More Controversy over MoM Devices

This month, a leading research group reversed its previous
position on the safety and efficacy of hip resurfacing devices as they compare
to total hip arthoplasty (THA).  The
California Technology Assessment Forum
released a new review of
these devices concluding that, based on current peer-reviewed literature, hip
resurfacing is not necessarily a better alternative than the current standard
of care (THA).

This is a step backward for supporters of the hip
resurfacing technique; just last year CTAF supported the position that hip
resurfacing could be a better alternative to THA for some patients.  However, as author Dr. Judith Walsh pointed
out, the group’s previous assessments acknowledged lack of clinical trials
directly comparing the two procedures.

Total Hip
Arthoplasty (THA) Vs. Hip Resurfacing

In case you are not familiar, total hip arthoplasty is the
same as a “total hip replacement”. This means that both the femoral head and
the acetabulum are replaced with artificial devices. In a hip resurfacing
procedure, the femoral head is left intact and an acetabular component is
inserted. Hip resurfacing has been promoted to younger patients, for whom THA
is not expected to last for the rest of their life. Reports of earlier return
to function and less restriction on function have made it more attractive for
younger patients, as well.

However, as CTAF’s 2011 report notes, there are downsides to
resurfacing. It can be a more complicated surgery, one that only specifically
trained surgeons should perform. It also can lead to avascular necrosis over
time, as the favored approach can devascularize the femoral head.

Hip Resurfacing Arthoplasty


CTAF October 2011

Using a set of 5 criteria in a “technology assessment” (TA),
they evaluated three most common metal-on-metal (MoM) hip resurfacing systems. The
systems must meet the established criteria in order to confirm that resurfacing
provides notable benefits over THA. Three important criteria were not met. From
their analysis of peer-reviewed studies on the matter, they found that (1) the
technology (of hip resurfacing) did not improve health outcomes; (2) the
technology was not as beneficial as any established alternatives; and (3) the
improvement is not attainable outside of the investigative setting.

Limitations and
Further Study

According to the New York Times, a hip resurfacing
expert criticized the report for failing to take into account a number of
benefits for certain patients, including reduced potential for dislocating
joints and increased mobility. Dr. Edwin P. Su, an orthopedic surgeon at the
Hospital for Special Surgery in New York, argues that active men who are younger
than age 65 are good candidates for resurfacing and he sees significant
benefits for that group of patients.

CTAF acknowledges that many questions remain as far as long-term
results of resurfacing, THA, and revision surgeries. They also do not claim
their findings to be conclusive. However, the review did succeed in challenging
previous assumptions about resurfacing vs. THA. Dr. Walsh concludes that, based
upon CTAF’s review, “It is [now] incumbent upon the hip resurfacing community
to prove the efficacy and safety of MoM hip resurfacing in randomized clinical
trials, rather than subjecting young patients to significant potential harm
over their lifetimes.”

According to the New York Times, other prominent orthopedic
groups are planning to take a closer look at hip resurfacing and whether or not
it provides true advantages over THA.