The beginning: Total Hip Replacement (THR)
In the 1930s, Dr. Phillip Wiles from the Middlesex Hospital in the United Kingdom designed and implanted the first Total Hip Replacement. The records of these hip replacements were lost during the second world war, but one patient is said to still have their implant in situ more than 30 years later.
Dr. GK McKee was at the time a trainee with Wiles, and following this appointment began development of various THR designs during the 1940s and 1950s. Most of these designs were met with rapid failure.
The McKee Farrar Cemented Cobalt Chrome THR was the first widely used and successful THR from the 1960s onwards.
By the 1970s, there were three types of THR that were in common use, the McKee, Charnley and Ring types.
Over the years, there have been many experiments with different designs, different fixations, and different materials. There has been much success using metal femoral components with Polyethylene cup liners. Unfortunately, wearing of these Poly cup liners creates tiny particles of Polyethylene which triggers a response from the bodys system. As the body tries to absorb these particles, it also absorbs some of the surrounding bone, leading to component loosening. This process is called Osteolysis, and is a major cause of implant failure. With this in mind, many surgeons are leaning towards UN-Cemented systems, which are coated with a bone in-growth surface. Normally after just six weeks one can expect to see sufficient bone in-growth to allow the patient to resume a normal healthy lifestyle.
What has been shown however is that the metal alloy Cobalt Chrome has performed remarkably well in prosthetic hip surgery over the last 40+ years.
Today, THR is the most successful form of prosthetic implant surgery. Failure of below 1% per year is seen from prosthesis implanted by specialist THR centres. Failure rates as high as 9% at 5 years can be seen from implants carried out by general hospitals, and an average 27% of patients have a poor long term outcome (Trent regional Arthroplasty study).
THR has proven to be very successful in the more mature & elderly patient group, however it has performed unreasonably poor in the younger , more active patient group. A different approach was necessary, and many believe Hip Resurfacing to be the answer to the problem.
The future: Hip Resurfacing
Sir John Charnley carried out the first Hip Resurfacing in the 1950s. He used Teflon bearing surfaces, which unfortunately wore out within two years of implantation. This was not a failure in concept, but rather a failure of materials. This material failure was to plague the medical community for a further 30 years.
The 1970s saw the next significant developments of hip resurfacing, with surgeons using the same materials used in the best THRs of the day. Charnley, Wagner and Amstuts converted to metal femoral heads, with Polyethylene acetabular components which were Poly-cement fixed.
55% of these resurfacings failed within 6 years after implantation. It was clear that Polyethylene could not be used in part of the bearing material.
In 1989 in the United Kingdom, it was decided to trial a new bearing material combination, which used the same material in Resurfacing as what had been successfully used in THR for more than 30 years.
The first implantation was carried out in February 1991. Various fixation methods were tried, and after 3 years it was clear that the best option was:
1.A cement fixed Chrome Cobalt femoral component,
2. Along with an un-cemented, Hydroxyapetite (HA) coated Chrome Cobalt acetabular component.
After meeting with several failures in the early stages, due to material failures, in the period March 1994 to December 1999, Ronan Traecy F.R.C.S, Eric Isbister F.R.C.S, Derek McMinn & 11 trainees performed 1720 Hybrid Resurfacings.
From 1720 implantations, there were just 17 failures.
Recent results for the 10 year period (1991-2001) should be released in early 2002.
These results look very promising.
There are now more than 70 surgeons performing the Birmingham Hip resurfacing (BHR) in the U.K alone. More than 12 in Belgium, 15 in Germany, and many other surgeons from south Africa to Australia to Japan.
There are also other similar forms of resurfacings being implanted such as the U.S produced Conserve Plus (C+) device.
Although in many countries Resurfacing is still in its trial phase, there are countries such as Belgium, where resurfacing is rapidly becoming the standard procedure for hip replacement surgery.
Whilst there I met several people that had the BHR resurfacing, and just considered it 'the norm'.
The 1970s saw the next significant developments of hip resurfacing, with surgeons using the same materials used in the best THRs of the day. Charnley, Wagner and Amstuts converted to metal femoral heads, with Polyethylene acetabular components which were Poly-cement fixed.
55% of these resurfacings failed within 6 years after implantation. It was clear that Polyethylene could not be used in part of the bearing material.
In 1989 in the United Kingdom, it was decided to trial a new bearing material combination, which used the same material in Resurfacing as what had been successfully used in THR for more than 30 years.
The first implantation was carried out in February 1991. Various fixation methods were tried, and after 3 years it was clear that the best option was:
1.A cement fixed Chrome Cobalt femoral component,
2. Along with an un-cemented, Hydroxyapetite (HA) coated Chrome Cobalt acetabular component.
After meeting with several failures in the early stages, due to material failures, in the period March 1994 to December 1999, Ronan Traecy F.R.C.S, Eric Isbister F.R.C.S, Derek McMinn & 11 trainees performed 1720 Hybrid Resurfacings.
From 1720 implantations, there were just 17 failures.
Recent results for the 10 year period (1991-2001) should be released in early 2002.
These results look very promising.
There are now more than 70 surgeons performing the Birmingham Hip resurfacing (BHR) in the U.K alone. More than 12 in Belgium, 15 in Germany, and many other surgeons from south Africa to Australia to Japan.
There are also other similar forms of resurfacings being implanted such as the U.S produced Conserve Plus (C+) device.
Although in many countries Resurfacing is still in its trial phase, there are countries such as Belgium, where resurfacing is rapidly becoming the standard procedure for hip replacement surgery.
Whilst there I met several people that had the BHR resurfacing, and just considered it 'the norm'.
So why is Resurfacing a better option for many people needing hip surgery?
There are many reasons why Resurfacing seems to be better than THR for many patients. The simple survival & longetivity statistics quoted above are reason enough in themselves.
If the failure rate of a resurfacing is less than 2percent at 9 years, compared to the results of THRs implanted over the same period, doesn't it make sense to at least have a resurfacing as a time buying product, to gain extra years before a primary THR is necessary. Infact there are many who beleive that a resurfacing could lastmore than 20 years, or even a whole lifetime.
That brings us to the main drawback of resurfacing... The fact that it is a new procedure, and is lacking the long term result data, compared to THR surgery. The truth is, nobody knows how long a resurfacing should last, and even if they did, much depends on the individual, the kind of activities they do after surgery, the health problem they had making surgery necessary, and a whole range of other factors.
Some reasons that I personally beleive that resurfacing is better are as follows.
1. The whole implant is anatomically shaped, and after implantation, mimicks almost exactly a natural hip.
2. The surgical procedure is much less invasive. In THR it is necessary to totally remove the femoral neck and the femoral head. Considering that most patient requiring surgery simply have problems with the acetabular, or the surface of the head, or the cartilage in between, isn't removing this much natural bone a little extreme if it is not necessary?
3. In Resurfacing, the neck and head are not removed. The surface of the femoral head is shaped to exactly fit the ball of the femoral side of the prosthesis. Although some bone is removed on the head itself, the area retains its natural shape and strength.
What this also means is that if in the future the Resurfacing should ever fail, conversion to a THR can be done as a straight foreward PRIMARY THR, rather than a more complicated SECONDARY THR REVISION. Therefore the patient has gained several years before the first THR, and therefore has gained several years befor a second THR must be implanted, which is a more difficult surgery & often the outcome is worse than the primary THR implantation.
(SEE THR REVISION MOVIE and THR REVISION WITH ALLOGRAFT in my favourite link section)
4. The metal baring composition of a Cast Cobalt Chrome femoral resurfacing component, with a Cast Cobalt Chrome acetabular resurfacing component is a combination that has a proven, safe 40 year history in British hip replacement surgery.
5. In a Resurfacing prosthesis, Polyethylene is not used as a baring material. Polyethylene wear debris has been proven to cause Osteolysis.
This is where the bodys own defense system releases organisms to eat away the Polyethylene debris, but unfortunately they cannot recognise these small partiacles. Even more unfortunate is that as Poly debris cannot be attacked, these organisms, having a mission to complete, attack the nearest best thing...... Your own bone!
What this normally leads to, is the bone surrounding the prosthesis been weakened, and sometimes this can allow the prosthesis to loosen. When this happens, a revision surgery is necessary to implant a new prosthesis, or refix the current prosthesis.
A large percentage of THR failures have been caused by Poly-induced Osteolysis.
6. In a Resurfacing prosthesis, normally Orthopaedic cement is not used to attach the acetabular side of the prosthesis. This cement has also been shown to lead to Osteolysis, and component loosening.
Cement is used to attach the femoral side of the prosthesis, but in 10 years of modern resurfacing surgery with a BHR, there has never been a case of femoral component loosening
A small percentage of THR failures have been linked to Cement-induced Osteolysis.
A small percentage of THR failures have been linked to loosening due to cement wear.
7. A Resurfacing Acetabulum component is normally attached to the natural acetabulum through a special bone ingrowth surface. The BHR uses a system which is actually CAST in to the component as it is made.
This ingrowth surface is known as HYDROXY APETITE.
Under a magnifying glass, the outer surface of the component appears to be covered in very small beads. Around two weeks after implantation, your body has already started growing new bone tissue which work their way in to the tiny spaces between these beads.
After around six weeks, the bone ingrowth is quite substantial, and the acetabular cup should be solidly held in place.
(The American Conserve plus device has its own ingrowth surface, which made up of Titanium beads,and are plasma sprayed on the the outer surface of the acetabular cup. There has been some speculation that because it is necessary to heat the prosthesis to a high temperature in order to attach these beads, the strength of the prosthesis is compromised. Even if this is so, i think that we must accept that the C+ device has proven itself very well so far, and any strength lost during this process is so small that it is not worth worrying about).
8. With a THR, a stem is inserted in to the femoral canal, inside the femur. This space is not hollow, but contains fat and marrow. This fat and marrow are compressed inside the femoral canal by the THR stem being forced in to position. Fat and marrow are forced out of the bone, and in to the circulatory system.
This can lead to rapid development of blood clots which can settle in the heart, brain and legs.
This can lead to a whole range of symptoms such as Deep Vein Thrombosis in the legs. This can be very dangerous, and does not necessarily happen immediately, but sometimes shows up several years after surgery.
9. Because the Resurfacing does not have a long stem, instead a short support pin which only goes through the femoral head and settles in to the neck, the risk of Deep Vein Thrombosis and blood clots is dramatically reduced.
10. Resurfacing has simillar post surgery restrictions as does a THR surgery. The first six weeks sees several restrictions being set in place such as not bending your leg more than 90 degrees from your body line, not crossing over your legs and therefore having to sleep with a large pillow between your legs to stop them crossing over in your sleep.
11. After this six week period, many patients return to a pretty much normal lifestyle. In general, after around half a year, Resurfacing patients can do almost every activity that a person with normal hips can do. Resurfacing patients can go running, jogging, mountain climbing, play tennis, squash, karate, judo, football, soccer, rugby and just about any other daily and sporting activity.
It has been recommended that Resurfacing patients DO NOT take part in activities such as Bunjee jumping and Parachuting.
If the failure rate of a resurfacing is less than 2percent at 9 years, compared to the results of THRs implanted over the same period, doesn't it make sense to at least have a resurfacing as a time buying product, to gain extra years before a primary THR is necessary. Infact there are many who beleive that a resurfacing could lastmore than 20 years, or even a whole lifetime.
That brings us to the main drawback of resurfacing... The fact that it is a new procedure, and is lacking the long term result data, compared to THR surgery. The truth is, nobody knows how long a resurfacing should last, and even if they did, much depends on the individual, the kind of activities they do after surgery, the health problem they had making surgery necessary, and a whole range of other factors.
Some reasons that I personally beleive that resurfacing is better are as follows.
1. The whole implant is anatomically shaped, and after implantation, mimicks almost exactly a natural hip.
2. The surgical procedure is much less invasive. In THR it is necessary to totally remove the femoral neck and the femoral head. Considering that most patient requiring surgery simply have problems with the acetabular, or the surface of the head, or the cartilage in between, isn't removing this much natural bone a little extreme if it is not necessary?
3. In Resurfacing, the neck and head are not removed. The surface of the femoral head is shaped to exactly fit the ball of the femoral side of the prosthesis. Although some bone is removed on the head itself, the area retains its natural shape and strength.
What this also means is that if in the future the Resurfacing should ever fail, conversion to a THR can be done as a straight foreward PRIMARY THR, rather than a more complicated SECONDARY THR REVISION. Therefore the patient has gained several years before the first THR, and therefore has gained several years befor a second THR must be implanted, which is a more difficult surgery & often the outcome is worse than the primary THR implantation.
(SEE THR REVISION MOVIE and THR REVISION WITH ALLOGRAFT in my favourite link section)
4. The metal baring composition of a Cast Cobalt Chrome femoral resurfacing component, with a Cast Cobalt Chrome acetabular resurfacing component is a combination that has a proven, safe 40 year history in British hip replacement surgery.
5. In a Resurfacing prosthesis, Polyethylene is not used as a baring material. Polyethylene wear debris has been proven to cause Osteolysis.
This is where the bodys own defense system releases organisms to eat away the Polyethylene debris, but unfortunately they cannot recognise these small partiacles. Even more unfortunate is that as Poly debris cannot be attacked, these organisms, having a mission to complete, attack the nearest best thing...... Your own bone!
What this normally leads to, is the bone surrounding the prosthesis been weakened, and sometimes this can allow the prosthesis to loosen. When this happens, a revision surgery is necessary to implant a new prosthesis, or refix the current prosthesis.
A large percentage of THR failures have been caused by Poly-induced Osteolysis.
6. In a Resurfacing prosthesis, normally Orthopaedic cement is not used to attach the acetabular side of the prosthesis. This cement has also been shown to lead to Osteolysis, and component loosening.
Cement is used to attach the femoral side of the prosthesis, but in 10 years of modern resurfacing surgery with a BHR, there has never been a case of femoral component loosening
A small percentage of THR failures have been linked to Cement-induced Osteolysis.
A small percentage of THR failures have been linked to loosening due to cement wear.
7. A Resurfacing Acetabulum component is normally attached to the natural acetabulum through a special bone ingrowth surface. The BHR uses a system which is actually CAST in to the component as it is made.
This ingrowth surface is known as HYDROXY APETITE.
Under a magnifying glass, the outer surface of the component appears to be covered in very small beads. Around two weeks after implantation, your body has already started growing new bone tissue which work their way in to the tiny spaces between these beads.
After around six weeks, the bone ingrowth is quite substantial, and the acetabular cup should be solidly held in place.
(The American Conserve plus device has its own ingrowth surface, which made up of Titanium beads,and are plasma sprayed on the the outer surface of the acetabular cup. There has been some speculation that because it is necessary to heat the prosthesis to a high temperature in order to attach these beads, the strength of the prosthesis is compromised. Even if this is so, i think that we must accept that the C+ device has proven itself very well so far, and any strength lost during this process is so small that it is not worth worrying about).
8. With a THR, a stem is inserted in to the femoral canal, inside the femur. This space is not hollow, but contains fat and marrow. This fat and marrow are compressed inside the femoral canal by the THR stem being forced in to position. Fat and marrow are forced out of the bone, and in to the circulatory system.
This can lead to rapid development of blood clots which can settle in the heart, brain and legs.
This can lead to a whole range of symptoms such as Deep Vein Thrombosis in the legs. This can be very dangerous, and does not necessarily happen immediately, but sometimes shows up several years after surgery.
9. Because the Resurfacing does not have a long stem, instead a short support pin which only goes through the femoral head and settles in to the neck, the risk of Deep Vein Thrombosis and blood clots is dramatically reduced.
10. Resurfacing has simillar post surgery restrictions as does a THR surgery. The first six weeks sees several restrictions being set in place such as not bending your leg more than 90 degrees from your body line, not crossing over your legs and therefore having to sleep with a large pillow between your legs to stop them crossing over in your sleep.
11. After this six week period, many patients return to a pretty much normal lifestyle. In general, after around half a year, Resurfacing patients can do almost every activity that a person with normal hips can do. Resurfacing patients can go running, jogging, mountain climbing, play tennis, squash, karate, judo, football, soccer, rugby and just about any other daily and sporting activity.
It has been recommended that Resurfacing patients DO NOT take part in activities such as Bunjee jumping and Parachuting.
John Charnleys total Hip replacementm
Sir John Charnley
No comments:
Post a Comment