2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


A Trend in Improving Oxford Knee Scores at a Single Centre Over a 20 Year Period: Examining the Influence of Surgical and Patient Variables

Payam Tarassoli, MBChB, BSc, DipSEM, MD, FRCS, Sydney, NSW AUSTRALIA
Myles R. J. Coolican, FRACS, Sydney, NSW AUSTRALIA
David A. Parker, MBBS, BMedSc, FRACS, Sydney, NSW AUSTRALIA

Sydney Orthopaedic Research Institute, Sydney, New South Wales, AUSTRALIA

FDA Status Not Applicable

Summary

A time series analyis of Oxford Knee Scores across a 20 year period

Abstract

Background

and objectives
In recent years patient reported outcome measures (PROMs) have emerged as invaluable instruments with which to assess clinical practice in a meaningful way and guide future interventions. The Oxford knee score (OKS) is a 12-item PROM specifically designed and developed to assess function and pain after total knee replacement (TKR) and has been thoroughly validated since its inception in the late 90s. This study aimed to explore the variation in reported OKS at one year following TKR, over a 20 year period of use at our institute. Furthermore, we aimed to determine if any variations could be attributable to recorded patient or surgical variables, in particular the introduction of intraoperative navigation.

Methods

A retrospective analysis was carried out on prospectively collected data from patients undergoing single primary or bilateral simultaneous TKR at a single centre from October 2002 until December 2022. SPSS 29 was used to with descriptive statistics explore the distribution of demographic data and 50 patient centred moving averages were calculated for the primary outcome variable of OKS and secondary variables (outcome and demographic) across the 20 year period. Linear regression used to determine temporal means and strength of association with date of surgery (time) for variables. A secondary analysis was undertaken to explore the influence of navigation on OKS, using matched control design for potential confounders of baseline characteristics of BMI, age, sex and pre-operative (preop) OKS. Two matched comparisons of intramedullary instrumentation (IM) vs. navigation, and established (beyond an early adoption phase of 6 months) vs mature navigation were carried out.

Results

Following exclusions for inflammatory arthropathy and previous surgery (other than arthroscopy), 4126 patients with OKS scores collected at one year (range 11-14 months) post operatively (postop), were available for analysis, with preop scores available for 3453. The postop OKS was moderately correlated with the time and increased from a mean of 38.9 to 43.3 (R2 = 0.532, p<0.01). Analysing patients carried out with navigation only reduced the strength of association with postop OKS (R2=0.303, p<0.001). In contrast, preop OKS showed a weaker association with time (R2=0.274), and this association disappeared completely when analysing navigated patients only (R2=0.01). No significant associations were found between age, preop BMI or change in OKS (pre to 1 year postop). Matched control analysis showed that the IM group (350 patients) had a significantly lower postop OKS than with a matched cohort of 454 patients with navigation (39.1 vs 41.3 p<0.001), and established vs late navigation showed a smaller difference (40.1 vs 41.5 p<0.001).

Conclusions

This study shows significant improvements in postop OKS with time, which is independent of baseline BMI, age and preoperative OKS. Whilst the introduction of navigation was associated with a significant difference in postop OKS, the trend of improving OKS persisted beyond a period of the established use of navigation, suggesting that other factors such as improved post operative rehabilitation may also have a significant impact.