Re: 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
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.
University College Hospitals, London
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11. Development and validation of a discriminating functional hip score Konan S, Tahmassebi J, Haddad FS. Podium 620, AAOS meeting 2011.