribution made by that individual estimate to the overall pooled estimate, weighted by the standard error of that 
individual series.
Survival 
(%; 95% CI)
Weight
(%)
15 years
Abdeen et al (2010)11
Callaghan et al (2005)12
Dixon et al (2005)13
Gill et al (1999)14
Hernigou et al (2009)15
Hernigou et al (2009)15
Kim et al (2018)16
Kim et al (2018)16
Macheras et al (2017)17
McCalden et al (2017)18
Nakamura et al (2017)19
Newman et al (2009)20
Oliver et al (2018)21
Schiavone Panni et al (2017)22
Vessely et al (2006)23
Subtotal
20 years
Callaghan et al (2013)24
Callaghan et al (2010)25
Epinette et al (2014)26
Eriksen et al (2009)27
Gill et al (1999)14
Subtotal
0·32
1·07
0·90
1·49
0·90
8·08
2·64
2·64
22·45
39·91
7·33
0·07
1·01
2·24
8·95
100·00
10·54
37·74
24·95
2·88
23·89
100·00
 88·7 (71·8–91·8)
 97·0 (89·0–100·0)
 92·6 (86·0–98·0)
 98·6 (90·5–99·8)
 91·0 (85·0–97·0)
 92·0 (90·0–94·0)
 99·0 (93·0–100·0)
 99·0 (93·0–100·0)
 98·8 (97·6–100·0)
 96·4 (95·5–97·3)
 96·2 (94·1–98·3)
 78·7 (56·2–100·0)
 92·3 (84·9–96·2)
 94·7 (90·9–98·5)
 93·7 (91·8–95·6)
 96·3 (95·7–96·9)
 90·8 (83·0–97·0)
 96·5 (92·6–100·0)
 91·4 (87·2–96·3)
 84·4 (70·8–97·6)
 98·6 (90·5–99·8)
 94·8 (92·5–97·1)
15 years
Argenson et al (2013)28
Foran et al (2013)29
Newman et al (2009)20
Yang et al (2003)30
Subtotal
20 years
Argenson et al (2013)28
Foran et al (2013)29
O’Rourke et al (2005)31
Parratte et al (2012)32
Subtotal
25 years
O’Rourke et al (2005)31
66·37
18·88
6·43
8·32
100·00
32·80
22·25
25·11
19·84
100·00
100·00
 83·0 (79·0–87·0)
 93·0 (83·0–98·0)
 89·8 (74·3–100·0)
 84·6 (73·3–95·9)
 85·5 (82·2–88·7)
 74·0 (67·0–81·0)
 90·0 (79·0–96·0)
 84·0 (76·0–92·0)
 83·0 (74·0–92·0)
 81·9 (77·9–85·9)
 72·0 (58·0–95·0)
30100 50 1004020 70 908060
A
B
Number 
of series
Total number of 
arthroplasties at the 
start of the series
Pooled survival 
estimate (95% CI)
Total knee replacement
15 years 15 4137 96·3% (95·7–96·9)
16·8 years 2 228 96·3% (93·5–99·0)
18 years 2 572 93·8% (81·0–96·0)
19 years 2 356 96·1% (92·8–99·4)
20 years 5 763 94·8% (92·5–97·1)
20·8 years 1 160 86·9% (80·4–91·5)
22 years 1 163 82·1% (76·2–88·0)
23 years 1 489 89·0% (82·0–93·0)
Unicondylar knee replacement
15 years 4 387 85·5% (82·2–88·7)
16 years 1 113 81·3% (67·7–94·8)
20 years 4 437 81·9% (77·8–85·9)
22 years 1 140 84·0% (75·0–93·0)
25 years 1 136 72·0% (58·0–95·0)
Table 2: Pooled estimates of survival for each available timepoint
Articles
www.thelancet.com Vol 393 February 16, 2019 659
(92·5–97·1) at 20 years. Figure 2A shows a forest plot for 
the meta-analysis of data on TKRs derived from case 
series at 15 years and 20 years.
Pooled survival at each timepoint is shown in table 2. 
When we rounded survival at timepoints that were 
not exactly 15 years or 20 years down to the closest 
time point (to include as many case series as possible in 
our analyses), pooled survival was 96·3% (95% CI 
95·7–96·8) at 15 years and 92·0% (90·1–93·8) at 
20 years (appendix).
Seven unique case series reported survival for 742 UKRs, 
with follow-up ranging from 15 years to 25 years. 
Four series reported survival at 15 years (387 UKRs), 
four at 20 years (437 UKRs), and one at 25 years 
(136 UKRs). Not all series reported survival at exactly 
15 years, 20 years, or 25 years, and some series reported 
survival at more than one time point. Pooled analysis of 
data derived from case series reported at exactly 15 years, 
20 years, and 25 years showed an all-cause construct 
survivorship of 85·5% (95% CI 82·2–88·7) at 15 years, 
81·9% (77·9–85·9) at 20 years, and 72·0% (58·0–95·0) 
at 25 years. Figure 2B shows a forest plot for the meta-
analysis of the data on UKRs derived from case series 
at 15 years, 20 years, and 25 years.
Pooled survival at each timepoint can be seen in table 2. 
When we rounded survival at timepoints that were not 
exactly 15 years, 20 years, or 25 years down to the closest 
timepoint (to include as many series as possible in our 
analyses), pooled survival was 85·3% (95% CI 82·0–88·6) 
at 15 years, 82·2% (78·6–85·9) at 20 years, and 72·0% 
(58·0–95·0) at 25 years (appendix).
The search of joint replacement registry reports 
yielded 47 series reporting TKRs and five reporting 
UKRs. The estimates from these series all originated 
from the Australian and Finnish registries. The other 
four arthroplasty registries with 15 years of potential 
follow-up did not provide survival estimates that were 
broken down by implant type, and therefore we could 
not use them in our analyses.
All 47 TKR series reported survival analyses at 15 years 
(299 291 TKRs), 20 series reported survival at 20 years 
(88 532 TKRs), and 14 series at 25 years (76 651 TKRs). The 
pooled survival data derived from registry data showed 
an all-cause construct survivorship of 93·0% (95% CI 
92·8–93·1) at 15 years, 90·1% (89·7–90·4) at 20 years, and 
82·3% (81·3–83·2) at 25 years. We obtained 15 year 
estimates from both the Australian and the Finnish 
registries and the 20 year and 25 year estimates were 
exclusively from the Finnish registry.
We obtained all data on UKRs exclusively from the 
Finnish registry. All five UKR series reported survival 
analyses at 15 years (7714 UKRs), four series reported 
Figure 3: Forest plot of estimates for reported survival of total knee 
replacements from registry reports at 15 years, 20 years, and 25 years
Survival
(%; 95% CI)
Registry Weight
(%)
15 years
AGC/AGC
Advance/Advance II
Advantim/Advantim
Duracon/Duracon
Genesis II CR/Genesis II
Genesis II CR/Profix Mobile
Genesis II Oxinium CR/Genesis II
Genesis II PS/GenesisII
Kinemax Plus/Kinemax Plus
LCS CR/LCS
LCS CR/MBT
LCS CR/MBT Duofix
MBK (Zimmer)/Nexgen
Maxim/Maxim
Natural Knee II/Natural Knee II
Nexgen CR/Nexgen
Nexgen LPS/Nexgen
PFC Sigma CR/MBT
PFC Sigma CR/PFC Sigma
PFC Sigma PS/PFC Sigma
Profix/Profix
Scorpio CR/Series 7000
Scorpio PS/Scorpio+
Scorpio PS/Series 7000
Anametric
Guepar hinged
Kinematic stab
Duracon
PCA Interax DI
AGC V2
AGCV2/Maxim
AGC Dual articular
Duracon Rotating Hinge
Duracon TS
Kinematic Rotating Hinge
PFC Sigma
PFC Sigma RP
NexGen
Maxim
Link Endo-Model
Arge
Genesis II CR
TCIV
Performance
PCA
Freeman-Swanss
Synatomic Townley
Subtotal
20 years
Anametric
Guepar hinged
Kinematic stab
Duracon
PCA Interax DI
AGC V2
AGCV2/Maxim
AGC Dual articular
Duracon TS
Kinematic Rotating Hinge
PFC Sigma
NexGen
Maxim
Link Endo-Model
Arge
TCIV
Performance
PCA
Freeman-Swanss
Synatomic Townley
Subtotal
25 years
Anametric
Guepar hinged
Kinematic stab
Duracon
AGC V2
AGC Dual articular
Kinematic Rotating Hinge
PFC Sigma
Link Endo-Model
TCIV
Performance
PCA
Freeman-Swanss
Synatomic Townley
Subtotal
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Australian
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
1·77
0·70
0·51
8·58
5·96
0·39
0·26
2·15
0·74
5·08
4·38
2·38
0·24
0·34
0·89
7·09
2·65
2·15
4·38
0·95
4·38
5·08
0·66
0·39
0·14
0·02
0·11
13·41
0·10
7·09
0·17
0·13
0·24
0·05
0·02
7·09
0·14
5·08
0·89
0·11
1·49
0·54
0·22
0·27
0·28
0·16
0·13
100·00
0·43
0·13
0·28
32·92
0·41
18·52
0·16
0·12
0·30
0·07
10·75
24·19
2·24
0·26
4·93
0·80
1·12
1·09
0·78
0·49
100·00
3·29
1·03
0·98
33·31
31·37
0·92
0·52
2·36
2·02
6·12
6·12
6·62
3·17
2·18
100·00
 92·6 (91·4–93·6)
 92·2 (90·3–93·8)
 93·6 (91·2–95·3)
 92·9 (92·4–93·4)
 94·2 (93·6–94·8)
 88·8 (86·2–90·9)
 89·0 (85·7–91·5)
 93·4 (92·3–94·3)
 91·5 (89·6–93·0)
 92·2 (91·5–92·8)
 93·9 (93·2–94·6)
 92·8 (91·8–93·7)
 92·0 (88·5–94·5)
 88·9 (86·1–91·1)
 89·4 (87·8–90·9)
 95·6 (95·0–96·1)
 93·7 (92·7–94·5)
 93·9 (92·8–94·8)
 94·9 (94·1–95·5)
 92·7 (91·1–94·1)
 94·5 (93·8–95·2)
 93·3 (92·6–93·9)
 91·5 (89·5–93·1)
 88·5 (85·9–90·6)
 83·2 (79·4–87·1)
 78·4 (69·6–88·4)
 90·9 (86·6–95·4)
 92·2 (91·8–92·6)
 73·9 (69·4–78·8)
 90·6 (90·1–91·2)
 89·9 (87·5–94·6)
 90·2 (86·2–94·4)
 91·7 (88·7–94·7)
 82·8 (76·8–89·3)
 79·7 (70·7–89·8)
 92·9 (92·3–93·4)
 93·8 (89·9–97·8)
 96·1 (95·5–96·8)
 90·3 (88·8–91·9)
 82·6 (78·3–87·3)
 93·1 (91·9–94·3)
 96·2 (94·2–98·2)
 87·0 (83·9–90·2)
 85·0 (82·2–87·8)
 70·0 (67·3–72·8)
 88·2 (84·6–91·9)
 68·7 (64·7–72·9)
 93·0 (92·8–93·1)
 76·5 (71·5–82·0)
 78·4 (69·6–88·4)
 85·7 (79·4–92·5)
 89·7 (89·1–90·3)
 69·8 (64·6–75·4)
 87·4 (86·6–88·2)
 85·6 (77·5–94·6)
 80·7 (71·4–91·3)
 82·8 (76·8–89·3)
 72·2 (60·2–86·6)
 89·8 (88·8–90·9)
 95·9 (95·2–96·6)
 88·6 (86·3–90·9)
 77·3 (70·9–84·3)
 92·1 (90·6–93·7)
 84·5 (80·8–88·5)
 82·2 (79·0–85·5)
 63·7 (60·5–67·1)
 87·4 (83·6–91·4)
 61·9 (57·2–67·0)
 90·1 (89·7–90·4)
 76·5 (71·5–82·0)
 78·4 (69·6–88·4)
 80·3 (71·3–90·5)
 87·1 (85·5–88·8)
 84·1 (82·4–85·8)
 80·7 (71·4–91·3)
 72·2 (60·2–86·6)
 86·2 (83·2–95·6)
 77·3 (70·9–84·3)
 84·5 (80·8–88·5)
 80·3 (76·5–84·2)
 61·0 (57·4–64·8)
 85·5 (80·3–91·0)
 55·9 (49·8–62·7)
 82·3 (81·3–83·2)
30100 50 1004020 70 908060
Articles
660 www.thelancet.com Vol 393 February 16, 2019
survival at 20 years (3935 UKRs), and four series at 
25 years (3935 UKRs). The pooled survival data derived 
from registry data showed an all-cause construct 
survivorship of 76·5% (95% CI 75·2–77·7) at 15 years, 
71·6% (69·6–73·6) at 20 years, and 69·8% (67·6–72·1) 
at 25 years.
Forest plots for the meta-analysis of data derived from 
joint replacement registry reports for TKR and UKR are 
provided in figures 3 and 4.
A comparison of the point estimates at each timepoint 
for the two sources is shown for TKR and UKR (figure 5).
Discussion
The question of how long does a knee replacement last is 
frequently asked by patients, and to date, we have not had 
a generalisable answer. The implant itself is fundamental 
to the survival outcome of surgery and each individual 
series should be considered as a different patient 
cohort. We have used individual estimates for each implant 
to synthesise a single pooled estimate, weighting the 
estimates according to standard error. This type of analysis, 
which derives an overall estimate according to how 
frequently each implant has been used, is unique to our 
study. The pooled registry data presented here show that 
82·3% of TKRs and 69·8% of UKRs last 25 years. Only 
one case series reported the 25 year survival of UKRs 
(72·0%, 95% CI 58·0–95·0) and no TKR series provided 
25 year results. Case series at 20 years of follow-up suggest 
better survival of TKR and UKR than comparable registry 
data. Although survival of a knee replacement prosthesis is 
important, it is not the only measure of success. One in 
five patients who undergo TKR for osteoarthritis reports 
an unfavourable pain outcome after surgery,33 and given 
our results, not all these patients seem to undergo revision 
surgery. The age of the patients in our study is similar to 
that reported by the largest national registries, such as 
the National Joint Registry for England, Wales, Northern 
Ireland, and the Isle of Man (NJR) and the Swedish Knee 
Arthroplasty Register (SKAR), suggesting that our data are 
likely to be generalisable. The proportion of female patients 
appears to be higher in the Finnish Arthroplasty Register 
than in the Australian registry or the pooled results of the 
case series, and this high proportion might affect the 
generalisability of the results. Given the secular changes in 
the sex distribution of patients receiving knee replacements 
seen in the SKAR, we expect this effect to be small.34 In 
Figure 4: Forest plot of estimates for reported survival of unicondylar knee replacements from registry 
reports at 15 years, 20 years, and 25 years
Survival 
(%; 95% CI)
Registry Weight
(%)
15 years
Oxford Phase II
Oxford Phase III
Milller-Galante Unicondylar
Milller-Galante II
Miller-Galante I
Subtotal
20 years
Oxford Phase II
Milller-Galante Unicondylar
Milller-Galante II
Miller-Galante I
Subtotal
25 years
Oxford Phase II
Milller-Galante Unicondylar
Milller-Galante II
Miller-Galante I
Subtotal
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
Finnish
2·57
41·67
4·80
35·80
15·16
100·00
1·80
10·26
58·34
29·60
100·00
1·88
11·33
60·50
26·28
100·00
 74·8 (67·5–82·8)
 74·1 (72·2–76·0)
 67·1 (61·8–73·0)
 85·8 (83·8–87·9)
 64·1 (61·0–67·3)
 76·5 (75·2–77·7)
 58·3 (45·4–75·0)
 62·2 (56·3–68·7)
 81·6 (79·0–84·2)
 56·0 (52·4–59·7)
 71·6 (69·6–73·6)
 53·4 (39·5–72·4)
 60·0 (53·6–67·0)
 80·0 (77·2–83·0)
 51·8 (47·6–56·4)
 69·8 (67·6–72·1)
30100 50 1004020 70 908060
Figure 5: Comparison of pooled survival estimates for knee replacements 
from case series and registry reports at 15 years, 20 years, and 25 years
(A) Total knee replacements. (B) Unicondylar knee replacements. The size of the 
circle representing each point estimate is proportional to the total number of 
hip replacements at the start of all the series contributing to that pooled 
estimate. Bars indicate 95% CIs. TKR=total knee replacement. UKR=unicondylar 
knee replacements. 
Su
rv
iv
al
 (%
)
60
70
80
90
50
100
A
4137 TKRs at start
(15 series)
763 TKRs at start
(five series)
299 291 TKRs at start
(47 series)
387 UKRs at start
(fourseries)
7714 UKRs at start
(five series)
437 UKRs at start
(four series)
3935 UKRs at start
(four series)
136 UKRs
at start
(one series)
3935 UKRs
at start
(four series)
88 532 TKRs at start
(20 series)
76 651 TKRs
at start
(14 series)
Case series pooled estimate
Registry reports pooled estimate
15 20 25
Su
rv
iv
al
 (%
)
Time since surgery (years)
60
70
80
90
50
100
B
0
0
Articles
www.thelancet.com Vol 393 February 16, 2019 661
the NJR, the median age of patients undergoing knee 
replacement surgery is 70 years and 57% are women, 
and similarly the SKAR reports the mean age of patients 
having knee replacements in 2016 to be 69 years and 
57% of patients to be women.2,34
The higher survival estimates at 20 years reported by 
case series are notable, but not surprising. Similar find-
ings were seen by Pabinger and colleagues,35 who reported 
the mean proportion of TKRs needing revision to be 
50% higher in registries than in case series. We also saw 
the same effect in our analysis of the survival of hip 
replacements.36 Differences in reported survival between 
registries and case series could be due to bias inherent to 
the reporting of case series, including selection and 
reporting bias. Our results support this theory by showing 
publication bias in case series. Several registry TKR 
construct series report survival that is well below our 
pooled estimate (figure 3); however, this effect is not 
present in case series (figure 2A). These findings suggest 
that the most poorly performing constructs are not 
reported and published in case series.
We identified 34 systematic reviews in our search, many 
of which attempted to report pooled survival of knee 
replacement. However, almost all these reviews focus on 
the comparison of different types of knee replacement 
(cemented vs cementless, mobile vs fixed bearing, or UKR 
vs TKR); we believe that, methodologically, these reviews 
are susceptible to selection bias, and we therefore created 
one pooled result for each type of knee replacement. In 
2017, van der List and colleagues37 published a review that 
gave a 15 year survival estimate extrapolated from shorter-
term data and only included cementless implants, and so 
is susceptible to selection bias. Only 15·1% of all primary 
knee operations in the 2016 NJR were reported to use 
cementless implants, and so their results are not 
generalisable.3 A study in 2014 by Niinimaki and co-
workers38 analysed Finnish registry data to estimate the age 
and sex-adjusted survival of TKR and UKR at 15 years. The 
authors provide 15 year survival estimates of 88·7% 
(95% CI 88·5–88·9) for TKR and 69·6% (68·2–70·9) for 
UKR, figures that are lower than the estimates produced 
by our pooled analyses. These findings might be because 
Niinimaki and co-workers38 only used data from 1985 to 
2011, and did not include results from the Australian 
registry. The authors noted the varying survival between 
different implants, further supporting our differentiation 
by the implant used. Analysis of the UK Clinical Practice 
Research Datalink database by Bayliss and colleagues39 
estimated survival of total knee re placement to be 89·7% 
(95% CI 87·5–91·5) at 20 years, which is consistent with 
our analysis.
We excluded ten articles that did not report CIs and 
seven that did not report all-cause construct survival. 
These articles could have increased the number of 
series included in our study by 50%, which further 
highlights the heterogeneity and low-quality reporting 
of case series. The methods of survival analysis varied 
among identified articles, with many using Kaplan-
Meier;40 however, life-table methods, such as those 
described by Armitage,41 were also used.11 Some articles 
reported 15 year survival of implants before 15 years 
mean follow-up had been reached, and therefore did 
not meet our inclusion criteria. We noted a trend 
towards the use of a competing risks method, believed 
by some to be a more accurate estimate of survival, 
given the high mortality seen in arthroplasty cohorts.42–45 
As we discuss in another paper,46 competing risks and 
Kaplan-Meier methods are not more or less accurate 
than each other, but simply report different phenomena. 
The heterogeneity observed in case series reinforces 
the importance of results from arthroplasty registries 
that are more consistent in their use of analysis 
techniques.
Our study did have some limitations. Our pooled 
data were not adjusted or stratified by patient factors 
that might have a role in determining survivorship, 
such as age, sex, or indication for the primary procedure. 
This detail is not provided in the data available to us 
and would require collaboration between registries 
with individual patient data. We provide an aggregated 
estimate for survival in all patients and, to our 
knowledge, this report is the first of its type with this 
length of follow-up. As with all survival reports, we 
cannot account for a surgeon’s willingness to revise a 
knee replacement based upon individual patient factors. 
This revision threshold might change between countries 
and affect the generalisability of results between 
nations. Our pooled registry results are drawn only 
from Australia and Finland, with 20 year and 25 year 
TKR data and all UKR data coming exclusively from 
Finland. Although this small number of countries 
provides limited geographical capture, the number of 
knee replacements included from registries is still far 
greater than that from case series; for TKR this number 
is 299 291 compared with 6490 knees, and in UKR this 
number is 7714 compared with 742 knees. We excluded 
papers that were not written in English, which removed 
nine further series. If all these case series had met the 
inclusion criteria, they might have altered our pooled 
results, but we expect this effect would have been small. 
We assume that survival estimates are equivalent to 
risks, for generating pooled estimates, and although the 
assumption that no cen soring occurs (patients dying 
with a knee replacement in situ) is clearly violated, this 
assumption provides a useful method of aggregation in 
the absence of individual patient-level data. The number 
of UKRs at risk in the 25 year follow-up group was less 
than 25 constructs in two of our included registry series. 
Although the accuracy of Kaplan-Meier estimates 
should be questioned when the number at risk is this 
small, this sample size is reflected in the weighting of 
estimates for our pooled results. The strengths of our 
study include an inclusive and comprehensive design, 
a-priori inclusion criteria, and a realistic interpretation 
Articles
662 www.thelancet.com Vol 393 February 16, 2019
10 Slim K, Nini E, Forestier D, Kwiatkowski F, Panis Y, Chipponi J. 
Methodological index for non-randomized studies (minors): 
development and validation of a new instrument. ANZ J Surg 2003; 
73: 712–16.
11 Abdeen AR, Collen SR, Vince KG. Fifteen-year to 19-year follow-up 
of the Insall-Burstein-1 total knee arthroplasty. J Arthroplasty 2010; 
25: 173–78.
12 Callaghan JJ, O’Rourke MR, Iossi MF, et al. Cemented 
rotating-platform total knee replacement. a concise follow-up, at a 
minimum of fifteen years, of a previous report. J Bone Joint Surg Am 
2005; 87: 1995–98.
13 Dixon MC, Brown RR, Parsch D, Scott RD. Modular fixed-bearing 
total knee arthroplasty with retention of the posterior cruciate 
ligament. A study of patients followed for a minimum of fifteen 
years. J Bone Joint Surg Am 2005; 87: 598–603.
14 Gill GS, Joshi AB, Mills DM. Total condylar knee arthroplasty. 16- to 
21-year results. Clin Orthop Relat Res 1999; 367: 210–15.
15 Hernigou P, Manicom O, Flouzat-Lachaniete CH, et al. Fifteen year 
outcome of the ceraver hermes posterior-stabilized total knee 
arthroplasty: safety of the procedure with experienced and 
inexperienced surgeons. Open Orthop J 2009; 3: 36–39.
16 Kim Y-H, Park J-W, Kim J-S. 2017 Chitranjan S. Ranawat Award: 
doescomputer navigation in knee arthroplasty improve functional 
outcomes in young patients? A randomized study. 
Clin Orthop Relat Res 2018; 476: 6–15.
17 Macheras GA, Galanakos SP, Lepetsos P, Anastasopoulos PP, 
Papadakis SA. A long term clinical outcome of the Medial Pivot Knee 
Arthroplasty System. Knee 2017; 24: 447–53.
18 McCalden RW, Hart GP, MacDonald SJ, Naudie DD, Howard JH, 
Bourne RB. Clinical results and survivorship of the GENESIS II total 
knee arthroplasty at a minimum of 15 years. J Arthroplasty 2017; 
32: 2161–66.
19 Nakamura S, Ito H, Nakamura K, Kuriyama S, Furu M, 
Matsuda S. Long-term durability of ceramic tri-condylar knee 
implants: a minimum 15-year follow-up. J Arthroplasty 2017; 
32: 1874–79.
20 Newman J, Pydisetty RV, Ackroyd C. Unicompartmental or total 
knee replacement: the 15-year results of a prospective randomised 
controlled trial. J Bone Joint Surg Br 2009; 91: 52–57.
21 Oliver WM, Arthur CHC, Wood AM, Clayton RAE, Brenkel IJ, 
Walmsley P. Excellent survival and good outcomes at 15 years using 
the press-fit condylar sigma total knee arthroplasty. J Arthroplasty 
2018; 33: 2524–29.
22 Schiavone Panni A, Falez F, D’Apolito R, Corona K, Perisano C, 
Vasso M. Long-term follow-up of a non-randomised prospective 
cohort of one hundred and ninety two total knee arthroplasties using 
the NexGen implant. Int Orthop 2017; 41: 1155–62.
23 Vessely MB, Whaley AL, Harmsen WS, Schleck CD, Berry DJ. 
The Chitranjan Ranawat Award: long-term survivorship and failure 
modes of 1000 cemented condylar total knee arthroplasties. 
Clin Orthop Relat Res 2006; 452: 28–34.
24 Callaghan JJ, Beckert MW, Hennessy DW, Goetz DD, Kelley SS. 
Durability of a cruciate-retaining TKA with modular tibial trays at 
20 years knee. Clin Orthop Relat Res 2013; 471: 109–17.
25 Callaghan JJ, Wells CW, Liu SS, Goetz DD, Johnston RC. Cemented 
rotating-platform total knee replacement: a concise follow-up, at a 
minimum of twenty years, of a previous report. J Bone Joint Surg Am 
2010; 92: 1635–39.
26 Epinette J-A. Long lasting outcome of hydroxyapatite-coated 
implants in primary knee arthroplasty: a continuous series of 
two hundred and seventy total knee arthroplasties at fifteen to 
twenty two years of clinical follow-up. Int Orthop 2014; 38: 305–11.
27 Eriksen J, Christensen J, Solgaard S, Schroder H. The cementless 
AGC 2000 knee prosthesis: 20-year results in a consecutive series. 
Acta Orthop Belg 2009; 75: 225–33.
28 Argenson J-NA, Blanc G, Aubaniac J-M, Parratte S. Modern 
unicompartmental knee arthroplasty with cement: a concise 
follow-up, at a mean of twenty years, of a previous report. 
J Bone Joint Surg Am 2013; 95: 905–09.
29 Foran JRH, Brown NM, Della Valle CJ, Berger RA, Galante JO. 
Long-term survivorship and failure modes of unicompartmental 
knee arthroplasty. Clin Orthop Relat Res 2013; 471: 102–08.
30 Yang S, Hadlow S. Unicompartmental knee arthroplasty: 
is it durable? NZ Med J 2003; 116: U627.
of survivorship accounting for all revision operations 
and not a limited or biased subset of a particular 
indication for revision. From the patient perspective, 
any subsequent re-operation carries risks, and therefore 
all revisions should be counted.
In conclusion, pooled survival derived from case series 
appears to show a more optimistic estimate than pooled 
registry data. Given this finding and the bias inherent in 
published case series, we believe registry data to be the 
more accurate estimate. Not enough information is yet 
available to tell us exactly how long a TKR or UKR lasts; 
however, using available arthroplasty registry data, 
82% of TKRs and 70% of UKRs last 25 years in patients 
with osteoarthritis (video).
Contributors
JTE was responsible for study concept, design, screening, data extraction, 
data analysis, and writing of this manuscript. RWW and JPE completed 
the second screening of abstracts, second extraction of data, and review 
of the manuscript. AWB and MRW were responsible for study concept, 
design, and writing of the manuscript. AS was responsible for study 
concept, design, data analysis, and writing of the manuscript.
Declaration of interests
We declare no competing interests.
Acknowledgments
This study was supported by the UK National Institute for Health 
Research (NIHR) Biomedical Research Centre at the University 
Hospitals Bristol National Health Service (NHS) Foundation Trust and 
the University of Bristol, UK. The views expressed in this publication are 
our own and not necessarily those of the NHS, the NIHR, or the UK 
Department of Health. JTE was supported by a joint National Joint 
Registry of England, Wales, Northern Ireland, and the Isle of Man and 
Royal College of Surgeons of England fellowship. AS was supported by a 
Medical Research Council (MRC) strategic skills fellowship 
(MR/L01226X/1). We thank the library and information service at 
Southmead Hospital, North Bristol NHS Trust for their help in 
recovering full-text articles.
References
1 Carr AJ, Robertsson O, Graves S, et al. Knee replacement. Lancet 
2012; 379: 1331–40.
2 National Joint Registry. 14th annual report. National Joint Registry 
for England, Wales, Northern Ireland and Isle of Man. 2017. 
http://www.njrreports.org.uk/Portals/0/PDFdownloads/NJR%20
14th%20Annual%20Report%202017.pdf (accessed April 21, 2018).
3 Kassam AM, Dieppe P, Toms AD. An analysis of time and money 
spent on investigating painful total knee replacements. 
Br J Med Pract 2012; 5: a526.
4 Kallala RF, Vanhegan IS, Ibrahim MS, Sarmah S, Haddad FS. 
Financial analysis of revision knee surgery based on NHS tariffs 
and hospital costs: does it pay to provide a revision service? 
Bone Joint J 2015; 97-B: 197–201.
5 National Institute for Health and Care Excellence. Total hip 
replacement and resurfacing arthroplasty for end stage arthritis of 
the hip. Technology appraisal guidance. Feb 26, 2014. 
https://www.nice.org.uk/guidance/ta304 (accessed May 17, 2018).
6 National Joint Registry. Prostheses used in hip, knee, ankle, elbow and 
shoulder replacement procedures 2016. 14th annual report 2017. 
http://www.njrreports.org.uk/Portals/0/PDFdownloads/NJR%20
14th%20AR%20Prostheses%20used%20in%20joint%20
replacements%202016.pdf (accessed July 12, 2018).
7 Moher D, Liberati A, Tetzlaff J, Altman DG, PRISMA Group. 
Preferred reporting items for systematic reviews and meta-analyses: 
the PRISMA statement. BMJ 2009; 339: b2535.
8 Ouzzani M, Hammady H, Fedorowicz Z, Elmagarmid A. Rayyan—a 
web and mobile app for systematic reviews. Syst Rev 2016; 5: 210.
9 Wylde V, Beswick AD, Dennis J, Gooberman-Hill R. Post-operative 
patient-related risk factors for chronic pain after total knee 
replacement: a systematic review. BMJ Open 2017; 7: e018105.
See Online for video
Articles
www.thelancet.com Vol 393 February 16, 2019 663
31 O’Rourke MR, Gardner JJ, Callaghan JJ, et al. Unicompartmental 
knee replacement: a minimum twenty-one-year followup, end-result 
study. Clin Orthop Relat Res 2005; 440: 27–37.
32 Parratte S, Pauly V, Aubaniac J-M, Argenson J-NA. No long-term 
difference between fixed and mobile medial unicompartmental 
arthroplasty. Clin Orthop Relat Res 2012; 470: 61–68.
33 Beswick AD, Wylde V, Gooberman-Hill R, Blom A, Dieppe P. 
What proportion of patients report long-term pain after total hip or 
knee replacement for osteoarthritis? A systematic review of 
prospective studies in unselected patients. BMJ Open 2012; 2: e000435.
34 Swedish Knee Arthroplasty Register. 2017 annual report. 
http://www.myknee.se/pdf/SVK_2017_Eng_1.0.pdf (accessed 
Aug 3, 2018).
35 Pabinger C, Berghold A, Boehler N, Labek G. Revision rates after 
knee replacement. Cumulative results from worldwide clinical 
studies versus joint registers. Osteoarthr Cartil 2013; 21: 263–68.
36 Evans JT, Evans JP, Walker RW, Blom AW, Whitehouse MR, 
Sayers A. How long does a hip replacement last? A systematic 
review and meta-analysis of case series and national registry reports 
with greater than 15 years of follow-up.Lancet 2019; 393: 647–54.
37 van der List JP, Sheng DL, Kleeblad LJ, Chawla H, Pearle AD. 
Outcomes of cementless unicompartmental and total knee 
arthroplasty: a systematic review. Knee 2017; 24: 497–507.
38 Niinimaki T, Eskelinen A, Makela K, Ohtonen P, Puhto A-P, 
Remes V. Unicompartmental knee arthroplasty survivorship is 
lower than TKA survivorship: a 27-year Finnish registry study. 
Clin Orthop Relat Res 2014; 472: 1496–501.
39 Bayliss LE, Culliford D, Monk AP, et al. The effect of patient age at 
intervention on risk of implant revision after total replacement of 
the hip or knee: a population-based cohort study. Lancet 2017; 
389: 1424–30.
40 Kaplan EL, Meier P. Nonparametric estimation from incomplete 
observations. J Am Stat Assoc 1958; 53: 457–81.
41 Armitage P. Statistical methods in medical research. Michigan: 
Wiley, 1971.
42 Coviello V, Boggess M. Cumulative Incidence estimation in the 
presence of competing risks. Stata J 2004; 4: 103–112.
43 Melton JTK, Mayahi R, Baxter SE, Facek M, Glezos C. Long-term 
outcome in an uncemented, hydroxyapatite-coated total knee 
replacement: a 15- to 18-year survivorship analysis. 
J Bone Joint Surg Br 2012; 94: 1067–70.
44 Patil S, McCauley JC, Pulido P, Colwell CW. How do knee implants 
perform past the second decade? Nineteen to 25-year followup of 
the press-fit condylar design TKA. Clin Orthop Relat Res 2015; 
473: 135–40.
45 Pritchett JW. Bicruciate-retaining total knee replacement provides 
satisfactory function and implant survivorship at 23 years. 
Clin Orthop Relat Res 2015; 473: 2327–33.
46 Sayers A, Evans JT, Whitehouse MR, Blom AW. Are competing risks 
models appropriate to describe implant failure? Acta Orthop 2018; 
89: 256–58.
	How long does a knee replacement last? A systematic review
and meta-analysis of case series and national registry reports
with more than 15 years of follow-up
	Introduction
	Methods
	Search strategy and selection criteria
	Abstract screening and data extraction
	Data analysis
	Role of the funding source
	Results
	Discussion
	Acknowledgments
	References