Trends in knee arthroscopy and subsequent arthroplasty in an Australian population: a retrospective cohort study

BACKGROUND Knee arthroscopy is a common procedure in orthopaedic surgery. In recent times the efficacy of this procedure has been questioned with a number of randomized controlled trials demonstrating a lack of effect in the treatment of osteoarthritis. Consequently, a number of trend studies have been conducted, exploring rates of knee arthroscopy and subsequent conversion to Total Knee Arthroplasty (TKA) with varying results. Progression to TKA is seen as an indicator of lack of effect of primary knee arthroscopy. The aim of this paper is to measure overall rates of knee arthroscopy and the proportion of these patients that undergo subsequent total knee arthroplasty (TKA) within 24 months, and to measure trends over time in an Australian population. METHODS We conducted a retrospective cohort study of all adults undergoing a knee arthroscopy and TKA in all hospitals in New South Wales (NSW), Australia between 2000 and 2008. Datasets obtained from the Centre for Health Record Linkage (CHeReL) were analysed using negative binomial regression. Admission rates for knee arthroscopy were determined by year, age, gender and hospital status (public versus private) and readmission for TKA within 24 months was calculated. RESULTS There was no significant change in the overall rate of knee arthroscopy between 2000 and 2008 (-0.68%, 95% CI: -2.80 to 1.49). The rates declined in public hospitals (-1.25%, 95% CI: -2.39 to -0.10) and remained relatively steady in private hospitals (0.42%, 95% CI: -1.43 to 0.60). The proportion of patients 65 years or over undergoing TKA within 24 months of knee arthroscopy was 21.5%. After adjusting for age and gender, there was a significant decline in rates of TKA within 24 months of knee arthroscopy for all patients (-1.70%, 95% CI:-3.13 to -0.24), patients admitted to private hospitals (-2.65%, 95% CI: -4.06 to -1.23) and patients aged ≥65 years (-3.12%, 95% CI: -5.02 to -1.18). CONCLUSIONS Rates of knee arthroscopy are not increasing, and the proportion of patients requiring a TKA within 24 months of a knee replacement is decreasing in the age group most likely to have degenerative changes in the knee.