HIP REPLACEMENT AND RESURFACING:
CURRENT CONSIDERATIONS REGARDING METAL-ON-METAL
ARTHROPLASTY
Michelle L. McIsaac, Robert C. Lee, Tom Noseworthy
Centre for Health and Policy Studies, University of Calgary
May 4, 2007
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This pre-assessment document is based on a limited synthesis of existing reviews,
evaluations and health technology assessments. This document is meant to be an
overview of the topic and does not represent an exhaustive or systematic review.
FOREWORD
Acknowledgements:
Production of this report has been made possible by a financial contribution from
Health and Wellness and under the auspices of the Alberta Health Technologies Decision
Process initiative: the Alberta model for health technology assessment and policy
analysis. The views expressed herein do not necessarily represent the official policy of
Alberta Health and Wellness.
We thank Anita Blackstaffe (University of Calgary) for her contributions to the
analysis of the data provided by Alberta Health and Wellness.
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LIST OF ABBREVIATIONS
THR
CoC
DJD
MoM
M-MHR
OA
RA
RCT
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Total hip replacement
Ceramic-on-ceramic
Degenerative joint disease
Metal-on-metal
Metal-on-metal hip resurfacing
Osteoarthritis
Rheumatoid arthritis
Randomized controlled trial
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ABSTRACT
This Review summarizes the findings of seven recent health technology reviews on
metal-on-metal hip resurfacing (M-MHR). Specifically, this Review assesses findings
pertaining to:
•
•
•
•
•
Appropriate clinical indications for M-MHR
Safety
Efficacy/effectiveness
Patient outcomes
Cost/cost-effectiveness
Overall, the seven reviews found the evidence on the subject to be lacking in both
quantity and quality; only one randomized controlled trial was reviewed. M-MHR is
generally deemed suitable for young (<65 years), active, and otherwise healthy patients.
Nonetheless, due to the lack of comparative evidence, the appropriate clinical indications
for M-MHR are currently not known. M-MHR is generally regarded as having similar
risks to patients as total hip replacements (THRs), although any procedure using metalon-metal (MoM) may cause metal ion release. However, there is insufficient evidence
regarding health outcomes (i.e. carcinogenicity and cardiotoxicity) related to metal ion
release in the body. Most reviews conclude that further investigation on effectiveness
(relative to other approaches) and long-term effectiveness need to be completed before
conclusive evidence of M-MHR effectiveness can be drawn. Nonetheless, observational
studies suggest improved patient outcomes (reduced pain, quicker recovery, etc.)
associated with M-MHR; therefore it is thought to be a promising alternative to THR. MMHR has higher upfront costs than currently used standards of care. Downstream costs
of this treatment are uncertain and contingent on long-term revision rates. Based on this
limited review of the cited works, M-MHR would not be a preferred form of arthroplasty
in the majority of patients. By the same token, this approach appears to have sufficient
merit for a selective group of patients and therefore should not be completely dismissed.
In summary, long-term controlled and observational studies need to be performed in
order to appropriately address the merit and appropriateness of M-MHR.
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1. INTRODUCTION
Degenerative joint disease (DJD) causes pain and reduces function. Implantation of a
prosthetic joint is a common surgical intervention intended to alleviate symptoms of DJD
when other interventions (physiotherapy, drug-based treatments, etc.) are not successful.
Total hip replacement (THR) has been the primary and preferred surgical approach for
these patients. Since the inception of THR approximately 30 years ago 1, an important
limitation has become apparent; the need for revision surgery. Revisions are required
when the prosthesis deteriorates due to wear and tear. Revisions are most notably a
concern for younger, more active patients who are likely to ‘outlive’ a THR prosthesis.
Metal-on-metal hip resurfacing (M-MHR) has been presented as an alternative to THR
for younger, more active patients due to purportedly lower revision rates and superior
patient outcomes. At present, many orthopedic surgeons in Canada and internationally
are offering this alternative to patients. The goal of this summary is to review current
considerations regarding M-MHR using relevant literature reviews (health technology
assessments and systematic reviews).
2. BACKGROUND
Degenerative joint disease (DJD) is the degeneration of cartilage and bone in a joint.
This results in chronic pain and stiffness 2. The main underlying causes of DJD are
osteoarthritis (OA), and to a lesser extent rheumatoid arthritis (RA) and trauma.
International data suggest that the prevalence of OA and RA are approximately 1-2% and
0.5%, respectively and that OA and RA account for 75% and 6% of DJD cases 3.
2.1 Epidemiology
In Alberta, over 300,000 individuals are likely affected by OA and RA 2. The exact
prevalence of DJD is unknown. In 2006, there were approximately 3,100 patients and
3,200 procedures relating to hip disease in Alberta (see Table A1 for a description of the
health service codes included), this has increased almost 60% since 1997 (Figure A2).
There is variation regarding the utilization of these services across health regions in the
Province. Capital Health Region and the Calgary Health Region perform substantially
more hip procedures than other health regions in the Province. In 2006, Capital Health
performed 40% and the Calgary Health Region performed 33% of all hip procedures in
Alberta (Figure A3).
In 2006, more females in Alberta underwent hip procedures than males (Figure A4), and
older patients were more likely to be receiving these services than younger individuals.
Individuals aged 65 and older represented 66% of patients receiving these services
(Figure A5); nonetheless, there were over 1,000 patients under the age of 65 who are
receiving hip procedures. In 2006, THR represented 74% of hip procedures in Alberta,
hemiarthroplasty (partial arthroplasty; i.e. replacement of only the femoral head with a
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prosthesis) was the second most common procedure representing 24% of hip services
(Figure A6).
2.2 Treatment
2.2.1 Watchful waiting
Watchful waiting with non-surgical management is considered a treatment option for
patients with DJD. It involves patient monitoring, anti-inflammatory drugs, medication
for pain, and supportive activities such as physiotherapy. Watchful waiting is more
common in younger patients, as THR in such patients is often postponed due to higher
revision rates associated with longer life expectancy 4.
2.2.2 Total hip replacement (THR)
A THR removes the entire femoral head and neck; these are replaced with a ball and stem
that fits inside the femur. There are various THR prostheses available, including a
polyethylene liner with a metal ball, metal-on-metal (MoM) THR, and ceramic-onceramic (CoC) THR.
Outcomes of THR are generally considered to be good in terms of reducing pain,
improving functional status and health-related quality of life, and having high survival
rates. Nonetheless, THR revisions are common in younger patients due to the longer-life
expectancy and higher activity level of these patients. Swedish data reports revision rates
of 26.5% and 29.2% (at 13 years) for males and females younger than 50 years of age,
compared to revision rates of 4.3%-12% and for patients older than 60 years of age 5.
2.2.3 Metal on metal hip resurfacing (M-MHR)
M-MHR involves removing and replacing the surface of the femoral head with a metal
hollow cap that fits into a metal acetabular (hip socket) cup 6. The metal-on-metal
bearings currently use high carbon-cobalt-chromium alloy. Other types of hip
resurfacing include metal-on-polyethylene, and CoC bearings. Table A7 contains a list of
various types of M-MHR devices, and Table A8 reports the six devices approved for use
in Canada (as of 2005) 7.
A purported benefit of M-MHR compared to THR is a more ‘natural’ loading of the joint;
presumably increasing tolerance for strenuous exercise, and reducing the chance of
dislocation. Additionally, because more bone is preserved in M-MHR, there appear to be
more options if a revision is required 2.
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2.3 Clinical indications
There is no consensus on the appropriate clinical indications for M-MHR 6. The target
group to date has been younger, more active patients. This younger, more active group
has higher rates of revision surgery for THR than older patients, due to their longer lifeexpectancy and potential of a more active lifestyle. The M-MHR technique removes less
bone from the femur than THR, so revision surgery is purportedly less complex. Studies
to date on M-MHR generally select younger (<65 years of age, occasionally <55 years of
age) active patients with DJD (often limited to OA or RA) who also meet the criteria for a
THR 2. However, limiting the patient group to this category is not substantiated by
available evidence, potentially causing bias. This may also be impeding conclusions
about appropriate clinical indications; as such selectivity does not facilitate large sample
sizes or valid comparisons among patient groups (e.g. comparing various patient groups
who receive M-MHR with those who receive THR).
Osteopenic disorders, Gaucher’s disease, deformity of the head of the femur or the
acetabulum, and destructive arthritis have been considered contraindications for M-MHR
2
. Overall, clinical indications and contraindications have not been thoroughly studied.
Definitive conclusions cannot be drawn regarding the appropriate clinical indications,
groups that are expected to yield the most significant clinical benefit, and the proportion
of patients that could benefit from M-MHR.
3. EVIDENCE OF SAFETY AND EFFICACY
3.1 Methods of literature review
Seven high-quality reviews were examined for this summary (see table A9 in the
appendix). Most of these studies included a systematic review of the literature, with the
most recent systematic review current as of October 2005 5.
3.2 Safety
Overall, M-MHR is expected to result in similar risks to the patient as THR, including
blood loss, infection, deep venous thrombosis, nerve injury, hip dislocation, and very
rarely pulmonary embolism 2. A notable safety concern relates to metal wear debris.
There are several reports of elevated cobalt and chromium concentrations in serum and/or
urine of patients who have received metal hip implants (although comparators in these
studies were not cited) 5. The potential serious toxicological effects of elevated metal
ions in the body relate to carcinogenicity and cobalt cardiotoxicity. However, there is
inadequate evidence of a link between increased levels of cobalt and chromium
associated with hip prostheses and adverse health outcomes 5. Additional high-quality,
long-term studies are needed to provide a more conclusive understanding of the safety of
MoM THR and M-MHR.
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3.3 Efficacy/effectiveness
The main efficacy measures reported in the literature have been survival rates and
revision rates post-M-MHR. Although procedure-related deaths were not reported, high
survival rates were reported; 94-98% for short follow-up periods (2.8-3.5 years) 5.
Revision rates of the M-MHR prostheses currently used in Canada are expected to range
from 0.3-3.6% for a short follow-up period (2.8-3.5 years) 5. The seven reviews captured
several observational studies and one relevant randomized controlled trial (RCT). Most
observational data suggests a clinical benefit associated with M-MHR, however RCTs are
important in order to demonstrate the relative effectiveness and any additional clinical
benefit that M-MHR might have over current standards of care. Vendittoli et al. (2006) 8
evaluated the outcomes of M-MHR (Durom system) versus MoM THR (Zimmer system)
in a RCT with over 200 patients. Although this study represents the highest level of
evidence reviewed, the comparator of the MoM THR is not standard in Alberta. The
study found that M-MHR had longer surgical times (average of 16 minutes longer) and
shorter hospital stays (approximately 1 day shorter) than MoM THR. Follow-up was too
short to capture any significantly different revision or survival rates; although the MMHR system had slightly higher rates of revision (1.9% compare to 1% for MoM THR).
No long-term randomized studies have been completed, making conclusions regarding
the long-term relative effectiveness of M-MHR difficult.
3.4 Patient Outcomes
The main patient outcomes reported in the literature have been pain scores and functional
status. Specifically, Harris hip scores (measures pain, walking function, range of motion
etc.) and SF-12 (measure physical and mental health) are the most commonly reported
health outcomes measures 5. Studies show improvement in these scores and statistically
significant improvement was demonstrated in four studies (1 Harris hip, 2 SF-12, and 1
UCLA hip score (measures pain and function)). Further, there is an expected
improvement in the range of motion (flexion, rotation, etc.) following M-MHR 5.
Observational studies also suggest that there may be quicker recovery associated with MMHR, therefore patients can return to normal daily activities (including work) sooner 2.
A RCT comparing M-MHR to MoM THR 8 found that at a follow-up of one-year patients
had fairly similar outcomes; with the M-MHR group doing slightly better and returning to
daily activities more quickly 8. Overall, M-MHR appeared to yield better patient
outcomes than current standards of care in younger patients.
3.5 Summary of review findings
In general, the reviews evaluated for this Report did not find the available evidence on
M-MHR to be of high quality. Most data collected addressing M-MHR was
observational and came from purposely selected younger, healthier, more active patients.
Further, no long-term data on effectiveness or safety was available. Due to the lack of
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long-term comparative evidence, conclusions can not be drawn on the value of M-MHR,
as compared to THR or other standards of care.
The conclusion of most national and international reviews is that further controlled
studies with long-term follow up periods should be completed before definitive
recommendations can be made 5. Nonetheless, NICE recommends M-MHR “as one
option for people with advanced hip disease who would otherwise receive and are likely
to outlive a conventional primary total hip replacement,” and that data be collected via a
national registry on the clinical and cost-effectiveness of the technology 3.
4. COST
M-MHR is generally expected to have a higher up-front cost than THR 7. In Ontario, the
estimated prosthesis cost for M-MHR ranges from $4,300 to $6,000 a, and THR protheses
cost approximately $2000 5. Two RCTs of M-MHR versus THR (one remains
unpublished) indicate that M-MHR has a longer surgical time than THR 7. In Alberta,
non-randomized data from the Alberta Hip Improvement Project show that there is no
statistically significant difference in surgical time between M-MHR and THR 9. Both
randomized and non-randomized evidence demonstrate shorter in-patient length of stay
post-surgery for M-MHR compared to THR. The Alberta Hip Improvement Project
calculated the up-front costs of M-MHR, ceramic-on-ceramic (CoC) THR, and other
THR. This demonstrated equivalent surgical times, shorter length of say for M-MHR,
and higher device cost of M-MHR. They calculated the up-front costs of M-MHR, CoC
THR, and other THR to be $11,661, $10,929, and $11,226, respectively. An Ontario
economic analysis (using Ontario costing data) estimated the total up-front cost for hip
resurfacing to be approximately $15,000 5. Although up-front costs are likely the major
cost driver, other costs such as the cost of clinical training and costs incurred outside of
the hospital are important to consider when making cost comparisons. Further,
downstream costs should be considered, but due to the lack of long-term follow up data
any potential downstream costs or savings are speculative.
4.1 Budget Impact
Alberta Health and Wellness paid over $3 million dollars for hip services in 2006, which
has doubled in the last decade (Figure A10). About 64% of this was for services rendered
to patients 65 years and older. Although there is some indication that M-MHR is
currently being performed to some extent in Alberta, there was no information available
to the team on the extent of this practice, how it is being billed, or the proportional costs
to Alberta Health and Wellness and the Health Regions performing M-MHR.
a
Costs are in 2005/2006 Canadian dollars. Inflation was calculated using the Bank of Canada inflations
calculator (http://www.bankofcanada.ca/en/rates/inflation_calc.html) and currency converter
(http://www.bankofcanada.ca/en/rates/exchform.html).
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An analysis in Ontario assessing a M-MHR policy for individuals needing a THR who
are under the age of 55 showed that the net budget impact over a 5-year period is
expected to range from $500,000 to $4.7 million 5. Nonetheless, without better data on
effectiveness and the target population, it is difficult to develop a reliable estimate of
budgetary impact 4.
4.2 Cost-Utility
There is wide variation in cost-utility assessments of M-MHR. The Alberta Hip
Improvement project estimated the cost-utility of M-MHR of $4,827 per quality-adjusted
life year (although the comparator was unclear, thus suggesting that this is not referring to
the incremental cost-utility) 9. A cost-utility analysis from the UK compared M-MHR to
THR and watchful waiting followed by THR in both the younger, more active population
and the older, more active population. The analysis found that THR proved to be a better
procedure (yielded better health outcomes and was less costly) than M-MHR for both
younger and older active patients. However, M-MHR was likely to yield better health
outcomes and be slightly more expensive than watchful waiting followed by THR for
younger, more active patients (approximately $20 to $2000 per quality-adjusted life year,
with longer time horizons becoming more cost-effective and potentially cost saving) 4.
Uncertainty in outcomes, especially long-term outcomes, means that estimates of costeffectiveness are based on assumptions and not on reliable evidence. Cost-utility
analyses to date have shown that the estimated revision rate accounts for a large degree of
variation in the study results 3, therefore better long-term data of effectiveness are
required in order to reliably assess the long-term cost-utility of M-MHR.
5. CONCLUSION
THR is a commonly used surgical intervention to treat degenerative hip disease. The
employment of M-MHR could potentially reduce the rates of revision and improve
patient outcomes for younger more active patients. Nonetheless at this point in time,
there is no compelling evidence that M-MHR will greatly reduce revisions and improve
patient outcomes in the long-term; therefore, the actual clinical benefit of these prostheses
remains unknown.
The body of literature on M-MHR is limited in both quality and scope. Long-term safety
(especially with regards to metal ion release) and efficacy data are not available beyond 4
years. The selective inclusion of patients and small sample size of these studies do not
allow for comparisons among patients subgroups, therefore restricting any inference
about the groups of patients who are the most likely to benefit from M-MHR, and what
the appropriate clinical indications for M-MHR should be. No reductions in short-term
mortality, other adverse events, or costs have been unequivocally demonstrated. The
primary potential benefits of M-MHR lie in the expected short-term improvement in
patient outcomes and the expectation that M-MHR could cost less in the long-term.
Based on the current evidence many concerns remain unanswered and the outcomes of
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widespread adoption of M-MHR are uncertain. It is clear that M-MHR should not be
considered a preferred treatment for all patients; however M-MHR could be beneficial
(and indeed cost less) for certain patient groups. Appropriate patient groups and/or
clinical indications for M-MHR remains unclear; suggesting that un-biased, comparative
studies (likely RCTs) should be undertaken, with due regard to appropriate clinical
indications/candidates, incremental effectiveness, and long-term follow-up. Further, an
economic analysis is necessary to fully assess the opportunity cost of M-MHR.
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APPENDIX
Table A1: Description of the Health Services Codes Included for Hip Disease
Procedures in Alberta
Health Service
Description
Code
92.8 B
Arthroscopy (Arthroscopy, hip-diagnostic)
92.8 C
Arthroscopy (Arthroscopy, hip, therapeutic intervention, including
debridement/drilling, etc.)
93.21
Arthrodesis of hip
93.59A
Other total hip replacement (Total hip arthroplasty)
Other arthroplasty of hip (Resection arthroplasty of hip)
93.6 A
93.6 B
Other repair of hip (Surgical hip dislocation with trochanteric flip,
osteochondroplasty +/- labral repair)
93.69A
Other repair of hip (Congenital dislocation of hip with acetabuloplasty or iliac
osteotomy, or shelf)
93.69B
Other repair of hip (Hemiarthroplasty hip with uncemented prosthesis)
93.69C
Other repair of hip (Hemiarthroplasty hip with cemented prosthesis)
93.99PC
Total hip arthroplasty, physician first assistant
93.99PD
Total hip arthroplasty, nurse first assistant
Source: Alberta Health and Wellness, 2007 10
Number of Procedure Services
Figure A2: Trend of Number of Hip Disease Procedures in Alberta: 1997-2006
4000
3500
3000
2500
2000
1500
1000
500
0
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year
Source: Alberta Health and Wellness, 2007 10
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1,400
1,200
1,000
800
600
400
200
Northern
Lights
Peace
Country
Aspen
Capital
East
Central
David
Thompson
Calgary
Palliser
0
Chinook
Number of Procedure Services
Figure A3: Total Hip Disease Procedures in Alberta by Health Region: 2006
Health Region
Source: Alberta Health and Wellness, 2007 10
Figure A4: Total Hip Disease Procedures in Alberta by Gender: 2006
Female,
59.3%
Male,
40.7%
Source: Alberta Health and Wellness, 2007 10
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Figure A5: Total Hip Disease Procedures in Alberta by Age Group: 2006
0 to 25,
0.6%
26 to 50,
7.2%
65 & Older,
66.1%
51 to 64,
26.1%
Source: Alberta Health and Wellness, 2007 10
Figure A6: Total Hip Disease Procedures in Alberta by Procedure Type: 2006
Total hip
arthoplasty,
74.4%
Hemiarthoplasty,
23.7%
Other, 1.1%
Arthoscopy,
0.8%
Source: Alberta Health and Wellness, 2007 10
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Table A7: Types of Metal-on-Metal Hip Resurfacing
Device Name
Manufacturer
Conserve Plus
Wright Medical Technology
Birmingham Hip Resurfacing (BHR)
Smith & Nephew (formerly Midland)
Cormet
Corin Medical, Ltd.
Durom (Bonesave in the UK)
Zimmer
Articular Surface Replacement (ASR)
Depuy (a division of Johnson and Johnson)
ReCap Femoral Resurfacing System
Biomet
ADEPT
Finsbury Orthopedics, Ltd
N/A
ICON
N/A
Nemoto Shokai (Japan) and Tornier (France)
Source: www.activejoints.com 11
Table A8: Devices approved for use in Canada by Health Canada (as of 2005)
Device Name
Approval Date
Birmingham Hip Resurfacing
2002
Conserve Plus
2004
ReCap Femoral Resurfacing System
2004
Durom Hip Resurfacing
2003 (special access approval)
Cormet 2000
2004 (special access approval)
Articular Surface Replacement
2004 (special access approval)
Source :CCOHTA, 2005 7
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Table A9: Main Findings of Reviews
Review source
(date)
Type of review
Alberta Bone and
Joint Health
9
Institute, (2006)
Technote/ primary
research
Safety
Efficacy/Effectiveness
- consequence of
metal ion release
unclear
- 3 month follow-up no
significant difference in
effectiveness of M-MHR
vs. THR
- revision rates of MMHR vs. THR uncertain
Medical Advisory
Secretariat, Ontario
Ministry of Health
& Long-term Care,
5
(2006)
HTA
- insufficient
evidence regarding
risk of cancer and
cobalt cardiotoxicity
- femoral neck
fracture not common
(0.4%-2.2% in shortrun)
Wyness, L. et al.
(2004) 12
Systematic Review
- N/A
Alberta Heritage
Foundation for
Medical Research
2
(2002)
Technote
- risk of complication
comparable to THR
- some concern of
metal toxicity and
increased risk of
cancer
- N/A
- improvements in health
outcomes from baseline
- high survival
- case-series evidence
shows M-MHR to be
effective in younger
patients (in short-run)
- revision rates 0.3%-3.6%
at 2.8-3.5 years
- sparse effectiveness data
- relative effectiveness
uncertain
- only short-term data
available
- no firm conclusions can
be made
- no controlled
comparative studies
- inadequate follow-up
Vale, L. et al.
4
(2002)
Systematic Review/
HTA
National Institute for
Clinical Excellence,
3
(2002)
Technology
Appraisal Guidance
National Horizon
Scanning Centre,
6
(2000)
Horizon scanning
review
5/4/2007
- limited data on
dislocation rates but
expected to be
minimal (0.05%)
- few complications
reported by literature
- N/A
Costs
- long-term cost-effectiveness
unknown
-2004/05 CoC THR most
cost-effective for patients <56
years in year 1
- M-MHR total implant cost
$11,661
- 5 year net budget impact
$500,000 - $4.7 million
- M-MHR total implant cost
$15,000
- cost-effectiveness uncertain
- UK device cost $4,500$5,000 and procedure cost
$12,000
- no comparative evidence
- revision rates of 0-14%
at 3-years
- 91% pain-free at 4 years
- THR more effective and
less costly than M-MHR
- M-MHR more effective and
less costly than watchful
waiting at 20 years for
patients <65 years
- no randomized evidence
- limited evidence on time
to device failure
- revision (THR and MMHR) ranges from 0%14.3%
- lack of controlled trials
and inadequate follow-up
- high survival
- good health outcomes
- manufacturer costeffectiveness analysis at 5
years for <65 years found the
incremental cost per quality
adjusted life year $35,000£
- cost-effectiveness uncertain
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Figure A10: Trend of charges to Alberta Health and Wellness for Hip Disease
Procedures: 1997-2006
Procedure Amount Paid
3500000
3000000
2500000
2000000
1500000
1000000
500000
0
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Year
Source: Alberta Health and Wellness, 2007 10
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REFERENCES
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(2) Alberta Heritage Foundation for Medical Research. Metal-on-metal hip
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(3) National Institute for Clinical Excellence. Guidance on the use of metal on metal
hip resurfacing arthroplasty. Systematic review. 2002.
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systematic review of the effectiveness and cost-effectiveness of metal-on-metal
hip resurfacing arthroplasty for treatment of hip disease. Systematic review.
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(5) Ontario Ministry of Health and Long-Term Care. Metal-on-metal total hip
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(6) National Horizon Scanning Centre. Metal on metal resurfacing hip arthroplasty
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(7) Canadian Coordinating Office for Health Technology Assessment. Minimally
Invasive Hip Resurfacing. 2005.
(8) Vendittoli PA, et.al. A prospective randomized clinical trial comparing metal-onmetal total hip arthroplasty and metal-on-metal total hip resurfacing in patients
less than 65 years old. Hip International 2006;16:S73-S81.
(9) Alberta Bone and Joint Institute. Metal-On-Metal Hip Resurfacing for Young
Active Adults with Degenerative Hip Disease. 2006.
(10) Alberta Health and Wellness. Hip Codes Data. 2007.
(11) Hip Resurfacing Surgery. ActiveJoints 2007;Available at: URL:
www.activejoints.com.
(12) Wyness L, Vale L, McCormack K, Grant A, Brazzelli M. The effectiveness of
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