Patient safety after partial and total knee replacement

In his Comment (Oct 18, p 1405) about the controversies in prosthetic surgery for knee osteoarthritis,

Justin Cobb makes several statements regarding the utility and focus of joint registries in general and specific allegations regarding the probity of the National Joint Registry for England, Wales, and Northern Ireland (NJR). These comments need redress.

Cobb states that the NJR is industry-funded and implies that there is collusion to restrict access to unicompartmental knee replacement. This statement is incorrect. The NJR is funded by the tax-payer and owned by the UK Government. From April, 2014, going forward, industry also made a financial contribution to the NJR in return for postmarket surveillance data.

Cobb also states that Justin Hunt and colleagues

stop short of commending unicompartmental knee replacement compared with total knee replacement “to avoid conflict with the stream of registry publications promoting unicompartmental knee replacement over total knee replacement”. This comment also seeks to question the probity of the NJR, suggesting larger scale collusion is occurring. This assertion is also incorrect. Unique among joint registers, the NJR allows independent researchers to use the NJR dataset. The two papers that form the substance of Cobb’s argument

^, 

are exemplars of this process. Investigators of these studies, one of which was internal

and the other independent,

both had access to the NJR dataset. They have contrasting arguments, but use different study designs and analysis methods. We were encouraged that The Lancet published both studies side by side

^, 

to stimulate the debate that Cobb suggests the NJR wishes to close down.

MP is Medical Director of the NJR and JMW is chair of the research sub-committee of NJR. MP reports fees from Johnson and Johnson.