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38
excellent accuracy and precision within 1° and
1mm. Several alterations of IR technology
went through multiple cycles of improvements
and other options such as electronic magnetical
(EM) tracking or ultrasound technologies
aroused but were not as successful and, more
importantly, not as accurate and reliable than
IR technology [35].
CAS in knee replacement confirmed over the
years its benefits on leg alignment, component
position, reduction of surgical invasiveness
such as blood loss and fat embolism reductions
without increasing the number of complications
[62, 63, 64, 65]. Most recently, a few studies
showed improvement in short term functional
outcomes and lower revision rate with the use
of CAS in TKA [66, 67, 68]. Accurate
intraoperative measurements has undoubtedly
shed lights on current insufficiencies of
conventional instrumentations [69]. The usual
separation between measured resection and
gap managements techniques is not satisfactory
and CAS is currently generating thousands of
datasets that will help to understand more
precisely the effects of each steps performed
during these two techniques. Indeed, mid-
flexion instability and unpredicted knee
kinematics are still issues to be solved to
improve TKA results [70]. For years, brilliant
scientists have done a kind of reverse
engineering in analysing a multitude of factor
of knee anatomy, investigating knee kinematic
characteristics to design better implant and
instrumentations. However, there is an obvious
discrepancy between current knee biomecha
nical knowledge and what is really applicable
in surgery. Navigation is certainly filling the
gap between the two.
More recently, robotic came back stronger than
before. Significant technical innovations have
made these tools more reliable, more user-
friendly and more ergonomically fit to normal
orthopaedic surgical practice. One of the most
recent tools is the PFS robot (precision free-
hand sculpture robot), which is the first
handheld robot using CT-free navigation
technology. This tool relies on concept already
described above, with four phases (set-up,
registration, planning and execution) and the
use IR technology. This small new robot is one
of numerous technological tools that are now
available to surgeon to secure the knee
replacement procedures [71, 72].
Conclusion
I was lucky enough to be part of the birth of
CAS in TKA following all early developments
that are now accessible to any surgeon. These
tools have been through extensive cycle of
evaluation, trial and error processes, and have
now reached maturity. Most of these systems
can now be used on a routine basis as any
conventional instrumentation to perform TKA.
I personally went through five phases so far:
1.
Prototypal phase
2.
Measured resection technique
3.
Gap management software development
4.
Refinement of the technique and intelligent
use of data collection
5.
New tools in the surgical tool box.
Each of them has brought technical advances,
more knowledge in knee anatomy and
kinematics and finally improvement of TKA
outcomes.
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Literature