To The Editor:
The clinical results of contemporary total knee replacement are excellent.
Survivorship rates of 90% to 95% at ten years have been reported from both
Norwegian1 and Swedish2 knee registries. If the results
are so good, is there a need for new technology?
The high demand for primary total knee replacement surgery3 has
inevitably led to a similar demand for revision surgery. This is undesirable
for patients and expensive for the National Health Service purchasers of
health care. Many revision implants cost over £3000 ($5205) for the
implant alone. Total costs often exceed £20,000 ($34,704).
Reducing of the rates of failure and revision is
multifactorial4,5. Improvements in design, materials, and surgical
technique are all important. Accurate mechanical alignment and ligament
balance ensure optimal kinematic performance and wear, which in turn improve
long-term outcome6.
All contemporary total knee replacement systems have dedicated instruments
or jigs to assist the surgeon in accurately aligning and locating the
instruments. Computer-assisted surgery and image-guided surgery have been used
to assist the orthopaedic surgeon to perform stereotactic neurosurgery and are
now available to assist the orthopaedic surgeon to navigate during joint
replacement, cruciate ligament reconstruction, and osteotomies. The available
systems differ, but they rely on light-emitting diodes, emitting or reflecting
from instruments attached to bone markers or instruments. Some of the earlier
designs require preoperative computerized tomographic scanning, but the newer
systems do not7,8. Studies have shown that these systems can
improve alignment by significantly reducing the number of
"outliers"9,10.However, mechanical alignment itself is
based on a surrogate outcome indicator, and it remains to be proven whether
this benefit will result in significantly better long-term outcomes and
reduced failure rates.
Image-guided total knee replacement surgery is still relatively new. It can
improve alignment, has the potential to assist ligament balance, can provide
immediate feedback to the surgical team, may assist in reducing the learning
curve, may contribute to teaching, and may provide documentation at key stages
of the surgical procedure. These systems are expensive, although the costs
will inevitably decrease if volume increases. At the moment, operative time is
extended but should decrease with enhanced surgical experience and further
development of the systems. Some experienced knee surgeons would point out
that total knee replacement is essentially "a soft-tissue
operation" and that a skilled surgeon using contemporary jigs can
achieve excellent clinical results with use of proven implants without adding
cost, extending operative time, or potentially harming the patient. Skeptics
may say that industry is pushing technology to maintain or gain market share.
However, many surgeons with experience with image-guided surgery are impressed
with the ability to check bone cuts intraoperatively and to enhance ligament
balance. This immediate feedback allows intraoperative fine-tuning of the
procedure with potential benefit to the patient. So is image-guided surgery on
the cusp of global introduction, or will it expand and then wither because of
the cost or doubts about safety and increased operative time? Some countries,
including Germany and France, have already embraced this technology, but
whether it achieves global acceptance is presently uncertain.
Computer-assisted orthopaedic surgical technologies are in the early phases
of development and implementation. The appropriate roles for these
technologies are not yet clear. However, as with all new technologies that
have been introduced into orthopaedic surgery, the successful application of
computer-assisted technologies will require a constructive and constant
interaction among the technology experts in this field, orthopaedic surgeons,
and the industries that are and will be responsible for making these
technologies available. Therefore, it is very important that this interaction
be encouraged and expanded.
The successful outcome of a total knee replacement requires proper patient
selection, appropriate perioperative management, and precise surgical
technique. Computer-assisted orthopaedic surgical technologies seek to ensure
that the surgical technique that is used achieves its alignment goals
accurately and reproducibly. Computer-assisted orthopaedic surgery can help
orthopaedic surgeons to achieve these goals in a number of ways: (1) by
improving the accuracy and reliability with which all instruments, including
both manual and computer-assisted instruments, are used; (2) by stimulating
the development of more precise manual instruments; (3) by clarifying the
alignment goals for individual patients with specific deformities; and (4) by
encouraging the development of implants that can be inserted with increased
accuracy and reproducibility and reduced surgical exposure. Surgeons who have
acquired experience with the first-generation computer-assisted orthopaedic
surgical total knee replacement systems have recognized and reported these
benefits.
The greatest initial benefit of computer-assisted orthopaedic surgical
total knee replacement systems is that they make it possible, for the first
time, to clarify the relationships between surgical technique and all of the
other factors that affect the outcome of a total knee replacement.
Computer-assisted orthopaedic surgical total knee replacement tools make it
possible for orthopaedic surgeons to achieve their alignment goals with
measurable precision and reproducibility. Therefore, it is now possible to
determine in what ways and to what extent factors such as implant design,
physical therapy, and patient characteristics affect the outcomes of total
knee replacement.
Current computer-assisted orthopaedic surgical systems have a number of
substantial drawbacks and limitations, including substantial costs, as we
pointed out in the report on our initial
experience10.
However, the potential benefits of this technology to orthopaedic surgery are
so substantial that it is essential that orthopaedic surgeons gain experience
with these technologies so that they can provide appropriate guidance for the
elimination of these drawbacks and limitations.
Experienced surgeons, including those who consistently report excellent
results with use of current surgical techniques, know that the current total
knee replacement procedure is far from optimal. Accurate, appropriate,
reproducible surgical technique is not the only factor that will lead to the
optimization of the procedure, but it is certainly a prerequisite.
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