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Which factors determine the wear rate of large-diameter metal-on-metal hip replacements? Multivariate analysis of two hundred and seventy-six components.
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Medical management of osteonecrosis of the hip: a review
[ 12 July 2013 ]

Meeting Update: Contemporary Challenges in Hip Surgery: Course Chairman Martyn Porter

Contemporary Challenges in Hip Surgery 26th - 27th June 2008, Wrightington Hospital, Wigan, UK


Course organizer: Mr Martyn Porter

86 delegates from 7 countries attended this meeting held over 2 days at the conference centre in the grounds of Wrightington Hospital. The meeting covered many aspects of primary and revision hip replacement, resurfacing, avascular necrosis of the hip and hip impingement problems. The faculty of surgeons from Wrightington was joined by with many world experts on these issues including Dan Berry from the Mayo Clinic and Jean-Pierre Vidalain from Annecy. A few of the meeting highlights are discussed below

Resurfacing

Derek McMinn, designer and pioneer of the Birmingham Hip Resurfacing (BHR) gave a lecture on his experiences with the development of resurfacing. He showed how the results of implant had changed depending on the manufacturing technique, in particular the heat treatment process used. In his 1996 cohort of patients, where the implants had been double heat treated he reported an 86% survival at 10 years, however in the years up to 1996, where the implants were not double heat treated the survival was 96%. Discussion of issues relating to metal wear were also covered and Derek presented research to show that in-vivo metal ion concentrations were lower in patients with a BHR with a low diametrical clearance (around 100 microns) compared to a standard BHR with a clearance in the order of 300 microns. He re-iterated the importance of acetabular cup placement in terms of inclination angle suggesting that a cup with an inclination angle of 55 degrees or over was highly likely to fail due to edge loading.

Martyn Porter chairs a discussion on resurfacing

 

 

 

 

 

 

 

 

 

 

 

 

Marci Maheson from Cardiff then detailed the differences in design that constitute the so-called 4th generation of resurfacing implants such as the ASR from DePuy. A reduction in bone removal and reduced diametrical clearance were some of the proposed advantages of these designs however concerns were raised regarding potential deformation of the thinner sockets leading to clutching as well as the lower sector angles of these sockets potentially leading to earlier edge loading. Marci analysed the joint registry data on outcome from resurfacing and suggested that some of the poorer results from the newer generations of implants maybe related to the learning curves of surgeons performing newer procedures rather then the implants themselves.

Martyn Porter (Wrightington) then presented his experience at dealing with 13 cases of ALVAL (aseptic lymphocyte dominated vasculitis and associated lesion) following resurfacing. This was one of the largest series currently reported and Martyn described the first case he had seen in terms of the clinical and surgical findings of massive soft tissue necrosis and brown necrotic material causing pain and instability in a patient after resurfacing arthroplasty. Martyn described the histological features of this condition as originally documented by Willert et al (JBJS(Am) 2005) but commented that those authors had not necessarily replaced the metal-on-metal bearing couple in those patients which he thought was a vital part of the treatment of this condition. Of the patients described all had been revised with standard primary total hip implants with ceramic-on-ceramic, metal-on-poly or ceramic-on-poly bearings. All patients had good resolution of symptoms with good functional results, albeit at early follow up. Martyn summarized the current understanding of this condition by stating that whilst we know that ALVAL is a cause of failure in hip resurfacing due to metal ions, it does not appear to be implant specific and revision seems to reliably treat the symptoms. We still do not know the rue incidence of the condition, whether it is a patient specific response to normal ion levels (a hypersensitivity) or a normal reaction to ion overload. We also do not know whether implant positioning is important and the extent of soft tissue recovery after revision surgery.

John Timperley from Exeter then gave a presentation pointing out how the popularity of resurfacing had been driven in part by the media and the implant companies. He suggested that a more scientific introduction of new technology would be appropriate.

Revision Hip Surgery


Dan Berry from the Mayo clinic presented his surgical technique of extended trochanteric osteotomy (ETO) for removal of femoral stems in revision surgery. He described a modified technique preserving the posterior and anterior capsule of the hip to reduce dislocation risk post-operatively.

Jean-Pierre Vidalain from Annecy (the originating centre for the popular Corail stem) demonstrated a technique for removal of a well fixed uncemented stem using flexible osteotomes and stout 1.8mm K wires. He suggested that most stems can be removed this way and only occasionally do they need to perform and extended trochanteric osteotomy. Commenting on stem length after osteotomy, Jean-Pierre said they often use a stem of the same length as that removed rather than one longer as would be traditional. In contrast, Dan Berry indicated that he would have a low threshold for doing an ETO and would always use a longer stem.

Avascular Necrosis of the Hip (Osteonecrosis of the Hip)


Tim Board (Wrightington) started off this session with an overview of the aetiology and classification of osteonecrosis. He reported that whilst the pathophysiology of this condition is not yet well understood, there is an increasing list of conditions associated with AVN of the hip. The number of clotting disorders associated with AVN has increased and there is some evidence to suggest that treatment with anticlotting agents such as clexane may be of value in these patients. Tim suggested that patients with early AVN may benefit from haematological referral. After reviewing the numerous classification systems he suggested that the most important factors were the presence of femoral head collapse and this would guide treatement and the size of the lesion as this is one of the strongest prognostic factors. Tim also discussed the results of bisphosphonate treatment for pre-collapse AVN and suggested that despite the limitations of the one randomized controlled trial available, there was growing evidence that this may well be a valuable treatment modality.

Dan Berry (Mayo Clinic, USA) then discussed the surgical treatment options. In a very frank discussion he made it clear that there was very little level 1 evidence to support any of the common treatment options (core decompression with or without graft, osteotomy, tantalum rod insertion) for precollapse lesions. He described the difficulties of conducting appropriate randomized trials in surgery. For post-collapse patients he advocated total hip replacement as the favoured option. He suggested that whilst the historical results of hip arthroplasty in these patients have been worse than for patient with osteoarthritis, the expected results using modern designs of THA are likely to be better.

Richard Villar (London) then described his experience with partial femoral head resurfacing procedures. He had performed 14 such operations and at a follow-up of 3 years, 4 had been revised to hip replacement (or complete resurfacing). Whilst he said the results were less than satisfactory, the 4 revision were performed in patients with osteoarthritis rather than AVN. He commented that his current indications for this operation were young patients with a small femoral head defect and no evidence of osteoarthritis.

Derek McMinn (Birmingham) then reported his experience of using the Birmingham Hip Resurfacing in patients in AVN. He reported less than satisfactory results (in the order of 90% survival at 10 years) with the standard prosthesis. He said that this had led him to develop the Birmingham Mid Head Resection prosthesis (BMHR) which uses an uncemented stem in the axis of the femoral neck which is frustoconical in shape. A larger resurfacing head is attached to the stem and this articulates with a standard resurfacing socket. He detailed the iterations in design that led to the current form. This prosthesis is not yet widely available but is being used as part of a multicentre prospective trial.

(last updated 05/07/08 TB)


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