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The post approach which I employ is traditionally known as
the muscle sparing approach and the anterior and
anterolateral approaches which is very popular in the U.S
and some parts of Europe are the muscle compromising
approaches.
The muscle here refers to the Abductor group or the muscles
which lift your leg sideways and is the most important
muscle of the hip. The post approach spares this completely.
However some muscle have to be cut in any approach to get
access to the hip and in the post approach, one cuts the
short ext rotators which are flimsy , small muscles in the
back of the hip. These are stitched back. These muscles are
relatively unimportant as the main ext rotator is the
gluteus maximus which again is undisturbed.
Increasingly surgeons the world over are realizing the
importance of preserving capsule over the neck of the femur
in resurfacing surgery especially in cases where there is
little or no arthritis as in AVN and the blood supply comes
from outside bone( extra-osseus) , in contrast to full blown
arthritis where the blood supply to a large extent changes
to inside bone( intra-0sseus) .
This NCP approach ( Neck Capsule Preserving ) for
resurfacing surgery was developed here in Chennai. The other
benefit of the NCP approach is the fact the capsule is also
repaired back completely so that the surgeon can
confidentently advise patients that there wont be any
restrictions post-op. The repaired capsule will prevent the
patient from doing any awkward movement even inadvertently.
Vijay Bose.
consultant orthopaedic surgeon
Chennai
Summary of Advantages - Posterior vs. Anterior Approach:
The posterior approach for hip resurfacing has the following
advantages now that the instrumentation has been redesigned
specifically for that approach:
1. No important muscle groups are sectioned.
2. There is no release of the abductor muscles. They are the
most
important muscles stabilizing the hip during walking and
other
activities.
3. The gluteus medius and minimus remain intact. The only
muscle
groups that are released are the short rotators that are
repaired at
the conclusion of the procedure. However, no important gait
or
other disturbances results from a release even if they are
not
repaired because the rotation is accomplished by other
muscles. One
of the two insertions of the gluteus maximus tendon which
extends
the hip may be released and if so then repaired. The other
insertion
remains intact and there has been no significant
physiological
damage to date.
4. The new instrumentation facilitates a smaller incision
especially
in thin individuals. A longer incision is necessary in well
muscled
or overweight patients. A slightly longer incision is
necessary in
resurfacing than when the head and neck are amputated in
conventional THR. In hip resurfacing the surgeon must work
around
the head and neck to be able to prepare the acetabulum and
implant
the socket accurately. Hip resurfacing is technically more
demanding
and takes slightly longer. Since hip resurfacing is an
anatomical
replacement, leg length equalization is facilitated and more
precise. Leg length equalization in THR is more demanding,
less
certain and requires an intra-operative X-ray.
5. The anterior approach requires removal of some of the
abductor
muscles for either hip resurfacing or THR. Even though they
are
repaired this reattachment may not be 100% successful.
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