Total knee replacement is a very successful treatment for knee arthritis, can it be improved?

On June 9th, 2011, posted in: Uncategorized by admin

With total knee replacement being such a successful treatment for arthritis of the knee, can it be improved? 

 Survival rates for total knee replacement at 20 years are now reaching 80%. 10 year survival is in the region of 95%.

 In the past Surgeons have looked at survival rates, range of movement and x-ray findings following knee replacements.  More recently  interest has been shown in patient recorded outcome measures particularly with regard to patient satisfaction.  In the UK we now have National Joint Registry which has been recording data on hip and knee replacements since 2004.  A recent survey of 8,000 total knee replacements from this survey showed that the satisfaction rate following total knee replacement was 82%.  Similar research in Scandinavia, North America has shown comparable satisfaction rates for this surgery.  When one looks at total hip replacement the satisfaction rates are in the mid to high 90’s. 

 So why are patients not so satisfied after knee replacement surgery compared to hip replacement surgery?

 Reviewing the patients who were surveyed in the UK study, the reason for dissatisfaction was residual pain and functional limitation. 

How can knee replacement be improved ?

 To achieve better pain relief and improved function, knee surgeons are working with biomechanical engineers to design implants that replicate normal function and normal joint movements, so that the implanted knee replacement will be indistinguishable from that of the knee in its healthy state.

This happens in the majority of total hip replacements.  Patients often do not feel any discomfort or limitation in movement following a successful hip replacement operation.

 You may well ask , considering knee replacement surgery has been around for 30 yrs why has this issue not been fully resolved ?

The  knee is a very complex joint.  As the knee goes from full extension to full flexion there is rotation as well as flexion of the joint.  There is not a single axis of rotation about the knee.  In fact there are many axes of rotation as the knee flexes.This is one of the reasons that reproducing normal knee movement is so difficult with knee replacement surgery.  If one compares it to the hip, the hip is a simple ball and socket joint which is very congruous.  In engineering terms this is quite easy to replicate.  The knee joint, which is the biggest joint in the body, is an incongruous joint with opposing surfaces which rely on the ligaments and also the menisci to give it stability throughout its range of movement.

 Over the past decade we have seen new technologies advance in total knee replacement surgery. Factors affecting the wear of the implant have been addressed.  As surgeons we are performing less invasive type of surgery to preserve the soft tissues, computer guided surgery and patient matched instrumentation is evolving  to aid correct placement of knee prosthesis

 So where are going in the next decade?

 In the next decade I forsee that knee replacement surgery will go down 2 different pathways. One pathway will see the development of guided motion knee replacements. This will involve changing the shape of the articular surfaces to try and replicate the function of the menisci and cruciate ligaments, which are sacrificed during standard total knee replacement surgery.  The other pathway we will see is the introduction of compartmental knee replacement surgery.  We are already familiar with and have good results with uni i.e. one compartment replacement surgery. Systems are being developed where one can replace more than one compartment in the knee joint, for example if a patient has patellofemoral arthritis and medial compartment osteoarthritis, patellofemoral joint replacement plus a medial compartment joint replacement.  This is obviously complex and demanding surgery, however the advantage of this approach, is that one retains the cruciate ligaments of the knee and also in this case the lateral compartment of the knee joint with the lateral meniscus and therefore knee function should be normalised.

Will tissue engineering techniques ever supersede Knee replacement surgery?

 Looking far into the future one can for see that biological joint replacement would be the way forward with the use of chondrocytes and stem cells to try and repair damage to the articular surfaces.  We are seeing success in treating articular cartilage defects in younger patients with bone marrow stimulation techniques and chondrocyte implantation, however these techniques have not proven reliable in the treatment of osteoarthritic knee as yet.

 The demand for total knee replacement is increasing year on year in the UK.  With an aging population one can expect this demand to continue increase .  Patients also have extremely high expectations of surgery.  A patient now wants a joint replacement which will allow them to return to a normal lifestyle.  Surgeons and engineers are very aware of this and this is primary driver to develop the ‘forgotten’ knee replacement.

 Richard Carrington

read more