RE: active vs. inactive lifestyle after resurfacing?

[Guest guest]

Thank you Dr. Bose (and thank you Dr. Selvey) for posting here.

I believe intended this forum for all persons interested

in hip resurfacing. Please don't feel you aren't welcome because

you have not been a patient yourself. Your unique perspective is

deeply appreciated.

Thanks.

Lois

C+ 3/27/03 Dr. Mont

Re: active vs. inactive lifestyle after

resurfacing?

I am an orthopaedic surgeon practicing in India and have done about

120 BHRs here in India. I have a special interest in hip and

shoulder surgery. I visit this group at times as i find it very

interesting and informative. I fully understand that it is a

patients forum and it is not meant for medical personnel . However,

as Dr. Selvey who is an orthopaedic surgeon has raised some

queries, i thought it was appropriate for me to address it. I now

find that i am very late to address the query and many others in the

group have already given very precise and correct explanations. I

am just adding some more information to what has already been posted.

His comparison of resurfacing to uni-comparmental knee

replacement was very valid and I couldn't agree more that the

selection of patients must be strict for the outcomes to be good.

This is true for any surgery.

The belief that resurfacing removes more bone in the acetabulum is

completely false. In my experience , hip resurfacing removes exactly

the same amount of bone as hip replacement. I am sure all

resurfacing surgeons would concur with this view. In the recently

concluded International resurfacing forum meeting in Malaga, there

was a paper presented by R. Field from London which concluded after

a well designed study that average size of the acetabular component

used in resurfacing is lesser than the average size used in THR .

The bigger head size is accounted for by the thinner acetabular

shells . The acetabular component is only 6 or 8 mm thick for any

given head size in BHR. In contrast a thick poly is mandatory for a

metal on poly bearing in THR making the outer diameter the same.

Preparation of acetabulum in BHR is exactly the same as in THR.

The second point raised by Dr. Selkey is the lack of solutions when

faced with a failed resurfacing femoral component and a well fixed

acetabular component. This is also not true as it ha

The so called Jumbo metal on metal THR using the same resurfacing

bearing on a conventional THR stem is becoming popular as a primary

option in patients who cannot have resurfacing like after non-union

femoral neck fracture. I have done jumbo MoM modular head THR as the

primary surgery in 9 patients who could not have resurfacing for

technical reasons. This will be the option to choose in case of a

femoral failure in resurfacing. This would take 20 minutes to

perform for any hip surgeon. This ofcourse represents a simple and

straight forward solution.The development of the modern metal on

metal resurfacing was primarily influenced by the >35yrs

survivorship of Metal on metal THR done in the 60's which did not

have manufacturing flaws.( of course those that had manufacturing

flaws in the pre-computer, pre-quality control era failed within a

couple of years of implantation) .Thus the large head metal on metal

bearing is likely to perform well even when mounted on a

conventional THR stem though it would not match that of resurfacing .

(the inside -out loading of bone in Jumbo MoM THR is unphysiological

compared to the outside -in anatomical loading of a resurfacing

prosthesis. The stem is certainly a weak link in Jumbo Mom THR and

the patient must " protect' it by curtailing activities.)

Dr. Selvey comments on high impact sports after hip resurfacing

surgery are very valid and only time holds the answer for this one.

Dr. Vijay Bose

India

----- Original Message -----

From: Selvey

To: surfacehippy

Sent: Tuesday, August 19, 2003 10:53 PM

[Guest guest]

Humm...

I assume that jarring is a force on the hip for some small time interval, so

that if we were looking at a plot of force as a function of time where time

was along the x axis and we would see a spike.

The abstract I was reading words things as follows:

" In the first patient the median peak forces increased with the walking

speed from about 280% of the patient's body weight (BW) at 1 km h-1 to

approximately 480% BW at 5 km h-1. Jogging and very fast walking both raised

the forces to about 550% BW; stumbling on one occasion caused magnitudes of

720% BW. In the second patient median forces at 3 km h-1 were about 410% BW

and a force of 870% BW was observed during stumbling. During all types of

activities, the direction of the peak force in the frontal plane changed

only slightly when the force magnitude was high. "

Right now I am reading the phrase " median peak forces " to be the median of

all the " peak forces " measured on the hip. I do not have access to the full

article. I think the question that you are raising is, " Does the equipment

that measured the forces on the hip do so with a small enough time interval

that these -- jarring spikes -- would be detected. I would hope so, or it

would seem to significantly dampen the value. But I don't have know.

RE: active vs. inactive lifestyle after

resurfacing?

writes:

" If you are putting an uncemented component into bone then you

rely on bony " intergrowth " to the back surface of your impalnt. If you

over

stress that interface with jarring impact you could potentially cause

micro

fracture at the interface and interfere with the " bond " between the two

interfaces. This could ultimately give rise to loosening. "

Does anybody know of some papers/studies on how bony ingrowth responds

to

different types of stress? Does the bone at the interface respond to

stress

like a " bone-bone " break such the things like weight training are

actually

helpful or is it more like a metal where fatigue will come in w/ usage?

Also, walking at 1 km/h puts a force of about 2.8*(body weight) on the

hip

joint, walking at 5 km/h yeilds 4.8*(body weight) and jogging about

5.5*(body weight). [G Bergmann J. Biomech 26 [1993]]. Walking at a rate

of

three miles/hour doesn't seem all that fast -- sort of normal walking,

yet

it yelds a force multiplier on the hip of 4.8. If you go to jogging you

move up only a factor of 0.7. I'm not sure how well accepted these

numbers

are, but if this is in general true it would seem that the difference

between normal walking and running in terms of forces felt by the hip

are

not all that dramatic. The question becomes -- why do we consider

walking

to

be " low-impact " but running " high impact " ?

[Guest guest]

Yes! See below...

RE: active vs. inactive lifestyle after

> resurfacing?

> >

> >

>

>

>

[Guest guest]

Hi ,

Don't know about my bravery.............. I think I only started to grasp

the issues involved in what he managed to do and the potential risks I was

facing after the event.........about 3 weeks post op......smile.

Thankgoodness blind faith sometimes has its own rewards .......... though I

must say he did go to lengths to point these out to both me and my sister

who is a GP and came with me to check it all out.............. Preop I was

just totally obsessed with just having it done and keeping anything from

stopping it.........i.e. I was even fretting about the state of his health

........... worrying that he wouldn't get the flu etc........and postpone it

etc.............smile.

Dr. Len is known as one of Aust finest re hip surgery.......... I was told

there wasn't anything he couldn't do with a hip joint......... so I always

felt I was in good hands........ It did startle a few others what I was

planning to do though........

I was just thinking of the people who go back doing endurance type

activities that you guys warn against............. I guess they do them for

much the same reasons as the rest of us enjoy simple things..........because

they can.......... and I half suspect they would give a THR a thrashing

too.......... in fact we hear of people who do ........... for there is a

mentality in existance that anything a BHR can do, a jumbo head THR can do

equally well.............

Edith LBHR Dr. L Walter Sydney Australia 8/02

> Dr Walter is a brave man, so are you.

>

> Your surgery sounds awesome in the true sence of the word. Totally

> sympathise with your motivation for having the surgery.

>

>

[Guest guest]

Dear Dr Vijay Bos

Thanks for your insite. As you mentioned many of my queries had already

been answered. I am glad you concur with them.

Regards

Selvey

Re: active vs. inactive lifestyle after

resurfacing?

I am an orthopaedic surgeon practicing in India and have done about

120 BHRs here in India. I have a special interest in hip and

shoulder surgery. I visit this group at times as i find it very

interesting and informative. I fully understand that it is a

patients forum and it is not meant for medical personnel . However,

as Dr. Selvey who is an orthopaedic surgeon has raised some

queries, i thought it was appropriate for me to address it. I now

find that i am very late to address the query and many others in the

group have already given very precise and correct explanations. I

am just adding some more information to what has already been posted.

His comparison of resurfacing to uni-comparmental knee

replacement was very valid and I couldn't agree more that the

selection of patients must be strict for the outcomes to be good.

This is true for any surgery.

The belief that resurfacing removes more bone in the acetabulum is

completely false. In my experience , hip resurfacing removes exactly

the same amount of bone as hip replacement. I am sure all

resurfacing surgeons would concur with this view. In the recently

concluded International resurfacing forum meeting in Malaga, there

was a paper presented by R. Field from London which concluded after

a well designed study that average size of the acetabular component

used in resurfacing is lesser than the average size used in THR .

The bigger head size is accounted for by the thinner acetabular

shells . The acetabular component is only 6 or 8 mm thick for any

given head size in BHR. In contrast a thick poly is mandatory for a

metal on poly bearing in THR making the outer diameter the same.

Preparation of acetabulum in BHR is exactly the same as in THR.

The second point raised by Dr. Selkey is the lack of solutions when

faced with a failed resurfacing femoral component and a well fixed

acetabular component. This is also not true as it ha

The so called Jumbo metal on metal THR using the same resurfacing

bearing on a conventional THR stem is becoming popular as a primary

option in patients who cannot have resurfacing like after non-union

femoral neck fracture. I have done jumbo MoM modular head THR as the

primary surgery in 9 patients who could not have resurfacing for

technical reasons. This will be the option to choose in case of a

femoral failure in resurfacing. This would take 20 minutes to

perform for any hip surgeon. This ofcourse represents a simple and

straight forward solution.The development of the modern metal on

metal resurfacing was primarily influenced by the >35yrs

survivorship of Metal on metal THR done in the 60's which did not

have manufacturing flaws.( of course those that had manufacturing

flaws in the pre-computer, pre-quality control era failed within a

couple of years of implantation) .Thus the large head metal on metal

bearing is likely to perform well even when mounted on a

conventional THR stem though it would not match that of resurfacing .

(the inside -out loading of bone in Jumbo MoM THR is unphysiological

compared to the outside -in anatomical loading of a resurfacing

prosthesis. The stem is certainly a weak link in Jumbo Mom THR and

the patient must " protect' it by curtailing activities.)

Dr. Selvey comments on high impact sports after hip resurfacing

surgery are very valid and only time holds the answer for this one.

Dr. Vijay Bose

India

RE: active vs. inactive lifestyle after

> resurfacing?

> >

> >

>

>

>

[Guest guest]

I have no doubt that the equipment would carry out continuous readings and

pick up the change in force quite simply. However if you are measuring the

MEDIAN PEAK forces, I assume this is the average measurement of the maximum

forces achieved with each step. The part of your graph of interest would

be the slope of the curve rather than the highest point the force reaches.

In addition to that stumbling will cause forces with higher peaks but I

suspect with a similar slope to running. If you stumble every now and then

that is a risk of day to day life. Running by contrast would be putting the

stress of a stumble through each step that you take?

I am afraid I am also just trying to interpret with half the info.

Selvey

RE: active vs. inactive lifestyle after

resurfacing?

writes:

" If you are putting an uncemented component into bone then you

rely on bony " intergrowth " to the back surface of your impalnt. If

you

over

stress that interface with jarring impact you could potentially cause

micro

fracture at the interface and interfere with the " bond " between the

two

interfaces. This could ultimately give rise to loosening. "

Does anybody know of some papers/studies on how bony ingrowth responds

to

different types of stress? Does the bone at the interface respond to

stress

like a " bone-bone " break such the things like weight training are

actually

helpful or is it more like a metal where fatigue will come in w/

usage?

Also, walking at 1 km/h puts a force of about 2.8*(body weight) on the

hip

joint, walking at 5 km/h yeilds 4.8*(body weight) and jogging about

5.5*(body weight). [G Bergmann J. Biomech 26 [1993]]. Walking at a

rate

of

three miles/hour doesn't seem all that fast -- sort of normal walking,

yet

it yelds a force multiplier on the hip of 4.8. If you go to jogging

you

move up only a factor of 0.7. I'm not sure how well accepted these

numbers

are, but if this is in general true it would seem that the difference

between normal walking and running in terms of forces felt by the hip

are

not all that dramatic. The question becomes -- why do we consider

walking

to

be " low-impact " but running " high impact " ?

[Guest guest]

Hi ,

I am not sure that I would agree that the slope of the curve is most

important. In other words, it is not the rate of change of the force

that is most important, but the force itself. If force is being

measured, and these people know what they are doing, then they are

digitizing quickly enough so that they are getting the peak force. If

the force is digitized every milisecond which is easy to do, that would

be fast enough to catch the peak force. I have also made some

measurements of peak forces walking and running and generally got

numbers that were somewhat less then those quoted. If someone is

interested in walking gently, the peak forces at normal walking speed,

slightly less than 3 mph, could be as low as 1 g. It also depends on

the shoes the person is wearing and the surface walked on.

Dennis

> I have no doubt that the equipment would carry out continuous readings

> and

> pick up the change in force quite simply.  However if you are

> measuring the

> MEDIAN PEAK forces, I assume this is the average measurement of the

> maximum

> forces achieved with each step.   The part of your graph of interest

> would

> be the slope of the curve rather than the highest point the force

> reaches.

> In addition to that stumbling will cause forces with higher peaks but I

> suspect with a similar slope to running.  If you stumble every now and

> then

> that is a risk of day to day life.  Running by contrast would be

> putting the

> stress of a stumble through each step that you take?

>

> I am afraid  I am also just trying to interpret with half the info.

>

>

> Selvey

>   RE: active vs. inactive lifestyle after

>     resurfacing?

>

>

>       writes:

>

>       " If you are putting an uncemented component into bone then you

>       rely on bony " intergrowth " to the back surface of your impalnt. 

> If

> you

>     over

>       stress that interface with jarring impact you could potentially

> cause

>     micro

>       fracture at the interface and interfere with the " bond " between

> the

> two

>       interfaces.  This could ultimately give rise to loosening. "

>

>

>       Does anybody know of some papers/studies on how bony ingrowth

> responds

>   to

>       different types of stress? Does the bone at the interface

> respond to

>     stress

>       like a " bone-bone " break such the things like weight training are

>   actually

>       helpful or is it more like a metal where fatigue will come in w/

> usage?

>

>       Also, walking at 1 km/h puts a force of about 2.8*(body weight)

> on the

>   hip

>       joint, walking at 5 km/h yeilds 4.8*(body weight) and jogging

> about

>       5.5*(body weight). [G Bergmann J. Biomech 26 [1993]]. Walking at

> a

> rate

>   of

>       three miles/hour doesn't seem all that fast -- sort of normal

> walking,

>   yet

>       it yelds a force multiplier on the hip of 4.8.  If you go to

> jogging

> you

>       move up only a factor of 0.7. I'm not sure how well accepted

> these

>   numbers

>       are, but if this is in general true it would seem that the

> difference

>       between normal walking and running in terms of forces felt by

> the hip

>   are

>       not all that dramatic. The question becomes -- why do we consider

>   walking

>     to

>       be " low-impact " but running " high impact " ?

>

>

>      

[Guest guest]

Hello,

These comments might be a bit off focus but perhaps you will find them

to be of interst.

I spent quite a bit of time researching the cause of my osteoarthritis

only to find one, or both of the following were likely the cause of my

problem. While your discussion involves post operative wear concerns,

the initial cause might have some bearing on this discussion string.

1. Medium level direct trauma to the hip joint while palying rugby

approximately 10 years ago without appropriate recovery caused a hip

allignment concern. This, when amplified by continued play and lack

of appropriate pre-sports stretching for seven years to follow has

taken its toll on my left hip.

2. Years of competitive downhill ski racing, especially with the speed

and joint angle achieved in Giant Slalom event promoted long range hip

capsule wear. Originally published in a Slovanian sports medical

journal, this concept is otherwise unreasearched but often experienced

among my ski racing peers.

In both situations it seems the real damage was the result of a

misalligned hip capsule and medium to high impact activities. I expect

the same will be true (hopefully to a lesser extent) to a resurfed

joint.

Steve C.

LBHR DeSmet 1-2003

>

> > I have no doubt that the equipment would carry out continuous

readings and pick up the change in force quite simply. However if you

are measuringthe MEDIAN PEAK forces, I assume this is the average

measurement of the maximum forces achieved with each step. The part

of your graph of interest would be the slope of the curve rather than

the highest point the force reaches.

> > In addition to that stumbling will cause forces with higher peaks

but I suspect with a similar slope to running. If you stumble every

now and then that is a risk of day to day life. Running by contrast

would be putting the stress of a stumble through each step that you take?

> >

> > I am afraid I am also just trying to interpret with half the info.

> >

> >

> > Selvey

> > RE: active vs. inactive lifestyle

after resurfacing?

> >

> >

> > writes:

> >

> > " If you are putting an uncemented component into bone then

you rely on bony " intergrowth " to the back surface of your impalnt. If

you over stress that interface with jarring impact you could

potentially cause micro fracture at the interface and interfere with

the " bond " between the two interfaces. This could ultimately give

rise to loosening. "

> >

> >

> > Does anybody know of some papers/studies on how bony ingrowth

responds to different types of stress? Does the bone at the interface

respond to stress like a " bone-bone " break such the things like weight

training are actually helpful or is it more like a metal where fatigue

will come in w/ usage? Also, walking at 1 km/h puts a force of about

2.8*(body weight) on the hip joint, walking at 5 km/h yeilds 4.8*(body

weight) and jogging about 5.5*(body weight). [G Bergmann J. Biomech 26

[1993]]. Walking at a rate of three miles/hour doesn't seem all that

fast -- sort of normal walking, yet it yelds a force multiplier on the

hip of 4.8. If you go to jogging you move up only a factor of 0.7.

I'm not sure how well accepted these numbers are, but if this is in

general true it would seem that the difference between normal walking

and running in terms of forces felt by the hip are not all that

dramatic. The question becomes -- why do we consider walking to be

" low-impac but running " high impact " ?

[Guest guest]

Thanks for the kind words from many - it has been very informative and fun

being part of this group but I fear my wife may sue for divorce if I spend

much more time locked to my PC. I will therefore have to sign off but if

any of you have queries of any kind would be happy to answer individual

questions if I am able to.

Best of luck to all of you.

Be reassured that the vast majority of your OS have your interest at heart.

If not least because their own egos do not allow them to tolerate their

patients doing badly. (I know myself how traumatic it is when a patient

gets an infection or other complication. You forget all the patients that

are happy and beat yourself up about your single complication.)

They do however face a dilema because almost every orthopaedic problem can

be addressed by more than one approach. Your THR vs Surface replacement

debate is a classic example. Even within each procedure different surgeons

may use a different technique. You therefore as a surgeon have to find a

technique that suites you as a surgeon and produces good results for your

patients. It is not always a good idea to take up a new procedure because

it will have a learning curve associated. If you embark on this new

procedure you can be branded a cowboy by your pears and if you dont a

dinosaur by your patients.

In addition to that OS and their families have to eat and if the OS doesnt

operate they dont eat. Therefore they face a further dilemma because they

are running a business and thefore if they choose to stick with the

operation that know produces good results then they expose themselves to

criticism because they are trying to " protect their patch. "

At the end of the day we have to have the " pioneers " who are brave enough to

learn or develop new techniques. However those who don't are not wrong

either.

Having said all of that there will always be surgeons who present themselves

in an arrogant way but these are not representative of the profession. I

have travelled around the world and OS as a group tend to be very different

to other medical specialists. Perhaps because we have traditionally been

the brunt of many of the medical professions jokes, if you take yourself too

seriously you dont risk getting into OS.

Best of luck - I will be back I am afraid

[ Selvey]

Re: active vs. inactive lifestyle after resurfacing?

At first I shared your view about many OS's being in it only for the money

but after more careful considereration I feel many real do care. They want

something that they know has a decent track record. They remember the early

failures. My local OS handles my followup exam and when I was researching

options enabled me see a very well known revision expert (who knows the

resurf developers personally). He wanted me to be comfortable with my

choice and informed. We agreed to disagree but I know he was trying to help

and had my best interests at heart. Just for the record, my local OS is Dr

Hadesman. Time will tell if I made the right choice ... I believe I

did. Stan aka Wolf (C2K 17Jan02 Dr Gross)

flo1dude2@... wrote:

Hi

I have to say I admire and respect you as you seek more information about

hip

resurfacing. My opinion of many of the OS's I've contacted had been

really

lowered when it was obvious to me that the particular surgeon had not kept

up

with the updates of resurfacing. That and the fact the insurance

companies

refuse to objectively examine the breakthroughs in technology. With the

exceptions of Dr DeSmet, Dr Gross and the others that deal with the trials

here in

the states, I felt the OS's and the insurance companies are only in it for

the

money and screw the best interest of the patient. Coming to this site you

demonstrate to me a genuine concern, interest and objectivity in learning

the

facts.

You are a breath of fresh air and renew my faith in mankind. GODSPEED.

Sincerely

Lloyd

Pre-op Dr DeSmet RBHR

[Guest guest]

Comments???? (From Duke University)

Risks: The following complications are specific to all metal implants and in

addition to complications associated with a total hip replacement:

1. Release of metal debris (metallosis) can occur with all metal

implants. These implants produce corrosion products that are biologically

active and may cause chronic inflammatory reactions that can lead to

loosening of the implant. It is reported that the concentration of metal

debris is higher if the prosthesis is worn or loose, or if the joint is

infected. It is not clear what the normal levels of ions in human tissue

should be; however, animal studies show that cobalt doses up to 1000 times

normal may be tolerated. Larger doses than that can induce anemia, loss of

appetite and weight, an increase in the number of red blood cells, lesions

in mucous membranes, local malignant skin tumors, and death.

2. Although inconclusive, there is concern that extensive metal ion

release may cause changes to the immune function which may lead to lymphomas

and leukemias.