Phil Walmsley

Range of movement correlates with the Oxford knee score after total knee replacement: A prediction model and validation

BACKGROUND Patient reported outcome measures are widely used in the evaluation of outcomes after Total Knee Replacement (TKR) in joint registries and large studies. The aim of this study was to assess the relationship between the Oxford knee score (OKS) and range of motion (ROM) after TKR, and to construct and validate prediction models of ROM from the measured OKS. METHODS Eight hundred sixty patients reviewed five years postoperatively and 273 patients reviewed nine to 10 years postoperatively completed an OKS. Of these, 808 (94%) and 226 (83%) patients, respectively, had a complete dataset (knee extension and ROM) and formed the study cohort. RESULTS Regression analysis demonstrated a significant correlation between the OKS and ROM (r=0.38, p<0.001) after adjusting for other confounding variables (age, sex, body mass index, and knee extension). A prediction model was constructed and validated using a second cohort of 226 patients at nine to 10 years after their TKR. Intraclass correlation demonstrated good reliability (r=0.60, 95% CI 0.47 to 0.69) between predicted and actual measured ROM for this group. However, when the OKS is used in isolation the reliability of the predicted ROM is diminished (intraclass correlation r=0.41, 95% CI 0.24 to 0.55). CONCLUSIONS The OKS is an independent predictor of ROM after TKR. It is also possible to predict ROM from the OKS, but the reliability of this is improved when other independent predictors such as age, gender, body mass index (BMI) and degree of knee extension are also acknowledged.

Ten-Year Results of the Press Fit Condylar Sigma Cobalt–Chrome Total Knee Replacement

&NA; Total knee arthroplasty (TKA) is reliant on safe and effective implants. The Press Fit Condylar Sigma Cobalt‐Chrome (PFCSCC) was introduced in 2006, but no reports have examined long‐term failure rates and patient‐reported outcome measures (PROMs). The primary aim of this study was to assess survival outcomes of the PFCSCC at 10 years after implantation. Prospective data collection was performed on all patients undergoing primary TKA in one orthopaedic department using this prosthesis exclusively from February 1, 2006, to January 31, 2007. Follow‐up was at 10 years. Survival analysis was performed using two primary outcome measures: (1) all‐cause joint revision and (2) aseptic revision. Secondary outcomes measures included the American Knee Society Score (AKSS) and Oxford Knee Score (OKS). In total, 249 knees of 233 patients underwent primary TKA. Mean patient age was 66.7 years (range 34‐80), and mean body mass index (BMI) was 30 kg/m2 (20.7‐40.1). Reviewing all causes of revisions, 14 joints (5.6%) of 14 patients required reoperation. Of these, nine were for deep infection, including six in the first year. Four (1.6%) underwent aseptic revision. Mean AKSS changed from 47.6 to 90.4 (n = 140; p < 0.001) at 10 years, and mean OKS changed from 38.3 to 23.2 (n = 149; p < 0.001). Prospective analysis of consecutive TKA cases using this design of prosthesis demonstrated high survival rates of 94.4% (all‐cause revision) and 98.4% (aseptic revision) at 10 years. Postoperative gains in PROMs were sustained at 10 years. These real‐world data represent a substantial extension to previous reports for the PFCSCC and suggest that it is not prone to late mechanical failure.