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Corin wins
prestigious awards
Corin received two prestigious
awards this month for the Optimized
Positioning System (OPS™) in Sydney,
Australia and New York, USA.
Good Design Award
The first from The
Australian Good
Design Awards
where our OPS™
hip technology was
a recipient in the
Medical and Scientific Category. This
award recognises superior examples of
good design across a broad range of
industries and design disciplines. There
are seven main categories for the awards
and 25 sub-categories, representing one
of the most diverse range of submissions
in the world. The judges commented: “A
definite game changer for the medical
industry. Corin’s OPS™ technology
has been very carefully designed and
developed to offer a completely new and
innovative approach to hip replacement
surgery and will have a positive impact
on both surgeons and patients alike.
continued on page 3...
C
ompany update
4
TriFit TS™ optimising
biomechanics
Corin appoints Paul Berman as
Mr Andrew Shimmin
President US operations Corin USA
10
Balancing the patello- femoral joint in TKR
Mr Andrew Toms
12
Calendar of events
Forthcoming global meeting and
exhibitions calendar
COMPANY NEWS
United
Kingdom
Corin UK continues its
journey into the science
of patient specific hip
arthroplasty, with the
continued roll out
of the world first OPS™ technology to
leading orthopaedic centres across the
UK. Following our successful first case
at the Nuffield Orthopaedic Centre in
Oxford with the OPS™ we have added
the University Hospital of Coventry and
Warwick, Swansea and a number of key
centres in London to our team of partners
in this drive to change the way healthcare
providers look at hip replacement and
implant positioning ensuring the best
possible outcomes for patients.
Our dedicated team of sales and
marketing professionals are working
closely with key hospital staff and
together we are discovering how best
to utilise the technology for a better
patient experience. We have gained
commitments from many of the
leading UK arthroplasty surgeons to
become early evaluators for the OPS™
programme; this promises to be an
exciting and successful time for Corin UK.
Italy
Inaugural product
training event for
Corin Italia
On 16-17 June a group
of Italian sales specialists
gathered in Friuli near Corin
Italy’s base of operations for the first
of three product training courses to be
run in 2015. The aim was to provide
the sales team with the opportunity to
undergo in depth product training on
the key products being marketed by
Corin Italy and our distribution network
nationwide. The training focused on the
key brands, MiniHip™, MetaFix™, TriFit
TS™, Trinity™, the innovative ECiMa™
Vitamin E HXLPE and Unity Knee™,
Corin’s flagship total knee offering.
OPS™ was also covered and we look
forward to introducing OPS™ as part
of our strategy moving forward. The
training generated an active exchange
of ideas and views within the group and
feedback has been extremely positive.
In combination with Corin’s iPad apps
we believe that this training event
will enable us to apply the knowledge
transferred during this course and we
look forward to further educational
events during the remainder of 2015.
2
Company update
Corin appoints Paul Berman as President Corin USA
Corin Group PLC is pleased to announce the appointment
of Paul Berman to President US Operations, Corin USA.
Paul brings extensive experience in global orthopaedics,
which will be instrumental in continuing and accelerating
the success of Corin USA. Prior to joining Corin, Paul held
key leadership roles with Stryker Orthopaedics, including
Vice President Mako Field Service, Vice President
European Orthopaedics, and Vice President Global Knee
Marketing. Before Stryker, Paul was Marketing Director
at DePuy Orthopaedics and Marketing Manager Eli Lilly
Pharmaceuticals. Paul holds a BA from Central Connecticut State University, an
MSc in Psychology from State University of New York, and an MS in Management
from Rensselaer Polytechnic Institute. Paul, his wife Marie and their two children
currently have relocated to Tampa, FL, the home of Corin USA.
In a recent conversation with Russ Mably, COO Corin Group PLC, Paul
described his perspective on Corin USA…”What attracted me to Corin was
the Company’s pace of responsible innovation and its clear commitment to
personalised medicine patient satisfaction. Corin’s portfolio is comprehensive
and rapidly expanding, including a full line of proven, but contemporary femoral
stems, an outstanding modular cup system, and state-of-the-art total and unicompartmental knee systems.”
But it’s what’s beyond Corin’s admirable implant innovation that really excites
Berman; “Corin’s innovations in procedural advancements are the real game
changer. Our recent acquisition of the “Optimized Positioning System” (OPS™)
in Australia will provide personalised, functional positioning of hip implants in a
way that has not been possible with other more costly, complex technologies.
OPS™ simplifies the surgical procedure while potentially reducing cost and risk of
dislocation, edge loading and premature implant failure. Our goal at Corin, in the US
and globally, is not to pontificate over the inevitable evolution in healthcare. Rather,
we will be the leader in providing tangible, timely solutions for personalised care
and patient satisfaction.”
When Russ asked Paul his near-term plans for the US market, he was very clear;
“Corin’s US business has never been better positioned, with a growing talent base,
a full reconstructive product offering, new procedural innovations, and strong
double-digit growth, we are transitioning from an ‘other’ brand to the fastest
growing orthopedics company in the US. Top-three priorities to continue this
momentum are 1). Expand our US distribution network, 2). Continue leveraging the
expertise and insights of surgeons to advance personalised medicine and patient
satisfaction, and 3). Stay true to our philosophy of being nimble and easy to do
business with.”
We are excited to have Paul as a member of Corin’s leadership team and look
forward to continued success in the US market.
continued from page 1... This is a world class product, proudly designed and developed in Australia and well worthy of
design recognition.”
The week long judging process involved 30 local and international design experts and culminated in a Good Design Awards
gala evening at the end of May in Sydney, Australia. The OPS™ team were on hand to receive the award on behalf of
the Company. Bede O’Connor (Business Development, Optimised Ortho) commented “It’s great to be recognised as a
successful innovation group. A lot of people worked for many years to get the OPS™ technology to this point, it’s nice to get
peer respect for the effort.”
Medical Design Excellence Awards
Within two weeks Corin’s OPS™ received
a second crystal award in the Implant and
Tissue Replacement category from the
Medical Design Excellence Awards (MDEA).
Paul Berman (President US Operations) and
Jim Wyzard (Corin’s New York distributor)
were in attendance to accept the award at
the gala dinner in New York on 9 June.
The Medical Design Excellence Awards is a
prestigious competition that fosters innovation
by honoring the highest caliber medical
devices on the market today and is the
Medtech industry’s premier awards program.
Since its inception in 1998, the
mission of the MDEA has been to
recognise significant advances
in medical product design and
engineering that improve the
quality of healthcare delivery
and accessibility. Designed
to focus attention upon the
complexity of product development
and to showcase examples of what
can be achieved when it is well done,
the MDEA celebrates the achievements
of medical product manufacturers,
their suppliers, and the many people
behind the scenes—engineers,
scientists, designers, and
clinicians—who are responsible
for the groundbreaking products
that are saving lives, improving
patient healthcare, and
changing the face of Medtech.
Andy Sutcliffe, Group Marketing Director at Corin commented, “OPSTM is a first of
a kind procedural innovation within the orthopaedic field and it’s great to get global
recognition for this achievement. The combination of patient specific optimised
positioning alongside the company’s strong hip portfolio and rapidly expanding global
distribution network, provide a strong foundation for future growth of the company. Our
vision for the future is to lead in the area of personalised healthcare”.
Responsible Innovation
3
TriFit TS™ – optimising biomechanics
Export
Corin have
continued
to expand
the geographic
reach of its sales channels over the
past five years with more than 40
markets globally implanting Corin
products. Through our distribution
network, we have more than 350 people
collaborating in our partner companies
around the world. In recent years, we
have managed a portfolio transition,
with key markets now utilising Corin’s
focus brands such as Unity Knee™,
Trinity™ and TriFit TS™. A strong
education program is followed, with
many markets sending delegates to the
European training facilities e.g. Mülheim
and Centres of Excellence around the
globe to support brand activity.
“Through recent registrations across
our portfolio which include high
potential markets such as Brazil and
India, we have a strong platform
to increase our global, yet diverse
business”, states Nico Brezan,
Head of Export. Corin would also
like to continue market expansion
and is looking for partners in new
geographies. If you are interested
please contact Corin via the following
link; http://www.coringroup.com/
corin_worldwide/distributorsales_
agent_inquiries/.
CT analysis vs. blade stems
65.0
Mr Andrew Shimmin,
The Avenue
Hospital, Windsor –
Melbourne
Total hip arthroplasty is one of the most
successful interventions in modern day
medical practice, with many implants
demonstrating 95% survivorship at up to
ten years. But have we really solved all the
issues and do today’s implants provide an
optimal solution for today’s ageing, more
active patient population? Let’s look at the
blade stem philosophy in particular. We know
these stems do well in global registry data1
but equally we see challenges associated
with reproducing optimal biomechanics2, and
anthropometric fit3,4
Various articles have also been published
showing issues of migration and subsidence
of current blade stem5,6 designs.
Several factors contribute to a successful
prosthesis. As part of the global development
team for TriFit TS™, including Professor Fares
Haddad (UK), Mr Jon Bare (Australia) and Dr
Paul Beaule (Canada) our objectives were to
address many of these long standing issues.
We looked at three specific areas
1. Conformity
2. Versatility
3. Stability
1. Conformity
Germany
In May, Corin GSA held
another successful
workshop for Corin´s
short stem MiniHip™ and
the Unity Knee™ system
at the MEDucation centre close
to Düsseldorf. Experienced surgeons
were explaining the philosophy behind
the implant to impart their knowledge
and to give a better understanding for
surgeons who want to start using the
MiniHip™. In combination with guest
surgeries which are regularly offered
and organised by the Corin GSA team,
it is an excellent tool to reduce the
learning curve to get the best results
for patients. Dr Kothny from the
Munich Ortho Center led the MiniHip™
short stem session and Dr Keller from
the St. Elisabeth Hospital in Herten
presented the Unity Knee™ session.
Attendees commented on how
valuable these workshops are in small
groups and how they provide a real
benefit to exchange ‘tips and tricks’ of
the implant and approaches.
4
Historically many stem designs were unable
to restore optimal biomechanics. Many of
the current stems that surgeons use have an
inappropriate CCD angle – often established
from legacy products designed to pass
regulatory testing.
The anatomical CCD angle is typically
125°-128°, as has been shown in numerous
studies. Restoration of biomechanics is very
important, and rendered virtually impossible
with many competitor systems with historical
designs and higher CCD angles.
Study
Dataset
(femurs)
Mean
offset
Mean
CCD
Noble, et al.
100
43
125
Rubin, et al.
32
47
123
Blaimont, et al. 166
47
124
Massin, et al.
41
123
200
In developing TriFit TS™ over 250 CT scans
from around the world were used to create
a picture of patient anatomies. The design
of TriFit TS™ was based on the findings of
this data to ensure accurate fit. This stateof-the-art analysis was performed at an
independent centre under a UK governmentfunded research and development project.
60.0
55.0
Head Height (mm)
COMPANY NEWS
50.0
45.0
40.0
35.0
30.0
25.0
20.0
20.0
30.0
40.0
50.0
Head offset (mm)
60.0
European CT data
Corin TriFit TS™ standard
DePuy Trilock BPS STD
Biomet Taperloc (original) STD
Biomet Taperloc Microplasty STD
Biomet Taperloc complete STD
Smith and Nephew Anthology STD
Stryker Accolade TMZF 127°
Stryker Accolade TMZF 132°
Zimmer ML taper STD
Zimmer ML taper (Reduced Neck) STD
Many stems have two offsets to try and
accommodate biomechanics but actually
this is always a compromise between offset
and leg length. TriFit TS™ however offers
‘direct lateralisation’, making it simple to
adjust offset (while maintaining leg length)
should the surgeon need to, in cases
where the joint space is a little lax. Leg
length can be adjusted with the modular
head options as is routine during a hip
replacement procedure.
Competitor stem with two CCD angles
Decrease offset
Increased
leg length
135°
129°
Increase offset
Decreased
leg length
135°
129°
OPS™ goes live
in Austria
TriFit TS™ has been anatomically designed
to fit patient anatomy, and restore
biomechanics. Many systems offer an
increasing neck length with size. This is in
actual fact contrary to the independent CT
analysis used in the design of TriFit TS™.
There was no correlation between femur
size and neck length – however, as the
femur gets bigger, the offset increases. This
is why TriFit TS™ grows laterally, and has
consistent incremental growth throughout
the size range.
First European implantations using
Corin’s OPS™ technology
Dr Thomas Ramsauer and Dr Michael
Antosch from Oberndorf-Salzburg
clinic have implanted one of the first
OPS™ cases in Europe as the system
was launched across the European
market place.
Proximal-lateral growth
1.3mm
3. Stability
Central-lateral growth
1.4mm
Distal-lateral growth
1.4mm
2. Versatility
Modern implants need to be available with
instrumentation to allow insertion through a
number of different surgical approaches.
The TriFit TS™ instrumentation has been
designed to enable exact seating of the
definitive stem to the resection line. This is
facilitated by the newest in rasp technology,
using diamond toothed rasps that have a
helical path, providing an effective 0.2 to
0.3mm press-fit. A simple and effective
instrument platform is designed to enable
exact seating of the stem every time. TriFit
TS™ also conserves bone through a 50°
neck resection, at the greater trochanter
and in the diaphysis for long-term stability.
Many competitor stems have excessive
stem length compared to TriFit TS™.
Not only this, they are larger in the M-L
dimension distally. This can be an issue as
blade stems are designed to load proximally,
if they ‘hang-up’ distally the desired proximal
loading can be compromised. The risk for
blade stems that have excessive length
is that in the short to medium-term they
will subside. This has been reported in the
literature for the Accolade stem6. TriFit TS™
has been specifically designed with the use
of 250 CT scans and analytical software to
limit the possibility of these issues occurring.
In conclusion, TriFit TS™ had been
developed with a full awareness of the
issues seen with this type of stem, using
Corin’s independent, external governmentfunded analysis and extensive testing.
We are sure TriFit TS™ will be a dramatic
improvement on other stems of this type.
References
1. NJR, 2012
2. Lowry, C, et al.
3. Noble, et al.
4. Rubin, et al.
5. Jacobs et al. 2009.
6. White et al. 2012.
Having just implanted their tenth
Corin OPS™ hip system Dr Thomas
Ramsauer commented “for the
first time in orthopaedic history we
can now provide a patient specific
solution for total hip replacement
using a simple imaging protocol
and Corin’s advanced Dynamic
Simulation package”.
Dr Antosch continued “For many
years we have been using generic
safe zones which do not account
for significant changes in implant
orientation during functional activities.
We are now able to understand how
each individual patient moves and
account for patient specific sagittal
movements in defining an optimal
implant orientation”.
Dr Ramsauer and Dr Antosch will
form a key part of our growing
key opinion leader user group and
training resource and welcome
surgeon visitors as we expand the
reach of this revolutionary technology
in orthopaedics.
170
160
150
lateral
stem
length
Length (mm)
140
130
120
110
100
BIOMET
Taperloc
Zimmer
ML Taper
DePuy
Corin
TriLock BPS
TriFit TS™
90
Stryker
Accolade
TMZF
Stryker
Accolade II
80
70
n=11
n=13
n=14
n=13
n=12
n=13
Responsible Innovation
5
Augmenting gluteal tendon repairs with
LARS™ synthetic ligament
Dr Greg Janes,
Perth Orthopaedic
and Sports
Medicine Centre –
Australia
Greater trochanteric pain syndrome (GTPS)
is estimated to affect between 10% and
25% of the population in industrialised
societies1. Recent improvements in the
understanding of the pathology of GTPS
have revealed that degenerative changes
and tears of the gluteus medius or minimus
muscles at their tendinous insertions, similar
to rotator cuff tears seen in the shoulder2,
are the most common cause of GTPS1,3,4.
Although Walsh5 et al. reported
approximately 90% good results with suture
repair alone, our earlier experience with
suture and anchor-based surgical repairs
resulted in good initial pain relief but high rerupture rates of up to 31% at 12 months6.
What is the role of LARS™ in gluteal
tendon repairs?
We hypothesised that the high failure
rate of standard repairs was due to the
inability to mechanically protect the repair
in the post-operative period. Rotator
cuff repairs are routinely protected in an
abduction sling post-operatively. This is
simply impractical in gluteal tendon repairs.
The use of the LARS™ to augment the
repair is seen as an attempt to decrease
the mechanical stress of the repair in
the ambulating patient thus providing
an improved mechanical environment to
facilitate improved healing rates.
LARS™ is a third generation synthetic,
incorporating a high strength, novel
design technology which minimises
post-operative strength loss and
material degradation7,8,9. As
an augment, LARS™
provides immediate strength and stability
to the repair, with increased resistance to
elongation and low rupture rates, thereby
potentially facilitating rapid return to function
and pain elimination post surgery10,11,12.
We have carried out in excess of 150 hip
abductor repairs augmented with a LARS™
ligament since 2010 and recently published
a paper on an initial study composed of
a consecutive series of 22 patients with
hip abductor tears treated surgically with
a LARS™ reinforced repair10. This paper
describes the surgical technique employed.
All patients were assessed pre- and postoperatively at 12 months using the Oxford
Hip Score (OHS), Short-Form Health Survey
(SF-36) and Visual Analogue Pain Scale
(VAS). Significant improvements were
reported for all patient reported outcome
measures. All patients were satisfied or very
satisfied with the procedure at 12 months.
LARS™ roadshow
– Australia
Following the success of previous
Corin Academy education events
on the Ligament Augmentation and
Reconstruction System (LARS™),
and in-line with the commitment to
Responsible Innovation, Corin Australia
recently hosted a series of cadaveric
skills workshops in three east coast
locations – Brisbane, Sydney and
Melbourne (20, 21 and 23 May 2015).
Each workshop covered the use of
LARS™ in arthroscopic and open
knee ligament surgery, including
PCL, augmented ACL reconstruction,
posterolateral corner (PLC), MCL, as
well as augmented gluteal tendon
repair in the hip.
Work is now being undertaken on a larger
study using a slight modification of the initial
surgical technique. These patients are being
assessed pre- and post-operatively by an
independent observer and will be reported
in due course.
References
1. Williams BS et al. Anaesthesia and Analgesia. 2009
2. Bunker TD et al. JBJS [Br] 1997
3. Bird PA et al. Arthritis Rheum. 2001
4. Kingzett-Taylor A et al. J Roentgenol. 1999
5. Walsh M et al. J Arthroplasty. 2011
6. Davies H et al. Hip Int. 2009
7. LARS laboratory testing. Data held on file, Corin
Group PLC 2005
8. Ardern et al. J Arthroscopy. 2010
9. Mascarenhas et al. MJM. 2008.
10.Bajwa AS et al. Hip Int. 2011
11.Bucher TA et al. Hip Int. 2014
12.Holroyd B et al. European
Musculoskeletal review. 2009
The expert international faculty
comprising Mr Simon Coleridge, Dr
Greg Janes, Dr Chris Kondogiannis
and Dr Peter Annear were joined
by more than 50 surgeon delegates
from all over Australia who attended
the courses to learn about, and gain
valuable hands-on experience in the
use of LARS™ in various knee and
hip soft tissue applications.
Corin Australia recently celebrated its
14,000th LARS™ ligament implanted
nationwide. With over 60 published
clinical papers, including recent
Australian articles covering hip, knee
and ankle indications, the evidence
base and utilisation of the LARS™
ligament continues to grow intra- and
extra-articularly.
Corin would like to thank the faculty
for their continued support for the
Corin Academy educational program.
6
Not all short stems are the same
Professor
Jörg Jerosch,
Johanna-Etienne
Krankenhaus Germany
So-called ‘short stemmed’ prostheses have
been specifically developed for the needs
of younger patients. Although short stem
arthroplasty has been around for more than
30 years, their use has begun to increase in
recent years.
Many short stem prostheses are available,
but the differences between them are
considerable in some cases. Three main
classifications are based on resection plane –
femoral neck preserving, partial femoral neck
preserving and femoral neck resecting.
In use since 2009, MiniHip™ is a partial neck
preserving stem based on extensive analysis
of patient CT data1. The metaphyseal, femoral
neck-filling design aims to allow simultaneous
reconstruction of individual patient anatomies,
without the need for a large number of stems
or a modular neck system.
One paper3 recently published revision
rates in short stem THA and showed
revision rates per 100 component years;
NICE (National Institute for Health and Care
Excellence) recommends below 1. The
following results were achieved for short
stems in use today:
Stem
Revisions/100 component years
Metha
1.2
Optimys
3.17
MiniHip™
0.55
Fig. 3: Revision rates per 100 component years
The paper also looked at the ability to
recreate biomechanics and found only five
of the 19 stems able to accurately recreate
biomechanics, one of which was MiniHip™.
The reduction of the offset seen in many
stem designs leads to instability of the hip,
which is then compensated for by the use
of a longer head. This in turn leads to leg
extension. One paper4 reported that in 410
patients, mean limb lengthening following
total hip replacement was 3.9mm.
In a multi-centre analysis of 250 patients
treated with MiniHip™, the results shown in
Fig. 4 were achieved5;
Post-operative change
+/-
Offset
0.29
0.45
CCD angle
-0.51
4.10
Leg length
0.09
0.36
Fig. 4: Change in pre-to post-operative offset of the CCD
angle and the leg length of the 250 patients’ hips
Fig. 1: MiniHip™ implantation
Primary stability of the stem
The compelling question still remains on
whether bone preservation is still the most
important feature. I would suggest other
factors are of greater importance – such as
reconstructability of the individual patient’s
anatomy, primary stability of the stem and
long-term bone preservation.
Reconstructability of the individual
patient’s anatomy
In a comparison of different short stem
systems, the individual hip geometry shows
distinct differences. In our own study, we
investigated the reconstructability of 100
coxarthrosis with nine different short shaft
systems2. The CCD angle in the patients
studied ranged from 117° to 149°. The
results varied between 41% and 92% (Fig. 2).
MiniHip ™
Mayo
Metha
CFP
Fitmore
Proxima
CUT
Silent
Nanos
71
73
At first glance it might be assumed that short
stem systems have a lower primary stability
due to the short anchor line. When reviewing
this it is important to differentiate neck
resecting stems and partial femoral neck
preserving stems. Neck resecting stems
behave basically as standard stems and
define themselves through their anchoring
mode in the femoral shaft. Partial neck
preserving stems however, make use of the
femoral neck, resulting in a posterior-anteriorposterior (PAP) fixation including anchoring of
the femoral neck (Fig. 5).
Long-term osteological competence
of the implant
In some short stem prostheses,
hypertrophy is found in the tip of the
prosthesis in the Gruen zone 3 – thought
by some authors to be connected with
thigh pain and problems with distal
fixation6. My DEXA data with MiniHip™
shows a significant decrease in bone
mass in the first three months, which
we attribute to the surgical trauma and
reduced activity. Twelve months after
implantation an increase in bone mass is
seen in Gruen zone 1 and 7 particularly
but not in zones 3 and 4 (Fig. 6).
Fig. 6: DEXA results after femoral neck part conserving
short stem prosthesis
Data available to date seems to
suggest MiniHip™ preserves bone at
the time of operation and loads it in a
physiological way, leading to long-term
bone preservation. MiniHip™ has also
been shown to be able to recreate
biomechanics, another important factor
in the long-term survivorship of a stem3,5.
References
1. Jerosch J et al. Orthopädische Praxis. 2009
2. Grasselli Ch et al. Baden Baden. 2011
3. Oldenrijk JV et al. Acta Orthop. 2014
4. Gill IR et al. Hip Int. 2008
5. Jerosch J et al. Epub. 2011
6. Knight JL et al. J Arthroplasty. 1998
92
88
89
80
79
41
69
0
20
40 60 80
Fig. 2: Reproduction of offset (within 2mm) and CCD angle
(within 2°) of 100 patients with osteoarthritis
100
Fig. 5: High primary stability of MiniHip™ due to the axial
fixation PAP
Responsible Innovation
7
ICJR review
templated scans of the patients’ femora
obtained at the time of the Optimized
Ortho protocol for OPS™ acetabular
planning. Following 3D templating,
the osteotomy is planned, then the
Patient-Specific Guide is designed and
3D printed.
The International Congress for Joint
Reconstruction (ICJR) and the European
Knee Associates (EKA) combined this
year to hold the first ‘World Arthroplasty
Congress’ in Paris. This was the first
global meeting dedicated to the exchange
of surgical innovation, cutting-edge
science, and practical knowledge related
to joint arthroplasty. Dr Ed Marel (Sydney,
Australia) presented a number of podium
presentations outlining his experience
with the innovative OPS™ technology and
clinical results to date. Below is a summary
of three of these papers.
33 patients received a Trinity™
acetabular component and an
uncemented TriFitTS™ femoral
component through a posterior
approach. The femoral osteotomy
for all patients was performed using
the Patient-Specific Instrument. The
achieved level of osteotomy was
confirmed by comparing the planned 3D
resection to the post-op AP X-ray. Mean
difference was 0.7mm 28 patients had
less than 1mm difference.
Sagittal pelvic tilt in the standing, supine
and flexed seated positions
Pre-operatively, 100 consecutive to total
hip replacement patients had their pelvic
tilt measured in three positions to assess
functional flexion and functional extension:
2. Standing–from lateral standing X-ray
The functional anteversion in the
squeaking group at the time of ‘seatoff’ was significantly less than the silent
control group, leading to an increased
incidence of posterior edge-loading and a
mean CPRD of-2.3mm. This was primarily
attributable to the increased anterior tilt
of the pelvis in the seated position of the
squeaking group.
This study is to investigate the incidence
of edge-loading in squeaking and
matched controlled silent ceramic
hips, using dynamic musculoskeletal
modelling software that simulates each
patient performing activities associated
with edge-loading. 54 patients 18 in the
squeaking group and 36 in the control
group were modelled performing two
functional activities using the Optimized
Ortho Post-operative Kinematics
Simulation software.
3. Flexed seated – from lateral X-ray at
‘seat off’ as the centre of gravity comes
over the feet to stand
The position of the pelvis in the sagittal
plane changes significantly between
functional activities. The extent of change is
specific to each patient.
As a result of the functional changes in
pelvic position, cup orientations during
dislocation and edge-loading events
are likely to be significantly different
to those measured from standard CT
and radiographs
Objectives
An Investiga
tion into the
Ceramic-on-C
Dynamic Loa
eramic Total
ding of
Hip Replacem
ents and its
Relevance to
Squeaking
Pierrepont JW;
Feyen
University of
1
1,3
Sydney, NSW,
2
H; 2Baré JV; 2
Young D; 3Miles
rne
Australia; 2Melbou
Orthopaedic
BP; 2Shimmin
Acetabular cup
AJ
Australia; 3Optimiz
ed Ortho, NSW,
orientation
Australia
has been show
ceramic THR
bearings [1,2].
n to be a factor
defined from
Currently all
in edge-loadin
Method of Ana
recommend
static measurem
g of ceramic-oned guidelines
the pelvis, and
ents with the
lysis
for cup orien
thus acetabular
patient supin
tation are
rising, bendi
e [2-4]. Howe
cup, during
ng, gait etc)
ver, the positi
activi
ties
is
assoc
objective of
likely different
on of
iated with edgethis
from when
loading (chair
matched contr study is to investigate
the patient
the incidence
is
olled silent ceram
that simulates
of edge-loadin supine [5-7]. The
ic hips, using
each patient
g in squeaking
dynam
ic
musculoskeletal
performing
and
activities assoc
iated with edge- modelling software
Methods
loading.
Eighteen patien
ts with repro
Table 1. Match
1W
Fig 3. a) Schemati
squeaking in
Riddell; 2JV Baré; 1,3JW
1University
c showing the
their ceramic-on- ducible Characteristic ed characteristics of the groups
Pierrepont; 3CZ Stambouz
Patch to Rim
Joint Reaction
Edge-loading
of Sydney, NSW, Australia; 2
Distance (CPRD)
Force (JRF)
total hip arthro
(range)
Group
Melbourne Orthopaedic
ceramic
ou; 4E Marel; 2AJ Shimmin
CPRD = -2.2mm
at the centre
is described
true rim of the
Group, VIC, Australia; 3
Squeaking
of the contact
as the arc length
plasties were
liner; b) A negative
Hips (n)
Optimized Ortho, NSW,
patch. The Contact
between the
and edge-load
from a previo
Silent Contro
CPRD implies
recru
Australia; 4Peninsula
edge of the
ing has
ited
Introduction
the contact
l
contact patch
Orthopaedics, NSW,
us study invest
patch has passed
across the articulatin occurred. c) An Optimized
18
and the
Australia
over the true
Ortho polar
incidence of
igating the Mean BMI (kg/m2)
g surface.
rim of the liner
plot showing
36
noise in largeMuch of the accuracy
the track of
27.0 (19.2 the contact
32.8) 27.2
Materials and Metho
ceramic bearin
of implanting uncemen
patch
diameter Maximal hip flexion
(19.6 - 33.0)
(°)
relies on the accuracy
ted
gs
ds
109 (90 - 130)
of the femoral neck osteotom femoral components
had a Delta [1]. All 18 patients Cup Inclination
Resu
Thirty-three patients
109
lts
(90 - 140)
(°)
received an uncemen
y.
Motion aceta
35.1 (22.7 This study looks at a
44.0) 37.5
component (Corin, UK)
ted Trinity™comp
bular Cup Anteversion (°)
onent r(DePu
concept for a new patient
acetabula
(20.0 - 52.0)
Table 2. Result
and an uncemented
y Orthopaedi
Optimized Ortho (Sydney,
16.0 (6.6 - 24.8)
specific instrument
s ± SD (range
TriFit TS™ femoralWarsa
(Corin, UK) through
cs,
Beighton Score
w IN),
from
)
Australia), a division
compone
19.5 (7.8 - 32.1)
a posterior approach
Group
ntwith head sizes
of Corin Group (Cirences
UK), designed and printed
.
1.7
The
A
(0.0
patients
40–48
femoral
contr
7.0)
was performed using
osteotomy for
mm. All had
ter,
ol group
in 3D from CT-templ
Squeaking
1.4 (0.0 - 5.0)
all
of 36 patien
the Patient Specific
a reproducib
ated scans of the patients’
femora obtained at
Silent Contro
Standing pelvic
below, Fig 2.
ts with Delta
Instrumesquea
le squeak durin
k were recru
the time of the Optimize
l
nt illustrated
p
-1.8°
value
tilt
Motio
±
7.4°
ited from the
g deep
n bearings who
d Ortho protocol for
acetabular planning,
-1.2° ± 7.6°
matched as
silent cohor
OPS™
Fig 1. Following 3D
(-18.0° – 9.4°)
had never exper flexion.
presented in
t of the same
templating, the osteotom
(-14.1° – 12.9°)
planned, then the Patient
Table 1. For
NS
ienced a
to investigate
Supine pelvic
original
y is
Specific Guide is designed
data analysis,
tilt
2.6° ± 5.2°
any statistical
a student’s t-test study [1]. They were
and 3D printed.
4.9° ± 5.4°
significance
(-8.8° – 10.4°)
between the
(two-tailed)
(-5.5° – 16.0°)
groups.
was used
NS
All 54 patien
Flexed seated
ts were mode
pelvic tilt
12.6° ± 13.2°
lled performing
Ortho Posto
5.1° ± 8.9°
(-13.5° – 30.3°)
perative Kinem
Pelvic tilt change
(-9.8° – 26.4°)
p < 0.05
atics Simulation two functional activities
postoperative
from
using
CT scan enabl
software (Optim
-4.4° ± 4.8°
supine to stand
the Optimized
virtually ident
ed 3D coord
-6.2° ± 4.6°
ized Ortho,
(-13.9° – 4.8°)
ified for each
inates of soft
Australia), Fig
Pelvic tilt change
(-21.1° – 4.6°)
Fig
patient in ScanI
tissue and bony
1. A
NS
from
P (Simplewar
14.4° ± 12.1°
stand to flexed
landmarks to
e, UK). Three
seated
6.3° ± 10.6°
be
(-9.2° – 31.0°)
lateral radiog
Cup Inclinat
(-18.3° – 27.8°)
raphs,
p < 0.05
ion at “seatFig 2, provid
ed pelvic and
33.4° ± 6.6°
off”
lumbar
spine param
36.2° ± 6.5°
(22.8° – 49.0°)
eters
Cup Anteversion
(21.3° – 48.3°)
NS
positions, used in the functional
at “seatas
8.1° ± 14.4°
off”
the patient-spec inputs to define
21.1° ± 9.9°
(-10.4° – 36.0°)
ific
kinem
(-1.9 – 38.4°)
atics in
p < 0.001
the simulation.
Posterior CPRD
Using these
(mm)
-2.5 ± 5.6
the softw
inputs,
2.9 ± 3.9
are calcul
(-9.4 – 8.7)
ates
dynamic force
(-6.5 – 10.5)
p < 0.001
at the replac the
throughout
ed hip
the
GT: -5mm
n AJ
plots the contatwo activities and
4 Shimmi
LT: 9mm
a)
bearing using ct patch on the
Fig 1. Images
hon S;Australia; , Australia
from the Optimized
eir
a
6 McMa
th
,
Hertz
standard medical
Ortho Postopera
ian contact
NSW
ic, VIC
algorithm [8],
had
imaging, the
tive Kinematic
on M; zed Ortho, aedic Clin
software runs
two functiona
Simulation software.
as it traces
tients xion and
l activities: sit-to-stan
a patient-sp
5 Solom 3
hop
ecific rigid body
Using the
Optimi
across
d and steppingar Ort
articulating
ent pa
fle
dynamics analysis
up with the
ré JV;
6 Malab
4
tralia;
of
surface, Fig
contralateral
lacem ctional
leg.
BP; Ba , NSW, Aus Australia;
all the squea
3. As
hip rep sess fun
king subjects
; 3 Milessity of Sydney ists, NSW,
total
did so in
deep flexion,
cial
to as
lter LR
ver
the minimum
ecutive
ions
; 1 Wa tralia; 2 Uni hopaedic Spe
d
posterior
nt JW
Aus
Ort
0 cons ree posit
Contact Patch
b)
rrepo ics, NSW, 5 Sydney
a)
y
th
ly, 10
2,3
Metho
to Rim
Fig 2. Patient Specific
gravit
E; Piela Orthopaed , Australia;
rative ured in
Instrument for Femoral
of
Distan
pe
e
1 Marel
Osteotomy:
VIC
LL
as
ce
will be increased by:
b)
3D Model and Operative
(CPRD
Pre-o tilt me
1 Peninsu
4mm
Photos
Group,
n:
e centr
be calculated ) can
aedic
Offset will be increased
ay
as th
lvic
tensio scan
”
by: -1mm
x-r
pe
Orthop
ex
as
e
off
al
the
urn
The achieved level of
at
CT
on
nding
minimum
4 Melbo
osteotomy was confirme
functi
distance
– from lateral sta x-ray at “se
IMPLANTS: SHELL:
d postoperatively by
3D/2D registration, using
pine
between the
54mm
STEM: #5, Std, 135 MetaFix
eral
doing a
from
the
1. Su
edge of
HEAD: +4mm
m lat
ing –
of the planned 3D resected Mimics X-ray module (Materialise, Belgium),
Fig 1. Optimized Ortho
the contact
OPS planning algorithm
Stand
d – fro t to stand
femur
patch
height. The surgeon
involves
ate
to
3D
2.
templating
the
and
can elect to alter the
postoperative AP radiograp
lt
from CT to recreate
image was then scaled
plan, if required
the true rim
the native head
e fee
xed Se
h. The
and the difference
lvic Ti
of the
3. Fle s over th
Pe
between
achieved
ceram
the
al
level
planned and
of osteotomy was measured
ic liner, Fig
come
(Imatri Medical,
Sagitt
posterior CPRD 3. A
Method of Validation
Fig South
Africa).
2. An example
of the three
with a
c)
functional radiograp
Ortho simulatio
negative
n - standing,
hs used to define
flexed seated
value
the patient-sp
1) Postoperatively,
and step-up.
Fig 4. One of
is
Results
ecific kinematic
d)
the squeaking
indicative of
a 3D/2D
s in the Optimized
2) The image was
patients: a)
18.3° radiograp
posterior
Supine AP X-ray
hic inclinatio
then scaled and
registration matched
shows a statically
n and anteversio
edge-loadin
The patient’s
The mean difference
the
“well-orientated”
Conclusions
n, respective
pelvis has rotated
the difference between
g.
ly; b) Supine
between the planned
cup at 34.2°
anteversion
planned 3D resected
posteriorly
position from
and
planned
by 6°; d) Flexed
7.4° from the
tive)
and achieved osteotom
CT; c) Standing
was 0.7mm, with a range
femur
supine position
seated position.
standing position,
and achieved level
1. Edgeposition.
y level
t (nega n
increasing the
The patient’s
of
reducing the
to the postoperative
loadin
0.1mm
of
Til
osteotom
–
6.6mm.
c
functional cup
g
pelvis has rotated
functional cup
is
y
dependent upon
lvi
xio
AP
anteversion
was measured, Fig 4.
anteriorly 25.1°
to only 3.5°
hip and the
Only 1 patient had a
from the
rior Pe
not just the
radiograph, Fig 3.
hip fle hip
at the time of
ral
kinematics of
difference of more than
“seat-off”.
three
Poste tective in
Seated
in
-dime
Neut
ed
t
the
3mm.
living by chang
nsional motio
Flex
pelvis. All three
Pro
but no
ing the locati
n of the femur
Of the 33 patients, 28
g)
factors influe
2. Sagittal
on of the bearin
had a difference of less
, but also the
tting), n (standin
nce
d
pelvic
(si
the
Refe
)
an
likelihood of
than 1mm.
kinematics are
g contact patch
force vector
sio
es
sitive
(ASIS
edge-loadin
individual pelvic
across the 1. McDonnell,renc
Standing
highly variab
in relation to
exten
S.M., et al.,
g during an
The incidence
Tilt (po sion
Plane tal when
le between
arising from
the
rotati
c
c
of noise generation
true
the large-diame
ons
activi
lvi
lvi
rim
have a subst
individuals and
total hip bearing.
edge-loadin
ty of daily 2. Esposito,
ter Delta Motion
of
Pe
exten
Bone Joint
ceramic
rizon
ior Pe
antial effect
between differ the liner.
C.I., et al., Wear J, 2013. 95-B(2): p. 160-5.
terior
d ho
Anter tive in hip t in hip
3. The funct g as a patient rises from
in alumina-ontotal hip replacement
ent functional
s: a retrieval alumina ceramic
the An nding an
Supine
a chair or durin on the functional orien
no
loading. J Bone
8
ional anteversion
analysis of
Joint Surg Br,
activities. Given
3. Lewinnek,
edge
tation
Protec g), but ng)
from
2012. 94(7):
g gait is specif
sta
G.E., et al.,
p. 901-7.
in
group, leadin
Dislocations
din
these
replacement
ic to each indivi of the acetabular cup,
after total
arthroplasties.
asured l when
g to an increa the squeaking group at
hip(stan xion (sitti
60(2): p. 217-20.
J Bone Joint
the likelihood
Surg Am, 1978.
dual.
6
the time of
attributable
sed incidence
was me vertica
fle
T., et al., Study
of 4. hipMasaoka,
“seat-off” was
of hip joint dislocation
of posterior
arthroplasty
. Int Orthop,
lvic tilt to the
after total
4. Acetabular to the increased anterior
5. Lazennec,
significantly
2006. 30(1):
edge-loadin
J.Y., et
p. 26-30.
s)
tal pe
tilt of the pelvis
supine, simulated al., Acetabular anteversion
less than the
cup orientation
4
g and a mean
with CT in
Sagit symphysi
patient population.standing, and sitting positions
silent control
in the seated
during activi
Patients with
Clin Orthop
1103-9.
Relat Res, 2011. in a THA
position of the CPRD of -2.3mm. This
ties associated
large anterior
469(4): p.
6. Philippot,
pubic
was primarily
R., et
squeaking group
2
pelvic tilts in
with edge-loadin
Lewinnek referenceal., Pelvic balance
e.
in sagittal
planes in the
.
and
sitting positions.
g is likely very
supin
in ceramic-on- deep flexion might be more
Orthop Traumatol standing, supine and
p. 70-6.
differ
Surg
Res,
2009. 95(1):
ent from when
ceramic bearin
7. DiGioia,
susceptible
0
A.M.,
these patien
to posterior
supine, Fig 4.
measured from et al., Functional pelvic
lateral standing
orientation
ination
ts can be identi gs, as a consequence of
edge-loadin
Clin Orthop
b)
and sitting
-4.2°
radiographs
45° incl eversion
g and
8. Mak, M.M. Relat Res, 2006. 453: p.
a
.
customised
t
272-6.
c)
and Z.M. Jin,
-2
Analysis of contact
ceramic-onto accommoda fied pre-operatively, cup significant decrease in cup squeaking
25° ant
lvic Til
ceramic hip
joint replacement mechanics in
Mech Eng H,
ral
te these indivi
anteversion.
orientation
2002. 216(4):
lum
s. Proc Inst
rior Pe
p. 231-6.
Neut
and bearing
dual patterns.
If
Poste e acetabu and
Disclosure One
-4
choice could
or more of the
th
Seated
ed
authors are
be
Flexed
paid consultan
Causes re inclin ed
ts to Corin Group.
mo
One of the authors
-6
Fig 3. 3D to 2D registration
is a sharehold
to be re antevert
er of Corin Group.
postoperative AP radiograph of the resected femur to the
Fig
ding
4.
Measurement
mo
Stan
of the difference between
the planned
osteotomy level and
Tilt
-8
that achieved
Pelvic lum
ior
Fig
5. Resection level deviation
from plan. 33 consecutive
Anter e acetabu d
cases, 2 surgeons, 1
plane
implant system
th
Supine
ed an
ons
l
gittal
Causes s inclin
Positi
les
ed
Seated
the sa functiona
to be antevert
Flexed
ch
less
lvis in
Seated
n • A ea
ing and
patien
■■
Planning and measurement of cup
placement in the supine position
can lead to large discrepancies in
orientation during more functionally
relevant postures
■■
Previously defined
‘safe zones’ might not be appropriate
for all patients as
they don’t account
for the dynamic
behaviour of the pelvis
■■
Optimal cup
orientation is likely
patient-specific and
requires an evaluation
of functional pelvic
dynamics to preoperatively determine the
target angles
Clinical accuracy of a
patient specific femoral neck
osteotomy guide
and
pine
Deviation, mm
0
5
10
15
20
25
30
1.
Table
Pelvic
Tilt in
, Stand
Supine
Concl
Flexed
2.2°
ng
Standi
ANTERIO
IOR
POSTER
35
Conclusions
s
usion
t specific femoral neck
the pe betwee ecific to
osteotomy guide was
n of
ly
is sp • This femora
made from pre-operative
c)
l neck osteotomy guide
positio
ificant
ange
3D planning from CT.
4°
showed very good clinical
to 30.
• The ges sign tent of ch
• A larger
-1.6°
-36.1°
accuracy in the first group
Supine
pelvicstudy into planned and
b)
chan es. The ex
of patients.
achieved leg length and
4°
ges in n and
to 16.
an
iti
offset is underway.
4.3°
ch
-20.4°
tiv
io
l
ac
.
tiona g dislocat cantly
nt
nc
vic Tilt
19.2°
tie
fu
to
Pel
ifi
°
rin
e
pa
-9.6
Mean
of th ations du to be sign dard CT
Seated
vic Tilt
a)
Range
Flexed
result
an
ely
ient
in Pel
ng to
Disclosure One or more
anges
of the authors are paid
Standi
As a n, cup or ts are lik d from st
consultants to Corin
•
2. Ch
Group. One of the authors
le
°
en
is a shareholder of Corin
Tab
3.9
Group.
nding
positio ading ev e measure
to Sta
0°
t in
Supine
-lo
to 32.
emen e
-25.9°
edge nt to thos
-5.9°
se to
p plac
larg
, or cloesting
of cu
differe diographs.
to
°
small
Tilt
to 5.6
ment
1 are large, sugg
more
Pelvic
lead
-17.7°
Mean
Table
ry
and ra
easure n can
ring
m
ted in ges are ve
.
du
d
en
ing
ge
es
an
nd
Ran
pr
ran
to Sta the
positio ientation
ning
lvic tilt respective
of
pine
e
of pe
• Plan supine
58%
m Su
be
lues rtantly, th lation.
in or stures.
rly fro tension. is rotation
an va
not
po
popu
the
sterio
ies
po
in ex ated. Th
The me . More im ross the
lvic tilt
ed po
unt
might
panc
vant
ac
in pe e the
rotat anteversion xed Se
neutral variation
nes” don’t acco
discre nally rele
Fle
rease
as
tients
al
ing to A 32° inc ll decre
of pa function
afe zo
ey
a wide
wi
92%
Stand
s
functio
ed “s nts as th
.
ated
rease ly from in flexion.
ble 2,
[1]
Se
fin
lvis
inc
°
Ta
de
In
xed
ion
terior
ion
an 20
rotat
l patie r of the pe
usly
ed an antevers ing to Fle more th
cific
al
io
tat
This
r
pe
ro
ev
by
al
-s
nd
fo
on
nts
nt
viou
• Pr opriate
patie es functi ) from Sta acetabulum
patie l pelvic
beha
as
tation ion of the
appr dynamic
na
likely
decre
ior ro
ers
e
ion is of functio the target
(anter al antev
for th
on
n
ientat
ine
functi
cup or evaluatio y determ
al
im
an
ativel
• Opt requires
ed cup
e-oper
Assum tion:
and
to pr
orienta °
mics
40°/20
dyna .
angles
lts
Resu
Group, VIC,
Clinical Accuracy of a
Patient Specific Femo
ral Neck
Osteotomy Guide
g, Su
tandin
the S sitions
Po
Tilt in
elvic d Seated
P
l
ta
Flexe
Sagit
This study looks at a concept for
a new patient-specific instrument,
designed and printed in 3D from CT
8
Edge-loading is dependent upon not just
the three-dimensional motion of the femur,
but also the force vector across the hip
and the kinematics of the pelvis. All three
factors influence the likelihood of edgeloading during an activity of daily living
by changing the location of the bearing
contact patch in relation to the true rim of
the liner.
An investigation into the dynamic
loading of ceramic-on-ceramic total
hip replacements and its relevance
to squeaking
1. Supine – from CT scan
■■
The software calculates the dynamic
force at the replaced hip throughout
the two activities and plots the contact
patch on the bearing using a Hertzian
contact algorithm, as it traces across the
articulating surface. As all the squeaks
occurred in deep flexion, the minimum
Contact Patch to Rim Distance (CPRD)
can be calculated. A posterior CPRD with
a negative value is indicative of posterior
edge loading.
ATION
R ROT
N
ROTATIO
ation
cup nagiv
urate
inacc
. Acta
p. One
s tilt makes acetabular
Grou
Corin
ence
Pelvic
et al.,
nts to
Refer
eck, B.
consulta
Lemb
1.
re One
Disclosu
e of the
or mor
authors
are paid
. 76(4)
ica, 2005
paed
Ortho
of the
authors
3.
: p. 517-2
of
eholder
is a shar
Corin
p.
Grou
If you are interested in looking
at these posters in more detail
please visit the following link
www.coringroup.com/icjr or
scan the QR on the left.
Global opinions
Dr Carlo Callea
Casa Di Cura
Giovanni XXIII
Monastier
Treviso - Italy
it is indicated in nearly all the trophic and
morphological disorders. The instrument
set is simple and reliable, and makes its
positioning intuitive.
Dr Carlo Callea has over 40 years of
experience in hip and knee surgery and
is the Head of Orthopaedic Surgery at
Casa di Cura Giovanni XXIII in Monastier,
Treviso, Italy. He is also a Consultant for
the Department of Prosthetic Surgery
at Casa di Cura Città di Udine and Villa
Salus in Trieste. His Group has a yearly
workload of more than 1,200 joint
replacements which mainly consist of hip
and knee primary and revision implants.
What are your thoughts on the use of
ceramics today in hip replacement?
What do you see as the ongoing
challenges in total hip replacement
today? Have we made any progress
over the last ten years?
As things stand, the main challenges lie
in extending the indications for surgery
in younger patients, and in more active
people and athletes. The hunt is therefore
on for increasingly reliable, biocompatible
materials that will last longer and produce
more satisfactory results. Research has
led to enhanced femoral component
design. The socket component is still
an open issue, often causing hard-tosolve problems in revision surgeries. The
acetabular component is demonstrably
responsible for major failures.
Surgical techniques now tend to cause
far less damage to muscle and tendon
groups, but fitting the two components
of the prosthetic joint together correctly
in every patient is still a challenge.
Dislocation and mobilisation may occur
with components that appear to be well
positioned. There is a definite need for
clear positioning guidelines to ensure
that every procedure is tailored to the
individual patient.
How do you decide on the correct
stem philosophy for treating your
patients? What are the overall
considerations driving your optimal
stem choice?
There are a number of factors that come
into play when choosing the stem, such
as the patient’s gender, age and activity
level, as well as bone morphology. Other
factors include existing or potential
pathologies that may affect the holding
strength of bone as time goes by.
What led you to your choice of
mainstream hip replacement today?
What benefits does this system offer
to your patients and practice?
I use the TriFit TS™, in the main I think
this stem represents a modern patient
matched solution. Anatomically designed,
the stem is adapted to the different
femoral canal shapes, so it is indicated
for a wide range of patient indications.
It does not require an aggressive
preparation of the femur. For this reason,
position the prosthesis (20-25 minutes).
Any intraoperative complications can
be readily controlled with this approach.
However, it is necessary to check the
stability of the implant during surgery
to avoid posterior subluxations and
damage to the sciatic nerve. The
speed of the procedure plus the
ability to effectively check the position
and congruence of the prosthetic
components means restoring hip
functionality more quickly, shortening
the duration of aided weight-bearing
and reducing the risk of infection. All
this increases the chances of long-term
success and faster functional recovery.
What led you to your choice of surgical
approach today? What benefits does
this approach offer to your patients
and practice?
I started using the posterolateral approach
many years ago and am still using
it today. For me the posterolateral
approach is the most anatomical one;
it allows me to constantly monitor
the position of the implant
components. There is a lower
incidence of subsequent
periprosthetic ossification
compared to other
approaches, and above
all it is totally safe for
the gluteus medius
muscle. Skilful use
of this approach
enables me to
quickly and
successfully
I have been using ceramic, initially
coupled with polyethylene, for around
35 years. For the last 15 years I’ve
opted for ceramic-on-ceramic bearing
couples on all my hip replacements. The
reason is because of the outstanding
biocompatibility and extremely low
friction factor, which determines
negligible particle release. This solution
has done away with ‘particle disease’,
a well-known issue associated with
polyethylene or metal-on-metal bearing
surfaces. The enhanced hardness of
BIOLOX® delta ceramic material has
also eliminated the very slight risk of
breakage of earlier ceramics. After
implanting thousands of ceramic-onceramic implants, I’ve hardly come
across any cases of squeaking. I believe
ceramic-on-ceramic bearings are ideal
for hip replacements and I use them
in all of my patients, be they young,
active patients in whom the implant is
expected to survive for many years, or
older patients in whom I need to allay
the risk of short-to-medium-term failures
and thus the need for revision surgery
that might be unfeasible or entail major motor problems.
Conformity | Stability | Versatility
Responsible Innovation
9
Balancing the patello-femoral joint in total knee replacement:
A clinician’s perspective
1. Balancing the patellofemoral
mechanism: Optimising implant geometry
Whilst total knee arthroplasty (TKA)
demonstrates excellent long-term
survivorship, patient satisfaction is still a
significant issue with over 10 - 20% of
patients exhibiting patient dissatisfaction
post TKA. In particular anterior knee
pain is a common complication post
TKA, affecting 18-28% patients1 and
plays a significant role in delayed
rehabilitation and time back to work.
The prevalence of anterior knee pain
can be largely associated with elevated
forces on the patellofemoral joint (PFJ)
and increased quadriceps effort, thereby
rendering this phenomena as activity
dependant with incidence of pain almost
double during stair climb/descent
versus walking on a flat surface1.
Forces on the PFJ are highly dependent
on the distance between the PFJ, the
patient weight as well as centre of
rotation (COR), which explains why
different activities despite equivalence
in tibio-femoral angle may exert wide
variations in patello-femoral reaction
forces and contact pressures. During
normal daily activities the PFJ becomes
exposed to forces between 0.5 - 9.7 x
body weight, whilst sporting activities
create forces that approach up to 20 x
body weight. Given these considerable
forces as well as the fact that the
extensor mechanism can be up to 30%
weaker in patients undergoing TKA2, it is
not surprising that if the surgeon doesn’t
take steps to carefully balance the PFJ,
it becomes particularly susceptible to
post surgery complications.
Whilst historically restoring balance in
the PFJ wasn’t a primary focus in TKA,
in recent years extensive research has
been conducted studying the anatomy,
kinematics as well as role of the PFJ
in patient satisfaction. Several factors
appear to contribute to balancing the
PFJ during TKA; some of these factors
are surgeon dependent, whilst others
are attributable to the knee system
employed. One of our objectives with
the Unity Knee™ was to design a
modern knee system, which not only
optimised implant geometry but also
incorporated an advanced instrument
platform to help facilitate PFJ balance:
10
When examining a TKA implant two key
parameters contribute to the function of
the PFJ, the first is the geometry of the
PFJ articulation and the second is the PFJ
moment arm i.e. the distance between the
COR of the implant and the PFJ.
PFC Sigma
1.73mm at 30° flexion
Recent knee kinematic studies demonstrate
that the patella tracks lateral to the mid-line
of the femur only deviating 1mm mediolaterally throughout range of motion3,4.
The evidence base
"The natural patella tracks laterally
with its most posterior position being
4.2 ± 1.3mm lateral to the anatomic
axis, deviating 1 ±1.3mm mediolaterally from this position through
range of motion."
Lateral offset at 30°
1.73
Lateral offset at 0°
6.1
Triathlon
0.72mm at 30° flexion
Lateral offset at 30°
0.72
Lateral offset at 0°
4.9
Unity Knee™
4.43mm at 30° flexion
N
M
L
K
J
I
H
G
F
E
A
D
Lateral offset at 30°
4.43
Lateral offset at 0°
6.0
B
"The translation of the sulcus from the
midline in patients requiring TKA was
5 ± 1mm in a lateral direction... This
study demonstrates that the sulcus of
the trochlear groove is not located in
the midline as traditionally represented,
but is lateral to the midline in both
osteoarthritic and normal knees."
Unlike the native patella track, traditional
knee implants incorporate patella tracks
which are centrally positioned through
flexion, only lateralising beyond 30˚ of
flexion into extension. The Unity Knee™,
on the other hand, has been designed
with a lateralised anatomic patella track
which remains lateral to the mid-line
through range of motion, providing a
more forgiving and anatomic patellofemoral articulation, assisting to minimise
constraint on the extensor mechanism.
This coupled with multiple thickness
centred dome and medialised dome
patella options, with complete intraoperative flexibility, allows the surgeon to
fine tune the position of the patella as well
as restore the PFJ offset to the patient’s
individual anatomy in order to minimse
soft tissue releases and patella constraint.
In terms of PFJ moment arm, traditional knee
implants were designed with a multi-radius
sagittal profile in the active flexion arc as this
was considered to be anatomic at that time.
However, these implants resulted in an anterior
shift of the COR of the knee due to paradoxical
anterior femoral motion, in other words
reducing the PFJ moment arm when going
from extension to flexion. As a consequence
these implants (labelled as ‘control’)
demonstrated elevated forces, particularly from
mid-flexion onwards compared to non TKA
subjects (labelled as ‘normal’).
Quadriceps Tension (N)
Mr Andrew
Toms, Princess
Elizabeth
Orthopaedic
Centre, Exeter
Contemporary knee designs
demonstrate a reduction in lateral offset
of the patella track at 30° and onwards
into flexion. Unity Knee™ on the other
hand maintains a lateralised patella track
throughout range of motion.
1000
800
600
400
200
0
15
30
45
60
75 90
Knee Flexion (degrees)
D’Lima et al5,6 have shown that implants
with a longer moment arm (LMA’)
provided 5-20% reduction in quadriceps
forces and 8-18% reduction in patellofemoral compression forces, statistically
significant at flexion angles greater than
50˚ compared with traditional implant
designs (‘Control’).
COMPANY NEWS
Traditional 'J' curve design
Collateral
ligament
laxity in mid
flexion
Collateral
ligament
tension in
deep flexion
Motion pathways
demonstrating anterior
femoral translation from
extension to flexion
Modern single radius design
Recent research however has challenged
these traditional multi-radius sagittal design
concepts and Unity Knee™ has been
designed with a single radius sagittal profile
in the active flexion arc, which has proven
to be more friendly to the PFJ by minimising
paradoxical motion and maintaining a
posteriorly located COR, providing a longer
moment arm through range of motion. This
in turn maximises quadriceps efficiency,
reducing PFJ stresses in an attempt to
support patient rehabilitation and recovery.
2. Balancing the patello-femoral
mechanism: Implant positioning
Whilst implant design is a significant
contributor to PFJ balance, implant position
also plays an important role in restoring
the PFJ offset as well as patella height and
position so as to support PFJ function post
TKA. The incidence of patella baja has
been reported in 25-34% of TKA patients7
resulting from joint-line proximalisation
during surgery.
In order to facilitate PFJ balance, we
need to pay particular attention to jointline preservation both in extension and
flexion whilst performing a TKR. The Unity
Knee™ varus/valgus jig incorporates depth
of resection adjustments to compensate
for distal femoral wear in order to restore
patella height and position. In addition the
Unity Knee™ incorporates a medial and
posterior referencing sizing system which
preserves the posterior joint-line, maintaining
the posterior condylar offset, therefore a
posterior centre of rotation and longer PFJ
moment arm throughout range of motion.
Femoral size is also a significant contributor
to PFJ stresses and quadriceps function
post surgery. Oversizing can tend to overstuff
the PFJ resulting in elevated pressures whilst
undersizing reduces the PFJ offset which
results in an increased quadriceps effort. In
order to minimise this effect Unity Knee™
incorporates nine femoral sizes with 3mm
AP shift between sizes, a 7˚ angled anterior
femoral flange and 1-2mm AP adjustability
to accommodate individual patient anatomy
and fine-tune implant positioning.
Finally, both femoral valgus and rotational
position impact patella tracking. Femoral
rotation in particular influences stability
and alignment in flexion as well as PFJ and
tibiofemoral joint mechanics8. Excessive
internal or external rotation can result in
patella maltracking and tilt9 which in turn
can cause reduction in patella contact area
and elevated contact pressures10. Recent
research has highlighted that anatomic
landmarks can be unreliable in defining
femoral rotation with both intra- and interobserver variability seen in identifying
these landmarks11. In order to minimise
this effect, as well as to provide the
surgeon flexibility, in choosing both femoral
varus/valgus and rotational position to
suit individual patient anatomy, the Unity
Knee™ system has been designed with
adjustable varus/valgus and rotational
settings and incorporates an integrated
soft tissue balancer providing the surgeon
with intra-operative tools to optimise
patella tracking taking into consideration
the knee soft tissue envelope.
To summarise, restoring PFJ balance and
function plays an important role in patient
satisfaction post TKA and shouldn’t be
treated as a secondary consideration
during total knee surgery. A surgeon
should be mindful of the various factors
which can contribute to PFJ function
when choosing a TKA system. One
should ensure both the implant and
instrument platform have been designed
to provide the necessary tools so that
the surgeon can accommodate individual
patient anatomy and PFJ balance thereby
optimising its function post TKA.
References
1.Bourne et al. CORR. 2010
2.Silva et al. JOA. 2003
3.Eckhoff et al. CORR. 1996
4.Amis et al. CORR. 2010
5.D’Lima et al. CORR. 2001
6.D’Lima et al. The Knee. 2005
7.Newman et al. JBJS. 1999
8.Merican et al. Knee Surg Sport Traum Arth. 2011
9.Verlinden et al. JBJS. 2011
10.Takeuchi et al. JOA. 2005
11.Victor et al. Orthop Traumatol Surg Res. 2009
Early experience with Unity Knee™
Average two year follow-up from two
centres – Prof R Wittenberg, MD, Dr T
Paszicsnyek, MD.
Since first implantation in March 2012,
the Unity Knee™ has been implanted in
over 20 countries with more than 2500
surgeries completed to date. We report
on our early experience with this modern
knee system, designed to facilitate MCL
isometry and mid-flexion stability.
Between March 2012 and April 2013, we
implanted the Unity Knee™ in a total of
97 patients at two investigational sites.
Site 1 (Herten, Germany) used the CR
Unity knee in 51 patients, of which 12
patients underwent patella resurfacing.
Site 2 (Graz, Austria) used the PS
Unity knee in 46 patients with patella
resurfaced in all patients. The results
for the whole cohort at two years postoperative are listed below:
Table 1: Patient outcomes and survivorship for
the Unity Knee™ at 2 years postoperative
Mean AKSS Score
Mean AKSS Pain Score
Mean ROM Score
Kaplan-meier survivorship
% KM 100
survivorship
0
84.89 ± 13.78
42.53 ± 12.59
23.54 ± 2.20
100%
1
years post-operative
2
Radiographic review by an independent
reviewer found no signs of aseptic
loosening, no measurable changes
of tibial vertical migration and/or
subsidence >2mm, or progressive
radiolucent lines. On examination
all except one patient demonstrated
excellent antero-posterior and mediolateral stability in the knee.
Total knee designs with a single
sagittal radius in the active flexion
have demonstrated good to excellent
results. Our early experience with the
Unity Knee™ system demonstrates good
survivorship and patient outcomes
with no significant differences between
the CR and PS prosthesis and patella
resurfacing. As per design intent, this
implant system has demonstrated
excellent knee stability in the short-term.
The Unity Knee™ data being collected
by the UK National Joint Registry (NJR)
as part of Beyond Compliance also
supports our data, showing no revisions
in 91 implantations since the first
recorded usage (maximum implant time
2.9 years). In comparison, the combined
revision rates for all other TKAs listed
on the NJR were 0.4% at one year, 1.0%
at two years, and 1.5% at three years.
We will continue to report our research
on outcomes of the Unity Knee™ in
larger patient cohorts and for longer
time periods.
Responsible Innovation
11
COMPANY NEWS
The Conservative Hip LAB, Mülheim
acetabular
advanced
bearing
solution. The
limitations of
existing highly
cross-linked
polyethylenes
will be
discussed, along
with the introduction
of the advanced
technological innovation
of vitamin E polyethylene
(ECiMa™). With a
combination of lectures,
interactive sessions and
debates below followed by
a cadaveric session in the
afternoon. Our experienced
key opinion leader faculty
are drawn from across
the globe to help you
understand and debate these
issues and other key topics in hip
replacement surgery, to further your
practice and benefit your patients.
The next Conservative Hip LAB will take
place 4 November 2015 in Mülheim,
Germany.
Patient demographics are changing
and whilst we are seeing an ageing
population overall, those seeking surgical
interventions are often younger, more
active and more demanding than ever
before. This inevitably has an impact
on current THA practices globally, but
questions remain.
This meeting will focus on some of these
issues and the importance of conserving
bone, preserving soft tissue and restoring
biomechanics. This comprehensive
course aims to specifically provide
delegates with an in-depth understanding
of Corin’s MiniHip™ and TriFit TS™
stems, combined with
the Trinity™
Hip ca
dave
ric wo
Mulhe
rksho
im | 4
p
Nove
mber
2015
Confirmed faculty
Professor J Jerosch (course lead)
Johanna-Etienne-Krankenhaus, Neuss, Germany
Dr C Kothny
Clinic Dr Decker, Munich, Germany
Prof J Simon
University Hospital Pellenberg, Pellenberg, Belgium
Mr G Stafford
Elective Orthopaedic Centre, Surrey, England
For more information on this course
please go to http://www.coringroup.
com/corin_academy/surgeon_
meetings/meeting_calendar/
Mr D Whitwell
Nuffield Orthopaedic Centre, Oxford, England
Mr D Woodnutt
Morriston Hospital, Swansea, England
Calendar of events 2015
Venue
Dates
Annual Meeting of the South African Orthopaedic
Association (SAOA)
Champagne Sports Resort,
Drakensberg, Bloemfontein, South
Africa
31 Aug - 3 Sept
European Orthopaedic Research Society (EORS)
23rd Annual Meeting
Wills Memorial Building of Bristol
University, Bristol, UK
2 - 4 Sept
11th Bath Biomechanics Symposium
University of Bath, UK
14 Sept
BOA
(British Orthopaedic Association) Annual Congress
ACC Liverpool, Liverpool, UK
15 - 18 Sept
28th ISTA Annual Congress
Hilton Vienna, Vienna, Austria
30 Sept - 3 Oct
Bristol Hip Meeting
The Bristol City Centre Marriott, Bristol,
UK
1 - 2 Oct
ÖGU
Salzburg, Austria
1 - 3 Oct
AOA (Australian Orthopaedic Association)
Brisbane, Australia
11 - 15 Oct
Zenith Total Ankle Replacement LAB
Vesalius Clinical Training Centre, Bristol, 16 Oct
UK
DKOU 2015 (Deutscher Kongress für Orthopädie
und Unfallchirurgie)
Messe Süd, Berlin, Germany
20 - 23 Oct
Conservative Hip LAB
Meducation Centre, Mulheim, Germany
4 Nov
AAHKS 25th Annual Meeting
(American Association of Hip and Knee Surgeons)
Sheraton Dallas Hotel, Dallas, Texas,
USA
6 - 8 Nov
SIOT Congress
Ergife Palace Hotel, Rome, Italy
7 - 10 Nov
Important: Not all products are available or cleared for distribution in all international markets. For more details, please
contact your local subsidiary or distributor by visiting the Corin worldwide section.
www.coringroup.com
www.linkedin.com/company/corin-uk-ltd
[email protected]
www.youtube.com/user/coringroup/
+44 (0) 1285 659 866 http://goo.gl/lSGdqA
Zenith™
International Total Ankle
Replacement LAB – 8 May 2015
Friday 8 May 2015 saw the latest
Corin Academy Zenith™ LAB meeting
take place in Bristol. The experienced,
international faculty were joined by
delegates from all over Europe. This
one day meeting gave delegates a
chance to learn about and discuss total
ankle replacement and the Zenith™
ankle prosthesis in particular. Topics
covered during the meeting included:
■■
Patient selection and indications
for total ankle replacement
■■
Zenith™ ankle replacement
implant design and materials
■■
Zenith™ TAR surgical technique
■■
Dealing with difficult TAR cases
■■
Delegates also gained hands on
experience with the Zenith™ Total
Ankle Replacement system
The Zenith™ TAR system offers:
■■
Instrumentation for accurate and
reproducible, parallel tibia and
talar resection
■■
Titanium nitride bearing
surface significantly
reducing insert wear
■■
Innovative Biomimetic
Cementless
Technology
coating for rapid
osseointegration
The next Zenith™ International Total
Ankle Replacement LAB is due to take place on Friday 16 October, to
register your interest please email
[email protected]
New OPS™ key
features animation
https://vimeo.
com/124498131
Optimized Positioning System
(OPS™) is an innovative technology
for use in total hip replacement
procedures. Utilising pre-operative
dynamic and functional simulation
combined with a unique intraoperative positioning system,
OPS™ provides predictive
optimised component positioning.