The Great Debate Meeting

The Great Debate

Early Intervention in the Hip and Knee

Held at the National Science Museum, London

23rd - 24th January 2009

Course Chairman: Professor Justin Cobb, Professor of Orthopaedics, Imperial College, London
Co-Chairman: Dr Andrew Shimmin from Melbourne, Australia

The focus of the meeting was early intervention for hip and knee disorders. This was a comprehensive review on current technologies for joint preserving procedures through to reconstruction and replacement surgery, comparing contrasting newer conservative treatments with tried and tested alternatives.

The faculty was sourced from the UK, Europe, North America, Asia and Australia. There were over 250 delegate attendees.

Martyn was talking in a section of "Gold Standard Arthroplasties". The talk was entitled, "Total Knee Replacement: The Wrightington Way".

In the way of introduction Martyn explained that the Charnley total hip replacement was regarded as the Gold Standard or benchmark which was useful comparing tried and tested implants compared with new designs and materials for the use in hip replacement. In a similar vein he was going to review the experiences at Wrightington and international literature in regard to the effacy of tried and tested knee replacements compared to some newer designs.

An editorial in the British Medical Journal by Moran and Houghton in 2000 identified that in 1970 total knee replacement was considered a poor operation. By the 1990s there was really a breakthrough in terms of implant design with a dominance of successful condylar type designs. The survivorship of condylar designs was in the region of 95 per cent at ten years and between 85 and 90 per cent at 15 years. It was pointed out the long term survival of knee replacements appeared to be better at these time periods than that of total hip replacement. Moreover total knee replacement resulted in a significant sustained improvement in all dimensions of health and the demographics and aging population predicted increasing demand in total knee replacement.

However, the results in terms of implant longevity of total knee replacement were good but there was some concern regarding patient satisfaction after total knee replacement. Most studies have shown that about 95 per cent of patients are satisfied with total hip replacement but in comparison several studies have shown that between 10 and 15 per cent of patients who have a total knee replacement are dissatisfied or very dissatisfied with the results of surgery and some of this dissatisfaction may be associated with lower pre-op mental health scores. In addition patients do not achieve comparable physical health compared to matched controls.

Activity following total knee replacement was also an issue. It was recommended that patients should be encouraged to remain physically active for general health and also for the quality of bone. However, only activities with low joint loads such as swimming, cycling or possibly power walking should be recommended and care should be taken for low intensity skiing or even hiking with patients who have knee replacement as this can place high stresses and produce high wear scenarios in patients of total knee replacement.

The topic of the session was Gold Standard Arthroplasties and the debate was Are they as good as they can be?

Based on functional limitations and satisfaction the answer was no in that although they fairly reliably allowed activities of daily living they did not allow normal function and furthermore there was an increasing revision burden because of issues of fixation and wear of the components. On the other hand one could argue yes in that although function is not normal most patients who have knee replacement do not want to play competitive football(!) and the revision burden is not predominantly related to implant design but is also a reflection on surgical technique, patient selection and indeed patient expectations.

When looking at newer designs it has to be recognised that innovation is not risk free taking into account examples of the 3M Capital hip in hip replacement and the PCA knee in knee replacement.

Innovation can also be expensive, often takes time to demonstrate clear benefit, ideas are often commercially driven and there can be a tendency to use new technology for technology sake rather than on an evidence base.

With regard to total knee replacements the considerations are:

1. Is there any evidence that any particular design or brand has superior longevity in terms of survivorship?
2. Is there any evidence that any particular design of knee replacement is superior in function?

Martyn described a variety of early knee designs in the 1960s to 1970s including the Mackintosh, load angle inlay, Attenborough and Sheehan Knee. All these knees had a fairly high revision rate and relatively poor function. The total condylar knee appeared in the late 1970s, early 1980s and the major attributes which contributed to a breakthrough in terms of success was the conformity of the femoral component producing less edge wear, high density polyethylene and good fixation with cement.

A paper by Rodriguez et al published in Clinical Orthopaedics indicated an 85 per cent survivorship at 21 years. In comparison the PCA (porous coated anatomic) knee replacement had high wear characteristics because of poor femoral conformity, thin high density polyethylene, heat press high density polyethylene and cementless fixation. The paper by Moran et al in 1991 JBJS demonstrated poor survivorship of PCA.

Moving on to evidence of survivorship from single surgeon series, often the innovative surgeons, a series of papers was presented with survivorships at 15 to 21 years between 80 and 90 per cent.

The experience from Wrightington was presented on 3,234 primary knee replacements implemented over a 26 year period as published by Pradhan and Porter in 2006. This described survivorships in the region of 40 to 60 per cent for the load angle inlay and Attenborough (early designs) and then good survivorship of 90 per cent with the total condylar at ten years. The later evolutions of the total condylar, the Kinematic or Kinemax had not led to significant improvements.

A more recent paper from Wrightington published in 2007 looked at 166 knees with a minimum of ten year follow up of the PFC which indicated survivorship of 97 per cent at ten years and these results were regarded as being good.

In terms of design innovations there have been a number of innovations since the total condylar including anatomical femoral components, modularity cruciate substitution, patella resurfacing, high flex knees, medial pivot knees, gender specific knees etc.

Although these design improvements were intuitive there was not a great deal of evidence in the orthopaedic literature they had led to specific improvements. For example it was not clear whether there was an advantage of asymmetrical versus symmetrical femoral component in total knee. Deep knee flexion was not shown to be a requisite for patient satisfaction and there was no difference in a patient recorded outcome study between mobile and fixed knee replacement in a multi centre randomised control trial.

A paper by Jacobs (Cochran review 2005) looked at a metra analysis of randomised control trials to ascertain whether posterior cruciate ligament retention sacrificed or substitution was best. The conclusions that so far there was no solid base for the decision to either retain or sacrifice the PCL with or without the use of a posterior stabilised design during total knee arthroplasty.

A knee arthroplasty trial (KAT) by Johnson et al in JBJS 2009 looked at metal backing of the tibia, patella resurfacing and mobile bearing and neither of these factors had an effect on early complications or functional recovery up to two years following surgery.

Kinematic studies had demonstrated better kinematics with bi-cruciate retention and an instrumented balance had created more medial movement.

Looking at register studies the Swedish Knee Arthroplasty Register as published in 2008 looked at the influence of implants, design and survivorship. One particular design of knee, the Nexgen had superior results compared to other designs but the Kinemax and the AMK fared less well.

There was also evidence in the register that the results in clinics in Sweden had improved over a ten year period.

Moving away from the implant but looking at the effect of surgical technique and volume of hospital and surgeon, there was considerable information in the literature demonstrating that the volume affected outcome, not just in relation to joint replacement surgery but also prostatectomy, neonatal surgery, carotid endotraectomy, cardiac surgery, shoulder surgery.

In relation to knee replacement a paper by Katz et al, JBJS 2004 indicated that if hospital volumes were greater than 200 and surgeon volumes were greater than 50 results were more favourable and specialty hospitals had better results than general hospitals. The conclusions of this presentation were that knee replacement surgery should not be regarded obviously as the first mode of treatment. It was advisable to consider more conservative options when possible. It was recommended common sense with patient selection. If total knee replacement is considered then it is important for both patient and surgeon to be realistic in terms of outcome. It is important to consider the influence of the surgeon as well as the implant and recommended that results published evidence is looked at for indicators of potential success. Total condylar knee introduced in the 1980s has had good survivorship with good functional results and as such there is not a great deal of evidence to suggest that in the last 20 or 30 years there has been a tremendous break through in terms of improving results or function. There is some anecdotal evidence of improvement in kinematics and there is some evidence from Register data that results have got better, probably through surgical education and surgical technique.

It was concluded that total knee replacement is a gold standard, that functional results could be improved dramatically and the results of total knee replacement in general are probably not as good total hip replacement in terms of function but are probably as good and possibly even slightly better in terms of survivorship/time to revision. The challenge is for us to become a better surgeon to improve outcomes and use a reliable implant with good proven track record.

In the session, How do we report knee function? David Beard, co-director of the orthopaedic engineering collaboration in Oxford pointed out there was a need for standardisation of knee scores.

Dr Philip Noble, Orthopaedic Surgeon from Baylor College in Texas explained that 11 per cent of patients were very dissatisfied after knee replacement. His work had received the 2006 Insall award.

Dr Andrew Amis, scientist at Imperial College asked the question, Do we need normal kinematics in a replaced knee? Richard Field, Consultant Orthopaedic Surgeon at the South West London Elective Orthopaedic Centre talked about failed clinical follow up. In particular Richard pointed out the cost of putting a knee replacement right. Mr John Skinner from the Royal National Orthopaedic Hospital discussed Registry data.

Mr Chris Ackroyd from Bristol talked about patella femoral replacement. He pointed out that the Avon knee had a 96 per cent survivorship at five years and that the function was comparable with that of a total knee replacement. He felt that good indications for patella femoral joint replacement was isolated patella femoral joint disease in patients less than 70 years of age, no significant axial or fixed flexion deformity and normal tibio femoral joint.

He felt that caution should be excised with patella alta or infra and in patients less than 30 years of age or greater than 70.

He thought there was a potential for disease progression in about 12 per cent and this had been an experience at five years with the Avon knee.

In 115 Avon patella femoral joints, 91 per cent were good or excellent. There had been a 9 per cent failure rate.

He differentiated between dysplasia of patella femoral joint with disease progression to the tibio femoral joint was pretty rare but more likely when the disease was secondary OA of the patella femoral joint.

Mr Ackroyd then described his 15 years experience of unicompartmental versus total knee replacements. Over this period there had been 6,065 knees, 20 per cent of which were unis and 70 per cent were totals. The survivorship of 408 St Georg Sled knees were 89 per cent at ten years.

He then described the 15 year results of randomised control trial of 102 patients, unicondylar arthroplasty versus total knee arthroplasty, the Kinematic versus the Sled. The results were comparable but function was better in the uni. He felt that unicondylar knees mobilised four times quicker, had better recovery, better function, better bone stock and were suitable in one in five cases.

Philip Cartier described his experience of fixed bearing unicompartmental knee between 1974 and 2008 looking at 2,299 unis and had a 94 per cent survivorship at 14 years.

Klaus Schlueter Brust discussed mobile unicompartmental replacements using the Corin Uniglide between 1991 and 2004. Looking at over 700 unis the incidence of dislocation was two per cent and loosening was two per cent.

Chris Dodd from Oxford then looked at the concept of unicompartmental replacement and ACL deficiency. It is recommended to have an intact anterior cruciate ligament for a unicondylar knee replacement. Therefore if a patient is ACL deficient and one wants to consider unicompartmental knee, it is recommended to reconstitute the anterior cruciate ligament either during the same time as carrying out the unicompartmental or in two stages, ie reconstruct the anterior cruciate ligament first followed by the unicondylar knee.

Mr Dodd reported on 15 patients with a mean age of 49 with a follow up of 3.8 years although he indicated there were now 39 patients who had had ACL reconstruction to accommodate a unicompartmental knee. So far there was no evidence of loosening, there was one bearing dislocation and one lateral disease progression and he felt the results were encouraging.

The option of osteotomy was described by Philip Lobenhoffer, particularly in young active patients. He described flexion osteotomy which reduces the tibia on the femur with PCL deficiency. He felt that sports activity was better in unicompartmental versus total knee and he recommended high tibial osteotomy in patients less than 55 years with a varus tibia.

In the debate on bi-compartmental versus tri-compartmental arthroplasties David Murray discussed the role of medial uni. He indicated about 80 per cent of disease was medial and about 50 per cent of patients had anterior knee pain. However, there was no relationship between anterior knee pain and osteoarthritis on the skyline.

He thought that the pain was caused by the medial osteoarthrosis and any patella femoral pain improved following Oxford unicompartmental knee and he did not feel that patella femoral arthritis was a contra-indication to the specific design of the Oxford unicondylar knee. However, when there was severe osteoarthrosis laterally with bone loss he thought that was a possible contra-indication to an Oxford knee, so he summarised by saying it was safe to basically ignore the patella femoral joint.

Mr John Skinner discussed the role of the Deuce replacement with limited experience to date.

Professor David Barrett from Southampton discussed the possibility of carrying out two or even three unicompartmentals, ie medial, lateral and patella femoral replacement in young active patients. These were very early preliminary results on a specific subset of patients.

Mr David Beverland from Belfast advocated that total knee replacement was excellent and he described 600 cemented LCS knee replacements when the PCL was resected. 20 per cent were dead at ten year follow ups and at a minimum follow up of ten years there had only been four revisions or 0.66 per cent, survivorship of 93.3 per cent with no osteolysis and wear.

Moving on to the Hip Session there was a discussion on function and longevity in hip replacement. Aldo Toni from Italy pointed out the hip registries could not detect impending failures and Fares Haddad from London pointed out that range of movement and activity were fairly poor discriminators of the high end of activity and there was a difference between what the surgeon reported and what a patient reported in terms of the outcomes and it was more important to take into account what the patient reported rather than the surgeon's views. With a study on hip resurfacing carried out in London, comparing hip resurfacing with hip replacement, there was a better Oxford and UCLA Activity Score at six months following surgery but no further significant difference at one year. However, on more detailed kinematic evaluation there were subtle differences using gait analysis of single stance phase running, sports and heavy work and there were indications that with more sensitive techniques that patients with resurfacing may have better function.

Philip Noble from Texas came with his experience on more detailed outcome assessment and looked at resurfacing versus total hip replacement. He pointed out the resurfacing implant was about four times the price of a hip replacement. With detailed scoring systems and questionnaires he looked at about 120 activities really based on patient experience. He thought these methods were suitable for research and not for routine follow up. Categories included movement and lifestyle, exercise and sport, workout at the gym, watersports, running, biking, contact and team sports. He looked at 100 hip resurfacings and 66 non-operative controls. There was a three centre study involving the USA and Andrew Shimmin's group in Australia. They found somewhat paradoxically, that the patients with hip resurfacings actually did more than the controlled patients but he thought that there was evidence that they were in fact looking at different groups of people. Patients with hip resurfacing were three times more likely to be satisfied than patients undergoing knee replacements. However, although the patients with resurfacing could exercise they had more pain, 17 per cent, compared to only five per cent of controls and the indication was that patients with resurfacings would endure some discomfort to participate in sport.

On the Saturday David Murray from Oxford spoke about pseudotumours after hip resurfacing. He described the Oxford experience for 1,419 resurfacings of which there had been 26 pseudo tumours confirmed histologically. At eight years there was a four per cent revision for pseudotumours alone and they were more likely in females compared to males, aged less than 40 and small femoral head sizes less than 46. In males the overall incidence was 0.5 per cent, in females six per cent and in females less than 40, 25 per cent incidence.

Bill Walter Jnr from Sydney, Australia described his experience of ceramic on ceramic bearings, particularly in relation to squeaking noises from the hip. He pointed out that in his experience of over 3,000 ceramic on ceramic hips he only revised one hip because of squeaking. He felt that squeaking was associated with poor cup position, some impingement and edge load wear. He carried out some experimental work to demonstrate that this squeaking or noise from the ceramic was the result of resonance caused by increased friction in the joint. There was one particular type of design of an Accolade stem and a thin titanium shell and the potential of the ceramic liner to disassociate from the acetabular lining on walking created some fretting. It was possible that noise or squeaking from hips may be associated with a particular type of implant design, not just of the ceramic but also in terms of the other modular components within the hip joint.

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