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Friday, April 10. 2009
Patients and prospective patients are always concerned about
the complications that could occur after a hip resurfacing surgery. The typical
problems include femur neck fractures, dislocations, loose acetabular cups,
improperly positioned acetabular cups, high metal ions, infections,
pseudotumors, ALVAL and metalosis.
There has been a lot of discussion among patients on
discussion groups about the high metal ion issue and pseudotumors. I am
not a doctor or medically trained. I am a Patient Advocate, Hip
Resurfacing Patient and Mechanical Engineer. I had the opportunity to
attend the Second Annual U.S. Comprehensive Course on Total Hip
Resurfacing Arthroplasty October 24–25, 2008 Los Angeles, CA. I listened
to discussions about the metal ion issues and pseudotumors. I am going to
explain what I learned in simple, non-medical terms since that is all I can
do.
As an observer, I learned that the high metal ion issue has
occurred in a small number of cases as a post op problem after a hip resurfacing.
One of the most likely reasons, according to the experienced surgeons and
presenters at the course, was the incorrect placement of the acetabular cup
which resulted in additional wear on the bearing surface between the acetabular
cup and the femur cap component. The hip resurfacing device is really a
metal bearing made of High Carbon Cobalt-Chromium alloys.
A bearing is designed to equally spread out the load over the load bearing
components. If the components are not aligned properly, then only part of
the bearing is loaded resulting in much more wear in that area possibly causing a high
metal ion level. It was also
explained that women seem to have more problems with high metal ions than men.
Perhaps, this is due to the fact that most women use smaller sized hip
resurfacing devices which causes more loading on the bearing surfaces than the
men's larger sized devices.
When there is an abnormally high metal ion release from
misplaced components, it seems to
cause the surrounding tissue and bone to react adversely. The surrounding
tissue and bone tends to become abnormal. Some doctors call the
tissue reaction pseudotumors, AVAL (aseptic lymphocyte dominated vasculitis associated
lesion), & others call it metalosis. Whatever name given to the
abnormal reaction, it is not good to have this happening around the hip device
since it could become loose, pain could result and possibly more severe
medical reactions could happen.
There is concern among the hip resurfacing community about
the reactions to the very high metal ion issue. At this time, to my
understanding, there is not a standardized blood test available. Different
labs use different methods and tests. There are not yet any specific
guidelines as to what levels are too high for metal ions. There is a lot
of research being done, but there are no standards yet.
This makes a surgeon's job to define and solve problems due
to high metal ions difficult. Some doctors feel that
patients with very high metal ions should have a revision of their hip
resurfacing to a ceramic on ceramic THR. They don't want to take chances
that even more serious problems could develop due to the high metal ions.
Normally, from what I understand, the high metal ions are probably due either to the
incorrect position of the acetabular cup causing very high wear on the hip
resurfacing bearing device or due to the use of a small hip resurfacing device
causing excessive loading on the bearing surfaces. So once again, the learning
curve and experience of hip resurfacing surgeons is very important to
prospective patients along with proper patient selection. It takes a great deal of experience to consistently
place the acetabular cups at the proper angle and to know which smaller patients
can successfully receive a hip resurfacing.
That is my layman's explanation of the high metal ion issue.
I am posting a number of abstracts below by surgeons attending the Second Annual
U.S. Comprehensive Course on Total Hip Resurfacing Arthroplasty October 24–25,
2008 Los Angeles, CA. Their articles will help explain more about the high metal
ion issue, the small device issue used in many women and the acetabular cup
placement issue.
Read More by Clicking Here
Friday, April 10. 2009
"The results also confirm clinical ion level measurements that steep cup angles can substantially increases wear"
Presented at the 2nd Annual Total Hip Resurfacing
Arthroplasty Course in LA Oct. 2008
By: John Fisher
Co-Authors: Ian Leslie, Sophie Williams, Eileen Ingham, Graham
Isaac
Institute of Medical and Biological Engineering
University of Leeds
Background: There are considerable variations in metal ion
levels and metallic wear rates in patients with metal on metal resurfacing. In this in
vitro study the effect of design variables of head diameter and bearing clearance and
patient variables of cup and head position on metal ion levels and wear rates are were
investigated. Methods: Hip joint simulator studies were carried out on size
39mm and size 55mm metal on metal resurfacing with the same design. Size 55mm
diameter bearings with 110 micrometer diametrical clearance were compared to size 54mm
diameter with larger >250 micrometer diametrical clearance. The wear rates of
size 39mm bearings with a standard cup position of 45 degrees, were compared to a
steep cup position of 60 degrees and to a steep cup position combined with micro
separation associated with head offset deficiency.
Results: Initial bedding in wear rates and ion levels were
higher with size 39mm bearings compared to size 55mm, but in long term after 15
million cycles there was no difference in the steady state wear rates. Bearings with the
larger diametrical clearance had higher initial wear and steady state wear rates at
five million cycles. Cup position and head position resulted in much greater
increases in wear. For the 39 mm bearings, a 60 degree cup position resulted in a 9 fold
increase in wear. A steep cup and microseparation resulted in a 17 fold increase in wear
after two million cycles and a 39 fold increase in wear compared to the long term steady
state wear rate.
Conclusions: The study confirmed clinical ion level studies of
increased wear with larger clearance bearings. The results also confirm clinical ion
level measurements that steep cup angles can substantially increases wear. The
study also indicates that offset deficiency and microseparation may be responsible for
extremely high wear rates and ion levels found in some retrievals and some patients.
Further work is needed to investigate effect of different head sizes with steep
cups and microseparation and the effect of version.
Friday, April 10. 2009
"The results also confirm clinical ion level measurements that steep cup angles can substantially increases wear"
Presented at the 2nd Annual Total Hip Resurfacing
Arthroplasty Course in LA Oct. 2008
By: John Fisher
Co-Authors: Ian Leslie, Sophie Williams, Eileen Ingham, Graham
Isaac
Institute of Medical and Biological Engineering
University of Leeds
Background: There are considerable variations in metal ion
levels and metallic wear rates in patients with metal on metal resurfacing. In this in
vitro study the effect of design variables of head diameter and bearing clearance and
patient variables of cup and head position on metal ion levels and wear rates are were
investigated. Methods: Hip joint simulator studies were carried out on size
39mm and size 55mm metal on metal resurfacing with the same design. Size 55mm
diameter bearings with 110 micrometer diametrical clearance were compared to size 54mm
diameter with larger >250 micrometer diametrical clearance. The wear rates of
size 39mm bearings with a standard cup position of 45 degrees, were compared to a
steep cup position of 60 degrees and to a steep cup position combined with micro
separation associated with head offset deficiency.
Results: Initial bedding in wear rates and ion levels were
higher with size 39mm bearings compared to size 55mm, but in long term after 15
million cycles there was no difference in the steady state wear rates. Bearings with the
larger diametrical clearance had higher initial wear and steady state wear rates at
five million cycles. Cup position and head position resulted in much greater
increases in wear. For the 39 mm bearings, a 60 degree cup position resulted in a 9 fold
increase in wear. A steep cup and microseparation resulted in a 17 fold increase in wear
after two million cycles and a 39 fold increase in wear compared to the long term steady
state wear rate.
Conclusions: The study confirmed clinical ion level studies of
increased wear with larger clearance bearings. The results also confirm clinical ion
level measurements that steep cup angles can substantially increases wear. The
study also indicates that offset deficiency and microseparation may be responsible for
extremely high wear rates and ion levels found in some retrievals and some patients.
Further work is needed to investigate effect of different head sizes with steep
cups and microseparation and the effect of version.
Friday, April 10. 2009
Outcome of hip resurfacing may be dependent on experience
Link
http://www.orthosupersite.com/view.asp?rID=37423
By Gina Brockenbrough
February 27, 2009
LAS VEGAS — A new study links outcomes of hip resurfacing to the hospital volume
of resurfacing cases and, thereby, the surgeon’s experience.
To evaluate the impact of operative volume on hip resurfacing outcomes, Andrew
J. Shimmin, MBBS, FAOrthA, and colleagues used the Australian Joint Registry to
identify nearly 9,000 hip resurfacings performed at 196 hospitals between
September 1999 and December 2006...
..They found that 74% of hospitals performed fewer than 30 procedures during the
7-year study period, while 64% of hip resurfacings were performed at 16
"high-volume" hospitals, or those that performed more than 100 cases. Overall,
the researchers found that 3.1% of resurfacings were revised...
...They then compared the cumulative rate of revision at 4 years among the
hospital groups. At 4 years, the investigators discovered a 6% revision rate for
centers performing fewer than 25 cases, a 5.6% rate for those performing 25-49
cases, a 4.7% rate for hospitals doing 50-99 cases, and a 2.7% revision rate for
those performing more than 100 cases.
After adjusting for patient age and gender, the investigators discovered that
the risk for revision was 66% greater in hospitals performing the least amount
of cases.
"In this study, hospital volume is primarily a reflection of the operative
experience of the individual surgeons," Shimmin said at the American Academy of
Orthopaedic Surgeons 76th Annual Meeting, here.
"The outcome of hip resurfacing is strongly dependent on the experience of the
surgeon and hospital performing the procedure. Even when adjusted for patients’
age and sex, the risk of revision at low-volume centers was 66% greater than at
a higher volume center. This supports the need for increased training of
surgeons before undertaking hip resurfacing," he said.
Reference:
Shimmin AJ. The effect of operative volume on the outcome of hip resurfacing.
Paper #316. Presented at the American Academy of Orthopaedic Surgeons 76th
Annual Meeting. Feb. 25-28, 2009. Las Vegas.
Friday, April 10. 2009
I am a 55 year old male. I have been active all my life in various sports
which ultimately led to my hip cartilage damage. I had my right hip
resurfaced using the anterior approach November 2007 by Dr. Stefan Kreuzer,
a Birmingham hip. In Feb of this year, Dr Kruezer resurfaced my left hip
with a Cormet.
I am almost two months into the recovery and I am almost back to full
strength. There is still some numbness around the incision area, but I know
from experience that will improve over time.
Dr. Kruezer is clearly constantly learning and improving as my second
recovery is a few weeks ahead of my first.
My hospital stay was two days, I was walking the day of the surgery. I went
home and used the walker for three days and never needed a cane. A week
after my resurfacing, I was walking completely unassisted and even resumed
normal activities like shopping, etc. Road biking is my passion, after one
month I was training on a stationary bike; at five weeks I was back to
riding my road bike albeit carefully; last weekend at eight weeks, I rode 80
miles in just over 4 hours.
I would strongly advise anyone considering hip resurfacing to find out if
they are suitable for the anterior approach.
Nigel Church
Friday, April 10. 2009
Computer-Assisted Vs Conventional Mechanical Jig Technique in Hip Resurfacing Arthroplasty
Link
http://www.arthroplastyjournal.org/article/PIIS0883540307007292/abstract?rss=yes
Volume 24, Issue 3, Pages 341-350 (April 2009)
Jose Rafael E. Resubal, MD, FPOA, David A.F. Morgan,
B.Sc(Med), FRACS, FAOA
Received 16 June 2007; accepted 17 December 2007.
published online 15 February 2008.
Abstract
To compare the effectiveness of computer-assisted
surgery (CAS) and mechanical jig technique in hip
resurfacing arthroplasty, we reviewed 176 hip
resurfacing arthroplasty performed in 158 patients. The
initial 131 hips were resurfaced using the conventional
mechanical jig technique, and the remaining 45 hips with
the CAS technique. The demographic data of the patients
were similar for both techniques. Follow-up radiographs
taken 2 months after the surgery showed patients in the
CAS technique having a significantly better alignment of
the femoral component on the frontal and sagittal
planes. There was no difference in the risk of implant
notching on the femoral neck for both techniques. The
implant sizes were similar for both techniques; thus,
the amount of bone stock preserved was not technique
specific. Reprint requests: Jose Rafael
E. Resubal, MD, FPOA, Suite 1, Level 8, Arnold Janssen
Centre, Brisbane Private Hospital, 259 Wickham Terrace,
Brisbane, Queensland 4000, Australia.
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