Thanks for the
Using computer navigation in joint surgery is a double
edged weapon. While potentially it can reduce the number of
outliers, it can also cause tremendous deviations and
absurd placements which would never be done with
conventional jigs. I have seen many examples of this done
elsewhere and referred to me for revision surgery.
Generally the input to the computer is made by a technique
known as bone morphing where the surgeon uses pointer probes
to point out the various bony landmarks to the computer. If
the surgeon makes an error in this step then it obviously
carries on in all further steps leading to a faulty
placement. To argue that it removes human error is most
We have the brainlab navigation ( market leader in
navigation) in our unit since 2007 and I did a series of
cases at that time ( about 80 cases) . I have to say that
the femoral cap placement was inferior to my placement with
traditional jigs. However I found it useful when one had
distorted anatomy as in previous prox. femoral osteotomy. I
still use it for such cases.
There are many reasons in my opinion by which the
conventional jig is far superior to the navigation in hip
1. bone morphing with the pointer probes damages the neck
capsule which I protect passionately during hip resurfacing
surgery and which I am sure is one of the key elements for
my success rate.
2. I use navigation routinely during my Total knee
replacements as the aim of the TKR surgery is to allign the
components to the hip and ankle which are not visible in the
surgical wound. In contrast in hip surgery the goal is not
to align hip component to the spine , pelvis or knee/ ankle.
The aim is to align components to local landmarks in the
surgical wound, the location of which is given to the
computer by the surgeon. Then the computer gives back the
same information which the surgeon offered in the first
place. ( this is unlike the TKR where the computer picks up
the hip on merely moving the hip and not morphing).
Arguments that the computer increases accuracy in hip
surgery is frankly absurd and have to be dismissed as
3. The concept of incorporating the combined anterversion
is now the key in operating on FAI ( Femoro- acetabular
impingement) which is the pathology in over 95 % of male
patients having primary osteoarthritis. This is a dynamic
assessment and can be done only with a jig using a lat
cortex pin and cannot be done with navigation.
Having said all of the above one must make a distinction
between what Prof. Cobb uses and what others use.
Prof . Cobb is the only one to my knowledge who uses a CT
based navigation. The CT gives information which the surgeon
cannot access unlike imageless navigation with all other
surgeons which depends on surgeon’s input based on bone
morphing that defeats the whole purpose of navigation.
In conclusion I would like to say that imageless navigation
has very limited role in hip arthroplasty ( eg previosely
operated cases) and is an excellent tool in Knee
CT based navigation for hips which is still not available
commercially ( which prof. Cobb uses) may have a significant
role in hip arthroplasty. This has to be balanced with the
radiation dose for routine CT to be applied universally(
approx 30 -50 conventional x-ray dose )
wishing you the very best
with best regards