Orthopedics to Take Center Stage in Coming Decade
February 8, 2000
The World Health Authority has decreed that 2000–2010 will
be the Bone and Joint Decade, and this is now being
supported by the United Nations. The rationale for this is
that joint diseases account for half all chronic conditions
is people over 65; back pain is the second leading cause of
sick leave; and osteoporotic fractures have doubled in the last
decade, so that 40% of all women over 50 will eventually
suffer from one. It is estimated that 25% of health
expenditure in developing countries will be spent on trauma-related care by the end of the decade, and many
children are deprived of normal development by crippling
diseases and deformities.
The aims of the decade include raising awareness of these
problems and reducing their effect by research and other
methods. One of the effects which has been seen
throughout the developed world is the growing use of
evidence-based medicine to assess the effectiveness of
treatments. The long-standing Scandinavian hip and knee registers provide a good example; iIn one case,
data from the registers led to the removal from the market,
in a relatively short time, of a bone cement with extremely
high failure rates. More recently, NICE (National
Institution for Clinical Excellence) has undertake review of hip
replacements in the UK. As recently as 1995, it was
reported that 70% of 62 hip replacements in routine clinical
use in the UK did not have published longer-term follow-up,
and the costs ranged (at that time) from £250 to £2,000. In
this case, the surgeon has no hard data on which to base his
decision as to which is the best hip replacement to use.
In terms of new materials for use in orthopedics there are
two major developments. The first is crosslinked polyethylene, which aims to reduce wear rates and thus implant
loosening produced by PE wear debris; of course currently
there is no clinical data. The second is the current
development of injectable graft materials, which are mixed in
the operating theater, injected into the patient, and allowed to
set, holding a fracture. In time, the artificial graft either dissolves in the body fluids or is resorbed
by cellular activity, leaving only the repaired
fracture. Research is being conducted in various centers around
the world, so it seems likely that someone will produce a version with sufficient initial mechanical properties and appropriate degradation rates.
Leading on from these total artificial materials are tissue-engineered implants. One such system is Carticel,
commercialized by Genzyme. Its main application, for
patients with focal lesions in the cartilage, involves taking
cartilage cells from a non-load-bearing areas of the
patientÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂÃÂs cartilage and multiplying them outside the body.
Once sufficient cartilage cells have been produced, the
surgeon makes a pocket over the damaged cartilage and
injects the cells into the pocket. This uses the patients own
cells, thus removing the risk of rejection or disease
transmission.
This is likely to be the first of many tissue-engineered
systems. The later ones will have a more permanent matrix
into which the cells will be placed to prevent them from escaping
from the required region. The other likely development is in
mechanically conditioning the cells so that they are ready for
their mechanical environment when they are placed in the
body. Within orthopedics, most cells are subjected to
mechanical loading, and their growth and turnover is
effected by this mechanical environment. If they can be
"trained" before they are implanted, then they should be
incorporated much more quickly. Typical applications of
these techniques are likely to be artificial cruciate
ligaments, cartilage, and—later—bone grafts, which will rely on
new materials to form the matrix.
Clearly, orthopedics has a range of exciting developments for
certainly the next decade and probably beyond. With the
aging population, patients are going to be more demanding
of their implants, are going to want to get back to sport in
their retirement, and to just get better and be more active.
This should also benefit their general health.—Professor Elizabeth Tanner, IRC in Biomedical Materials,
Queen Mary and Westfield College, UK
Reprinted from Medimonitor – Special Millennium Edition, published by Datamonitor.
