> 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
> 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
> 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
> 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,
> from Australia and one from the United Kingdom.
> They performed all procedures with the recently reintroduced
> Birmingham Hip Resurfacing System [Smith & Nephew]. The FDA
> the implant for sale in the United States last year.
> All surgeons used standard instrumentation and a posterior
> 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
> "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
> The surgeons tended to be more accurate in extreme cases of
> 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
> The longer-than-expected learning curve has huge implications for
> surgeons' success with this type of hip replacement, Back told
> Orthopedics Today.
> "Hip resurfacing is good. I think that is well proven. You have to
> choose your right cases, but it does take you longer than you
> to learn. I think medico-legally it does have some implications."
> For example, surgeons just learning the procedure should tell
> patients they are at the beginning of their learning curve and have
> not done many of the procedures, she said.
> In the United States where orthopedists begin practicing after
> completing fewer hip replacements than surgeons in the United
> Kingdom or Australia, "It actually means their learning curve may
> take them 10 years to get out of," Back said.
> Back said she wonders how, with the worldwide trend toward reduced
> orthopedic training hours, many new surgeons would be able to
> enough cases to become proficient with the technique.
> She ended her presentation saying it was difficult to extrapolate
> these findings into clinically relevant information since there
> still not enough long-term data about survivorship of resurfaced
> hips based on component placement.
> "Have we got any data past 5 years that says varus is worse than
> valgus? No. Does varus fail earlier? Not necessarily," she noted.
> When the paper was discussed, Back explained she also analyzed
> factors important to resurfacing outcomes, such as complications,
> operative time, cyst preparation and acetabular component
> and plan to present those in the future.
> For more information:
> Diane L. Back, FRCS, Ed Orth, Guy's and St. Thomas Hospital
> Health Service, Lambeth Palace Road, London, United Kingdom SE17EH;
> +44-20-7188-4435; diane.back@... She indicated she has no
> financial disclosures related to this article.
> Back DL, Smith JD, Dalziel RE, et al. Establishing a learning curve
> for hip resurfacing. #130. Presented at the American Academy of
> Orthopaedic Surgeons 74th Annual Meeting. Feb. 14-18, 2007. San