Total Hip Resurfacing: Marketing over Matter

Total Hip Resurfacing: Marketing over Matter

Everyone with common sense should realize that "marketing" does not always present a balanced view. Direct to consumer medical marketing has undergone rapid growth in the last few years, especially in the field of orthopedic implants. One of these items involves the concept of a "total hip resurfacing" or "surface replacement". There is a plethora of information available on the internet for the general public who hungers for the "new and innovative". In looking up total hip resurfacing on the internet, there were over 78,000 hits. In looking through the first 60 pages of listings, only a handful of sites actually presented the topic with an appropriately balanced view. There is no peer review governing process that controls the accuracy of health care claims on the web or in print media.

The University of Missouri School of Medicine web site appropriately states about hip resurfacing, "please read carefully since many promotional and marketing efforts may neglect to discuss this critical information". Is this is legitimate procedure? Yes. Many sincere, caring and highly respected physicians are doing this procedure. But this pendulum has swung far and fast and would likely not have done so if this were a procedure done primarily in more elderly patients at Medicare reimbursement rates. Is resurfacing better than total hip replacement? Is it more durable? Does it allow a higher activity level? There are no independent, well controlled studies that document any of these issues. Often claims do not hold up when studied by peer review and independent assessments, i.e. ("the two mini incision total hip replacement", the "female knee"). Many of the marketing claims of superior success compare resurfacing to historical total hip replacement (cement stems, smaller size femoral heads, older plastic design) which were often done in an older population group.

There are no independent comparable studies with similar age groups and disease process that compare resurfacing with modern total hip replacement that use larger femoral heads and hard metal bearings. Patient's individual expectations and personal bias may also make studies more difficult to validate. Those patients who actively seek the "new and innovative, cutting edge" procedures may be more likely to elicit a favorable response in the subjective aspects of their outcomes.

At the recent 2008 American Academy of Orthopedic Surgery (AAOS) annual meeting, this issue stirred much debate. Many nationally well-known joint replacement specialists had words of reservation. Dr. Capello stated, "The aggressive marketing is premature and the procedure needs more time in peer review". The results thus far show "unproven, undocumented benefit and unproven long term results". At the AAOS media briefing, Dr. Maloney stated that the direct to consumer marketing is "driving patients to ask for a procedure without really understanding what is involved or even if they are suitable candidates". Patients have now become "consumers" of marketing?

A "contemporary" total hip replacement in a young person involves bone ingrowth components and can have the same large head metal-on-metal ball and cup design as hip resurfacing. The only difference would be a stem that fits into the shaft of the femur bone. The long term fixation record of a bone ingrowth stem in the shaft of the femur with a wide variety of designs is near 95% at 15 to 20 years.

The hip resurfacing procedure has been controversial since its inception in the early 1970's. It was then offered as an alternative to "young patients" because of the high failure rate of standard cemented total hip replacements in young patients that were done at that time. The first group of studies with resurfacing had very high failure rates mostly due to materials issues. Metal head on metal socket design was developed in the early 1990's and solved most of the failures of resurfacing on the femoral side that were due to the plastic wear and loosening. Current designs of the resurfacing, however, still involve a cementing process of the metal cap onto the surface of the ball with an additional small peg in the neck of the hip bone. Failure of this fixation due to progressive collapse (necrosis) of the ball, or fracture of the neck of the femur, continue to be the main mechanism of failure for this design.

Most authors suggest that only 10% of patients in need of total hip replacement could even fit into the criterion for selection for the hip resurfacing procedure, which are quite specific and technical. These criterion include: normal bone density, head to neck ratio greater than 1.2, leg length difference of less than 1 cm, a neck/shaft angle greater than 120-130 degrees, absence of cysts greater than 1 cm, absence of excessive anteversion, and minimal bone deformity of the ball or socket. 1 , 2 If the indications were widened, the results would likely be even less favorable.

There is general consensus even among advocates and non-advocates that the technique for resurfacing is more demanding, exacting, and technically challenging than for total hip replacement. There is a steep leaning curve (higher early failure rates in the first 50-100 cases), the incision is larger than modern "small incision" total hip replacement surgery and the blood loss is also typically greater. 3 , 4 Higher failure rates have been shown in women, patients with osteoporosis, small bone size, history of avascular necrosis greater than 25% of the head, obese patients, those with bone deformities, cysts within the head, retained hardware from previous surgeries, and inflammatory arthritis.

Claims made by various marketing efforts:

  1. Easier to revise than total hip replacement when it fails:

    Response:

    This may or may not be true. There are no adequate studies with appropriate comparisons that have ever been done. Revision to a total hip replacement is not a "benign" procedure. In revision surgery there are increased risks of infection, blood clots, pulmonary embolus, and nerve injury. Are the results better when revising a hip resurfacing compared to revising a bone ingrowth stem? We don't know because it has not been sufficiently studied. Once an ingrowth femoral stem is well secured, its mechanical risk for loosening on its own is essentially negligible. It is worth doing a procedure that is more likely to fail just because it may be easier to revise?

  2. A more natural stress transfer of forces to bone:

    Response:

    This issue is valid but it is of questionable clinical importance. No failure or revision of an ingrowth femoral stem has ever occurred due to "stress transfer issues". This is especially true when only proximally coated implants are used. Would a more favorable process of stress transfer in resurfacing, make any difference with regard to the long term durability for higher intensity activity levels? Unknown, because this has never been studied.

    There are actually some negative changes of bone remodelling that have occurred within the neck of the femur bone just under the metal cap. Narrowing of the bone width of the neck raises some concerns about longer term survival potential due to possible fracture through this area of diminished strength.

  3. Elimination of thigh pain from the femoral stem:

    Response:

    Modern designs of total hip replacement typically involve flexible tapered stems and proximal ingrowth components in the femur bone. The thigh pain issue is now insignificant for most joint replacement specialists. Sup>5

  4. Saves more of your own bone:

    Response:

    This is true, but is that extra bone proven to be of any value? Given the excellent success rate of ingrowth stems as well as the extremely good success even with revision surgery of ingrowth stems, is it worth the risk of a higher failure rate just so more bone is available when the operation is redone? There is no study that shows revision of a resurfacing hip has any better long term success rate than revision of a bone ingrowth stem.

  5. Greater range of motion and lower risk for dislocation compared to "traditional hip replacement":

    Response:

    This may be true when compared to the older forms of total hip replacement that used smaller head sizes. Modern design hip replacements can use the same size femoral head as in resurfacing, so theoretically dislocation risk and range of motion should be similar. More independent studies need to be done.

  6. Wear is better than "traditional hip replacement":

    Response:

    Again, this is a false comparison since modern design total hip replacements also include metal-on-metal or ceramic components which have comparable wear as in the resurfacing.

  7. Allows greater activity level than "traditional total hip replacement":

    Response:

    Long term "high impact" activity levels of resurfacing have never been specifically studied. Those physicians that impose "no restriction" of high impact loading on their resurfacing patients, do so without supportive documentation. In principle, the secure ingrowth in a femoral stem of a modern hip replacement has a much more durable capacity for high impact loading than the more tenuous fixation of a short peg and a cemented cap on the upper femur bone. The initial motivation of resurfacing was due to failures of cement fixation in the highly active young people. Does it really make sense that this construct would now be more durable in the "young, high demand patient population"?

  8. Shorter rehabilitation time compared to "traditional hip replacement":

    Response:

    There are no independent studies that compares the same age group of patient and preop activity levels in the rehabilitation time of resurfacing versus modern design hip replacement. Some rehab protocols for resurfacing actually involve longer times of protection for the resurfaced femoral head to allow some of the compromised blood flow supply of the ball to recover.

Disadvantages of hip resurfacing include:

  1. Fracture risk - The technical demands of the procedure are much more exacting. Mild variations of positioning and technique can create weakness in the bone and subsequent increase in fracture risk. The blood supply to the bone is compromised by the procedure which impairs some of the local blood vessels providing nutrition to the ball of the hip joint. Collapse or deterioration of the strength of this bone (avascular necrosis) would lead to shifting of the implants and failure.
  2. Loosening risk - Cement, as we know historically, has the risk for breakdown and loosening especially under high load activities. This was the main tissues causing higher failure rates in young people with cemented total hip replacements. Why would we put so much faith in cement now to allow high impact activities on a resurfacing implant?
  3. Unable to adjust leg length – The criterion for selection for this procedure include a leg length difference of less than 1 cm. Because of the mechanics of application of the resurfacing cap on the femoral head, leg lengths cannot be adjusted. As a result, it is less predictable to have the capacity of equalizing leg lengths when a preop shortening is present.
  4. Unable to adjust "offset"- This involves adjusting the muscle tension about the hip for optimal efficiency and muscle strength. In routine hip replacement these adjustments can be made by the options built into the stem design. This cannot be adjusted with resurfacing.

In Europe and other places around the world, total hip resurfacing has been done for many years now with tens of thousands of patients. In general, these results have been very favorable. Is there any advantage to this procedure that justifies the higher failure rate when compared to the modern total hip replacement?

A recent study published in the Journal of Arthroplasty, February 2008 with follow-up at only two years shows a 3.3% overall revision rate. In women, the rate of failure was as high as 7.4%. 6

In the British Journal of Bone and Joint Surgery in the first 230 resurfacing procedures, the total mechanical failure rate of fixation was greater than 10% at four years. 7 Even in the favorable studies, the short term results show a 1-2% fracture/failure risk within the first 1-2 years. 8 , 9

CONCLUSION:

It is very difficult for the lay public to gleen the context,scope, and applicability of medical information on the internet. Often, promotional information and marketing materials in the media cloud the expected objective scientific nature of the information at hand. I encourage the public to seek multiple opinions especially when "cutting edge" issues and controversial procedures are involved.

In conclusion there are no comparable independent studies that can verify any of the superior claims of hip resurfacing when compared to modern design total hip replacement with large metal-on-metal heads and sockets. There are no studies with similar age population, disease process, or blinded independent observers that have yet been done in any numbers to justify this mass enthusiasm. The hip resurfacing procedure has always been controversial with results inferior to total hip replacement. Dr. Berend states in the Orthopaedic Journal "this is a solution to a nonexistent problem". As Dr. Cuckler stated "more reliable results are associated with metal-on-metal total hip replacement and it is still the optimal arthroplasty". 10

John G. Mayer, M.D.

Member:
American Association of Hip and Knee Surgeons.
American Academy of Orthopaedic Surgery.

Private Practice:
Libertyville, IL.

REFERENCES

1 Journal of Arthroplasty 2006, 21; 1822.
2 Journal of AAOS 2006, 15; 454-63.
3 Journal of Arthroplasty 2008. 23; 2; 318.
4 Dr. Lachiewicz-Panel AAOS meeting.
5 Journal of Arthroplasty 2000, 15; 505-511.
6 Journal of Arthroplasty 2008 23; 2. 318.
7 Journal of Bone and Joint Surgery Br 11: 1431-1438.
8 Orthodedic Clinics of North America 2005 36; 195.
9 Journal of Bone and Joint Surgery Br 87; 320-323 and 463-464.
10 Journal of Arthroplasty 2006 21; 4 supplement 74-76.

-JGM