Canadian Academic Experience with Metal-on-Metal Hip Resurfacing

Abstract

The current depth and breadth of experience in hip resurfacing in Canadian academic centers is not well known. This study endeavors to increase awareness of the prevalence of programs and current experience in a select number of representative teaching centers by examining the learning curve of high-volume surgeons. A questionnaire was sent to all academic centers in Canada to identify the volume of hip resurfacing, surgical approach, and type of prosthesis. In addition, five surgeons, not fellowship-trained in hip resurfacing, were selected for a detailed review of their first 50 cases, including survey of patient demographics, surgical approach, radiographic evaluation, complications, and revision. Eleven of 14 academic centers are currently performing hip resurfacing. All of these centers had performed more than 50 cases, with 10 of 11 of them having more than one surgeon performing the procedure. The posterior approach was found to be the most commonly utilized in surgeries. The overall revision rate was 3.2% at a mean time of 2 years, with femoral neck fracture (1.6%) being the most common cause for failure. The failure rate was comparable to other centers of expertise and lower than previously published multicenter trials. All surgeons reviewed were in specialized arthroplasty practices, which may contribute to the relatively low complication rates reported.

Full text

Bulletin of the NYU Hospital for Joint Diseases 2009;67(2):128-31128
O’Neill M, Beaulé PE, Bin Nasser A, Garbuz D, Lavigne M, Duncan C, Kim PR, Schemitsch E. Canadian academic experience with metal-on-metal hip
resurfacing. Bull NYU Hosp Jt Dis. 2009;67(2):128-31.
Abstract
The current depth and breadth of experience in hip resurfac-
ing in Canadian academic centers is not well known. This
study endeavors to increase awareness of the prevalence
of programs and current experience in a select number of
representative teaching centers by examining the learning
curve of high-volume surgeons. A questionnaire was sent to
all academic centers in Canada to identify the volume of hip
resurfacing, surgical approach, and type of prosthesis. In
addition, five surgeons, not fellowship-trained in hip resur-
facing, were selected for a detailed review of their first 50
cases, including survey of patient demographics, surgical
approach, radiographic evaluation, complications, and revi-
sion. Eleven of 14 academic centers are currently performing
hip resurfacing. All of these centers had performed more
than 50 cases, with 10 of 11 of them having more than one
surgeon performing the procedure. The posterior approach
was found to be the most commonly utilized in surgeries. The
overall revision rate was 3.2% at a mean time of 2 years,
with femoral neck fracture (1.6%) being the most common
cause for failure. The failure rate was comparable to other
centers of expertise and lower than previously published
multicenter trials. All surgeons reviewed were in specialized
arthroplasty practices, which may contribute to the relatively
low complication rates reported.
Hip resurfacing arthroplasty has become an ac-
cepted alternative to traditional stemmed total hip
arthroplasty in the young adult.1 Early and midterm
follow-up has shown comparable results to standard total
hip arthroplasty.2-9 However, complications unique to hip
resurfacing arthroplasty have been identified, and the impor-
tance of patient selection and surgical technique in avoiding
short-term failures has been emphasized.10
As awareness increases in the medical community and the
popular press, the demand for this procedure will continue to
rise. As with any new surgical procedure, a learning curve is
expected. Currently, there is little in the published literature
regarding the type of training and exposure and volume of
cases required to become proficient in this operative proce-
dure. Recent papers on multicenter trials looking at the early
outcome of hip resurfacing have shown higher failure rates,
compared to single-surgeon centers of expertise.11,12 The
purpose of this study was to evaluate the early experience
with metal-on-metal hip resurfacing in Canadian academic
centers and report on the learning curve for high volume
arthroplasty surgeons.
Materials and Methods
Between August and December of 2007, a paper survey was
mailed to the orthopaedic division of all academic institu-
tions in Canada. This one-page preliminary survey focused
on hip resurfacing arthroplasty, with regard to the number
of surgeons at each institution performing the procedure
and the type of implant and surgical approach used, as well
as volume. Institutions that initially failed to respond to the
mailed paper survey were then contacted via telephone and
the survey was completed over the telephone.
After completion of this initial survey, five surgeons
Canadian Academic Experience with
Metal-on-Metal Hip Resurfacing
Michelle O’Neill, M.D., F.R.C.S.(C), Paul E. Beaulé, M.D., F.R.C.S.(C), Ahmad Bin Nasser, M.D.,
F.R.C.S.(C), Donald Garbuz, M.D., F.R.C.S.(C), Martin Lavigne, M.D., F.R.C.S.(C), Clive Duncan,
M.D., F.R.C.S.(C), Paul R. Kim, M.D., F.R.C.S.(C), and Emil Schemitsch, M.D., F.R.C.S.(C)
Michelle O’Neill, M.D., Ahmad Bin Nasser, M.D., Paul R. Kim,
M.D., and Paul E. Beaulé, M.D., are from the University of Ot-
tawa, Ottawa, Ontario, Canada, where Dr. Beaulé is Head of Adult
Reconstruction at The Ottawa Hospital. Donald Garbuz, M.D., and
Clive Duncan, M.D., are from the University of British Columbia,
Vancouver, British Columbia, Canada. Martin Lavigne, M.D., is
from the Hôpital Maisonneuve-Rosemont, Université de Montréal,
Montreal, Canada. Emil Schemitsch, M.D., is from St. Michael
Hospital, University of Toronto, Toronto, Canada.
Correspondence: Paul E. Beaulé, M.D., Head of Adult Reconstruc-
tion, The Ottawa Hospital, University of Ottawa, 501 Smyth Road,
CCW 1646, Ottawa, Ontario, Canada; pbeaule@ottawahospital.
on.ca.

129Bulletin of the NYU Hospital for Joint Diseases 2009;67(2):128-31
were identified to assess the learning curve of each for their
first 50 resurfacing cases. The five surgeons selected met
the following criteria: 1. completion of a minimum of 50
resurfacing arthroplasty procedures, with a minimum of 6
months of follow-up; 2. no training in hip resurfacing during
their residency or fellowship; and 3. performed a minimum
of 100 elective total hip arthroplasties per year. The first 50
cases of hip resurfacing arthroplasty were reviewed by two
independent observers (MO, AN). Each case had a retrospec-
tive chart review for demographic data, medical and surgical
complications, and need for revision. In addition, a detailed
radiographic review was performed to assess for preoperative
neck-shaft angles, postoperative stem shaft angles, femoral
neck notchings, and acetabular component abduction angles.
Results
Survey of Canadian Academic Institutions
Twelve of the 14 Canadian Academic centers initially re-
sponded to the survey, with the two failing to respond later
contacted by phone for survey completion. Twelve of the 14
academic institutions had at least one orthopaedic surgeon
with experience in hip resurfacing arthroplasty. Of these 12
centers, 11 were still performing the procedure regularly at
the time of this survey. All of these 11 centers had performed
a minimum of 50 cases, with the most common approach
being posterior (Table 1). Only one center has discontinued
performing the procedure, due to an unacceptable early
complication rate.
Learning Curve in Five Surgeons
Demographic data for the 250 cases reviewed are summa-
rized in Table 2. An overall revision rate of 4.4% (11/250)
was found in the group, including intraoperative conversions
to stem total hip arthroplasty (Table 3). Individual surgeon
revision rates ranged from 0% to 12%. Femoral neck fracture
was the most common reason for revision at 1.6% (4/250),
which occurred at a mean time of 12 months (range, 3 to 20
months); all the patients were males, who had a mean age
of 51 years (range, 41 to 59 years). A posterior approach
was used in all surgeries. If one excludes the intraoperative
conversions to conventional total hip replacement, the revi-
sion rate for this series was 3.2% (8/250 hips). Two patients
also required reoperations on the day of surgery, one for
acetabular component repositioning and one for exploration
of a sciatic nerve palsy. The overall complication rate for this
series of 250 patients was 6.4% (Tables 4 and 5). All five
surgeons used the posterior approach; one surgeon utilized
a lateral approach for the first 13 cases before converting to
the posterior approach for the remainder of his cases. For
Table 1 Survey Results of All Canadian Academic Institutions
Program Cases Approach System No. Surgeons
1 No —
2 No < 25 Lateral C+ 1
3 Yes > 100 Posterior ASR 3
4 Yes > 100 Posterior D 2
5 Yes > 100 Post/Trochanteric slide C+ 2
6 Yes > 100 Posterior/Lateral ASR 1
7 Yes > 100 Posterior/Lateral CORMET 3
8 Yes > 100 Posterior BHR/C+ 2
9 Yes 50-100 Posterior/Lateral BHR 3
10 No
11 Yes†— — — 1
12 Yes > 100 Posterior BHR 3
13 Yes 50-100 Posterior/Lateral BHR 3
14 Yes > 100 Posterior/Lateral BHR/D 2
†Performing resurfacing but did not complete survey. BHR, Birmingham Hip* System (Smith & Nephew); C+, Conserve®
Plus (Wright Medical Technology); ASR™, DePuy ASR™/articular surface replacement; D, Durom™ (Zimmer).
Table 3 Revision Rates and Causes
Overall Revision Rate 11 4.4%
Femoral neck fracture 4 1.6%
Intraoperative conversions 3 1.2%
Acetabular loosening 2 0.8%
Persistent pain 2 1.6%
Revision Rate (Excluding
intraoperative conversions)
8 3.2%
Table 2 Demographics of All Surveyed Cases
Gender
Female 20%
Male 80%
Age (Mean) 49.9
BMI (Mean) 28.3
Diagnosis
OA 82%
Inflammatory 1%
AVN 5%
Posttraumatic 5%
Dysplasia 7%

Bulletin of the NYU Hospital for Joint Diseases 2009;67(2):128-31130
that surgeon, all complications and revisions were seen in
patients who underwent a posterior approach.
Radiographs for 241 of 250 cases were available for
review at the time of site visits. The mean pre- and postop-
erative neck-shaft angles were 132° (range, 118° to 151°)
and 139° (range, 122° to 155°), respectively. The mean
acetabular component abduction angle was 46° (range, 34°
to 64°). Subgroup analyses of the femoral neck fracture
cases showed a mean preoperative neck-shaft angle of 137°
(range, 134° to 138°) and a postoperative stem-shaft angle
of 137° (range, 128° to 145°).
Discussion
Hip resurfacing arthroplasty is still a relatively new proce-
dure, and its re-introduction to the orthopaedic community
is similar to that of unicompartmental knee arthroplasty.
However, there is still a lack of long-term clinical studies
to confirm its superior survivorship to the first generation
of metal-on-polyethylene hip resurfacing.1 There have been
several short- to midterm studies evaluating the early experi-
ence of this surgical technique, reporting survivorships of
94% to 99%.2-9 As with any new technology, patient selection
criteria and surgical technique issues have been identified as
important predictors of early failures, as well as a unique set
of complications associated with the procedure, in this case,
e.g., femoral neck fracture.13 Although single-surgeon high
volume clinical series have shown a comparable outcome
to traditional stemmed total hip arthroplasty,8 four recent
studies reporting on multicenter results with metal-on-metal
hip resurfacing have reported a 6% to 7.4% failure rate at
short-term follow-up.11,12,14,15 Consequently, the learning
curve associated with hip resurfacing has been argued to be
too steep to justify it being offered as a safe and efficacious
treatment for hip osteoarthritis.16 This argument has left some
unanswered questions as to the role of hip resurfacing in the
treatment of hip osteoarthritis.1 Hence, the importance of
examining the learning curve for this procedure in a group
of surgeons with no prior training, but with significant ex-
perience in total joint replacement.
The first purpose of this study was to identify how com-
mon this procedure was in Canadian academic centers.
Although hip resurfacing arthroplasty was being performed
in the majority of centers, the number of cases are less than
the overall volume of primary total hip arthroplasties. This
may reflect the lack of long-term clinical data for this new
technology and the appropriate caution surgeons are exercis-
ing over the apparent high, early complication rate.11 More
specifically, the institution that abandoned this procedure at
the time of review echoed the concerns raised by others in
the orthopaedic community regarding the safety and efficacy
of this procedure.
The overall revision rate in this series was 4.4%. By
excluding patients who underwent conversion to traditional
stemmed total hip arthroplasty at the time of the primary
surgery, the rate dropped to 3.2%. This is in sharp contrast
to a multicenter trial reported by Mont and colleagues that
showed an overall revision rate of 5.3%, with subgroup
analysis showing a revision rate of 13.4% in the first 292
cases, which decreased to 2% for the remaining 724 cases;
a reduction supporting the concept of a learning curve.15
Similarly, Kim and coworkers reported a higher than ex-
pected revision rate of 7% in a Canadian multicenter trial of
resurfacing.11 More importantly, they noted that the surgeon
with significant previous experience with this procedure had
no revisions, as opposed to the less experienced surgeons in
this clinical trial. A similar study out of Germany reported
on a series of 300 cases, with a 5% revision rate in the first
100 cases, a 2% revision rate in the subsequent 100 cases,
and a 1% revision rate in the final 100 cases.14 Stulberg and
associates recently published the early experience for the
Cormet™ resurfacing device (Corin, Cirencester, England)
U.S. Food and Drug Administration clinical trial and found a
7.1% overall revision rate.17 Our overall revision rate in this
study was significantly lower than the rate found recently by
Mont and colleagues, particularly in comparison to his initial
subgroup of 292 cases.15 It is also lower than the overall
revision rate found by Kim and coworkers11 and Stulberg
and associates.17 All five surgeons involved in this review
were subspecialty arthroplasty surgeons. Even without fel-
lowship training in hip resurfacing arthroplasty, their high
volume arthroplasty practices may account for this lower
than expected rate.
Femoral neck fracture (1.6%) accounted for the largest
portion of reported revisions in this survey. Marker and
colleagues reported an overall femoral neck fracture rate of
2.5%, noting that 12 of 14 fractures occurred in the first 69
cases, and the fracture rate dropped to 0.4% in the subsequent
cases.18 Shimmin and Back reported a 1.5% fracture rate
in a review of the Australian experience with resurfacing
arthroplasty.13 The femoral neck fracture rate of 1.6% in
this survey is comparable to the Australian experience, and
significantly lower than the initial 69 cases in the Marker
series.13 The increased awareness of optimum stem-shaft
placement, and avoidance of notching of the femur may
explain the lower rate in our survey. However, the fact that
the femoral neck fractures still occurred, despite appropri-
Table 5 Complications Continuing to Surgical
Intervention Without Revision
Peroneal nerve injury 2 0.8%
Acetabular malpositioning 1 0.4%
Traumatic intertrochanteric hip fracture 1 0.4%
Table 4 Complications Not Requiring Surgical
Intervention
Deep vein thrombosis 2 0.8%
Pulmonary embolism 1 0.4%
Cerebrovascular event 1 0.4%
Superficial infection 8 3.2%

131Bulletin of the NYU Hospital for Joint Diseases 2009;67(2):128-31
ate surgical technique and patient selection, indicates that
other factors may be important. For example, compromised
femoral head vascularity, secondary to the use of the pos-
terior approach, may represent the initiating insult for neck
fractures to occur.19 In regard to component placement,
valgus orientation has been shown to be favorable to im-
plant survivorship,10 with a recommendation of 140° ± 5°
for the ideal stem-shaft placement.20 Acetabular inclination
between 35° and 45° also has been recommended to avoid
higher levels of metal ion release.1 The radiographic results
of this series are comparable to that of other series, as well
as to the current recommendations.
An unacceptably high complication rate was not found in
these early cases of hip resurfacing arthroplasty in Canadian
Academic Centers. It should be noted that all surgeons in-
volved in this review were subspecialty-trained arthroplasty
surgeons with high-volume practices. It is unknown whether
these results can be applied to the Canadian orthopaedic
community at large. Long-term follow-up will be required
to define the overall role of hip resurfacing in the treatment
of hip osteoarthritis.
Disclosure Statement
Paul E. Beaule, M.D., F.R.C.S.(C), and Paul R. Kim,
M.D., F.R.C.S.(C), are consultants for Wright Medical
Technology. Clive Duncan, M.D., F.R.C.S.(C), Donald
Garbuz, M.D., F.R.C.S.(C), and Martin Lavigne, M.D.,
F.R.C.S.(C), are consultants for Zimmer. Emil Schemitsch,
M.D., F.R.C.S.(C), is a consultant for Smith Nephew. None
of the other authors have a financial or proprietary interest
in the subject matter or materials discussed, including, but
not limited to, employment, consultancies, stock ownership,
honoraria, and paid expert testimony.
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