Total hip arthroplasty versus resurfacing arthroplasty in the treatment of patients with arthritis of the hip joint: single centre, parallel group, assessor blinded, randomised controlled trial

BMJ 2012; 344 doi: (Published 19 April 2012)
Cite this as: BMJ 2012;344:e2147

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Haddad and colleagues make some interesting points regarding our trial and the place of hip resurfacing in the treatment of patients with severe arthritis. The trial did indeed involve many surgeons using several different approaches and several different implants. This was of course a deliberate policy; a ‘pragmatic’ trial reflects the variety of surgeons, approaches and implants used to treat patients across the NHS. With regard to collecting radiographic outcomes and metal ion data, these are important factors related to survival of hip implants in the longer term. There is little to be gained in reporting ion data during the “running in” period. 1 We have and will continue to collect this data on the patients in the study. However, the clear purpose of this trial was to find out whether patients perceive an early advantage of resurfacing. They did not. The issue of ceiling effect – in this case in the Oxford and Harris scores – is frequently discussed. We agree that in patients with hip conditions other than severe arthritis, ceiling effects are likely.2 However, there is actually little evidence that this is the case in patients having arthroplasty for severe arthritis; the Oxford Score in particular has a lower ceiling effect than other scores.3 Most importantly, the data presented in this trial did not show a ceiling effect, and indeed very few of the patients in either group achieved the highest possible hip scores.4 The Oxford Hip Score is the preferred tool of the Department of Health for all UK patients undergoing hip arthroplasty. 5 Surgeons who believe that hip resurfacing is functionally superior to total hip replacement may choose to use different outcome instruments in future clinical trials, but the onus will be upon them to justify their choices when more conventional measures do not show a difference. 1 Proc Inst Mech Eng H. 2006 Feb;220(2):269-77. The effect of 'running-in' on the tribology and surface morphology of metal-on-metal Birmingham hip resurfacing device in simulator studies. Vassiliou K, Elfick AP, Scholes SC, Unsworth A. 2 Patient-reported outcome instruments for femoroacetabular impingement and hip labral pathology: a systematic review of the clinimetric evidence. Arthroscopy 2011 Feb;27(2):279-86. 3 Patient-reported outcome in total hip replacement. A COMPARISON OF FIVE INSTRUMENTS OF HEALTH STATUS. J Bone Joint Surg [Br] 2004;86-B:801-8. 4 Quality criteria were proposed for measurement properties of health status questionnaires. J Clin Epidemiology 2007; 60: 34-42. 5

Competing interests: The work described in this manuscript has been funded through the Research for Patient Benefit scheme of the NIHR. The authors declare that they have received no support from any other organisation for the submitted work.

Matthew L Costa, Orthopaedic Surgeon

Juul Achten , Nick R Parsons, Richard P Edlin, Pedro Foguet , Udai Prakash, Damian R Griffin

University of Warwick, Warwick Clinical Trials Unit, Gibbet Hill Campus, Coventry

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Dear Sirs

Costa et al should be commended on undertaking a prospective randomised study. This is a laudable aim and one achieved all too infrequently in orthopaedics. It is a shame, however, that their paper does not have the necessary rigour or provide the detail that is really required to reach useful conclusions.

The authors do not describe the exact approach and technique used by their surgeons. The approach may have a significant impact on outcome, and it is widely known that at least one of the surgeons within that group favours a trans trochanteric approach for hip resurfacing and that this is associated with significant problems post-operatively, including the need for metalwork removal, which would worsen the outcome for that group over the first year1,2.

No radiographic or metal ion data is provided and thus the reader is unable to determine whether these are “good” or “bad” resurfacings or hip replacements 3-5.

No detail regarding the type of re-surfacing implant used has been included. It has become clear that there is a massive difference between the outcome of the Birmingham hip resurfacing implanted in appropriate positions by experienced surgeons and other implants that fare much less well 6-8 .

Very traditional and non-discriminating outcome measures have been used to measure function. These tests have a ceiling effect9,10. Moreover the arbitrary effect sizes mean that there is a high chance of a type 2 error; a 5 point difference in Oxford scores is of considerable magnitude. The reference provided (19) actually states that the minimum clinically significant difference (MCSD) is unknown and whilst 5 might be a good guess a figure of 3 or even 2 may be correct. This undermines the whole power calculation. No rationale or reference is provided for the Harris Hip Score MCSD, a difference of 8% seeming quite large when comparing successful procedures.

We have validated a task based functional assessment tool11 that shows a significant difference between THR and BHR patients with tasks that require balance and proprioception. The authors should consider using modern assessment methods that are designed to show differences in active patients after hip surgery.

Without the corroborative technical, radiographic and functional data, both this dataset and the cost-effectiveness data are invalid.

It is disappointing that this paper has been accepted in its current format.

Yours sincerely

Sam Oussedik
Sujith Konan
Fares Haddad
University College Hospitals, London

1. Cashman JP, Cashman WF. Comparison of complications in transtrochanteric and anterolateral approaches in primary total hip arthroplasty. Orthopedics. 2008 Nov;31(11):1085.
2. Horwitz BR, Rockowitz NL, Goll SR, Booth RE Jr, Balderston RA, Rothman RH, Cohn JC. A prospective randomized comparison of two surgical approaches to total hip arthroplasty. Clin Orthop Relat Res. 1993 Jun;(291):154-63.
3. Hart AJ, Matthies A, Henckel J, Ilo K, Skinner J, Noble PC.Understanding why metal-on-metal hip arthroplasties fail: a comparison between patients with well-functioning and revised birmingham hip resurfacing arthroplasties. AAOS exhibit selection. J Bone Joint Surg Am. 2012 Feb 15;94(4):e22
4. Langton DJ, Sprowson AP, Joyce TJ, Reed M, Carluke I, Partington P, Nargol AV. Blood metal ion concentrations after hip resurfacing arthroplasty: a comparative study of articular surface replacement and Birmingham Hip Resurfacing arthroplasties. J Bone Joint Surg Br. 2009 Oct;91(10):1287-95.
5. Hart AJ, Buddhdev P, Winship P, Faria N, Powell JJ, Skinner JA. Cup inclination angle of greater than 50 degrees increases whole blood concentrations of cobalt and chromium ions after metal-on-metal hip resurfacing. Hip Int. 2008 Jul-Sep;18(3):212-9. 1:
6. Reito A, Puolakka T, Pajamäki J. Birmingham hip resurfacing: five to eight year results. Int Orthop. 2011 Aug;35(8):1119-24.
7. Treacy RB, McBryde CW, Shears E, Pynsent PB. Birmingham hip resurfacing: a minimum follow-up of ten years. J Bone Joint Surg Br. 2011 Jan;93(1):27-33.
8. Baker RP, Pollard TC, Eastaugh-Waring SJ, Bannister GC. A medium-term comparison of hybrid hip replacement and Birmingham hip resurfacing in active young patients. J Bone Joint Surg Br. 2011 Feb;93(2):158-63.
9. Wamper KE, Sierevelt IN, Poolman RW, Bhandari M, Haverkamp D. The Harris hip score: Do ceiling effects limit its usefulness in orthopedics? Acta Orthop. 2010 Dec;81(6):703-7.
10. Marx RG, Jones EC, Atwan NC, Closkey RF, Salvati EA, Sculco TP. Measuring improvement following total hip and knee arthroplasty using patient-based measures of outcome. J Bone Joint Surg Am. 2005 Sep;87(9):1999-2005.
11. Development and validation of a discriminating functional hip score Konan S, Tahmassebi J, Haddad FS. Podium 620, AAOS meeting 2011.

Competing interests: I have received royalties and research support from Smith and Nephew but never in relation to hip resurfacing. Our department research research support from a number of industry partners

fares haddad, orthopaedic surgeon

Sam Oussedik, Sujith Konan

university college london hospitals, 235 Euston Road, London NW1 2BU

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Hip Resufacing Arthroplasty (HRA) was developed as a more conservative alternative to total hip arthroplasty (THA), for younger and more active patients. But is it really? A PRCT is an excellent way of answering this question, so Costa and his colleagues should be congratulated for undertaking this demanding surgical task.

However, they chose metrics which do not even consider the possibility of life outside a shopping mall: full marks can be reached in the Oxford Hip Score (OHS) if one can walk for half an hour, manage the stairs, and get dressed. The Harris Hip Score (HHS) has even lower expectations, full marks being obtained for surgical accuracy if the difference in leg length following surgery is less than an inch and a half!
Such low aspirations inevitably lead to ceiling effects. Unsuprisingly, very high scores have already been reported for both procedures in single arm studies out to 10 years (1) (2). When measured by these metrics, both operations work well. So a power calculation which demanded a 5 points superiority would only ever be obtained if one arm had had unexpectedly poor results. Thankfully neither did, but we are none the wiser regarding the primary hypothesis.

Top walking speed is a simply comprehended metric that is relevant to life expectancy, and function for active people. When measured using a treadmill, it has no ceiling effect. In February we reported that when closely matched for leg length, age, gender and OHS, HRA patients can match speed of normal controls, while THA patients are 9% slower[3] (figure 1). Shorter stride length at higher speeds seems to be the reason for the deficiency in THA. One possible explanation is the stiff piece of metal in the proximal femur which may hurt when the bone starts to flex.
A simple treadmill will suffice to generate this continuous variable. It is highly relevant to the active lives of young patients, and immediately comprehensible, unlike any PROM with ceiling effects.

The authors have done the difficult bit in conducting a randomized trial of hip arthroplasty. A simple treadmill test may allow them to detect what patients report: there is life outside shopping malls, but you won’t find it using the Oxford Hip Score.

1. Singh S, Trikha SP, Edge AJ. Hydroxyapatite ceramic-coated femoral stems in young patients. A prospective ten-year study. The Journal of bone and joint surgery British volume. 2004 Nov;86(8):1118-23.
2. Treacy RB, McBryde CW, Shears E, Pynsent PB. Birmingham hip resurfacing: a minimum follow-up of ten years. The Journal of bone and joint surgery British volume. 2011 Jan;93(1):27-33..
3. Cobb JP, Wiik AV, Lewis A, Amis AA. Hip resurfacing arthroplasty enables faster walking and longer stride length than total hip arthroplasty. Paper #657. Presented at the American Academy of Orthopaedic Surgeons 2012 Annual Meeting. Feb. 7-11. San Francisco.

Competing interests: None declared

justin cobb, Orthopaedic Surgeon

Anatole Wiik, Angus Lewis, Andrew Amis

Imperial College, charing cross hospital London W6 8RF

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