Intraoperative Patella Dimension Measurement in Asian Female Patients and Its Relevance in Patellar Resurfacing in TKA

Background: Implants used for total knee arthroplasty (TKA) in Asian patients are mostly produced based on anthropometry of the Western population, thus causing problem with patella sizing, especially in Asian females where the patellae are regarded to be smaller. This study is to define intraoperative patella dimensions in our female populations and compare them with current prosthetic systems available at our institution.

Methods: This is a cross-sectional study involving 156 TKA female patients with normal patellae. The patella height, width, thickness, medial and lateral articular facets' width and thickness, and the dome position were measured. The smallest implant size from 3 manufacturers was compared to the data obtained. Analysis using descriptive statistics was used to get the mean and median of anatomical patella dimensions, whereas the independent T test and one-way ANOVA test were used to compare the Malaysian female's patella dimensions with various implant sizes.

Results: The articular surface of the patella was found to have an oval shape with a width-height ratio of 1.31. The mean (SD) patella thickness, width, and height were 20.7 (1.85) mm, 40.7 (3.79) mm, and 31.3 (2.81) mm, respectively. Only 17.9% fit for smallest implant size from all 3 manufacturers. The oval-shape implant was suitable in 53.8% patients based on their width-height ratio. The dome position is 2.2 mm medial to centre.

Conclusion: These female patients have thinner and smaller patella, which are generally unable to accommodate patellar components based on the Caucasian database. Therefore, orthopaedic implant manufacturers should consider optimizing the thicknesses as well as widths of their patellar prostheses.