Dear Sir,

The National Joint Register has a wealth of valuable information and its power should lie in the very large numbers already available for analysis. It is curious however that different authors draw wildly differing conclusions when apparently using the same data set.

McMinn and his colleagues make the case for resurfacing arthroplasty (1), but Smith et al suggest a more limited role (2) while Griffiths et al make a very strong case on both clinical and economic grounds for the use of cemented metal on plastic hips replacements(3).

Orthopaedic surgery has repeatedly discredited itself by using unsatisfactory and untested implants(4). Selective extraction of data with extrapolation which may be based on personal bias is not the best way to inform patients, or indeed ourselves.
If some prostheses have a higher failure rate by 5 or 6 years after implantation, it seems highly improbable that those prostheses will give better long-term results than prostheses with better short-term performance.

Since results at even 10 years can only be regarded as medium-term, orthopaedic surgeons, their patients and those who fund this activity should exercise caution when interpreting publications which demonstrate such disparities since peer-review appears unable to eliminate the anomalies.

Yours faithfully,

Stephen Dalgleish
David Finlayson

References
1. McMinn DJ, Snell KI, Daniel J, Treacy RB, Pynsent PB, Riley RD. Mortality and implant revision rates of hip arthroplasty in patients with osteoarthritis: registry based cohort study. BMJ. 2012;344:e3319.
2. Smith AJ, Dieppe P, Howard PW, Blom AW. Failure rates of metal-on-metal hip resurfacings: analysis of data from the National Joint Registry for England and Wales. Lancet 2 Oct. doi:10.1016/S0140-6736(12)60989-1
3. Griffiths EJ, Stevenson D, Porteous MJ. Cost savings of using a cemented total hip replacement: an analysis of the National Joint Registry Data. J bone Joint Surg Br. August 2012;Vol 94-B no 8; 1032-1035
4. Cohen, D. How safe are metal on metal hip implants? BMJ 2012;344:e1410

Competing interests: None declared