Summary

Patellofemoral joint repalcements are safer than total knee repalcements and should be consdiered as a treatment option

Abstract

Background

Patellofemoral osteoarthritis affects 24% of symptomatic patients with knee pain; many of these are middle-aged women. Surgical options include a total knee replacement (TKR) or patellofemoral joint replacement (PFR). The study aims to describe and compare the safety and revision risk profiles of these two types of surgery.

Methods

All PFR records in the UK National Joint Registry from 2003 to December 2021 were linked to the Hospital Episode Statistics database. Using Poisson regression, a 30-day safety profile was created by plotting risk ratios, absolute risk and differences in risk of developing myocardial infarction, lower respiratory tract infection, urinary tract infection, stroke, delirium, deep vein/thrombosis, wound infection and death. A parametric survival model was used to model the overall survival of a PFR compared with TKR over time. Differences in hazard ratios were plotted by gender for PFR. Confounding was handled by inverse proportional treatment weighting. Reasons for revision were analysed and compared. Length of stay between both procedures was compared.

Results

69,960 records were available for analysis, comprising 662,141 TKR and 7,819 PFR. PFR procedures were significantly less likely to sustain complications than TKR: lower respiratory tract infection (RR 0.65, P=0.0106, CI 0.47 – 0.90), deep vein thrombosis/pulmonary embolism (RR 0.35, P=0.0001, CI 0.24 – 0.52), urine tract infection (RR 0.59, P=0.0090, CI 0.40 – 0.88), wound infection (RR 0.73, P=0.0058, CI 0.57 – 0.91) and death within 30 days of the surgical procedure (RR 0.36, P<0.0449, CI 0.14–0.98). Over 10 years, TKRs had a 95% (0.95-0.96) survival compared with 85% (0.84-0.86) survival with PFRs. Within the first 2 years, PFR was likely to be revised due to pain, while infection was the most common cause of revision for TKR.

Conclusion

Patellofemoral arthroplasty is an overall safer procedure than total knee arthroplasty, associated with a reduced length of stay. Despite the higher revision risk, patients should still be counselled for a PFR as it restores normal function to the knee joint