Dr. Bose Interview, Chennai, India

What surgical approach do you use-posterior or anterior?

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.

Photo: Dr. Vijay Bose

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.

Explain the advantage of the Posterior vs. Anterior Approach to Surgery
10/12/05

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.

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.

I have bone cysts, can I have a hip resurfacing?
The presence of a cysts by itself is not a contraindication for resurfacing. It does not preclude resurfacing automatically.

One must keep in mind that cyst formation is a natural occurence in osteoarthritis and is very common though the extent, quantity & location may vary. Cysts are ofcourse much more common and invariably present in AVN.

The  assessment of certain technical factors would the real  issue. This is based on the amount of residual bone after head preparation.  Some resurfacing prosthesis are thicker at the top and tend to replace more bone in the head  of the femur than other prosthesis. This is a great advantage in managing cysts as at the end of head preparation one is left with nearly 100%  head support in a majority of cases. The cysts get reamed away in bone that would have been removed anyway. The BHR is a good example of a prosthesis of this type.

The technical criteria which we we have been using in our centre (ARCH) for the last 7 yrs without any problems has been termed as 'mid-path recommendations' because we chose 50% as an arbitrary value when we started.

1. The criteria are an intact-head neck junction across the entire circumference to a height of 50% of profile cut (the actual height would vary depending on the size used)
2. Residual bone above the intack head neck junction must be atleast 50%

Dr. Sugano from japan has done an experiment where he removed 50% of head of fresh cadaveric bones and implanted a cemented resurfacing on them. He also implanted a cemented resurfacing on  an equal amt of fresh cadaveric bones with an intact head. He compared the mechanical strength of both in the lab and found the mech. strength to be equal in both groups.

The surgeon has to see the x-rays and CT scan before he can comment on a particular case.

I have tackled successfully some hips with significant cyst formation. See Webpage. Please see advanced OA with cysts and AVN.

Does Hip Resurfacing Remove More Acetabular Bone than a Total Hip Replacement?
One of my patients from India who has had a resurfacing, briefed me on the current discussion in the surfachippy forum regarding Dr. Klappers opinion of losing acetabular bone in an attempt to preserve femoral head bone in resurfacing. He wanted to know my opinion and I thought it would be appropriate for me to post my answer in this forum. Dr. Klapper's opinion is way off the mark. The acetabular size is the most important factor which determines the choice of femoral head size in resurfacing and one never removes more acetabular bone in hip resurfacings. In other words if I would be performing a conventional hip replacement on a given patient instead of resurfacing, I would be using precisely the same size acetabular component in both the surgeries.

I would go as far as saying that if we are taking out more acetabular bone in resurfacing than in conventional hip replacement, then in my opinion there is no role for resurfacing and it must be discontinued immediately. Acetabular conservation is as important if not more than femoral bone conservation and all resurfacing surgeons recognize and acknowledge this fact. The ability to put large heads in resurfacing stems from the fact that thin shelled acetabular components are possible with the modern metal on metal bearings. However when one uses polyethylene it has to have a large thickness,which in turn reduces the femoral head diameter, (assuming the acetabular outer shell diameter remains the same). The same argument holds true for ceramic on ceramic bearing to a lesser extent and therefore slightly large femoral head sizes than metal on poly is possible. However an anatomical size is currently possible only with metal on metal bearings.

I strongly object to the terminology of "large or jumbo head metal on metal hip replacement" that some surgeons use to describe the current versions of the total hip replacements which employ the same metal on metal bearing used in resurfacings. I point out in all my lectures that this variety of total hip replacement is the anatomical head replacement giving the same natural size (of the femoral head and the acetabulum) that the patient has in other normal hip and the conventional THR are indeed small head hip replacements. One must never lose this perspective. I hope this helps to clear the sudden doubt that was cast on the hip resurfacing principle recently.

What is the Age Limit for Hip Resurfacing?
The chronological age is not an absolute criteria. The physiological age, bone marrow density and the anticipated post surgery activity level of the patients are the deciding factors for the suitability of resurfacing procedure. X-rays must be reviewed by the surgeon to assess technical suitability. The youngest patient to undergo this procedure by Dr. Bose is 14 years old. The oldest male patient was 73 years old and the oldest female patient was 70 years old.

What is your take on Devices ?
Wrote to Vicky in an email on September 27, 2005, (please see below this response, an update on Dr. Bose new position on this, I am leaving this original response because my feeling is that there is pertinent information in it about the history of devices that have failed in the past.)
We, orthopedic surgeons find it difficult to weed out commercial promotional jargon from scientific data. I sure appreciate how difficult it would be for patients! Regarding the comparison of devices, the BHR was the original device and the others are copies of it. The BHR presently has a 9 year clinical history.

The 35 yr history of some metal on metal hip replacements (Ring & Mckee Faraar) was the major catalyst that led to the development of the BHR and the Birmingham designers took great care to duplicate the metal and clearances of the historical devices so that they can draw on the 35yr history. All other devices are deviances from the historical metal on metal THR devices and thus cannot draw on that history.

All other devices have a very short clinical history. Every manufacturer naturally will claim that their devise is the best and will quote varied reasons substantiating their claim. However, in any kind of joint replacement surgery, the track record is the most important feature and must be given exceptional importance. It is quite opposite of choosing a car, where the latest model is probably the best. The performance of a prosthesis when implanted may be quite different from lab tests. One can always exchange the car if it does not perform well but unfortunately in joint replacement things are not so simple!

The ASR (as all other prosthesis) have claims of superiority on lab testing. This is completely different scenario from how the implant behaves after implantation in a patient. Only time will tell as to which of these will work and which will fail.

Depuy (manufacturer) claims that the ASR is better because it is thinner than the BHR. Another manufacturer claims exactly the opposite i.e. that their product is thicker than the BHR and hence superior. Their opinion is that the thicker component serves the resurfacing cause better. The same goes for stem. Some of the new designs have smaller design claiming less stress shielding and some other have longer and thicker stems claiming to splint the neck of femur avoiding a fracture risk.

Thus you will find people changing some characteristics of the gold standard BHR and claim superiority. Some of these changes may indeed be good. However only time will tell whether they are desirable changes or fatal mistakes.

The history of orthopaedic surgery is littered with similar cases. One of the most important and well known is the Exeter THR stem which currently has the best results of a cemented hip replacement and can be considered to be the Gold standard. The manufacturer/developer surgeons decided to alter the surface treatment into a matt finish from a polished one. This resulted in a very high failure rate but it took 6-7 yrs for someone to work out the association. The Exeter stem then went back to its original polished stem. Who could a guessed that a surface finish of a non articulating part of a prosthesis would cause such a drastic change in results?

The responsibility of the surgeon is not confined to the surgery alone. Post op performance of the implant is also a surgeon's responsibility. This makes me cautious.

I am not a gambling man, hence I stick with the BHR. However, when the choice is not made by me, I do use other devices. Patients have requested specific devices and i have used them. In other instances surgeons have asked me to use other implants when I have gone over to other centres to help them do resurfacing surgery and I have complied. I have nothing against other implants but no one can deny that they are a bit of a gamble.
NOTE UPDATE:  sent to me on April 15, 2009 from Dr. Bose on his current position on device.

Which is better a BHR or an ASR ?
I was not keen to do the ASR when it was introduced. After a couple of years when surgeon friends told me that it was good and I saw the results, I tried it out in a phased manner.

Currently I use the BHR and ASR to almost about 50% each.

I make the decision based on technical preference in the particular patient. I think the BHR and ASR are best suited for opposite ends of the spectrum of patient and bone size.

One important advantage of the ASR is the small stem (peg) it has for the smaller sizes. This is the huge advantage in small built individuals as the proportion of the stem ( peg)to the residual bone is less. In contrast the BHR has a same size peg through all sizes. A large peg in a small head size has the potential problem of causing stress shielding . I almost never use the very small size BHR like the 38 anymore.

In very big built patients who are bound to return to sports etc very soon the BHR is the preferred option as the cup has a more high profile surface for bone contact with a plastic disc for heavy impaction. The ASR is more fine and seats without much impaction. This may be an advantage in relatively soft bone.

The other important way to harvest the advantage of prosthesis design is the selecting the prosthesis based on the amount of head bone involved. The ASR certainly removes less bone in the head than the BHR. This could be used to the advantage of the patient in a condition like ankylosing spondylitis where the problem is only in the articular cartilage with the bone being intact. Here the ASR scores over the BHR.

However in a pathology like AVN there is significant head involvement, the BHR has a distinct superiority as one would like to remove the diseased bone and replace it with the metal.

Osteoarthritis lies somewhere inbetween where some patients have significant head involvement where the BHR would be superior and in some others the head bone may be largely intact and the ASR would be a better option.

Thus I choose the prosthesis based on technical issues and employ it to the patient’s advantage. Thus in my practice both the ASR and BHR complement each other. After doing more than 200 ASR over the last 2-3 yrs , I am as impressed with the ASR as with the BHR.

I was one of the first to try out computer aided surgery for resurfacing. This has no advantage except in patient who have had previous surgery like a osteotomy . It has a very important disadvantage of removing all the capsule and soft tissues on the neck of the femur ( to take a computer reading known as bone morphing). This will compromise blood supply. I have to say that currently for resurfacing computer aided navigation is only a marketing tool for surgeons/ companies. Computer aided navigation is very beneficial in knee replacements where one has to align the knee components to the hip and ankle and I use it routinely for knee replacements.

Wishing you the very best

With best regards

Vijay bose
chennai
 

Could a Dislocation happen after hip resurfacing?
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!
 

I have a metal allergy, can I have a hip resurfacing?
"Allergy after artificial joints is an interesting issue. One must keep in mind that the co-cr-mo alloy has been in clinical use for 45 yrs and is present in 99% of all hip and knee replacement surgery. Even if a component is titanium the articulating part would be always co-cr-mo. Therefore metal sensitivity is not exclusive to metal on metal joints. It is a factor in every joint replacement surgery and therefore has been used in millions of patients. Skin allergy is quite different from deep tissue allergy which is mediated by different mechanisms of immune response by the body. Thus skin testing is of no value when trying to gauge deep tissue hypersensitivity. There have been reports of hundreds of patients who had skin sensitivity but went on to have very successful resurfacing. Only one thing can be said about deep tissue sensitivity at this point in time---it is very very rare.

What Precautions Should I Take Before Surgery?
It is advisable to avoid smoking completely. Blood thinners like aspirin and oral contraceptives should also be stopped for a minimum period of a week prior to surgery. NSAIDs like ibuprofen cause bone softening and must be avoided to the maximum extent possible. Paracetmol (Tylenol) or Proxyvon (Darvocet)  can be taken as alternative medications for the pain. It is advisable to stay in good shape prior to surgery by good aerobic exercises. However, this is a balance and unaccustomed exertion which causes severe pain should be avoided as this will provoke inflammation.

What is the Typical Recovery Time after a Hip Resurfacing?
At home they walk with a pair of crutches usually for about 10-15 days and when completely comfortable discard the crutch on the side of the operation first. Then when the other crutch is also felt unnecessary, this is also discarded. Walking, climbing stairs or cycling can be done for long periods of time.

There is no post –op restrictions after a Hip Resurfacing operation and the patient can use it as a ‘normal hip’. However the soft tissues around the Hip Joint, which were contracted at the time of the hip disease, will take time to relax following the excellent movement that has been restored in the hip. Hence if there is pain while attempting a certain activity like sitting on the floor, it implies the patient is not yet ready for that particular activity. One can give a gap of about a week and then try it again. Like wise the activity level improves in a stepwise manner till the soft tissues also become normal. Patient is ready for sports (inclusive of contact sport) at about 3 months post-op.

Tell me about Incision Length?
Yes, it is true that Minimally invasive approach has been proven not to have great benefits over a conventional incision in terms of blood loss, pain, or speed of recovery in the same surgeons hands. It is only of cosmetic value. All studies to investigate this have been done on two groups of patients in which a single surgeon employs the two approaches in the diff groups.

When a surgeon who is capable of doing a minimally invasive approach does a conventional approach it is logical that the conventional technique will be only marginally bigger and therefore advantages do not show up in studies. However if a minimally invasive approach of a surgeon is compared with a conventional approach of another surgeon who never does minimally invasive or never makes an attempt to reduce his incision size (within comfort levels)-the differences will show up.

When one compares an incision which is 5 cms for a particular procedure with another which is 50 cms for the same procedure-the differences will show up without any doubt.

However to see objective difference between an incision which is 5 cms and 8 cms it is difficult This is a question of degree.MIS approach has been accused to be just a marketing trick which has caused more harm than good. This is true in many instances however one must be careful not to confuse MIS surgery with the concept of minimizing incision size.

When surgeons are focused on doing a surgery with a pre-determined incision size like say 10 cms-they are hell bent on doing this through this incision even though they are struggling and probably getting many things wrong in the deep bone work. This is certainly not good. Scientific papers enumerating surgical disasters when this is employed is common place.

The other side of the coin is when surgeons chop up patients to extraordinary lengths. Certainly it is equally wrong to cut up tissues unnecessarily when the same can be accomplished to the same degree of accuracy by employing a much smaller incision. In other words it is certainly the duty of the surgeon to minimize the length of incision of any elective procedure but ensuring that he is comfortable and deep bony work is not compromised in any way. There should not be any predetermined length but the surgeon must consciously reduce incision size as a guiding principle. Undoubtedly a hip incision that goes all the way to the knee will have many other bad effects apart from the scar.Therefore there is no doubt that surgeons must be constantly striving to reduce incision size without compromising any other factor. However trying to work with a pre-determined incision size is frequently a recipe for disaster. It is also well accepted that revolutionary techniques like the two incision technique for THR in which the surgeons previous experience with THR is rendered completely useless is very risky when compared evolutionary techniques in which surgeons reduce incision size progressively.

Surgical speed is another interesting topic. The fastest hand that i have seen wield the scalpel in undoubtedly Ronan Treacy who can finish a resurfacing in 20-25 mts. However Mr. McMInn who invented resurfacing and who of course trained Mr. Treacy still takes close to two hours. The turnover time will be 3 hrs.  I still take close to two hrs for a resurfacing with a turnover time of 3 hrs. There are so many steps and no matter how fast you do them it takes that amount of time to do all the steps. The neck capsule preservation that i do takes extra time as well. Attempting to reduce incision size and using subcuticular absorbable stitches all add up the time taken for surgery. If I don't do all these I probably can finish in an hour. If I should finish a resurfacing within half an hour there is no doubt I will be skipping steps.

I have now done more than 500 resurfacings. I have had two failures so far. One was due to deep infection and the other was to head collapse which led to the development of the neck capsule approach.

Explain Minimally Invasive Approach to Surgery

Yes, it is true that minimally invasive approach has been proven not to have great benefits over a conventional incision in terms of blood loss, pain, or speed of recovery in the same surgeons hands. It is only of cosmetic value.

All studies to investigate this have been done on two groups of patients in which a single surgeon employs the two approaches in the diff groups. When a surgeon who is capable of doing a minimally invasive approach does a conventional approach it is logical that the conventional technique will be only marginally bigger and therefore advantages do not show up in studies. However, if a minimally invasive approach of a surgeon is compared with a conventional approach of another surgeon who never does minimally invasive or never makes an attempt to reduce his incision size (within comfort levels)- the differences will show up.

When one compares an incision which is 5 cms for a particular procedure with another which is 50 cms for the same procedure - the differences will show up without any doubt. However to see objective difference between an incision which is 5 cms and 8 cms it is difficult This is a question of degree.

MIS approach has been accused to be just a marketing trick which has caused more harm than good. This is true in many instances however one must be careful not to confuse MIS surgery with the concept of minimizing incision size When surgeons are focused on doing a surgery with a pre- determined incision size like say 10 cms - they are hell bent on doing this through this incision even though they are struggling and probably getting many things wrong in the deep bone work. This is certainly not good. Scientific papers enumerating surgical disasters when this is employed is common place.

The other side of the coin is when surgeons chop up patients to extraordinary lengths. Certainly it is equally wrong to cut up tissues unnecessarily when the same can be accomplished to the same degree of accuracy by employing a much smaller incision. In other words it is certainly the duty of the surgeon to minimize the length of incision of any elective procedure but ensuring that he is comfortable and deep bony work is not compromised in any way. There should not be any predetermined length but the surgeon must consciously reduce incision size as a guiding principle. Undoubtedly a hip incision that goes all the way to the knee will have many other bad effects apart from the scar.

Therefore there is no doubt that surgeons must be constantly striving to reduce incision size without compromising any other factor. However trying to work with a pre-determined incision size is frequently a recipe for disaster. It is also well accepted that revolutionary techniques like the two incision technique for THR in which the surgeons previous experience with THR is rendered completely useless is very risky when compared evolutionary techniques in which surgeons reduce incision size progressively.

Surgical speed is another interesting topic. The fastest hand that I have seen wield the scalpel is undoubtedly Ronan Treacy who can finish a resurfacing in 20-25 minutes. However Mr. McMinn who invented resurfacing and who of course trained Mr. Treacy still takes close to two hours. The turnover time will be 3 hrs. I still take close to two hrs for a resurfacing with a turnover time of 3 hrs. There are so many steps and no matter how fast you do them it takes that amount of time to do all the steps. The neck capsule preservation that I do takes extra time as well. Attempting to reduce incision size and using subcuticular absorbable stitches all add up the time taken for surgery. If I don't do all these i probably can finish in an hour. If I should finish a resurfacing within half an hour there is no doubt I will be skipping steps.

Explain AVN and Hip Resurfacing
7/20/05

Tony has informed me about the AVN discussion currently on surfacehippy. I have given the explanation of how a resurfacing works in AVN. I must apologize that it is long- winded and a little technical. However with the best of my efforts i could not make it any easier as it a complex concept to explain.

I have now done about 185 resurfacings for AVN cases over a 5 year period with many patients crossing the 4 yrs mark. It is interesting to note there has not been a collapse or fracture neck of femur even in a single patient.

It is wrong to think that the AVN continues forever in the femoral head. AVN is a one time event in which a strikingly similar sector of necrosis occurs in most femoral heads (anteo supero lateral
part.) due to blockage of presumably the same vessel in all patients. This sets off a series of changes which are is marked by sectoral collapse. This is primary collapse of AVN and most patients are likely to develop it. Any kind of core decompression / bone grafting is a surgical attempt at preventing /postponing this event. These joint salvage procedures (according to literature) achieves their goal in about 30 - 50% of cases.

The rest of the collapse (which at times is confused with primary AVN collapse) even by medical personnel is actually secondary mechanical collapse and this occurs because of 3 factors:

1. hip stiffness, (more the stiffness the more the likelyhood of secondary collapse)
2. wrong biomechanics leading to point loading.
3. soft bone (non wt bearing and NSAID abuse).

However once resurfacing is done secondary collapse will not continue as the normal biomechanics and range of movement is re established. The portion that is already collapsed (primary or secondary) has to be taken out and substitued with cement or bone graft at the time of surgery. This is a simplisitic explanation for peaple not familiar with the concept. However this does not represent the complete story.

Please read on if you are a medical personnel.

The 3rd type of collapse that can occur is specific to resurfacing and is called as 'Global AVN' tertiary collapse,or delayed primary failure of resurfacing. In this the resurfaced head slowely tilts and falls off over a period of months. This is the number one concern today in the field of hip resurfacing. There are many theories as to why this occurs but the most plausible one is that it is procedure induced and it involves disturbing the soft tissues of the neck and the head-neck junction of the femur (not the head of femur) at the time of surgery. One must keep in mind that AVN occurs in individuals following pretty trivial reasons like a fall, a single dose of steroid or surgery in the vicinity of the hip joint like intramedullary nailing of the femur. To assume that the varied approaches described for resurfacing (anterior, lateral, posterior & trochanteric osteotomy) will not cause AVN in the femoral head is naive. It is now increasingly becoming obvious that Apical, sectoral primary AVN is caused during the surgical approach in a very significant proportion of patients of any surgeon's series of hip resurfacings. However, this is not of any consequence and does not compromise the result.

In summary- the primary, sectoral classical AVN occurs in a majority of resurfacings during the surgical exposure even in cases which did not have AVN to begin with. However with the usage of low viscosity cement one performs a 'capituloplasty' on the head, similar to the vertebroplasty done in the spinal vertabrae with the injection of cement. This transforms the material under the resurfacing head into a composite of live bone, dead bone and cement.  If this composite is seated on a vascular and biologically favourable neck and head neck junction, then this composite performs well. (The biological status of the neck and head neck junciton is similar to health of a fracture fragment in fracture plating surgery.ie Soft tissue cover of a bone fragment is essential for the end arteries to supply no matter from where the blood is coming from) However for some resion the neck capsule and soft tissues get damaged then one gets 'global AVN' and the component drifts and fails. - termed as delayed primary failure. This is independent of the fact as to whether primary, sectoral AVN in the head was present before surgery or occured during the time of the surgery.

Therefore, resurfacings in AVN are no different from resurfacings done for other indications. However if secondary collapse has been left for too long it destroys the femoral head bone stock completely precluding hip resurfacing. If there is sufficient bone stock at the time of surgery a AVN resurfacing is likely to perform as well as any other resurfacing. The 185 AVN resurfacing represents roughly half of my series of about 400 cases.

Updated on May 2007 Dr. Bose was approaching 400 AVN cases with a.5% or less than 1% failure rate, some patients over the 7 year mark.

The longest followup has been 7&1/2 yrs and a lot of patients have crossed 5 yrs. I am not the only one who is having a good result with AVN. Prof Yoo from korea has not had a single failure yet for AVN resurfacing. The same goes for Dr. Sugano from Osaka, Japan. The 3 of us together have done more than 1,000 resurfacings for AVN.

AVN is much more common in Asia when compared to the rest of the world.

Derek Mcminn has a 10% failure rate for AVN when compared to 1% for osteoarthritis. The Australian jnt replacement registry also shows a slightly higher failure rate for AVN than for OA among the Australian surgeons.

In my opinion, I attribute the following reasons for the disparity in outcomes in Asia when compared to the rest of the world.

1. It is important to delay surgery in AVN. The more the delay the more the chance of doing a successful resurfacing.  However if one is very symptomatic obviously delay is not possible. I wait for sec. OA or at least jnt space narrowing before I do resurfacing.
2. Management of cyst is done in a better way by Asian surgeons as they deal with AVN much more frequently.
3. Retinacular vessel preservation which has been now documented to be important  in resurfacing by both Paul Beule from Ottawa and sugano from Osaka. The Retinacular vessel preservation is achieved by the neck capsule preserving approach. Other surgeons use other methods of preserving the retinacular vessels. The retinacular vessel preservation is much more relevant  in AVN than in OA.   In OA due to the intra osseus circulation even if the retinacular vessels are damaged, there is usually no problems although I like to preserve it even in OA cases. Since surgeons outside Asia deal predominantly with OA they are not too worried about retinacular vessels.

With best regards, Vijay bose, chennai
Thursday August 10, 2006