Comparison of five patellar height measurement methods in a Turkish adult cohort

Abstract

Aim: The aim of this study was to investigate the correlation between the methods traditionally used for patellar height measurements[Insall-Salvati (IS), Modified Insall-Salvati (MIS), Blackburne-Peel (BP), Caton-Deschamps (CD)] and the plateau-patellar angle (PPA)in Turkish adult population.Material and Methods: A cross-sectional retrospective study was conducted. A total of 100 lateral knee radiographs in 30° flexionwere analyzed by two blinded orthopedist independently to each other’s measurements. The average IS ratio, MIS ratio, BP ratio, CDratio and PPA measurement were calculated by taking the average of the measurement values of both observers. The inter-observerreliability for two observers was determined using intraclass correlation coefficients (ICC). Spearman rank correlation analysis wasperformed to analyze correlations between mean ratios/angle measurements.Results: The mean age at the time of the radiographs was 30.18 ± 5.78 (range:20-40) years, 60% were female, and 58 radiographswere of the right knee. The mean and standard deviations of the patella height measurements were found 1.05 ± 0.12 accordingto the IS ratio; 1.66 ± 0.29 according to the MIS ratio; 0.91 ± 0.15 according to the CD ratio; 0.84 ± 0.14 according to the BP ratio;24.74° ± 2.87° according to PPA measurement. There was highest inter-observer agreement between the two observers with an ICCof 0.926 (95% confidence interval: 0.89-0.950), excellent reliability, for the PPA measurement. Inter-observer agreement between twoobservers was good reliability for other measurements (IS, MIS, CD, BP). The highest correlation was between CD ratio and BP ratio,strong correlation, with a Pearson's correlation coefficient of 0.790.Conclusion: The PPA appears to be a feasible tool that can assess patellar height with higher reliability compared to the four mostcommonly used methods, in a Turkish adult population.