Mr. McMinn

I started back in 1991 with the antero-lateral approach to the hip for resurfacing. At that time we were worried about blood supply to the femoral head and on theoretical grounds the antero-lateral approach preserved the blood supply well. For many patients the approach was satisfactory but there were some problems. The exposure obtained in large patients was not good. This meant that heavy retraction had to be used, and heavy retraction caused trauma to muscle and other soft tissues which in turn led to heterotopic ossification. The other problem was that some patients had a permanent limp after my surgery as a result of the surgical approach. Please understand that the instruments were crude back then compared to today where newer designs of instruments would cause less tissue trauma and make the antero-lateral approach a better option. The sight of limping patients persuaded me to change my approach to the posterior approach. The theoretical objection to this approach was that it may cause more damage to the femoral head blood supply. It turns out that the problems with femoral head blood supply using the posterior approach are very rare, as you heard at the conference. The big advantage is that an excellent exposure can be obtained, giving the surgeon the best opportunity for perfect component positioning. As you heard, inaccuracy with respect to acetabular component positioning is badly tolerated and a high acetabular component inclination angle is the single biggest reason for early bearing failure following a metal on metal resurfacing. The other great advantage is that very little trauma to the soft tissues need occur with a posterior approach resurfacing. The other thing is that a mini-incision posterior approach can be done by those surgeons experienced in the resurfacing operation with good exposure and minimal tissue trauma. My unit published our mini-incision resurfacing results a few years ago, the average incision length was under 12 cm and measured component position was good.

There are two other surgical approaches to be considered by surgeons, but for different reasons these are not reasonable at this time.

The other issue is how well an inexperienced surgeon can be taught to reliably perform an uncomplicated resurfacing operation. It's no use talking about Ronan Treacy's or my own abilities in this regard as we have each performed well over 3,000 resurfacing procedures, and no matter how hard we work, we cannot make any impact on the world demand for this procedure. New surgeons therefore must be trained. As you heard, we tested how good newcomers to the BHR using the posterior approach really were and over 100 new surgeons, as well as Ronan and myself, entered our patients on the Oswestry Outcome Centre database. All those patients have been independently followed up. At 9 years post-op Ronan's and my results are still statistically significantly better, both with regard to failure requiring revision and also with regard to hip function. Never mind statistics, the fact is that the newcomer surgeons achieved very creditable outcomes, which means that the whole package with respect to training, patient selection, surgical technique and implant durability really does work. If anything in that mixture changes then the outcomes achieved may significantly change. To give you one example, during 1996, one year before I started the BHR, I carried out the Corin, double heat treated resurfacing which I designed. All the other ingredients of the package were the same.

Now that time has passed we can see the effect of one factor, implant design, on the outcomes. At 5 years there is no difference between the Corin and the BHR design on my outcomes. At 10 years, however, the Corin series has an 86 % implant survival whereas the BHR series has a 96 % implant survival. In addition, in the patients who have had the Corin resurfacing and have not been revised at 10 years, 20 % have osteolysis or early loosening. These features bode badly for the future. Heat treatment of the metal of the implant is not something that the surgeon can see, and I wasn't aware that the manufacturer had started to use this even though I was the implant designer! The implant looks the same as the historically proven, as-cast alloy and the early results give no cause for concern. The longer term sadly is a different matter. I understand your interest in the surgical approach, but it's the complete package that counts. For a patient, therefore, the key questions for their surgeon are: How long have you done metal on metal resurfacing? Am I a good candidate for hip resurfacing? Is my bone good enough? Do I have avascular necrosis which may increase the failure rate with hip resurfacing? Do I have dysplasia or any other condition which may seriously complicate the procedure and are you confident you can handle any difficulties? What surgical approach do you use and why? How were you trained and what was the resurfacing experience of your trainer? What are your results--- how many have you done and how many failures have you had? What are the hip scores in your resurfacing patients? What complications have you had with hip resurfacing? What type of hip resurfacing do you propose using on me? What are the results of that design used in a) the inventor’s hands and b) what are the results of that design of implant in the hands of independent surgeons e.g. what are that implants results on the Australian national register? If your surgeon is using a device with either no independent results or poor results on the Australian register the question to be answered is: Why are you using it e.g. are you paid to use it or is your hospital paid to use it by the manufacturer of the device?
 

Dr. Su:

I like the posterior approach for the excellent exposure that it provides (which is critical for the positioning of the implants) and the ease of recovery for the patient. There are some who believe a trochanteric flip (Ganz osteotomy) or anterolateral approach are better for the blood supply, but we saw from Mr. Treacy’s data that there wasn’t any difference in outcomes between the posterior and anterolateral approaches. Also, the recovery from the anterolateral and trochanteric flip tend to be more difficult, with protected weight bearing and avoidance of certain movements. Finally, if the muscles that were detached during the anterolateral approach don’t heal back to the bone, then this can be a serious problem. I don’t have much experience with the anterior approach, so I can’t really comment on that.

A final word is that I think there are many ways to skin a cat, and surgeons should use what they feel comfortable with.
 

Dr. Bose:

There are two ways to look at approaches to hip resurfacing or any hip arthroplasty. One is to view it with the amount of muscle damage done. The other is to view it in respect to the blood supply or the vascularity. The post approach is traditionally known as the muscle sparing approach and the anterior and anterolateral approaches are the muscle compromising approaches. These approaches are known as Hardinge approach or London hospital approach. There are many more modifications of this with slight variations but essentially they are the same and they disturb muscles to varying extents. 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. Interestingly there is now an anterior approach which is getting to be very popular for mini -THR and this is known as the mini Watson Jones approach or the micro hip approach. This does not disturb the abductor though it a ant. approach. However resurfacing cannot be done through this approach. Even when one does a THR the head has to be sawed off in place and then delivered out separately. Or in other words the hip cannot be 'dislocated' through this approach which precludes hip resurfacing. 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. It is largely accepted that the post approach is more conducive to early and complete return of function as it is muscle sparing. The ant approaches which disturb the gluteus medius will result in slower and incomplete return of function depending on the amount of muscle disturbed and the intactness of the muscle repair over long term. The younger and the more active the patient , the more would be the perceptible difference between the ant and post. approaches as regards function. Thus an elderly patient having a THR will appear to have the same result with either approach whereas a young patient having a resurfacing will have an obvious difference.

Michael Freeman , an English surgeon established in 1978, the fact that the blood supply in an osteoarthritic hip is different from a normal hip. In full blown arthritis the blood supply to a large extent changes to inside bone( intra-0sseus) from a pattern that is predominantly outside bone (extra osseus ).Therefore in osteoarthritis , any approach can be attempted without a risk to the blood supply. Hence in osteoarthritis, as the blood supply issue is taken out of the equation only the muscle damage is relevant and therefore post approach is better. In fact when Derek McMinn developed modern resurfacing , he first attempted it through the anterior approach and found so much of muscle damage that he decided to change to posterior.

However in non-OA indications like AVN , the situation is little different and the intra-osseus blood supply is not well developed. Increasingly it is becoming increasingly obvious that neck capsule preservation is vital in these non-OA indications. Hence we have developed the neck capsule preserving ( NCP ) approach where the end arteries to the neck and head -neck junction has to be preserved. We have been doing the NCP approach for the last 6 yrs in predominantly non-oA indications with excellent results.

Neck capsule preservation is not possible through the anterior approach and therefore the post approach is more suited for non-OA indications. The other benefit of the NCP approach is the fact the capsule is also repaired back completely so that the surgeon can confidently advise patients that there wont be any restrictions post-op. The repaired capsule will prevent the patient from doing any awkward movement even inadvertently. This is very useful in the first 6 weeks which is the time taken for a pseudo capsule to form when the surgeon does not stitch back the capsule . Therefore capsule repair is of relevance only in the 1st 6 weeks

The 3rd issue comes into play when a femoral component of a resurfacing is done uncemented. This is the situation where one has to be extraordinarily careful as even a little necrosis of the head bone would cause failure of the implant. When one uses cement, the cement converts the head into a 'composite' of live bone, dead bone and cement. Some bone unviablility is easily tolerated due to the presence of cement. Therefore in uncemented femoral resurfacing one has to use the Ganz approach or surgical dislocation where the blood> supply should preserved entirely. Although this appears to be desirable in theory for all resurfacing it has its own problems. It involves a trochanteric osteotomy and reattachment with screws. The pt has to be partial weight bearing for 6-8 weeks till the ostetomy unites. Prof Ganz from Berne developed this approach for non arthritic hips for pts in their 20s to treat femoral acetabular impingement (FAI). These patients have a completely normal pattern of blood supply (completely exta-osseus) and in spite of this, pts do not develop any problems. This technique is described as surgical dislocation and surgeons employ this for any condition that requires a dislocation of a normal ( non-arthritic) hips. The surgical dislocation is always done posteriorly.

Thus 3 different situations with regard to resurfacing need 3 different approaches and all of them are posterior! Anterior or posterior refers to which side the hip is dislocated and not on where the incision would be. Irrespective of whether anterior or posterior approach is done , the incision will always be on the side ( exactly lateral). So one cannot deduce approach employed by looking at the incision. Therefore the skin incision is same for both approaches.
Vijay Bose.
consultant orthopaedic surgeon
Chennai
 

Dr. Mont

The choice of approach to use for resurfacing has received much attention and I believe extra '"hype."  In multiple studies now published, there are no reported clinical differences in the short term and up to ten years of follow-up between anterior and posterior approaches.   I believe that any approach can be used and the surgeon should use what they feel most comfortable. 

Short-term differences that patients may report with either approach have to do with other factors in my opinion.  I use the antero-lateral approach because it affords me easy exposure, lower dislocation risk, less chance to disrupt the blood supply of the femoral head - among other reasons.  However, I have no problem with posterior approaches and am currently working on and performing an even more minimally invasive anterior approach in selected patients. Again, I would repeat that a recent prospective randomized study showed no differences in all three approaches.

In summary, the reasons I use the anterolateral approach are as follows:

1) easier to perform

2) less chance for dislocation

3) no difference in posterior approach at six months to one year or in long-term studies

4) increased range of motion from not having to repair the capsule

5) multiple studies showing decreased effect on femoral head blood supply  

Presently, I’m performing an anterior approach which does not go through any muscles. 

Dr. Brooks

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.

Dr. Lichtblau

The anterior vs. posterior debate isn't going to be resolved by one study of electrode blood flow. Most surgeons would agree that blood flow to the femoral head (most of which comes backwards via the femoral neck) is theoretically better preserved through an anterior approach. Much of this info comes from the work of Ganz, who did a lot of cadaver dissection to prove this. Having said that, there doesn't seem to be any evidence whatsoever that one approach or the other leads to a higher incidence of the femoral head dying after resurfacing surgery (so called ''avascular necrosis''). McMinn and Treacy, who have together the largest series of resurfacings in the world, both use the posterior approach, and there have not been any problems seen yet. I prefer the posterior approach because I am good at it, and I can perform the surgery quite fast through this exposure. Bottom line is that your surgeon should probably use the approach he/she is most comfortable with. Hope this info is of help to you.

Ethan Lichtblau, MD, FRCS(C)
Montreal, Quebec

Dr. De Smet

For the resurfacing procedure I always use the posterolateral approach for technical reasons. For a classic total hip replacement I changed after having performed 1800 procedures from lateral to posterolateral approach as well. The posterolateral approach does have many advantages: the abductors (gluteus medius muscle) responsible for normal gait remains intact, so less patients suffer from permanent abnormal gait after hip prosthesis. There is a much better view to place the components in a more correctly way (very important for revision surgery). There will be less repetitive muscle damage in revision surgery; there are fewer patients with complaints of trochanteritis (irritation of the bursa) compared to the lateral approach. The only disadvantage of the posterolateral approach is the larger incidence of dislocations in inexperienced hands / learning curve.

Dr. Amstutz

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 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.

Dr. Gilbert

I use the posterior because it is easy, fast, small incision, rapid recovery, regular table, no dislocations, and very good cosmesis.

The bone is well healed at 6-12 weeks. I allow running at 6 months. I do not use cementless resurfacing. I use Smith and Nephew Birmingham hip.

Dr. Rogerson

The most important reason I use the posterior approach is to spare the gluteus medius and avoid an abductor lurch after surgery which is fairly common with a lateral, antero-lateral and to a lesser extent anterior approach. Patients who desire to get active again are very dissatisfied if they have abductor weakness; if you detach a portion of the gluteus medius then you really have to protect its repair for 6 or so weeks after the surgery as Paul Beaule does. Another reason I like the posterior approach is the exposure one can attain for the femoral head and the ability to effectively use the stylus to get the guidewire in exactly the right position.