Mei Lin Tay: The Lifetime Revision Risk of Unicompartmental Knee Arthroplasty
Unicompartmental knee arthroplasty (UKA) and total knee arthroplasty (TKA) are effective treatment for patients with end-stage knee osteoarthritis. UKA can have intraoperative and post-surgical benefits compared with TKA, however is associated with a higher risk of revision. Current revision risk estimates are difficult for patients and clinicians to conceptualise. We therefore aimed to calculate the 'lifetime risk' of UKA revision as a more relatable estimate, and to compare these to TKA.
The lifetime risk of revision was calculated from all primary UKAS performed from 1999 to 2019 (n=13,481) captured by the New Zealand Joint Registry (NZJR). These were stratified by age, gender and American Society of Anesthesiologists (ASA) status.
The lifetime risk of revision for UKA was highest in the youngest patients (46-50 years; 40.4%) and lowest in the oldest patients (86-90 years; 3.7%). Lifetime risk of revision was higher for females (range 4.3%-43.4% cf. males 2.9%-37.4%) and patients with higher ASA status (ASA 3-4 range 8.8%-41.2% cf. ASA 1 1.8%-29.8%), regardless of age. The lifetime risk of UKA was two-fold higher than TKA (ranging from 3.7%-40.4% UKA, 1.6%-22.4% TKA) across all age groups. Increased risk of revision in the younger patients was associated with aseptic loosening in both males and females, and pain in females. Periprosthetic joint infections (PJI) accounted for 4% of all UKA revisions, in contrast to 27% for TKA; risk of PJI was higher for males than females for both procedures.
The lifetime risk of revision is a meaningful measure of arthroplasty outcomes and can aid patient counselling prior to knee arthroplasty. There is increased revision risk for younger patients, females and those with higher ASA status.
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