Evaluation of Patellar Dimension and Bristol Index in Asian Population: An MRI Study

Abstract Introduction: Restoration of patellar thickness is pivotal during a total knee arthroplasty (TKA). This study aims to evaluate the patellar dimension and Bristol Index of patellar width to thickness (BIPWiT) using magnetic resonance imaging (MRI) in Asian population.Methods: 101 MRI scans of young adults with normal patellofemoral joint (PFJ) age 17-40 were evaluated from January 2019 to December 2020. Exclusion criteria included patella-femoral pathology and degenerative joint disease. Data of gender, body height and weight were obtained from physical examination, while patella height, width and thickness were obtained using MRI measurement. Descriptive analysis was used to get the mean and standard deviation of patella dimension, whereas correlation between patella thickness with patella width and length were analysed using Pearson correlation and BIPWiT ratio was obtained by dividing the patellar width and patellar thickness. Results: Mean patellar length was 30.06 ± 2.94 (29.48-30.64); patellar width was 44.13 ± 4.44 (43.26-45.01); and patellar thickness was 23.89 ± 2.33 (23.43-24.35). Patellar dimension in male were significantly larger compared to female (P < 0.001). However, there was no difference in cartilage thickness between male and female (P = 0.305). There was strong correlation between patellar width and patellar thickness (r = 0.66; P < 0.001) with BIPWiT ratio of 1.85 ± 0.15.Conclusion: BIPWiT of 1.8:1 between patellar width and patellar thickness was recommended as a guide for patellar thickness restoration during TKA. There is no difference of patellar dimension between Asian and Western population in a healthy knee.Level of Evidence: Level III