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Improving the Value of

Primary Total Knee Arthroplasty:

the ATTUNE® Knee System

David A. Fisher, M.D.

Professor David Parkin

Page 2 of 20

Improving the Value of

Primary Total Knee Arthroplasty:

the ATTUNE® Knee System

David A. Fisher, M.D.

David A. Fisher, M.D.*, is a board certified and fellowship trained orthopaedic surgeon who

specializes in primary and revision knee replacement. He currently serves as Director of the Total

Joint Center of Excellence at OrthoIndy Hospital, Indianapolis, Indiana. In addition, he is an Assistant

Clinical Professor of Orthopaedic Surgery at the Indiana University School of Medicine.

Professor David Parkin

Professor David Parkin is an experienced health economist whose previous roles include serving in

academia as well as Chief Economist in one of the regions of the United Kingdom’s National Health

Service (NHS). He is currently a Senior Visiting Fellow at the Office of Health Economics, a non-

government entity in the U.K., and is an Honorary Visiting Professor at City, University of London.

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

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Improving the Value of

Primary Total Knee Arthroplasty:

the ATTUNE® Knee System

EXECUTIVE SUMMARY

TABLE OF CONTENTS

Total Knee Arthroplasty (TKA) is a successful and

common procedure that provides pain relief and

improved function in patients with osteoarthritis of

the knee. Despite the globally reported success of

this procedure, studies have shown that up to 20%

of patients are dissatisfied with the results of their

TKA. Given the increasing incidence in osteoarthritis

worldwide, changing patient demographics, and the

corresponding demand for TKAs, there is a need for

meaningful innovation that continues to raise the bar to

improve quality outcomes and meet the expectations of

all stakeholders in a cost-constrained environment.

The ATTUNE® Knee System was designed to help

address some of these shortcomings and improve

patient outcomes. Early clinical results with the ATTUNE

Knee provide insights into how this knee implant could

help provide value as demonstrated by survivorship,

improved patient reported outcomes scores and

reduced secondary procedures for complications such

as patellofemoral pain. Additionally, real world evidence

from one study that included a sample of U.S. hospitals

has shown that those patients treated with the ATTUNE

Knee experienced a shorter length of stay, and a higher

percentage of those patients with the ATTUNE Knee

were discharged directly home, compared to another

leading knee system. These outcomes may bring

benefits to clinicians, patients, providers, and payors.

The purpose of this report is to summarize the burden

of osteoarthritis, primary TKA as a treatment option for

those patients, approaches for evaluating TKA from a

clinical and health economic perspective, and assess the

available data on the primary ATTUNE Knee.

1 Osteoarthritis and Total Knee Arthroplasty

1.1 The Burden of Disease: Knee Osteoarthritis

1.2 Primary Total Knee Arthroplasty: A Surgical Treatment

1.3 Assessment of Outcomes

1.4 Measuring Patient Reported Outcomes (PROMS)

1.5 The Economics of Total Knee Arthroplasty

1.6 Barriers to Referral for Treatment

2 The ATTUNE Knee System

2.1 Improving the Performance of Total Knee Arthroplasty

2.2 Total Knee Arthroplasty Outcomes Using the ATTUNE Knee

2.3 Economic Benefits of the ATTUNE Knee

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1 OSTEOARTHRITIS AND TOTAL KNEE ARTHROPLASTY

1.1 The Burden of Disease: Knee Osteoarthritis

Osteoarthritis of the knee is one of the five leading causes

of disability among non-institutionalized adults in the

United States.1 According to the Centers for Disease

Control and Prevention, osteoarthritis affects 13.9% of

adults over 25 years of age, and 33.6% of those over 65.

In the United Kingdom, it is estimated that 18.2%

of those over age 45 have knee osteoarthritis.4 Patients

with knee osteoarthritis generally experience pain,

swelling, and unpredictable buckling of the knee; about

80% of patients have difficulties with mobility, including

25% who cannot perform major activities of daily living,

such as dressing themselves.46

The direct health care costs of nonsurgical management

of knee osteoarthritis, which include medication,

physical therapy, and pain center visits, are relatively

low, but there are large indirect costs in the form of lost

earnings, reduced work productivity, and disability benefit

payments.41,58 In addition, there are personal health costs

in terms of decreased activity level, increasing weight

and obesity with related health conditions, and chronic

pain management concerns including potential narcotic

abuse. Interventions that alleviate the burden associated

with osteoarthritis are therefore valued across multiple

stakeholders.

In patients whose knees have become excessively worn

or degenerated due to osteoarthritis, a Total Knee

Arthroplasty (TKA) to replace the damaged bone and

cartilage is a viable option. Modern TKA can be traced

back to the 1970s when John Insall implanted the first

total condylar knee system.33 Despite limited offerings

with this and other early TKA implants and instruments,

with strict indications and careful surgical technique, the

potential success of this operation became evident as

durable pain relief and improved function were benefits

patients could enjoy. With the hope of providing better

solutions for patients with knee osteoarthritis, newer

implants were needed to deal with the wide variety of

human knee anatomy as well as more complex primary

procedures and revision TKAs. This led to much research

into implant and instrumentation design in an attempt to

improve outcomes. By 1990, much of this work had come

to fruition, and the results of total knee arthroplasty now

demonstrate long-term survivorship. In a recent report

from the Australian Orthopaedic Association National

Joint Replacement Registry (AOANJRR), the durability of

total knee implants including more than 350,000 implants

showed 93.5% implant survivorship at 12 years,

meaning 93.5% of these implants were still functioning

well at 12 years.5

The long-term effectiveness of TKA means that morbidity

is reduced and as a result, so is the indirect cost burden.

However, in the short term, TKA is more expensive than

nonsurgical management, leading to increases in overall

short-term medical costs. For example, in the U.S. nearly

800,000 knee procedures are performed annually,2 at a

cost of over $24.8 billion.6

The increased economic burden needs to be weighed

against the cost of not undertaking the procedure – to

both payors and patients alike.

1.2 Primary Total Knee Arthroplasty: A Surgical Treatment

1.3 Outcomes Assessment

There are different ways to measure outcomes after TKA.

Outcomes related to the procedure and associated health

care services include readmissions, reoperations, and

revision surgery rates that can be measured over time.

Patient reported outcomes include patient satisfaction,

improvements in knee function, return to productive

employment and improvements in quality of life.

In general, outcomes of TKA have improved over the past

50 years. National joint implant registries have been in

place for many years in the U.K., Australia, New Zealand

and, more recently, the U.S. These registries track the

performance of specific total joint implants in the different

countries. Failure of an implant is reported as a revision,

and implant survivorship curves are used to describe the

The expansion in the number of total knee procedures is

projected to increase for the next 20 years as longevity

increases, patients seek earlier remedy from arthritic

conditions, and access to care improves. This increase in

numbers of procedures and the attendant costs will put

increasing financial stress on health care systems.38

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success in terms of the number of implants remaining in

service over time. The good longevity of contemporary

TKA has been reported in all joint registries with 10-year

revision rates of 4-5% (or 95% implant survivorship).9,11

Revision rates, however, may vary among different implant

types, with some implants performing better than others.

Differences between patient age groups have also been

noted with younger patients (under 55 years of age)

having a fivefold increased risk of revision in the first 10

years compared with older patients (over 80 years).36

This difference may be due to increased activity levels of

younger patients leading to wear and loosening of the

implants, or to higher expectations in the younger group,

which could lead to greater dissatisfaction and more

revision procedures.

Patient reported outcomes show improved patient

satisfaction, function and quality of life after TKA.60

Yet, 10-20% of total knee replacement patients may be

dissatisfied with their procedure.18 Issues that remain

for these patients include ongoing pain or discomfort,

stiffness, crepitation (noise or vibration with movement),

and difficulty squatting, kneeling, or negotiating stairs.19,

47,59,61 Research has been conducted to help identify

patient risk factors for complications and poor clinical

results. Patient factors that may contribute to a higher risk

of poor outcomes include a history of depression or mental

illness, morbid obesity, diabetes and chronic narcotic

use.34,35 Furthermore, some of these risk factors are

potentially modifiable conditions, and efforts are underway

to try to improve outcomes by optimizing comorbid

conditions prior to surgery. Some of these programs

include smoking cessation, weight loss for morbid obesity,

improved diabetes management, narcotic cessation, and

pre-operative physical therapy to improve muscle strength

and coordination.17,64 While the hope is that better

outcomes or at least lower episodic costs can be obtained

in these patients, the evidence is not complete.

TKA is a highly technical procedure, requiring surgical skills

to obtain adequate bone preparation and implant fixation,

but also soft tissue balancing to replicate knee function.

With such a major surgical procedure, patient and surgeon

satisfaction are linked. For the surgeon, the ability to

implant the device efficiently and reproducibly is extremely

important. Achieving optimal harmony of implant

positioning/alignment and soft tissue balance during

the procedure can affect the long-term satisfaction for

the patient and is part of the art of TKA.30 Furthermore,

the longevity of the reconstructed knee may be directly

related to the design and quality of initial fixation. Patient

satisfaction and outcome are at least partly determined by

specific implant design features including sizing options,

implant kinematics (how the implants track relative to

the native knee), the patellofemoral articulation, as well

as surgical techniques of implant rotation, soft tissue

balancing and alignment.

Improving patients’ health or preventing its decline is of

course the major aim of any health care intervention,

and an important feature of modern health service

provision is the ability to measure such improvements

via validated tools.

In 2006, the U.S. Food & Drug Administration stated,“The

use of PRO instruments is part of a general movement

toward the idea that the patient, properly queried, is the

best source of information about how he or she feels.”12

It is important to recognize that the objective of PROMs is

to measure patients’ perceptions of their health, not their

experiences of health care delivery. Health care delivery

surveys measure patients’ experience of, or satisfaction

with, the care that they receive, including such factors as

whether they are treated with respect and compassion,

they have a comfortable environment for their care,

and they are provided with enough information about

their care. While these are important quality measures in

their own right, and while PROMs may be influenced by

patients’ experience of health care delivery, the two are

separate and measured in different ways.

PROMs are validated questionnaires that ask patients to

assess their own health and their quality of life as a result

of their health, usually capturing changes over time –

especially pre- and post-intervention at specified time

points. The responses to the different questions are usually

processed to generate either a “profile” of health – a

combined summary of the responses that gives a picture of

health in different dimensions – or a number that gives an

overall score. There are many thousands of such PROMs

1.4 Measuring Patient Reported Outcomes

While objective physiological and functional measures

can tell us much about the effectiveness of health care

interventions, an important test is patients’ perceptions

of their health. This has led to the establishment of

Patient Reported Outcome Measures (PROMs) as a

key factor in evaluating the effectiveness and cost-

effectiveness of health care technologies.13

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available in multiple languages. Some of them are related

to a particular condition, treatment or symptom, and are

generally known as condition-specific or disease-specific

measures. Others are intended to be applicable,

in principle, to any condition and are usually called

generic measures.

The specialty of orthopaedics has been a leader in the

development and adoption of PROMs. The main generic

measures used to measure a person’s state of health with

knee problems are the EQ-5D and the SF-36.22,63 As

well as generating a “profile” in five and 12 dimensions

respectively, these enable a score to be calculated that

can be interpreted as the value of a patient’s health state

relative to best and worst possible health states.

The most widely used condition-specific PROMs for knee

osteoarthritis are the Oxford Knee Score (OKS)44 and the

Knee injury and Osteoarthritis Outcome Score (KOOS).56

The OKS has 12 questions, each of which generates a

score between zero and four. These are added together

to give an overall score between zero, meaning as severe

knee arthritis as possible, to 48, representing no knee

problems at all. KOOS by contrast does not calculate an

overall score, but generates scores from zero (extreme

symptoms) to 100 (no symptoms) in five subscales: pain,

other symptoms, daily living, sport and recreation, and

knee related quality of life. It is an extension of another

widely used measure, the Western Ontario and McMaster

University Osteoarthritis Index (WOMAC),16 which is

applicable to both hip and knee problems; a WOMAC

score can be derived from the KOOS questionnaire.

PKIP has four subscales (Confidence, Stability, Modify

Activities and Satisfaction), each of which generates

a score from zero to 10, where higher scores indicate

better knee function, and an overall score which ranges

from zero to 100. This has been shown in initial studies

to perform well in terms of key psychometric criteria

such as reliability, validity and responsiveness, which may

help discriminate the impact of different implant designs

and surgical techniques.25 It is important to note that

“satisfaction” here refers to the implant, which enables

a proper assessment of the procedure itself, rather than

more general patient satisfaction with the care that they

receive, which will be influenced by the environment in

which care is provided.

PROMs have many uses, but assessing the results of

a health care intervention usually requires changes in

health to assess outcome measures. Typically, this requires

patients to complete PROMs questionnaires both before

and after the intervention. For TKA, this may be referred

to as pre-operative and post-operative health states, or

baseline and follow-up. It is important to ensure that these

assessments are carried out at times that will properly

reflect the period over which improvements will be realized

and that there are further assessments for possible longer

term effects. For example, a common post-operative

PROMs assessment for TKA is six months, but, in some

cases, the follow-up will also be at one year or longer,

enabling a profile of changes over time to be assessed.

PROMs are widely used in clinical trials, but are also

increasingly used routinely in practice, for example in

joint registries. Since 2009 the National Health Service

(NHS) in England has required all health care providers,

both publicly and privately owned, to collect specified

PROMs for all patients funded by the NHS.13 PROMs are

collected before and after undergoing surgery for four

elective procedures, including hip and knee replacements.

Around 250,000 patients are invited each year to complete

questionnaires, which include both the EQ-5D and

the OKS, and the response rates are good: on average

95% of knee replacement patients complete the pre-

operative and 75% the post-operative questionnaire. In

New Zealand, TKA patients are also invited to complete

OKS questionnaires and their data have established that

each one-unit drop in the OKS at six months predicts a

9.9% increase in revision rates over two years,57 which

demonstrates the importance of PROMs data from a wider

health care perspective.

The English PROMs data are especially useful for examining

the overall effects of TKA in real world practice, rather

than in the experimental conditions required by clinical

trials. Averaging over all NHS providers in England in 2014-

2015,8 93.2% of knee replacement patients had improved

health specific to their condition, measured by the OKS,

and 80.5% had improved health more generally, measured

by the EQ-5D. The average PROMs scores for primary

knee replacement patients pre-operatively were 19/48

according to the OKS and 0.425 for the EQ-5D index.

At six months post-operative, primary knee replacement

patients reported OKS scores of 35 and EQ-5D index scores

of 0.739. The measured outcome of TKAs in the NHS

in England was therefore an average improvement per

patient of 16 in the OKS and 0.315 in the EQ-5D index.

The Patient’s Knee Implant Performance (PKIP) is a

relatively newer condition-specific PROM that has been

specifically developed to assess the functional status of

a patient’s knee from their own perspective, before and

after TKA.40 It was developed to address gaps in

other common PROMs by assessing a patient’s

satisfaction with their implant, which represents an

innovative approach to better understand the nuances

involved in outcomes for TKA patients.

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Within the hospital, there are fixed costs, and costs

associated with the surgical procedure itself, including

operating room staff, physicians, implants, and disposable

items to perform the procedure. There are also costs of

providing nursing care and therapy after surgery. Upon

discharge, patients usually continue rehabilitation that

can last for weeks or months, with the attendant costs

of ongoing treatments. Some of these patients require

placement in skilled nursing facilities or rehabilitation units.

Post discharge costs are a significant portion (up to 50%)7

of the overall episode of care. Bozic et al. found that up

to 35% of the episodic costs were related to care after

discharge.20 Unpredictable events such as complications

and readmissions can also add considerably to the

episode of care costs.

In many countries, a global evaluation of the episode of

care is a major focus. The mandatory bundled payment

initiatives in the U.S. are one example. These involve a 90-

day window of time where all associated costs are included

with the procedure. This process creates incentives for

hospital systems to better manage patient care following

total joint replacement procedures. Hospitals must manage

the total costs for a given procedure, including post-acute

care. Any complications and/or readmissions will greatly

increase chances of the hospital exceeding this fixed price

and therefore owing a penalty payment back to Medicare

(CMS). This puts additional risk on the providing hospital

but allows the payor, e.g., Medicare, better forecasting of

the cost of care to a given population.

In the NHS in England, health care providers are

reimbursed by health care commissioners under the

“Payment by Results” system. Each patient treated is

assigned to a Healthcare Resource Group (HRG), similar

to the Diagnosis Related Group (DRG) classification found

in the U.S. and other countries’ health care systems, for

which there is a “tariff” payment covering all inpatient

services. Knee replacements are one of a few procedures

that are reimbursed using a “Best Practice Tariff,” which

offers a much larger payment to providers who provide a

high standard of performance, such as minimum average

improvements in PROMs scores and good data provision,

including rates of registration with the National Joint

Registry (NJR). They also attract a special additional tariff

for post discharge rehabilitation care that follows a defined

clinical pathway, including specified numbers of nurse,

physiotherapist and occupational therapy appointments,

and consultant-led clinic visits.

With the growing population of patients needing TKAs,

it is critically important to minimize the total cost of this

procedure, subject to maintaining quality of care.

Globally, each element of cost for the episode of care

is under review for potential cost savings by hospital

systems. Length of hospital stay and post-discharge

disposition are two areas under review by payors and

providers. Decreasing length of stay clearly reduces the

cost of inpatient care and can be done safely, with many

patients now being discharged directly home within 48

hours and, in some cases, on the day of surgery.37 The

use of skilled nursing and rehabilitation units has also

been identified as high cost items associated with 35%20

-50%7 of the episode of care cost, and efforts to minimize

the use of these facilities are underway. The benefits of

post-discharge therapy (either in home or in outpatient)

are under review and at least one paper suggests it may be

unnecessary following TKA.23 Further study of this topic

will likely be forthcoming.

1.5 The Economics of Total Knee Arthroplasty

PROMs that, like the EQ-5D and the SF-36, generate a

single score representing the value of a health state can

be used to calculate Quality Adjusted Life Years (QALYs).

QALYs are a measure that combine length and health-

related quality of life into a single score. For example, a

person who enjoys a year without any health problems

would generate one QALY; someone who had a quality

of life value of 80% would have 0.8 QALYs for that year.

If there were an intervention that would cure the second

person’s health problem, they would gain 0.2 QALYs each

year. If that improvement lasted for 10 years, they would

gain two QALYs, the equivalent of two additional life years

with no health problems.

For example, the reported gain from TKA of 0.315 in the

EQ-5D index in the NHS in England suggests that if the

improvement is maintained over 10 years, there is a gain

of over three QALYs per patient. QALYs, combined with

costs, provide the building blocks to the formal economic

analysis of a given intervention used by organizations

like the National Institute for Health and Care Excellence

(NICE), in England.

QALYs are a particularly useful measure to ensure that

procedures, like TKA, that do more to improve people’s

quality of life than reduce mortality are judged fairly in

comparison with procedures that extend life expectancy.

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TKA is widely accepted as a highly cost effective means

of generating improvements in patients’ quality of life.

The cost of a health care intervention can be measured

by comparison with the next best alternative way of

managing the condition that it deals with. This gives an

estimate of the additional or ”incremental” cost of the

intervention. The cost is compared with the improvements

in patient outcomes, measured as gains in QALYS, that the

intervention generates compared with the best alternative

treatment option. Dividing additional costs by QALY gains

gives a cost-effectiveness ratio, an estimate of the cost of

generating an additional QALY using that intervention.

The inverse of this, Porter’s “Value” measure, shows the

amount of improved outcome generated by each dollar

spent on the intervention.52

In the U.S., Losina et al. analyzed Medicare data using a

modelling approach comparing lifetime costs and quality

of life for patients aged 65 and over who had end-stage

knee osteoarthritis.42 They estimated a cost-effectiveness

ratio of $18,300 per QALY gained, although for high-risk

patients this was much higher, at $28,100. The cost of

TKA and post-operative quality of life both affected the

level of cost-effectiveness achieved, but no other patient-

or procedure-related factors such as revision rates were

important to this outcome.

In the U.K., Dakin et al. analyzed data from a large,

randomized trial of different knee prostheses measuring

both costs and quality of life.27 They estimated an average

cost-effectiveness ratio of £5,623 per QALY gained, using

conservative assumptions about the extent of changes

in costs and quality of life due to TKA. This ratio is well

below £20,000 per QALY gained, which is a threshold

defined by NICE below which pharmaceutical and other

interventions are, without further qualification, accepted

for funding. Moreover, although patients’ age, gender and

baseline severity, as measured by ASA (American Society

of Anesthesiologists) grade and OKS score, impacted on

cost-effectiveness, there are very few eligible patients

for whom the cost per QALY gained exceeds the NICE

threshold. Although TKA costs more for patients who had

worse pre-operative health states, the greater QALY gains

that they achieved meant that it was more cost-effective

than for patients with only moderate symptoms. This study

also examined the impact of different assumptions about

factors that affect cost-effectiveness. This included the

length of stay in hospital following

the procedure, confirming that shorter hospital stays

would improve cost-effectiveness.

In 2016, Pennington et al. compared the relative cost-

effectiveness of different implants, using data from the

U.K. National Joint Registry.48 In identifying the most cost-

effective option, they found that the main determinant

was differences between the implants in the post-

operative quality of life that they generate for patients.

For the range of implants covered, factors such as their

cost and revision rates were not so important – improving

patients’ quality of life was found to be key. Moreover,

the quality of life differences between the implants were

relatively small, further emphasizing the importance of this

as a determinant of cost-effectiveness. What may appear

to be small changes in quality of life at a single point

of time can translate into large changes in QALYs if the

improvement is sustained over a long period of time. This

study covered TKAs implanted between August 2008 and

July 2012, since then, new implants have been introduced

which may affect the conclusions.

Additional benefits may be applicable to TKA patients

whose ability to work is affected by knee problems. TKA

will enable such individuals to continue working, which

is beneficial to society. These are known as indirect costs,

by contrast to the direct costs of health care that arise

from either TKA or its alternatives. Ruiz et al. estimated

the total additional direct costs of TKA over the lifetime

of a patient in the U.S. to be on average $20,635 in 2009

dollars, offset by a reduction in lifetime indirect costs of

$39,565.58 TKA therefore generates an average societal

savings of $18,930 per patient. Most of these savings

directly benefit patients by increasing their employment

potential and earnings, but there is a wider benefit to

society of increased production and reduced disability

payments.

A number of scientific studies in countries including

the U.S., U.K., Finland and Spain, have concluded that

TKA is the most cost-effective means of managing

osteoarthritis, according to standards that are widely

accepted in developed countries.27,39,42,45,48,54,55

The evidence suggesting that TKA is highly

cost-effective in terms of improvements to patients’

quality of life applies to all relevant age groups.

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National professional associations for orthopaedic surgeons

and the policy bodies of national health systems emphasize

that the decision to refer a patient for TKA should only

depend on individual clinical judgements that a patient will

benefit from treatment. In particular, decisions should not

be made using “scoring tools” that identify which patients

are eligible for referral. In the U.K., for example, NICE has

issued quality guidelines that instruct health professionals,

health care providers and health care commissioners not to

use such scoring systems.10 These guidelines also attempt

to drive consistency in equity of care provided across the

NHS in the U.K.

Sometimes, other eligibility criteria are used that are

equally arbitrary and are opposed by national bodies.

These include a requirement that patients lose weight or

stop smoking before they can be referred for TKA; that

patients must be experiencing extreme pain or disability;

and that patients must be under a specified age. None of

these are regarded as justifiable if they do not adversely

affect the likelihood of a patient benefiting from surgery.

The NICE guidelines state if there are to be referral

thresholds, these should not be based on such criteria,

or scoring tools, but on discussions between patient

representatives, referring clinicians and surgeons.

In the U.S., global payment models reward hospitals that

show decreased complications and readmissions following

TKA. These payment models could potentially create an

adverse incentive to screen patients and forgo surgery

on individuals that have a higher risk of a complication

or readmission. The unintended consequences of these

policies in the aforementioned major TKA markets, which

are aimed at minimizing short-term costs with approaches

to rationing, may lead to problems in the access to care

for many patients who would otherwise benefit from

this procedure. Potentially, such approaches could lead to

increased overall health care direct and indirect costs

in the longer term.

1.6 Barriers to Referral for Treatment

In an effort to improve the performance of contemporary

TKA, DePuy Synthes Companies designed the ATTUNE

Knee System with university researchers and a team of

35 experienced total knee surgeons from around the

world. The team set about studying surgical workflow,

implant sizing, kinematics, patellar tracking, ligament

balancing and instrumentation issues in-depth, and new

concepts were developed and tested in laboratories

around the world. This collaboration led to over 30

peer reviewed publications, more than 60 patents and

to the development of new methods to address clinical

problems through implant and instrument design and

manufacturing.

The ATTUNE Knee is a highly versatile implant system

with options for bearing design, kinematics, patellar design

and ligament balancing techniques. The instrument system

incorporates the use of low weight composite materials

designed to allow precise bone preparation, implant

balancing and implant insertion. Primary ATTUNE Knee

implants have been implanted since 2011, with

wide availability since 2013, and are used in countries

around the world.

Additional information about the ongoing in vivo studies is

available online (see Appendix Table 1).

Factors that can influence TKA outcomes include patient

demographics, implant design and the instruments that

help surgeons implant total knee devices with greater

precision. Standard surgical instruments and tools used

to insert total knee implants have proven more than

adequate to perform high quality TKAs in most surgeons’

hands. However, there is variability in surgeon experience

and skills in performing this complex operation. Surgical

efficiency can lower aggregate costs, improve outcomes

by reducing complications, and improve operating room

productivity. One study conducted at Duke University in

the U.S. showed that a surgical team dedicated to total

2 THE ATTUNE KNEE SYSTEM

2.1 Improving the Performance of Total Knee Arthroplasty

The evidence strategy for the ATTUNE Knee represents

the largest clinical program in DePuy Synthes’ history and

has been designed to extensively focus on measuring the

extent to which the ATTUNE Knee is meeting the unmet

needs of TKA patients and other key stakeholders.

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 10 of 20

National total joint registries offer the opportunity to

track implant-specific performance by means of patient

reported outcomes, reoperations, and revisions. Sweden,

New Zealand, Australia and the United Kingdom are some

of the countries that have national registries. Per the

2016 published report from the National Joint Registry

for England, Wales, Northern Ireland and the Isle of

Man (NJR),3 the three-year cumulative percent revision

rate for over 4,000 patients receiving the ATTUNE Knee

was 1.39% (NJR Table 3.28), which compares favorably

to the class of cemented implants, which had a 1.50%

cumulative percentage probability of revision (NJR Table

3.24). ATTUNE Knee survivorship data is also available

in the 2016 published report from the National Joint

Replacement Registry from Australia (AOANJRR).5 Per the

2016 AOANJRR, in which 4,831 ATTUNE Knees are being

tracked, the ATTUNE Knee estimated cumulative percent

revision was 0.5% (ATTUNE Cruciate Retaining), 0.4%

(ATTUNE Posterior Stabilized) at one year.6 This compares

favorably to the overall class of cemented total knee

arthroplasty (TKA) at one year, which has an estimated

cumulative percent revision of 1.0% (Tables KT9 and

KT22).5

While the science behind implant design has improved,

the evidence of improvement lies in patient perception and

function. Performance measures such as pain relief and

improved function are issues patients can relate to their

knee through the various measurement tools previously

described. With these tools, knee function and pain

can be assessed pre- and post-operatively. Furthermore,

improvements can be tracked to compare outcomes

between different hospitals, surgeons, and implants.

As described on the next page, a number of independent

single-center studies and company-sponsored multi-

center studies of the ATTUNE Knee have reported an

improvement in patient outcomes compared with

other knee implants. A prospective multi-center study

by Hamilton et al. compared 926 patients receiving an

ATTUNE Knee with a similar group of 845 patients who

received knee implants of other designs.31 Knee function

and patient satisfaction scores were collected using four

PROMs: KOOS, OKS, PKIP, and EQ-5D. Figure 1 shows that

at one-year post-operative, the ATTUNE Knee patients had

statistically better scores in most of these.

2.2 Total Knee Arthroplasty Outcomes Using the ATTUNE Knee

joint replacement improved the performance of those

procedures, improved on time starts, and increased

the number of cases by 29%.14 Attempts to improve

performance through professional education and training

are ongoing to ensure consistency in surgical process.

More training may be useful, potentially focusing on

surgeons who perform fewer cases than the academics

who typically publish.

If the performance of a higher quality knee reconstruction

led to shorter surgery time, shorter length of stay in

hospital, reduced utilization of skilled nursing facilities,

reduced time of recovery, higher patient satisfaction, fewer

complications and revisions, and lower overall costs of

care, it would be a significant improvement to the current

standard of care, which would benefit all stakeholders.

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 11 of 20

ATTUNE Knee

N

Figure 1. Patient reported outcome measures including condition specific (KOOS, PKIP, OKS) and generic (EQ5D) comparing the ATTUNE Knee and other knee systems,

p-values less than 0.01 are highlighted and considered statistically significant.31

KOOS

PKIP

Scale

Scale

Timing

Timing

(Covariate

Adjusted)

p-value for

Means

(Covariate

Adjusted)

p-value for

Means

N

N

NN

Leading Knee Brands

Leading Knee Brands

ATTUNE Knee

ATTUNE Knee

0-100

0-100

Min. 1yr.

Min. 1yr.

<0.0001

88.1 ± 13.5

74.4 ± 18.0

(38.4 ± 19.2)

(45.7 ± 21.5)

751

746

746

729

85.1 ± 15.7

71.3 ± 19.1

(35.0 ± 20.0)

(43.6 ± 21.9)

674 363

752 746

674 362

752 746

674 363

744 727

655 349

750 746

674 363

Unadjusted Mean ± SD, (Change from Pre-op Baseline)

Unadjusted Mean ± SD, (Change from Pre-op Baseline)

Min. 2yr. 0.0945

90.0 ± 13.587.6 ± 14.9 (37.0 ± 20.6) (37.3 ± 19.0)

Min. 1yr. 0.0001

87.2 ± 14.6

89.4 ± 14.5

84.6 ± 16.9 (38.6 ± 20.5) (42.8 ± 19.4)

Min. 2yr. 0.1599

87.6 ± 15.6 (41.1 ± 20.7) (42.9 ± 19.0)

Min. 1yr. 0.0016

80.9 ± 14.678.5 ± 16.9 (30.4 ± 22.5) (33.6 ± 21.2)

Min. 2yr. 0.1552

84.1 ± 14.982.5 ± 15.5 (33.8 ± 21.8) (35.6 ± 20.6)

Min. 1yr. 0.0013

59.9 ± 28.2

55.5 ± 30.4 (37.1 ± 31.1) (42.3 ± 29.7)

Min. 2yr. 0.2081

63.8 ± 28.4

61.2 ± 29.3 (42.9 ± 31.5) (45.1 ± 28.1)

Min. 1yr. 0.0034

73.2 ± 21.9

70.0 ± 23.3 (45.0 ± 25.8) (48.7 ± 25.6)

Min. 2yr. 0.0694

78.3 ± 21.2

74.9 ± 22.9 (49.7 ± 26.3) (52.2 ± 24.8)

0-100

0-100

0-100

0-100

Activities of

Daily Living

Overall

Pain

Symptoms

Function in Sport/

Recreation

Quality of

Life

EQ5D-3L

OKS

Scale

Scale

Timing

Timing

(Covariate

Adjusted)

p-value for

Means

(Covariate

Adjusted)

p-value for

Means

N

NN

Leading Knee Brands

Leading Knee Brands

-1-1

0-48

Min. 1yr.

Min. 1yr.

0.0109

0.9 ± 0.2

41.4 ± 6.4

(0.3 ± 0.3)

(18.4 ± 8.6)

746

750

746

742

0.8 ± 0.2

40.2 ± 7.4

(0.3 ± 0.3)

(17.1 ± 8.8)

672

672

362

362

Unadjusted Mean ± SD, (Change from Pre-op Baseline)

Unadjusted Mean ± SD, (Change from Pre-op Baseline)

Min. 2yr.

Min. 2yr.

0.7594

0.9 ± 0.2

42.3 ± 6.4

0.9 ± 0.2

41.4 ± 6.8

(0.3 ± 0.3)

(18.1 ± 9.1)

(0.3 ± 0.3)

(18.0 ± 8.9)

Overall

Score

Overall

Score

0.0032

ATTUNE Knee

0.0002

0.2033

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 12 of 20

Another presentation combined data from the Hamilton,

et al. study with an additional study on ATTUNE TKAs,

cumulatively totalling 2,370 ATTUNE Knees and 845 knees

from other leading knee systems performed

by surgeons from around the world. This analysis

assessed the outcomes of early “learning curve” defined

as the first 10 ATTUNE Knee cases, compared to

subsequent procedures. Average operating time improved

after the first 10 cases. Additionally, when the first 10

ATTUNE TKAs by an individual surgeon (learning curve

cases) were compared to later ATTUNE TKA cases,

there was no impact on the rate of intra-operative

complications, nor was there an impact on PROMs. These

results may be useful evidence for institutions when

considering adoption of a new product.21

Patellofemoral complications are one of the problems

encountered in TKA patients. Some patients may hear

noise as a grinding or clunking sound when moving their

knee from extension to flexion. This situation is caused by

the entrapment of soft tissue between the components

and can be associated with pain and impair certain

activities. Symptoms usually begin within 12 months

of surgery and have been reported in up to 18% of

patients after TKA.26 Patellofemoral complications have

been a cause of revision surgery in approximately 6% to

11.6%5,28,51 of revisions. Furthermore, patellofemoral

complications, especially crepitus and clunk, are more

common in posterior stabilized (PS) implants.

1) In a prospective study by Toomey et al.,62 patellofemoral

symptoms were specifically evaluated by patients and

investigators. At one and two years, the cumulative

incidence of symptomatic crepitus in patients with ATTUNE

PS Knee implants was significantly less than that of the

non-ATTUNE Knees, primarily the SIGMA PS Knee design,

(0.78% versus 2.53% at one year, and 1.21% versus

3.14% at two years). Furthermore, the risk of patellar

symptoms increased fourfold for patients achieving more

than 110 degrees of flexion with non-ATTUNE Knee

systems, while there was no increased risk in the ATTUNE

Knee patients with over 110 degrees of knee flexion.2

2) Martin et al.43 reported a single institution study

that compared the incidence of crepitus for subjects

implanted with the ATTUNE PS Total Knee (N=728) and

subjects implanted the SIGMA PS Total Knee (N=1165).

The results showed significantly less symptomatic

patellofemoral crepitus at both minimum one and

minimum two years post-operatively for the ATTUNE

Knee versus the SIGMA Knee design (0.14 versus 2.7%,

p<0.001 at minimum one year and 0.33% versus 2.3%,

p<0.001 at minimum two years).

3) Ranawat et al.53 compared 100 each of the ATTUNE

PS Knee with the SIGMA PS Knee. While not statistically

significant, the incidence of symptomatic crepitus at two

years was 1.0% for the ATTUNE Knee cohort compared

to 4.1% for the SIGMA Knee cohort. Their results also

demonstrated a statistically significant reduction in anterior

knee pain at two years post-operative (12.5% for the

ATTUNE Knee cohort versus 25.8% for the SIGMA Knee

cohort, p =0.02).

4) Another study by Indelli et al.32 also compared 100

patients each with the ATTUNE Fixed Bearing Knee and the

SIGMA Fixed Bearing PS Knee. The ATTUNE Knee group

had significantly less anterior knee pain (2% versus 9%),

higher flexion (123 degrees versus 115 degrees, p=0.009)

and more patients with over 130 degrees of flexion (37%

versus 16%, p=0.0008). Two patients in the SIGMA Knee

group required surgery for patellar clunk and there were

no revisions in the ATTUNE Knee cohort. The ATTUNE Knee

patients experienced a statistically significant (p=0.007)

reduction in the incidence of symptomatic crepitus (1%)

compared to the SIGMA Knee patients (5%).

The ATTUNE Knee was designed to improve the

patellofemoral articulation. The trochlear design of

the PS implant has a reduced thickness of the anterior

implant flange, and an altered box configuration that was

specifically designed to maintain patellar contact through

deep flexion and avoid entrapment of soft tissue as the

patellar implant slides over the box. The native patella has

a dome whose apex is closer to the medial edge of the

bone and, in a similar fashion, the ATTUNE Knee patellar

implants restore the dome to a medial position on the

patella. The patellar implant is available in a medialized

dome or medialized anatomic configuration. While each

is designed to restore the dome of the patella to the

original position on the patella, the anatomic version has

facets which can increase the contact area of the patellar

implant on the femoral component throughout the range

of motion. In addition to the above clinical studies which

demonstrated fewer patellofemoral complications, a

comparative, kinematic study in the U.S. of both patellar

component designs showed that study subjects with

medialized anatomic geometry achieved greater patellar

flexion (the angular orientation of the patella relative to

Four independent studies32,43,53,62 have

demonstrated fewer patellofemoral complications

and one biplanar fluoroscopy study15 demonstrated

improved patellofemoral biomechanics in the ATTUNE

Knee, compared to other knee systems, primarily

the well-performing SIGMA® Knee. This data

suggests that certain design features, including the

modified trochlear groove and corresponding patellar

articulation, may lead to fewer reoperations for

patellar symptoms in ATTUNE Knee patients compared

to primarily SIGMA Knee patients.

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 13 of 20

the femur) than those with the medialized dome during

lunge activity, and demonstrated patellofemoral kinematics

closer to that of the native knee.15 The anatomic patellar

design also has more polyethylene proximally which may

prevent ingrowth of the fibrous tissue meniscus that

eventually encircles most domed implants.

Recovery from TKA is a process that takes time. Most

patients will experience improvement in knee function

for up to 12 months following surgery; however, the

most rapid phase of this recovery is in the first six weeks,

when about 80% of recovery has occurred. This acute

recovery phase is mainly related to the soft tissue healing

and remodelling that occurs following the procedure.

Recovery rates vary between patients but, in general,

TKA patients will continue to have startup stiffness,

discomfort, difficulty sleeping through the night, and

weakness going up and down stairs for six to 12 weeks.

Efforts to enhance early recovery from TKA have included

pre-operative exercises, less invasive surgical approaches,

aggressive physical therapy pathways, pain management

protocols and educational efforts to help prepare patients

for the recovery phase of their treatment. While some of

these have been shown to reduce length of hospital stay

and made the recovery more tolerable for many patients,

surgical pathways and implant design may also contribute

to the speed of recovery.

While length of stay, rehabilitation time, and return of

function are multifactorial, implant design and surgical

technique may be contributing factors. The ATTUNE Knee

was designed to allow surgeons to provide stability and

anatomical reconstruction of the arthritic knee. With 14

primary femoral sizes, 10 tibial sizes, and one millimeter

increments in polyethylene thickness, the options to size

and balance the knee have been enhanced with the

ATTUNE Knee from other available systems. Improving

component stability was one way the designing surgeons

felt they could impact function with activities such as

climbing and descending stairs. Another effect of this

component stability may be enhanced post-operative

recovery. While patient reported outcomes up to two years

have favored the ATTUNE Knee versus other leading knee

systems, some early recovery data also lends support.

Specifically, a U.S. claims database study29 compared

1,178 ATTUNE Knee patients to 5,707 Stryker Triathlon®

knee patients implanted in 38 hospital systems that used

both products.

Sensitivity analyses in this study indicated that these effects

could not be explained by patient factors including age,

insurance or marital status.

A study from Germany on the early (six month) clinical

results with 55 prospective ATTUNE Knee patients

showed significant improvement in range of motion (112

degrees pre-op to 123 degrees post-op; p<.001) and

improved coronal stability throughout the range of motion

compared to pre-operative status.50 The stability tests

were carried out in a standardized fashion at zero, 30,

and 90 degrees of flexion. The study authors felt that the

improved kinematics observed in these patients were a

result of the femoral component design and the ability to

fine-tune the knee balance with one millimeter increments

in polyethylene thickness. An in-vivo fluoroscopic analysis

(video x-rays which allow researchers to study the relative

motion of the components during activities) of the ATTUNE

Knee gradually changing radius (ATTUNE GRADIUS™

Curve) compared to the SIGMA Knee multi-radius design

showed improved kinematic function and femoral roll-

back with the ATTUNE Knee.49 Both of these studies,

which focus on stability, are consistent with experimental

data performed by finite element analysis and previous

experimental laboratory research.24

The results showed a significant difference in the

length of hospital stay and use of extended care

facilities. The adjusted mean length of stay (LOS) for

ATTUNE Knee patients in this dataset was 0.19 days

shorter than for the Triathlon® patients (2.94 vs. 3.13;

p<0.001). The mean adjusted proportion of ATTUNE

Knee patients in this dataset who were discharged to

a skilled nursing facility (SNF) was 24.3%, compared

to 34.3% of the Triathlon® patients. The adjusted

odds of ATTUNE Knee patients in this dataset being

discharged to a SNF were 39% lower than for

the Triathlon® patients (Odds Ratio= 0.61; 95%

Confidence Interval: 0.50-0.75; p<.001).

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 14 of 20

Although a full cost and benefit profile for the ATTUNE

Knee does not currently exist, there is emerging evidence

that evaluates the economic implications of the ATTUNE

Knee System.

In a claims database evaluation of data from 2013-2014

of the ATTUNE Knee System versus the Triathlon® knee

system, within a sample of U.S. hospitals and surgeons,

the patients in the dataset who received the ATTUNE Knee

had a shorter length of stay; the length of stay for the

ATTUNE Knee patients was statistically significantly lower

than for Triathlon® patients, by an average 0.19 days

adjusted for case-mix.29 These results may be meaningful

in systems that are interested in reducing length of stay

and post-acute care. The ATTUNE Knee System could be

part of the care pathway that is aligned with the goals

of the healthcare system. Although small expressed in

per patient terms, this may be important where there is

a larger volume of patients, and, in the U.K. in particular,

lower length of stay has been found to reduce cost

sufficiently to improve the cost-effectiveness ratio.27 The

same study found that the adjusted odds of ATTUNE

Knee patients in the dataset being discharged to a skilled

nursing facility were 39% lower than for the Triathlon®

patients. Because such facilities are comparatively very

expensive, this may also improve cost-effectiveness.

Further research in this area would be beneficial.

Although revision rates and secondary procedures have

not been shown to impact on cost-effectiveness, the lower

reported patellofemoral complications32,43,53,62 that often

lead to reoperations, and the low revision rates for the

ATTUNE Knee reported in National Joint Registries5,9,11

suggests a source of reduction in overall costs.

Additionally, some studies indicate that there is evidence

of improved health related quality of life, as measured

by validated PROMs questionnaires, using the ATTUNE

Knee. For example, the study by Hamilton et al.31 showed

that ATTUNE Knee patients had consistently improved

one- year scores on a broad range of PROMs compared

with those patients who had other knee products,

although not all differences were statistically significant.

These improvements appear to be modest, which is to be

expected as TKAs in general have been shown to have a

positive effect on patients’ quality of life.60 However, as

the cost-effectiveness modelling evidence described earlier

shows, even a small improvement significantly raises cost-

effectiveness favorability when translated into gains in

Quality Adjusted Life Years.

These benefits have been observed in real world settings,

where many variables that effect LOS and other outcomes

that impact the value to payors and other stakeholders.

Advancements in the provision of TKA have reduced

the burden on patients with osteoarthritis of the knee

and technological advancements have led to improved

outcomes over time. The ATTUNE Knee has been

available for a number of years in a large number of

countries and was designed to improve patient outcomes

through advancements in implant design and surgical

workflow. The current data reviewed in this paper has

demonstrated improved outcomes compared to other

leading knee systems. Based on registry data collected

over time in multiple countries, the ATTUNE Knee

performs well in terms of implant survivorship to three

years; registry data will continue to be reviewed. For

the patient, this may mean enhanced recovery from

the surgical procedure (leading to earlier discharge,

and reduced follow-up requirements in some cases), an

earlier and higher return of knee function, and fewer

reoperations from procedure related complications

such as patellofemoral crepitation. The improvements

in function documented thus far include improved pain

level, activities of daily living, function in sports and

recreation, and quality of life after one year. For hospital

systems receiving bundled payments, decreased length

of stay and fewer transfers to extended care facilities

can reduce the cost of episodic care. These financial

savings could also benefit hospitals under the Healthcare

Resource Group (HRG)/Diagnosis Related Group (DRG)

reimbursement systems. Earlier discharge could assist

with capacity constraints, particularly where there are

extensive waiting lists for a wide variety of procedures.

Finally, for society more generally, the costs associated

with total knee arthroplasty may be lowered, which

could allow for more total knee patients to be treated or

scarce resources used to generate benefits in other areas.

Based on available data, the ATTUNE Knee appears to

be advancing outcomes for patients and creating value

for clinicians, providers and payors in a challenging and

dynamic healthcare environment. The DePuy Synthes

evidence program will continue to monitor the clinical

and economic performance of the ATTUNE Knee as more

data and longer term follow-up data becomes available.

2.3 Economic Evaluation of the ATTUNE Knee

CONCLUSIONS

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 15 of 20

Study registration

number

Type of

Study

Functional

Outcomes Fixation Survivorship Safety Health

Economics

NCT01497730 C 1 X X

NCT01746524 C 1 X X

NCT01754363 C X X X X

NCT02339610 C X 1 X

NCT02251535 IIS 1

NCT02358434 IIS 1

NCT02323386 IIS 1

NCT02204748

NCT02613338 IIS 1

NCT02532933 IIS 1

UMIN000020380 IIS 1

NCT02177227 IIS 1 X

NCT02256098 IIS 1

NCT02103504 IIS 1

NCT02791477 Indep 1

Legend

• NCT#: Study is registered on www.clinicaltrials.gov

• UMIN: Study is registered on UMIN-Clinical Trials Registry,

www.upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000023536

• 1= primary objective

• C=Company Initiated Study

• IIS= Investigator Initiated Study funded by DePuy Synthes

• Indep= Independent study not funded by DePuy Synthes

Appendix Table 1: Summary of studies on the ATTUNE Knee with additional information available on Study Registration Sites

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 16 of 20

This white paper was commissioned by DePuy Synthes

Companies, and the lead authors received compensation

for their time associated with the development of the

document. Additional consultation on content and editing

was provided by: Kim Dwyer PhD, Vanessa Danielson MSc

and Bronwyn Do Rego MSc of DePuy Synthes Companies.

*David Fisher, M.D. is a paid consultant for DePuy Synthes

Companies and is member of the ATTUNE Knee surgeon

design team.

1. Centers for Disease Control, www.cdc.gov/arthritis/basics/osteoarthritis.htm, last accessed.

2. ©2015 Global Data, 2016 MediPoint: Hip & Knee reconstruction- Global Analysis and MArket Forecast,

www.store.globaldata.com/market-reports/medical-devices/medipoint-hip-and-knee-reconstruction-

global-analysis-and-market-forecasts, last accessed 12-31-2015.

3. 13th Annual Report 2016 National Joint Registry for England, Wales, Nothern Ireland and the isle of

Man. Surgical data to 31 December 2015, www.njrcentre.org.uk/njrcentre/Portals/0/Documents/England/

Reports/13th%20Annual%20Report/07950%20NJR%20Annual%20Report%202016%20ONLINE%20

REPORT.pdf, last accessed 2-7-2017.

4. Arthritis Research UK, http://www.arthritisresearchuk.org/arthritis-information/data-and-statistics/data-by-

condition/osteoarthritis.aspx, last accessed 2-7-2017.

5. Australian Orthopaedic Association National Joint Replacement Registry Annual Report, Adelaide, AOA,

2016, last accessed 2-7-2017.

ACKNOWLEDGEMENTS AND DISCLOSURES

REFERENCES

Reason for Revision Number Percent

Loosening/Lysis 4990 28.1

Infection 3985 22.5

Patellofemoral Pain 2059 11.6

Pain 1535 8.7

Instability 1194 6.7

Patella Erosion 772 4.4

Arthrofibrosis 611 3.4

Fracture 486 2.7

Malalignment 403 2.3

Wear Tibial Insert 290 1.6

Metal Related Pathology 286 1.6

Incorrect Sizing 222 1.3

Other 897 5.1

Total 17730 100.0

Table KT7 : Primary Total Knee Replacement by Reason for Revision

DePuy Synthes Companies Improving the Value of Primary Total Knee Arthroplasty: the ATTUNE® Knee System

Page 17 of 20

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Kevin, Evaluation of in-Vivo Mechanics for Medialized Dome and Medialized Anatomic Patellofemoral

Geometries During Knee Extension and Lunge. International Society for Technology in Arthroplasty (ISTA):

e-Poster, Boston, MA, 10-5-2016.

16. Bellamy N, Buchanan WW, Goldsmith CH, Campbell J, Stitt LW, Validation study of WOMAC: a health

status instrument for measuring clinically important patient relevant outcomes to antirheumatic drug

therapy in patients with osteoarthritis of the hip or knee. J Rheumatol 1988;15:1833-40.

17. Boraiah S, Joo L, Inneh IA, Rathod P, Meftah M, Band P, Bosco JA, Iorio R, Management of Modifiable

Risk Factors Prior to Primary Hip and Knee Arthroplasty: A Readmission Risk Assessment Tool. J Bone Joint

Surg Am 2015;97:1921-8.

18. Bourne RB, Chesworth B, Davis A, Mahomed N, Charron K, Comparing patient outcomes after THA and

TKA: is there a difference? Clin Orthop Relat Res 2010;468:542-6.

19. Bourne RB, Chesworth BM, Davis AM, Mahomed NN, Charron KD, Patient satisfaction after total knee

arthroplasty: who is satisfied and who is not? Clin Orthop Relat Res 2010;468:57-63.

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