Surgical Approaches for Hip Resurfacing
Peter Brooks MD
Cleveland Clinic
Most hip replacement and resurfacing surgery in the USA, about
80%, is performed through a posterior approach. About 20% of US
hip surgeons prefer some variation of an anterior approach (antero-lateral,
direct lateral, trans-gluteal, or true anterior). Anterior
approaches are also more common in Europe and Canada.
In the posterior approach, the incision, dissection, and
dislocation of the hip joint are all performed posteriorly
(toward the buttock). The large gluteus maximus is split, and
the gluteus medius and minimus muscles (hip abductors) are
retracted, but not cut. A number of smaller muscles, the “short
external rotators” including piriformis, obturator internus,
gemelli, quadratus, and obturator externus, are cut, and the
tendon of gluteus maximus may also be partially divided. With
these out of the way, the posterior hip capsule is incised, and
the hip is dislocated posteriorly by turning the foot toward the
ceiling. The acetabulum and femoral head are then resurfaced,
the muscles and capsule are repaired, and the incision closed.
In the direct lateral approach, (or trans-gluteal approach as it
is also known), the incision is on the side of the hip, and from
there the dissection proceeds towards the front of the hip
joint. The hip abductors (gluteus medius and minimus) are split
in the line of their fibers, peeled off the greater trochanter
of the upper femur in continuity with upper fibers of the vastus
lateralis, and retracted anteriorly, allowing the anterior
capsule to be cut, and the hip to be dislocated anteriorly, with
the foot pointing down to the floor. During closure, these
muscles all tend to lie back where they belong, and since they
have not been cut across their fibers, there is no tendency for
their repair to pull apart. The antero-lateral approach is
similar, but retracts or detaches, rather than splits, the
abductors.
The true anterior approach can be adapted to hip resurfacing,
actually better than for hip replacement, since exposure to the
shaft of the femur is difficult (and not needed in resurfacing).
It is not popular among surgeons who operate on adults, but is
fairly common in pediatric orthopedics.
Different approaches have different issues. The posterior
approach is very well known in the USA, and BHR developers Mr
McMinn and Mr Treacy use it routinely as well. Theoretically it
should have a higher dislocation rate, due to the fact that
dislocation almost always occurs posteriorly, and this approach
disrupts all the potential restraints to posterior dislocation.
But dislocation after hip resurfacing is much less of a problem
than it is with hip replacement, due to the very large head
size. The blood supply to the femoral head stands a greater
chance of damage through the posterior approach, since that is
where the vessels mostly are. The important hip abductors
(gluteus medius and minimus) are left completely intact.
The direct lateral (trans-gluteal) approach has the advantage of
a lower dislocation rate, and less likelihood of damage to the
blood supply of the femoral head. In addition, no muscles are
actually cut across; they are just split, or teased apart in the
line of their fibers, which should lead to more reliable
healing. The exposure of the socket is a “straight shot”, since
the acetabulum is an anteriorly facing structure. The
disadvantages are that there is nonetheless surgical trauma to
the abductors which, if substantial, could cause a limp. There
are also reports of heterotopic ossification, although this may
occur with any approach.
The true anterior approach can be associated with injury to a
sensory nerve responsible for the side of the thigh (lateral
femoral cutaneous nerve), and the location of the incision in
the groin is not the cleanest part of the body. It is also by
far the least commonly used of these incisions for adult hip
surgery, so at least for the time being, we do not have a lot of
data.
The main thing to keep in mind is that any of these surgical
approaches can work just fine. All have been modified in many
ways as surgeons find better ways to do things. The most
important thing for a patient to decide is who will do their
surgery, not how it will be done. The surgeon, drawing on his or
her own training, experience and beliefs, will decide what works
best in their hands.
READ COMPLETE ARTICLE
Clinical Orthopaedics & Related Research. 463:90-97, October 2007.
Cobb, Justin P FRCS; Kannan, Vijaraj MD; Brust, Klaus MD; Thevendran, Gow MD
Abstract:
Hip resurfacing is a novel technique with a substantial learning curve resulting
in poor outcomes for many patients. We asked whether navigation would influence
this learning curve and accuracy of implantation. Twenty medical students
earning their degree in surgical technology participated in a randomized trial.
We provided instruction about the surgical technique, including the use of
conventional instrumentation, the use of a computed tomography-based planner for
hip resurfacing, and a navigation system. The 20 students were then split into
three groups undertaking these tasks in three different orders. Synthetic femurs
replicated normal, osteoarthritis, slipped capital femoral epiphysis, and coxa
valga. The mean error using the conventional method to insert a guidewire was
23[degrees]; using the computed tomography plan method it was 22[degrees]; and
using navigation was 7[degrees]. Students produced similar accuracy, even in
their first attempt, on difficult anatomy when provided navigation. Motivated
students rapidly achieved an expert level of accuracy when provided with
navigation. Learning a conventional method first did not improve performance,
even in difficult cases. Our data suggest navigation may play an important role
in reducing the learning curve in hip resurfacing arthroplasty and other tasks
in arthroplasty in which a high degree of accuracy is clinically important.
(C) 2007 Lippincott Williams & Wilkins, Inc.
READ COMPLETE ARTICLE
The issue of cup slippage in the immediate postop
period is a controversial one.
While bone ingrowth takes around 6 wks. - the
hydroxy apatite to bone chemical reaction can occur
much more quickly.
If we surgeons feel that the
cup is not perfectly tight ( press fit) during the
surgery then we restrict activities for a 6 -8 wk
period .This is done in the hope that no
precipitating event would occur that would tilt the
balance adversely till some stability occurs as we
have not achieved primarily stability during
surgery. I must say that most of these times we are
able to 'escape' component loosening.
I have done this a few times in my very early cases
, many years ago. Of course these days we get such
spectacular fixation of the cup primarily that many
of my patients are visiting the gym in 5-6 days
following surgery.
Achieving primary stability in the resurfacing
surgery is more difficult as by definition there are
no screws in the acetabular cup of a resurfacing as
the entire cup is an articulating part ( monobloc )
cup. This is different from a cup in a THR where the
surgeon can easily get additional stability by
putting some screws if an adequate press fit is not
achieved. Since a liner is always used in a THR cup
, this is feasible.
Thus the early cup loosenings
are certainly going to be more in resurfacings esp.
when the surgeon is in the learning curve.
An
extension of this concept implies, that surgeons who
use screws routinely for the cups in the THR may
find the resurfacing cup without screws more
difficult to install.
Another issue is that if the cup is installed very
loose , a fibrous fixation occurs - very similar to
non-union in a fracture situation. If this occurs
this will prevent bony incorparation of the cup
permanently. This cup is at risk for many years
following surgery. One of the things that we look
for in the postop films is the bony incorporation (
osteointergration) of the cup.
with best regards
vijay bose
chennai
Asian Regional
Center for Hip Resurfacing
Friday, October 5. 2007
It is truly unfortunate that this lady has sustained a dislocation of a BHR.
It is a commonly used statement that a BHR is as
'stable' as a normal hip.
However this is a highly
qualified statement.
This statement is true only if the following
criteria are met.
1. Native angles, inclination , offsets and all
anatomical parameters have to be replicated.. If
this is not done fully and only accuracy of say 80%
is obtained - then the stability is likely to be
approx in the region of 80% only. Having said this
,even in this situation, the stability is likely to
be many times that of a conventional THR. Therefore
I would not call it a surgical error. As surgeons,
we get better and better at this replication as we
gain experience.
2. The capsule should be repaired to capsule
preferably as it restores the joint
'proprioception'( or position sense). This would
kick in the event of a potential dislocation as it
would in a normal hip. If the capsule is repaired to
bone , it is many times better than doing nothing
but does not achieve the proximity to the stability
of a normal hip. Again it is not a surgical error if
capsule to capsule repair is not done but one cannot
expect natural stability.
3. Other factors that can potentially cause
dislocation like impingement must be carefully
addressed . The most common offender is the non
-restoration of the head neck offset. One must keep
in mind that the BHR is the Ferrari of hips and the
conventional THR is an old fiat.
Even if the Gear knob of a Ferrari is not the
right size for the driver it shows up because it is
pushed to the limit and built for performance.
However even if the chassis is broken in an old fiat
, it would probably go unnoticed by the owner as it
is never 'pushed' for performance. There are many
patients after THR s with trochanteric non-unions
going on for many years without even being aware of
it!
Coming to the specifics of this patient.- The
Relocated BHR is likely to be stable with time and
is unlikely to affect longevity. The only issue is
that this patient must avoid extremes of movement to
prevent another episode.
I hope this helps
with best regards
Vijay Bose
Chennai
Asian Regional
Center for Hip Resurfacing
