Low morbidity, few dislocations make hip resurfacing an option for young patients

“However, the role that proper surgical technique plays in resurfacing outcomes cannot be over emphasized. “Performing hip resurfacing is different than performing a total hip,” Beaulé said. And there is no getting around the learning curve.

Femoral neck fractures—a dramatic failure for patient and surgeon—is a technique-related complication that must be surmounted.

“Neck fracture remains one of the greatest limitations of resurfacing because it is unique to hip resurfacing,” Beaulé said. He cited varying fracture rates from the Journal of Bone and Joint Surgery ranging from 0.8% (Amstutz, 600-patient series) to 1.5% (Shimmin, 3,497 hips; Australian hip arthroplasty register).

On the plus side, patients with successful procedures stand to truly benefit from the procedure through activity restoration and thus maintaining better health and mental status.

Learning curve may be longer than thought for placing hip resurfacing components

It took surgeons 55 to 60 cases to get femoral components within 5° of planned placement.

By Susan M. Rapp
Orthopedics Today 2007; 27:12
May 2007

British and Australian researchers collaborating on a prospective study identified a longer-than-expected learning curve to accurately perform hip resurfacing arthroplasties.

Hip surgeons taking part in the study, all of whom had performed more than 1,000 hip surgeries, found they had to complete three-times more resurfacing surgeries than they expected in order to place the femoral hip resurfacing components within 5° of the desired neck/head angle, said Diane L. Back, FRCS.

The surgeons had initially estimated their learning curve at 10 to 20 cases, Back told Orthopedics Today.

"The results actually showed that it took 55 to 60 cases for most of our surgeons to get the femoral component where they actually planned it," she said.

Expect inaccuracies
These results only pertain to hip resurfacing, Back noted. Similar studies have not been conducted into the learning curve for other types of hip arthroplasty, so she hesitated to say whether the resurfacing technique's learning curve was longer.

Back and colleagues studied resurfacing arthroplasty because few independent studies had been performed on the technique's learning curve and she was curious how long it took surgeons skilled in basic tissue handling and hip surgery principles to master it.

Based on the results, she told others to expect their margin of error implanting the femoral resurfacing components to be high for the first few years, no matter how skilled they were.

Four surgeons participated
Back and colleagues prospectively analyzed the first 100 hip resurfacing procedures of four consultant orthopedic surgeons, three from Australia and one from the United Kingdom.

They performed all procedures with the recently reintroduced Birmingham Hip Resurfacing System [Smith & Nephew]. The FDA approved the implant for sale in the United States last year.

All surgeons used standard instrumentation and a posterior approach. Investigators focused on femoral component position, but also analyzed notching and other complications.

To determine how accurately they placed the femoral components, surgeons first marked the ideal implantation site on preoperative radiographs. Investigators then calculated the corresponding neck/head angle.

The surgeon who performed this hip resurfacing arthroplasty as part of this study ended up placing the femoral components in different locations than decided upon on in preoperative radiographs. The implants in this postop radiograph were 15° off in the patient's left hip and 5° off in the right from where the surgeon originally intended to place them.
Image: Back D

Radiographc angles
On postop radiographs investigators determined the neck/head angle of the implanted femoral component.

They compared the two angles, allowing a 5° difference, and saw extreme variations between planned and achieved implant position. They noted the positioning gradually improved as surgeons did more cases.

"They [were] starting to narrow in their variation, but there was still great variation in what they planned and what they actually achieved," Back said, during the American Academy of Orthopaedic Surgeons (AAOS) 74th Annual Meeting, where she presented the initial findings.

The surgeons tended to be more accurate in extreme cases of anatomic variation. "But, on the more common angles, they were not actually getting what they wanted," Back said.

For example, in one surgeon's series, implants were positioned between +20° and -20° of their intended location. Longer curve than expected. For complete article click on above link.

AAOS - Learning Curve
Establishing a Learning Curve for hip resurfacing
Podium No: 130

Wednesday, February 14, 2007 05:12 PM - 05:18 PM

Location: San Diego Convention Center, Room 6DE

Diane L Back, FRCS Ed Orth Chesham United Kingdom (n)
Jay D Smith, MRCS (n)
Rodney E Dalziel, MD Melbourne VIC Australia (a - Osteoz)
David Alexander Young, MD Windsor Victoria Australia (*)
John Skinner, FRCS London United Kingdom (a - Osteoz)
Andrew John Shimmin, MD Windsor Victoria Australia (a - Osteoz)

Moderator(s)
Thomas J Ellis, MD Portland OR (*)
Thomas A Malvitz, MD Grand Rapids MI (*)

Evaluated 4 consultants learning the procdure. The learning curve was longer expected with implications for proposed shortened training programmes and a reduction in operative experience.

With shortened training programmes advocated, we have established a learning curve for hip resurfacing in experienced consultants.

We prospectively planned the placement of a hip resurfacing prosthesis. Using CUSUM analysis we established how long it took for consistent placement of the prosthesis to take place.

Four experienced surgeons learning the hip resurfacing procedure were included, thus negating the need to learn basic surgical skills. Evaluating the first 100 cases of each, showed that the learning curve between planned and achieved implant position was in the order of 50 cases.

The learning curve was longer than estimated and has huge implications, with shortened training programmes and less operative exposure being advocated throughout the world.

2007 Annual Meeting Podium Presentations
Adult Reconstruction Hip 2: New Technology, Resurfacing THA; Navigation, Minimally Invasive Approaches

Femoral Neck Fractures Following Metal-on-metal Total Hip Resurfacing
Podium No: 123

Wednesday, February 14, 2007
04:12 PM - 04:18 PM

Location: San Diego Convention Center, Room 6DE

Michael A Mont, MD Baltimore MD (a,e - Wright Medical Technology)
Ronald Emilio Delanois, MD Lutherville MD (*)
Johannes F Plate, BS Heidelberg Germany (n)
Thorsten M Seyler, MD Baltimore MD (n)

Moderator(s)
Thomas J Ellis, MD Portland OR (*)
Thomas A Malvitz, MD Grand Rapids MI (*)

Risks for femoral neck fractures following resurfacing arthroplasty include intraoperative notching, female gender, and being overweight.

Metal-on-metal total hip resurfacing arthroplasty is recommended for young and active patients with advanced hip disease who are likely to outlive standard total hip arthroplasty. Femoral neck fracture as a result of stress shielding is well-documented in the literature. The purpose of this study was to analyze and determine the incidence of femoral neck fractures after metal-on-metal total hip resurfacing.

Between November 2000 and April 2006, 480 metal-on-metal total hip resurfacings were performed by the senior author, and data was prospectively collected in our database. The authors reviewed operative reports, patient charts, preoperative and postoperative radiographs to screen for any femoral neck fracture after metal-on-metal total hip resurfacing. Any relevant data concerning the occurrence of femoral neck fractures was then analyzed.

In 12 patients (13 hips) fracture of the femoral neck occurred as complication. Eleven of the first thirteen fractures occurred in the first 50 resurfacings performed. The incidence for fracture in these first 50 resurfacings was 22% versus 0.46% for the remaining series (2 out of 430). The incidence for femoral neck fractures in women was 4.4% (8 hips) and 1.6% for men (5 hips). The relative risk of fracture for women versus men was 2.75. The mean time to fracture was 75 weeks (range, 1-276 weeks). Seven (54%) fractures occurred within one year of surgery. In women, the mean time to fracture was 95 weeks (range, 1-276 weeks) and in men it was 48 weeks (range, 3-120 weeks). The mean BMI was 28.8 (range, 12-49) with 5 (38%) fractures occurring in patients with a BMI greater than 30. Anatomic and/or surgical bone management problems (large neck cysts, osteopenia, notching), surgical experience (head seating, cement mantle), and other patient factors (BMI, female gender) were indicated as common risk factors.

The risk of femoral neck fracture in metal-on-metal resurfacing appears to be multifactorial. These findings suggest that fractures occur more often in the early part of the learning curve of a surgeon. In addition, it appears that intraoperative notching, female gender, and obesity increase the risk for femoral neck fractures.

Here are abstracts of three studies that demonstrate the "learning curve" for doing resurfacings.

1. Proc Inst Mech Eng [H]. 2006 Feb;220(2):345-53.
   
   Lessons learned from early clinical experience and results of 300 ASR hip resurfacing implantations.
   
   Siebel T, Maubach S, Morlock MM.
   
   Between August 2003 and April 2005, 300 ASR metal-on-metal resurfacing hip endoprostheses were implanted by the first author and a fellow surgeon. The mean age at surgery was 56.8 years (18-75.9 years) and mean body mass index was 27.6 kg/m2 (range, 19-41 kg/m2). The mean follow-up time was 202 days. The mean Harris hip score improved from 44 pre-operatively to 89 at 3 months post-operatively. In total, eight (2.7 per cent) cases [five neck fractures (1.66 per cent) and three cup revisions (1 per cent)] were revised. Two neck fractures occurred within a group of seven cases of femoral neck notching detected postoperatively; one neck fracture occurred out of two cases of incomplete seating of the femoral implant. A significantly higher (p < 0.001) failure rate was observed for patients who had undergone a previous osteosynthesis of the proximal femur (three revisions in a group of 15 patients). Revision cases had a significantly greater body mass index (p = 0.031). A learning curve was evident from the reduction in revisions from 5 in the first 100 surgical procedures to 2 in the next 100 and 1 in the last 100. These results show the importance of accurate surgical technique and careful patient selection for fourth-generation hip resurfacing implants.
   
   The next study examined what problems led to resurfacing failures:
2. Proc Inst Mech Eng [H]. 2006 Feb;220(2):333-44.
   
   Biomechanical, morphological, and histological analysis of early failures in hip resurfacing arthroplasty.
   
   Morlock MM, Bishop N, Ruther W, Delling G, Hahn M.
   
   The present revival of hip resurfacing arthroplasty may be related to an increase in early failures owing to the challenging technique of the procedure. Fifty-five retrieved implants were analysed with respect to wear, cement mantle and cement penetration, fracture and head morphology, as well as standard
histology. Femoral neck fractures occurred in median after 102 days. The time to failure was shorter for older women. Major deviations from the suggested cement mantle thickness and cement penetration were found. Indications for high trauma during implantation leading to early failure due to weakening of the femoral neck were also observed. Some failures had signs of pseudarthrosis beneath the implant. Four different fracture patterns with different mean survival
times were identified. Observed wear was minor with the exception of that due to alignment mistakes (rim loading). The cups were not damaged by the
failures. Histological results indicate that avascular necrosis is not necessarily connected with this kind of endoprosthetic surgery. Most of the failures analysed can probably be attributed to the 'learning curve' effect, which is an unsatisfactory situation.
   
   And study three demonstrates that in the hands of an experienced surgeon, in this case Dr. McMinn of the UK, negative outcomes are minimal.
3. Metal-on-metal resurfacing of the hip in patients under the age of 55 years with osteoarthritis.
   
   Daniel J, Pynsent PB, McMinn DJ.
   
   The results of conventional hip replacement in young patients with osteoarthritis have not been encouraging even with improvements in the techniques of fixation and in the bearing surfaces. Modern metal-on-metal hip resurfacing was introduced as a less invasive method of joint reconstruction for this particular group. This is a series of 446 hip resurfacings (384 patients) performed by one of the authors (DJWM) using cemented femoral components and hydroxyapatite-coated uncemented acetabular components with a maximum follow-up of 8.2 years (mean 3.3). Their survival rate, Oxford hip scores and activity levels are reviewed. Six patients died due to unrelated causes. There was one revision (0.02%) out of 440 hips. The mean Oxford score of the surviving 439 hips is 13.5. None of the patients were told to change their activities at work or leisure; 31% of the men with unilateral resurfacings and 28% with bilateral resurfacings were involved in jobs that they considered heavy or moderately heavy; 92% of men with unilateral hip resurfacings and 87% of the whole group participate in leisure-time sporting activity. The extremely low rate of failure in spite of the resumption of high level occupational and leisure activities provides early evidence of the suitability of this procedure for young and active patients with arthritis.

AAOS February 2009 

Excerpt:

Physicians debate the importance of learning curve for hip resurfacing

Mastery of the procedure may prove difficult for surgeons with limited arthroplasty practices.

Hip resurfacing is becoming a popular choice for the surgical treatment of hip arthritis; however, there are still many controversies surrounding its use, according to two internationally respected hip surgeons.

One controversy — whether or not the learning curve for hip resurfacing is too steep – was the subject of a debate between Jay R. Lieberman, MD, and Andrew Shimmin, MBBS, FAOrthA, at a symposium held during the American Academy of Orthopaedic Surgeons annual meeting.

Four separate facets

Shimmin said four aspects of hip resurfacing add to its difficulty: patient selection; exposure; implant orientation; and postoperative management.

“The operation is for patients who will likely become increasingly active once rid of their disabling arthritic pain, ie, younger patients with few co-morbidities,” he told Orthopedics Today.

The Australian Registry data from 2008 indicated that the ideal indication was for men younger than 65 years with a primary diagnosis of osteoarthritis. He said those patients had a 2.4% cumulative revision hip resurfacing rate, compared to the total hip replacement rate of 2.8%" - Andrew Shimmin

How steep is the curve?

Lieberman said hip resurfacing procedures carry a learning curve that is far too steep for any nonspecializing physician to easily learn. While the procedure may offer distinct advantages if a surgeon performs it well, the price of performing it poorly can be costly.

Excerpt from Orthosupersite

A Simple, Reproducible Method for Centering the Guide-Pin in Hip Resurfacing

A Simple, Reproducible Method for Centering the Guide-Pin in Hip Resurfacing Arthroplasty
By Jared R. Foran, MD; Scott T. Ball, MD
ORTHOPEDICS 2009; 32:896

    With this technique, guide-pin placement and subsequent femoral head preparation can be performed accurately and efficiently without the need for additional instruments, navigation, or imaging.

Hip resurfacing arthroplasty has undergone a recent resurgence in popularity. A number of studies with short- to mid-term follow-up, as well as the Australian Hip Registry, have validated hip resurfacing as a viable alternative to traditional total hip replacement, particularly for younger, more active patients with good bone quality.1One of the drawbacks to the procedure is the greater technical difficulty, which has resulted in a well-described learning curve. Femoral-sided failures after hip resurfacing are typically multifactorial. It may be related to poor patient selection (eg, poor bone quality, osteoporosis, large cysts). Additionally, poor surgical technique has been implicated. Superior femoral neck notching and component malposition in varus have been associated with increased risk of neck fracture."

For full article Click Here