More than 80% of total knee replacements can last for 25 yearsBMJ 2019; 367 doi: https://doi.org/10.1136/bmj.l5680 (Published 31 December 2019) Cite this as: BMJ 2019;367:l5680
All rapid responses
I thank Cook et al (Ref 1) for their contribution to the BMJ Education regarding Total Knee Replacement (TKR) implant survival.
However I am very concerned about how they concluded from the systematic review and meta-analysis by Evans et al (ref 2) that:
"This study provides evidence that knee replacement surgery has better long term outcomes than was previously thought. The average age of someone in the UK having a total replacement is around 70 years. The procedure is often delayed, to reduce the chance of needing revision surgery at a later date.
This study shows that at least 80% of total replacements last for 25 years. This could mean that people are offered surgery at a younger age."
I am not aware Evans et al had ever suggested in this paper that patients should be offered surgery at a younger age just because the overall TKR survival rate is found to be at least 80% at 25 years post primary surgery.
Niinimaki et al (as referenced by the paper by Evans at al) in ther 2014 research using Finnish Arthroplasty Registry (Ref 3) stated clearly:
"In patients undergoing TKAs, patients 65 years or younger had an increased revision rate compared with patients older than 65 years (HR, 2.1; 95% CI, 1.9–2.2; p < 0.001)."
In accessing the Finnish Arthroplasty Registry (FAR) website (Ref 4), I found evidence that this 80% survival of TKR implants at 25 years mentioned by Cook et al is very much driven by data from older patients at time of primary TKR, where as the revision rates for patients who had TKR between 55-64 years is 20-25% at 25 years, and worse in patients < 55 years with 30-35% revision rate at 25 years.
Similar age difference in revision rates is demonstrated by the Australian National Joint Replacement Registry (ANJRR). In fact, the 2019 ANJRR report stated the TKR revision rate for patients <55 years is 17.8% at 18 years; for 55-64 years 11.7%, 65-74 years 7.0%, 75 years or older 3.6% (Table KT13 of the 2019 report - Ref 5)
As suggested by Evans et al, while "National Institute of Health and Care Excellence (NICE) set a UK benchmark in 2014, which stated that individual hip replacement components are only recommended if 5% or fewer need revision at 10 years, but no equivalent benchmark exists for knee replacement in either the medium (10 years) or long term". In fact the older standard NICE TA2 from 2000 recommended prostheses to "have rates of failure (or projected rates of failure) of 10% or less at 10 years or, as a minimum, a three year revision rate consistent with this" (Ref 6). Keeping in mind that even as just over 50% of hip replacement last 25 years (Ref 7), if we are to apply the more lenient and higher threshold of 10% revision rate at 10 years to apply to knee replacement, patients who are less than 55 years will never meet the acceptable tolerance of implant revision at 10 years (10-15% for FAR, 10.5% at ANJRR)
Therefore it seems irresponsible for anyone to advocate younger patients should be offered TKR surgery based on the results of 80% implant survival at 25 years derived from registry database heavily skewed towards patients aged 65 years and older. This may mislead clinicians and the greater public alike into a false sense of reassurance about having TKR at a younger age. Younger patients with end-stage knee osteoarthritis should be carefully counselled with the right and appropriate information rather than misguided presumptions.
Competing interests: No competing interests