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.
Article Type: Survey
Subject: Orthopedic surgery
Surgeons
Fractures
Authors: O'Neill, Michelle
Beaule, Paul E.
Nasser, Ahmad Bin
Garbuz, Donald
Lavigne, Martin
Duncan, Clive
Kim, Paul R.
Schemitsch, Emil
Pub Date: 04/01/2009
Publication: Name: Bulletin of the NYU Hospital for Joint Diseases Publisher: J. Michael Ryan Publishing Co. Audience: Academic Format: Magazine/Journal Subject: Health Copyright: COPYRIGHT 2009 J. Michael Ryan Publishing Co. ISSN: 1936-9719
Issue: Date: April, 2009 Source Volume: 67 Source Issue: 2
Accession Number: 247449422
Full Text: Hip resurfacing arthroplasty has become an accepted 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 importance 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 procedure. 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 institutions 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 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 retrospective 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 responded 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 summarized 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 revision 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 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 postoperative neck-shaft angles were 132[degrees] (range, 118[degrees] to 151[degrees]) and 139[degrees] (range, 122[degrees] to 155[degrees]), respectively. The mean acetabular component abduction angle was 46[degrees] (range, 34[degrees] to 64[degrees]). Subgroup analyses of the femoral neck fracture cases showed a mean preoperative neck-shaft angle of 137[degrees] (range, 134[degrees] to 138[degrees]) and a postoperative stem-shaft angle of 137[degrees] (range, 128[degrees] to 145[degrees]).

Discussion

Hip resurfacing arthroplasty is still a relatively new procedure, 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 experience 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 experience in total joint replacement.

The first purpose of this study was to identify how common 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 exercising 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 expected 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[TM] 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 coworkers (11) and Stulberg and associates. (17) All five surgeons involved in this review were subspecialty arthroplasty surgeons. Even without fellowship 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 appropriate surgical technique and patient selection, indicates that other factors may be important. For example, compromised femoral head vascularity, secondary to the use of the posterior 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 implant survivorship, (10) with a recommendation of 140[degrees] [+ or -] 5[degrees] for the ideal stem-shaft placement. (20) Acetabular inclination between 35[degrees] and 45[degrees] 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 involved 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.

References

(1.) Shimmin AJ, Beaule PE, Campbell PA. Current concepts: metal on metal hip resurfacing. J Bone Joint Surg Am. 2008;90(3):637-54.

(2.) Mont MA, Marker DR, Smith JM, et al. Resurfacing is comparable to total hip arthroplasty at short-term follow-up. Clin Orthop Rel Res. 2009;467(1):66-71.

(3.) Heilpem GN, Shah N, Fordyce MJ. Birmingham hip resurfacing arthroplasty: a series of 110 consecutive hips with a minimum five-year clinical and radiological follow-up. J Bone Joint Surg Br. 2008;90(9)1137-42.

(4.) Steffen RT, Pandit HP, Palen J, et al. The five-year results of the Birmingham Hip Resurfacing arthroplasty: an independent series. J Bone Joint Surg Br. 2008;90(4):436-41.

(5.) Hing CB, Back DL, Bailey M, et al. The results of primary Birmingham hip resurfacings at a mean of five years. An independent prospective review of the first 230 hips. J Bone Joint Surg Br. 2007;89(11):1431-8.

(6.) De Smet KA. Belgium experience with metal-on-metal surface arthroplasty. Orthop Clin North Am. 2005;36(2):203-13.

(7.) Amstutz HC, Beaule PE, Dorey FJ, et al. Metal-on-metal hybrid surface arthroplasty: two to six year follow-up. J Bone Joint Surg Am. 2004;86(1):28-39.

(8.) Vail TP, Mina CA, Yergler D, Pietrobon R. Metal-on-metal hip resurfacing compares favorably with THA at 2 years followup. Clin Orthop Rel Res. 2006;(453):123-31.

(9.) Amstutz HC, Ball ST, LeDuff MJ, Dorey FJ. Resurfacing THA for patients younger than 50 years: results of 2- to 9-year follow-up. Clin Orthop Rel Res. 2007;460:159-64.

(10.) Beaule PE, Dorey FJ, LeDuff MJ, et al. Risk factors affecting outcome of metal on metal surface arthroplasty of the hip. Clin Orthop Rel Res. 2004;(418):87-93.

(11.) Kim PR, Beaule PE, Laflamme GY, Dunbar MJ. Causes of early failure in a multicenter clinical trial of hip resurfacing. J Arthroplasty. 2008 Sep;23(6 Suppl 1):44-9.

(12.) Della Valle CJ, Nunley RM, Raterman SJ, Barrack RL. Initial American experience with hip resurfacing following FDA approval. Clin Orthop Rel Res. 2008; Epub Oct 24 ahead of print.

(13.) Shimmin A, Back D. Femoral neck fractures following Birmingham hip resurfacing. A national review of 50 cases. J Bone Joint Surg Br. 2005;87(3):463-4.

(14.) Siebel T, Maubach S, Morlock MM. Lessons learned from early clinical experience and results of 300 ASR hip resurfacing implantations. Proc Inst Mech Eng [H]. 2006 Feb;220(2):345-53.

(15.) Mont MA, Seyler TM, Ulrich SD, et al. Effect of changing indications and techniques on total hip resurfacing. Clin Orthop Rel Res. 2007;465:63-70.

(16.) Lachiewicz PF. Metal-on-metal hip resurfacing: a skeptic's view. Clin Orthop Rel Res. 2007;(465):86-91.

(17.) Stulberg B, Trier KK, Naughton M, Zadrilka JD. Results and lessons learned from a United States hip resurfacing investigational device exemption trial. J Bone Joint Surg Am. 2008;90(Suppl 3):21-6.

(18.) Marker DR, Seyler TM, Jinnah RH, et al. Femoral neck fractures after metal-on-metal total hip resurfacing: a prospective cohort study. J Arthroplasty 2007;22(7 Suppl 3):66-71.

(19.) Beaule PE, Campbell PA, Lu Z, et al. Vascularity of the arthritic femoral head and hip resurfacing. J Bone Joint Surg Am. 2006;88(Suppl 4):85-96.

(20.) Beaule PE, Lee J, LeDuff M, et al. Orientation of femoral component in surface arthroplasty of the hip: a biomechanical and clinical analysis. J Bone Joint Surg Am. 2004;86(9):2015 21.

Michelle O'Neill, M.D., F.R.C.S.(C), Paul E. Beaule, 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. Beaule, M.D., are from the University of Ottawa, Ottawa, Ontario, Canada, where Dr. Beaule 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 Hopital Maisonneuve-Rosemont, Universite de Montreal, Montreal, Canada. Emil Schemitsch, M.D., is from St. Michael Hospital, University of Toronto, Toronto, Canada. Correspondence: Paul E. Beaule, M.D., Head of Adult Reconstruction, The Ottawa Hospital, University of Ottawa, 501 Smyth Road, CCW 1646, Ottawa, Ontario, Canada; pbeaule@ottawahospital. on.ca.
Table 1 Survey Results of All Canadian Academic Institutions

                                                                 No.
Program                  Cases        Approach        System   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     C+        2
                                        slide
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 9             --           --             --        1
            ([dagger])
12        Yes            > 100        Posterior        BHR        3
13        Yes            50-100   Posterior/Lateral    BHR        3
14        Yes            > 100    Posterior/Lateral   BHR/D       2

([dagger]) Performing resurfacing but did not complete survey.
BHR, Birmingham Hip * System (Smith & Nephew); C+, Conserve [R]
Plus (Wright Medical Technology); ASR [TM], DePuy ASR [TM]/
articular surface replacement; D, Durom [TM] (Zimmer).

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%

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         8   3.2%
  intraoperative conversions)

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%

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%
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