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The Great Debate 2012 Hip and Knee Controversies

Discussion in 'Scientific Articles' started by Josephine, Jul 22, 2012.

  1. Josephine

    Josephine Forum Admin and Mother Hen Administrator

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    The Great Debate 2012
    29th/30th June​
    Mermaid Conference Centre, London, UK​


    Report on the meeting

    Friday 29th

    Session 1:Hip Arthroplasty: Surgical Techniques

    0830 Posterior approach: safe and sensible - Johan Witt

    Evidence shown how a posterior approach actually has less instance of
    dislocation than other approaches. Amongst many statistics shown were an overall dislocation rate of between 1-9% but that this was significantly reduced if the posterior capsule was repaired to the tune of 4.8-0.7%! Preserving the piriformis was also discussed and it was noted that though this made access a bit more difficult it was by no means impossible and reduced incidence of dislocation to that amazing 0.7%.

    It was cited that MIS seemed to result in better pain management and earlier discharge, it was difficult to exactly determine the factors involved.

    The posterior was definitely a good approach for developmental dysplasia of the hip (DDH) and other complex problems such as in revision and when the acetabular column needed to be accessed.

    Decrying the anterior approach, the speaker even added that “some will even sell you a table to do it on”!

    0840 Anterior approach: a real improvement? - Paul Beaulé

    Beaulé was much in favour of the anterior approach as, he said, it has the path with the least amount of fat, is intra-nerve and intra-muscular, leaves the abductors and short external rotators intact.

    He admitted there is a 67% incidence of neuropraxia with involvement of the lateral femoral cutaneous nerve but that these had no impact on function and resolved in 6-8 months.

    As for the minimal access procedures, they had a 3.1% dislocation rate and there could be difficulties with orientation of the implants with a 4% incidence of other complications. But overall, the anterior approach is “a great improvement” on others

    0850 Fixation: cement is all you need - Graham Gie

    Gie proclaimed that cemented sockets significantly outperform the uncemented, especially in the under 50s. Very low loss of calcar height over the years. Previously resorption of the calcar had often been noted.

    Version and length in the stem can be easily controlled when cement is used unlike with an uncemented where the reaming of the canal is what dictates this. The speaker reported his cemented patients all did better but more particularly in the young who had an 87% survivorship at 17years.

    Cemented cups have also been shown to have better survivorship in the long term.

    0900 Size matters for the femoral head - Rob Middleton

    The case for large heads was presented, citing they have less incidence of dislocation. The success of this was tri-fold: implant + surgeon surgery. He felt that the 36mm was more stable than the 32mm and that from 36mm upwards there was no increase in benefit.

    He admitted that there was certain issues with the larges head, including trunionosis and thinner poly liner in the cup which would obviously wear out more quickly than thicker ones.

    Trunion design has changed over recent years with them being larger, shorted, ridged for ceramic or smooth for metal balls. There can also be a large lever arm effect on some designs of longer trunion and micromovement which causes pitting, allows ingress of fluid with subsequent corrosion.

    Session 2: Hip Arthroplasty: The devil is in the detail

    1015 Femoral stem modularity: curse or comfort - Seth Greenwald

    Greenwald was not enamoured of the present modular system as he felt many of the problems presently arising were due to mismatches or interaction at the trunion. Such problems have been corrosion at the bearing, component fixation and stem design. There were too many joins which made for an increase in problems as revealed in the S-Rom, MP and Margron.

    There were issues with stability, often even compromises in structure and design with metal debris arising as a result of these issues.

    Fretting came from dynamic points such as displacements at the metal on metal interfaces both at the head/cup and trunion/ball. These factors influenced the success or failure of the procedure.

    Another point at issue was the offset which, in some femoral stems, was extreme leading to prosthetic fractures. If one then added to this a high BMI and an event such as a fall, disaster was almost certain to occur. Other contributory factors had to be high activity and bone health/mass.

    1025 Hip resurfacing: what is the future - Jeremy Latham

    Latham started by reminding us of the much vaunted Scott’s Parabola and how this was entirely pertinent to present day procedures.

    Scott’s parabola was conceived by British gynecologist J.W. Scott as a model to illustrate the cyclical “rise and fall of a surgical technique”: a procedure shows great promise at the outset, then becomes the standard treatment after producing encouraging results, only to fall into disuse later as a result of negative outcome reports and perhaps the availability of better new strategies.

    scott.f1.jpg

    He then got serious and cited follow-up results of 100% at 14 years.
    There was hope for hip resurfacing in the creation of a new material for a ceramic on ceramic.
    In spinal surgery, polycarbonate is being used for replacement vertebrae.
    The next phase in plastic inserts is using the new PEEKs or Poly Ether Ether Ketones which is going to enable an area of hardness and another area of more compliance in an insert.
    Another development is in cross linked polyethylene is the addition of Vitamin E which seems to increase its resistance to wear and lamination.

    1035 Taper geometry and trunionosis - Andy Manktelow (I worked with this young man!)

    Hip resurfacing is designed to be as it is but its success led to a hybrid of a large head on a standard stem in which, it seems, there lies the problem. Trunions are a male/female connection where design tolerances are crucial. The problems arise where there is inevitable micromovement leading to fluid intrusion which enables more micromovement and then corrosion. In hybrid stems (stem from one manufacturer and ball from another) there is almost always micromovement leading to pitting and corrosion. The speaker proposed that this was always going to be a problem in modular designs anyway but that mixing and matching devices was only going to increase the hazards. He felt this was probably a good reason to consider a return to monobloc.

    10.45 Alternative articulations in the hip - Paul Beaulé

    To be honest, this paper was a bit above my head! The speaker spent time going over the scientific detail of kinematics and kinetics.

    Session 3: Bearings

    1145 Metal on metal works well in the long term - Derek McMinn

    With his vast experience in MoM hip resurfacing and THR, McMinn declared that in his practice, metal ions in the blood did elevate in the first 6 years but then dropped to normal/almost zero in the following 10. He therefore argued that metal ions were not as much of a problem as some would have us believe. He also pointed out that ceramics do not produce metal ions!

    1155 The future is ceramic - William Walter

    Walter argued that ceramics were the material of choice as they were largely problem free, produced no by-products and were long lasting.

    1205 New poly is all you need - William Maloney

    Outlining the excellent history of this material, Maloney showed statistics of excellent survivorship and performance. He also listed the various improvements over the years and showed how the current product was a reliable performer with almost no evidence of wear or lamination as had happened in previous types.

    1215 Match your bearings to your patient - Thomas Schmalzried

    Schmalzried started with the obvious declaration that the biggest limitation in hip surgery is “us”! Things vary from patient to patient, some people are less tolerant to certain materials than others and place different demands up the devices resulting in lower overall wear and osteolysis.

    Session 4: Outcomes

    1400 Decision making in orthopaedics - William Maloney

    Flicking through a not inconsiderable amount of peer reviewed literature and websites, Maloney showed how there was little consistency in how surgeons chose the products they used. He showed how, though certain devices were considered to be the “gold standard” they were often the most expensive and no-one really wants to use them!

    In this, medical device reporting to agencies such as the FDA and joint registries were often misleading because their information trawling was “pretty useless” when trying to trawl information. He raised the question as to whether JRs do actually help fill the information gap or are they simply there to raise red flags to problems and issues.

    He proposed that JR questionnaires need to be more detailed with up to 4 levels of information and digitally entered so they were electronically accessible for research.

    1410 Benefits of registries: the long term truth - Henrik Malchau

    On the pro side, Malchau from Sweden argued that JRs were beneficial they were certainly not perfect were better than the alternative which was nothing. He defined how the Swedish registry works and showed how it had been beneficial to his research.

    1420 Limits of registries: reporting bias - Derek McMinn

    McMinn expressed his concern of the limitations of registries in the type of information garnered. He also considered there was distinct reporting bias as some hospitals were diligent about submitting the report cards and others were not.

    He cited an example of widely accepted chromosomal changes which were refuted by information trawled from a JR and also a series of one research that was widely reported by the Daily Telegraph!

    1430 Patient reported scores: avoid the ceiling effect - Fares Haddad

    Haddad discussed the various pain and function scores and how effective they were, suggesting there needed to be modifications in them all in order to get more accurate and meaningful results and to take in the more recent developments.

    1440 Life after hip arthroplasty: do outcome measures reflect reality- Thomas Schmalzried

    Key points of this paper were to wonder at people who felt so driven to improve ROM after joint replacement, particularly TKR. Also that it was often forgotten that the pre-op condition predicates the outcome.

    Session 5: Politics

    1555 Choose your surgeon not your implant - Martyn Porter

    Porter announced a new paper being published shortly entitled “Shared decision making” in which he defined the usefulness of involving the patient with the various choices in their surgery including approach and device.

    1605 Managing patient expectations - Richard Field

    Issues which Field had defined in this area included getting to know your patient! He added that scoring systems were a useful tool and that it was also useful to discuss expected recovery and outcomes with the patient.

    1615 Who decides implant choice: surgeons or politicians? - Tim Briggs

    Briggs had researched the demographics of joint replacement and found that 35% were 65 and 15% over 65. In his own surgery it was more 8-14%. Considering how many different items he commonly used, he found it was 6 hip and 4 knee devices. Choice was generally a departmental consensus. In all there were 121 implants in use having been using in 7,267 procedures. He concluded with the suggestion it was self evident that cheaper implants would allow more joint replacements to be done.

    1625 Indemnity insurance: should it dictate your practice? - Steve Cannon

    Product usage in the UK was guided and influenced by the National Institute for Clinical Excellence (NICE) but also by PMIs (private medical insurers) to a degree. The Medicines and Healthcare products Regulatory Agency (MHRA) were also involved to a certain extent.

    He cited a 10 year benchmark before any research could be considered dependable and that many devices had less than 3 years clinical evidence to support them. In clinical trials the most favourable evidence was overwhelmingly in favour cemented hips.This was supported by data from the National Joint Registry UK.

    There was also an increasing number of claims for clinical malpractice and referrals to the General Medical Council. Of recalls, 39% have been successfully sued by patients.

    1635 The media and hip resurfacing: is there a link - Richard Villar

    Press were inevitably going to be interested in medical developments and issues but this speaker was concerned about the frequency with which press articles actually misconstrued certain reports and developments and published articles which mislead the public.

    Saturday 30th

    Session 1: Technology

    0810 Landmark based navigation: a thing if the past? – David Barrett

    Barrett cited an article from 1984 titled “Does alignment even matter?” by L F Wallen

    For himself, he said that knee replacement is primarily a soft tissue operation and that kinematics matter too. Other important issues were rotational alignments and ‘lift off’ in movement. He also felt that too much flexion can cause tibial insert impingement with the results of lamination and chipping.

    0820 Patient specific cutting blocks ready for prime time - Adolph Lombardi

    It was more than obvious that Mr Lombardi wasn’t a proponent of this technique as he felt there would always be a need for the surgeon to dictate the actual surgery as custom made cutting blocks didn’t always allow for this.

    0830 Robots are waiting round the corner - David Morgan

    Morgan on the other hand was much in favour. He felt that various systems allowed for the objections posed by the previous speaker. Haptic system enabled tactile feedback during the surgery as did Acrobat.

    0840 Trust your surgeon not technology - Graham Gie

    Gie’s talk emphasised that computers were not always infallible and caution should be exercised.

    Session 2: Knee arthroplasty: surgical technique

    0910 Has knee replacement finished evolving - Seth Greenwald

    The Perfanova triad (?) dictated that the choice should be patient, kit, surgery

    0920 Flexion range: determined by surgeon or device? - Tim Wilton

    Wilton declared that pre-op functionality generally influences post-op functionality. That slackness and tightness were often difficult to adjust intraoperatively.

    He further questioned if a posterior tibial slope was necessary quoting that the 21% revision at 4-5 months in the Hi-Flex knee supported that question, that such a cut ended up trying to push the femur off the tibia with MUAs being performed because the knee ‘felt stiff’. He felt that a BSc in design didn’t always take into account the natural angles in the femoral and tibial condyles.

    0930 Should the mechanical Axis be zero? - Jean-Alan Epinette

    HKA line is questionable as femoral head offset can vary a lot. Is 0 degrees better - not necessarily. Do aligned knees perform better – not necessarily. Axis at neck in 75% of hips varied between 0-3 degrees meaning that alignment does not necessarily lead to better outcomes. One has to have respect for patient anatomy.

    0940 Stability: determined by surgeon or device - Adolph Lombardi

    Issues Lombardi discussed were restoration of medical axis, possibly using a constrained knee, checking the collateral, cruciate and patellar-femoral ligaments.

    As a final, determined declaration, he declared that instability was the surgeon’s fault!

    Session 3: Knee arthroplasty: the devil is in the detail

    1045 Single radius knee my choice - Thomas Schmalzried

    Schmalzried said he prefers to use single radius knees as they had excellent survivorship and were high flex.

    The ‘J’ curve was not affected as a result of which, the femur spent less time in articulation. There was also better recovery to the rate of about 98.6%.
    At several weeks post-op, the chair rise test was good with a lower instance of anterior knee pain.

    1055 Fixed or mobile bearings: what’s the evidence? - Christopher Dodd

    Dodd declared a preference for the Oxford unicondylar knee (naturally!) and cited papers from Fairbanks (Birmingham Orthopaedic Hospital) who found there was congruous contact between the two implants in all positions, that meniscal mobility was constant in the contralateral compartment and that medical compliance remained in both length and width.

    His own finding were that mobile bearings were fully congruous, more compliant and the kinetics were better. At 18 years the survivorship was 80%.

    He also felt that there was no specific difference between mobile TKRs and others. Oxford Knee Scores were much the same as were costs.

    1105 Medial pivot knees function better - Fares Haddad

    Haddad spoke about the MRK (medial rotation knee) and showed his early results were promising. The Total Knee Function Questionnaire Score (TKFQ) were good but there was a lot of data coming in soon.

    1115 Trochlear is the trouble in TKR - Derek McMinn

    McMinn spoke on the trochlea issues and the incidence of Patellar Realignment Surgery (PRS). He argued that there was no such thing as a perfect patello-femoral tracking and that.

    According to Merill Ritter, it was preferable to have better function. The PFL had to go between the condyles to work properly. It should also be bourn in mind that the femur is a spiral structure, not a straight one.

    McMinn then announced that work was being done on poly chemicals and the ability to mix standard and HXL poly in one device to meet the varying needs of bearings. Meaning that the edge of the insert could be hard whilst the centre was softer and more compliant.

    Session 4: Bone conserving arthroplasty

    1145 Lateral unis: the best performing knee replacement - Christopher Dodd

    Dodds went over some statistical papers including the Swedish Knee Arthropasty Register (SKAR) and return to work statistics. He had also looked at the Patient Reported Outcome Measures (PROMs) but found no difference between unicompartmental knees and total knee replacements. This also seemed to be repeated in the UK NJR which showed 9-95% in unis to 75% in totals. Most surprisingly there appeared to be a 10yr survivorship. However, the unis seemed to be unforgiving of internal rotation or proudness of the implants. He concluded that it has the potential to be the best but ‘not yet’!

    1155 Fixed medial unis work in the long term - Jean-Alain Epinette

    Reported that he had a 1-18 yr follow-up with the HA Inix knee

    1205 Isolated patella femoral replacement: worst performing knee arthroplasty in the registry Christopher Ackroyd

    Ackroyd spoke of his own practice which had 187 knees done between 1996 and 2002 with a good outcome of 89% at follow up. He revealed that ‘a lot of PKRs are not happy in the long term, some with radical pain’ which invariably arises from inaccurate sagittal cut, too much external rotation and oversized implants (also known as overstuffing) in the anterior compartment.

    He further purported that there was no evidence of the frequently claimed “rapid recovery” and that disease progression was invariably inevitable.

    1215 Bi-compartmental replacement is the answer - David Barrett

    Barrett on the other hand, refuted these claims saying that all this could be overcome by progressive compartment resurfacing – medial, patellar-femoral and lateral! He felt the ideal patient was a 70 yr old woman what was not particularly active. But a 50 yr old male would complain he had problems playing golf! This was because functionally, they were more demanding and tended to do things like cycling 1-7 miles.
     
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