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More than four decades have elapsed since the widespread
adoption of total hip arthroplasty for the treatment of
arthritic disorders of the hip joint. The treatment has
proved to be one of the most important surgical developments
of the 20th century, providing substantial pain
relief and improved quality of life for chronic arthritic
conditions in elderly patients. In recent years, as with
many areas of medicine, substantial research has been
undertaken in an attempt to optimise both materials and
design of hip replacement devices.
The
very early days of hip arthroplasty centred around use of
metal-on-metal bearings, developed largely in England. These
produced widely varying clinical results, due primarily to
vagaries in design and manufacturing capabilities. By the
mid-1970’s, metal-on-metal arthroplasty was all but
abandoned as Sir John Charnley’s technique for low friction
hip arthroplasty, using metal-on-polyethylene bearings,
became widely accepted. |
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The primary cause of failure of conventional
metal-on-polyethylene total hip arthroplasty is component
loosening. In many cases this loosening phenomenon is
associated with an osteolytic reaction, caused by the body’s
response to particles of polyethylene debris released from
the bearing surface. As
younger, more active patients presented with osteo-arthritic
hip conditions, the determination of how to treat this
potentially high risk group of patients became more
important. Once again, metal-on-metal hip arthroplasty came
back into consideration. |
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Cormet Hip
Resurfacing |
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Modern Hip Resurfacing was pioneered and developed by Corin, a
British company based in Cirencester, in the South-West of
England.
In the early 1990s, Corin developed a hip resurfacing device
that combines the principles of conservative arthroplasty
with metal-on-metal bearing technology – an innovation that
provides a solution for the treatment of younger patients
with osteoarthritis or rheumatoid arthritis of the hip.
In clinical use since 1991, with long-term multi-centre
results from a number of countries, Cormet Hip Resurfacing
implants are used by hundreds of surgeons around the world
and have been implanted
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in more than 16,000** patients. The Cormet Hip Resurfacing
implants are now approved by FDA for
use in the US, Cormet is the only system approved based upon
the results of a US based multi-center clinical trial. |
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Today, Corin is a leader in large diameter metal-on-metal
hip replacement and have developed the Cormet hip
resurfacing range into a system which addresses the needs of
the younger, more active patient.
Based upon the original design pioneered by Corin, Cormet
Hip Resurfacing is a conservative treatment for the younger,
more active, higher demand patient group which conserves
femoral bone, provides anatomical bone loading and
eliminates polyethylene.
Features of the Cormet system include:
- Extensive range of options, including cemented and cementless* femoral components and standard and dysplasia
cups*.
- Cormet femoral components are available in 2mm increments
from 40mm to 56mm outside diameter, and are manufactured to
exacting standards, ensuring optimum sphericity and surface
finish.
- Corin was the first to introduce Cementless* femoral
components in 1998 to give the surgeon more flexibility, by
eliminating the need to use bone cement. The femoral head
can be prepared and then an intra-operative decision can be
made between the cemented or cementless* head.
- Acetabular Cups are available in 2mm OD increments from 46mm
to 64mm* with two cup sizes for each head size, providing
surgical flexibility.
- An advanced dysplasia cup* is available for use in the
deficient acetabulum in both hip resurfacing and large
diameter total hip replacement. This unique design has the
benefits of easy introduction, improved cup positioning and
increased pullout resistance.
- Bi-coating is used on all cups and cementless* heads - a
plasma sprayed porous titanium coating overlaid with
hydroxyapatite provides excellent primary and long-term
fixation.
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Flexibility of Surgical Approach
Cormet has been developed into a comprehensive system which
allows the surgeon to decide which surgical approach and
device options he wishes to use and are appropriate for a
specific patient. Cormet instrumentation is suitable for
posterior, antero-lateral and other approaches including the
modified Ganz approach.
Clinical History
Excellent medium-term results have been published for the
Corin Resurfacing Hip system. A UK multi-centre (5 centres)
study with over 900 procedures shows a survivorship of 96.7%
in Osteoarthritic (OA) patients and 93% in patients with a
diagnosis other than OA at 9-10 years1. |
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Precision Instruments
The third generation of advanced instrumentation for Cormet
Hip Resurfacing allows smaller incision surgical approaches
to be used for Cormet Hip Resurfacing. The Cormet Precision
instruments eliminate the need for a complex, bulky head
centering jig. The vacuum introducer is a unique, patented
technology - standard theatre suction is used to attach the
cup to the introducer for implantation of the acetabular cup
component.The patented Precision head centring device
eliminates the need for a lateral pin and allows a |
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smaller incision to be used in both standard and
smaller incision approaches. The
instruments are simple to use, reducing operating time and
allowing more accurate, reproducible placement of the
femoral resurfacing component. |
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Wear Properties
Exacting production techniques developed during 17 years of
uninterrupted experience of manufacturing hip resurfacing
devices mean that the high carbon cobalt chrome Cormet
bearing surfaces are optimised to minimise wear. Optimal
sphericity, surface roughness and diametrical separation of
the components result in enhanced lubrication of the
bearing, which reduces wear, as well as providing effective
function and longevity.
Latest evidence2suggests that double heat treated components
(such as Cormet) provide superior wear properties in
challenging wear conditions when compared with as cast
components. |
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Optimom* Large Diameter
Metal-on-Metal Total Hip Replacement System |
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Corin has developed Optimom*, a metal-on-metal stemmed large
diameter total hip replacement, for patients in whom the
condition of the femoral head or neck does not allow
resurfacing. Optimom* combines the benefits of large
diameter metal-on-metal resurfacing arthroplasty with those
of a stemmed femoral prosthesis that does not depend on the
bone quality of the femoral neck.
Optimom* represents a significant advance in hip replacement
for the more active patient, as well as possibly providing
improved stability for revision and DDH patients at risk of
dislocation. Modular Optimom heads
may be used with any Corin approved stem, |
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providing a large diameter total hip replacement system with
all the advantages of a metal-on-metal bearing surface and a
large diameter articulation. |
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Stem Options
Optimom* is available with a range of Corin and approved
other hip stems for optimum flexibility and implant choice.
Improved Stability
The modular Optimom* system uses proven Cormet bearing
technology, providing a long-lasting device which is highly
stable. Large diameter heads are more resistant to
dislocation than small diameter heads. Between 3% and 6% of
conventional THR operations result in early post-operative
dislocation3. Reported dislocations of large diameter heads
are extremely rare.
Increased Range of Motion
Compared to conventional total hip replacement, the Optimom*
large diameter total hip replacement allows a greater range
of motion, permitting patients to return to high activity
levels. |
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References
1. R Spencer, M Bishay, S Krikler, U Prakash, P Foguet, D
Griffin, D Pring, M Norton & R Nelson 10 YEAR MULTI-CENTRE
EVALUATION OF THE CORMET HIP RESURFACING ARTHROPLASTY.
BRITISH HIP SOCIETY(BHS) Scientific Meeting, Leeds, UK, 2007
2. A Angadji, M Royle, S Collins, J Shelton “A Hip Simulator
Study on the Effect of Cup Inclinication on the Wear of ‘As
Cast’ and ‘Double Heat-Treated’ Metal-on-Metal Hip
Replacement”. ORS Meeting, March 2008, San Francisco
3. Burroughs BR, Hallstrom B, Golloday GJ, Hoeffel D, Harris
WH “Range of motion and stability in total hip arthroplasty
with 28-, 32-, 38-, and 44-mm femoral head sizes” j
Arthroplasty. 2005 Jan;20(1):11-9.
* Not cleared or approved for use
in the USA
** Internal document on file at Corin Group PLC, UK |
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