Dr. Brooks, Bose, Rogerson & Gross explain the Gantz Approach

[Pat Walter]

Gantz Approach by Dr. Brooks

Hi Pat,

You asked about the Ganz approach, which is also known as "surgical dislocation" of the hip for resurfacing.

This was described way back in 2001 by Prof. Reinhold Ganz in Berne, Switzerland. Resurfacing was being done in those days, although not so much by him, and he used it for all kinds of hip surgery from debridement to revision total hips. The key factor is that it is designed to preserve the blood supply to the femoral head. That is irrelevant in hip replacement because the femoral head is getting cut off anyway. In joint preservation procedures like FAI operations, labral repairs, removal of loose bodies etc and in hip resurfacing, it is important that the femoral head blood supply is respected.

Dr Ganz's major contributions have been his descriptions of the blood supply to the femoral head, and of femoroacetabular impingement (FAI) in the development of hip arthritis.

There is little question that the posterior approach routinely damages the blood supply to the femoral head. But there is also little question that this approach yields excellent outcomes in hip resurfacing, and is done by most US surgeons, about 80%. The pioneering surgeons McMinn and Treacy both use the posterior approach.

The early post-op femoral neck fracture risk is 1-2% in men, and 3-4% in women, and since these are likely "fatigue" fractures or accumulated microstresses, I would expect that blood supply is important in preventing them.

Proponents of the anterior approaches, myself included, like to preserve the blood supply to the femoral head. These approaches include the anterolateral (like me), the direct anterior, and Ganz. In that both the femoral neck and the acetabulum face anteriorly, and the common FAI lesions on the femoral neck are anterior, it makes sense to go in that way. If you want to see someone at their front door, why go in the back? Having said this, remember that experienced posterior surgeons have no trouble seeing everything, but a less experienced surgeon would struggle.

In all the anterior approaches, to get to the front of the hip you need to get the abductor muscles out of the way. You can retract them, split them, or cut them, but they have to be moved. 

Ganz cuts through the bone of the greater trochanter, where the abductors attach, moves the bone plus muscle out of the way, and gets in that way. On the way out, then, one has to reattach the bone using hardware: either screws or wires, and protect the bone until it heals by delaying weight-bearing. Of course, any time you cut a bone and put it together, there is a chance that it does not "knit" or heal, just like a fracture. This causes pain, broken or loose hardware, and probably more surgery to fix it.

In the anterolateral approach you can spread the muscles apart, peel them off the trochanter and reattach them, or cut them. It's better to spread them in the line of their fibers, not cut them. This is how I do it. The muscles heal side-to-side, held together, not apart, by contractions. The blood supply is preserved, and I have had only one fracture so far out of 1100+. Knock on wood.

Posterior surgeons, like McMinn and Treacy, and most others too, cut a number of small muscles, ("the short external rotators") and sometimes part or all of gluteus maximus, and repair them on the way out in an end-to-end manner. Where total hips have a tendency to dislocate posteriorly, resurfacing is so stable that it really isn't an issue.

We would view Ganz's approach as being un-necessarily complex, and adding the additional risks of non-healing trochanteric osteotomy or broken hardware to the procedure. If you're concerned with the blood supply, do another, less complex anterior type of approach.

There are indeed circumstances during revision total hip replacements where a trochanteric osteotomy is useful, e.g. for getting out old stems and cement, and then I do it. The method Ganz described of "sliding" the trochanter and leaving it attached to the quadriceps below is how I do it, and hats off to him for that.

I have said this before, but I'll say it again: don't go and talk a surgeon into an approach that you like. He/she should do what they always do. Pick the surgeon. Resurfacing is a difficult operation, so your surgeon has to be comfortable with what they are doing. ANY approach, anterior, posterior, Ganz, etc can give the same excellent results in the hands of the experienced surgeon, using a good device, in an appropriate patient.

Regards,

Peter Brooks MD, FRCS(C)

Cleveland Clinic

[Pat Walter]

Dr. Rogerson explains:

I am not enthused about the Ganz trochanteric flip approach for several reasons. It was developed to be less injurious to the femoral blood supply. Koen DeSmet showed that with the modified posterior capsulotomy approach that he, Bose and I use, that the blood supply compromise during surgery is not much different than with a trochanteric osteotomy. Also, the incidence of AVN even with the much more extensive posterior capsular release that McMinn initially used is extremely low. We are now over 600 cases and have not seen a case of AVN.

Problems with any trochanteric osteotomy including the trochanteric flip all relate to injury to the gluteus medius attachment which results in an abductor lurch weak and awkward gait afterward. In this young and very active patient population, one is hard pressed to protect them for 6-8 weeks on crutches so the trochanteric bone can heal. If the patient is even relatively non-compliant, one is left with a lifelong limp that is impossible to fix. That is why the posterior approach became almost universal in America and the Charnley trochanteric osteotomy was abandoned. Paul Beaule recently reported on his series with trochanteric osteotomy and had a significant number of complications relative to the abductor mechanism.

In summary, this "flip" technique is a solution to a problem (AVN) that barely exists with the modified posterior capsulotomy approach and is associated with a significant number of "limps" and restrictions for a very active group of patients.

Dr. John Rogerson

[Pat Walter]

Comments by Dr. Vijay Bose

The ganz trochanteric flip is an excellent approach for doing open FAI surgery, for fixing fracture on the femoral head ( pipkin #) and for doing osteotomy of the femoral neck in post SUFE situations. In these non - arthritic situations a surgical dislocation of the hip is warranted without damaging the blood supply and I employ it routinely for these indications.

However its use in hip resurfacing is a bit of an overkill.
It has been documented without a shadow of doubt that the post approach does not compromise the vascularity of the femoral head in an arthritic hip after resurfacing. Thousands of patients who have crossed the 10 yr mark with the post approach & BHR bear testimony to this.

Doing the ganz for resurfacing is a much more morbid procedure than a standard post approach. Any osteotomy will take more time to heal and recover function. The extended trochanteric osteotomy ( ETO) which is the bigger version of the Ganz flip will take about 6 months for the patient to regain function.

Intuitively the Ganz looks appealing as regards preserving blood supply but this issue is not relevant in an arthritic hip.

with best regards
vijay bose
chennai

[Pat Walter]

Approaches in hip resurfacing by Dr. Gross

The path that surgeons choose to arrive at the hip joint is called the "approach". There are many different basic approaches used for hip resurfacing. None has been proven to be superior to others based on valid scientific research. Basically, I recommend that a surgeon use the method that he/she is already most comfortable with when performing standard total hip replacement and modify it as needed for the more complex hip resurfacing operation. My preferred approach is the posterior. This is used in at least 70% of hip resurfacings done worldwide. The next most common approach is the lateral (two versions: anterior-lateral and direct-lateral). Finally the direct anterior and the Ganz (or trochanteric, or internal dislocation) approach are far less commonly used. All of these approaches are adapted slightly by different surgeons.

I am aware of one nonrandomized comparison study comparing the anterior lateral and posterior approaches by different surgeons published by Ronan Treacy that found no difference. Most clinical series on hip resurfacing are based on the posterior approach. In a comparative report that I published, we found that the results were slightly better with a minimally invasive posterior as opposed to a standard posterior approach. There is another variant of the posterior approach where a small cuff of hip capsule is left as a remnant on the neck of the femur. This is called the "vascular-sparing" posterior approach. Many surgeons have recommended this, but evidence is scant. I started using this routinely several years ago, but found no difference compared to the standard posterior approach. We are currently working on a paper on this topic.

The theoretical advantages of various approaches are:

1. Posterior: Less harm to abductor muscles
2. Lateral: Lower dislocation rate with smaller bearing THR
    Less disruption to the femoral head blood supply
3. Direct Anterior: Lower dislocation rate with smaller bearing THR
    Less disruption to the femoral head blood supply
4. Ganz*: Less disruption to the femoral head blood supply

* described by Dr. Reinhold Ganz of Switzerland for open hip impingement surgery. It has been used for hip resurfacing by some surgeons. The abductor muscles are detached from the remaining femur by cutting through the greater trochanteric bone. The bone is reattached by screws. Dr. Paul Beaule was one of the early proponents, but has abandoned this because of the high rate of trochanteric complications.

The theoretical disadvantages of the various approaches are:

1. Posterior: More disruption to the femoral head blood supply
    Higher dislocation rate with smaller bearing THR
2. Lateral: More Harm to the abductor muscles
3. Direct Anterior: None
4. Ganz: Problems with bone healing of the greater trochanter

My personal opinion (not scientific evidence) is that recovery is slower with the lateral and Ganz because patients need more restrictions to avoid damaging the detached/repaired abductor muscles. While failure of the muscles is relatively common and easily diagnosed with the Ganz approach because the bone (trochanter) repair is easily monitored on XR, this same problem exists with the lateral approaches but is more difficult to diagnose because muscles are not seen on XR.

Direct anterior approaches are rarely used. Reports are scant. Two meeting presentations that I am aware of show a very high rate of femoral neck fractures (>5%), probably because a lot of force is required on the bone when this approach is used. I am aware of no published results.

Actually complications are much more related to a surgeon’s experience, as opposed to the approach he uses. There is a lot of evidence to support this theory.

Therefore, the best advice that I can give you is to ask your surgeon how many hip resurfacing operations he has done through a certain approach and what his individual complication rate is (not what some paper says the rate is). Every experienced surgeon should keep track of his complications and publish them. Most surgeons believe they have fewer complications than they actually discover if they rigorously analyze and publish their own data. My data are published online for 2500 cases with a 92% rate of follow-up done using the posterior approach.

Regards,

Thomas P. Gross, MD
11/1/2011