Anatomical landmark for medialized patellar component in TKA

Purpose

The aim of this study was to show a concrete setting landmark in two component types of round and anatomical oval shapes using three-dimensional (3D) simulation analyses in total knee arthroplasty (TKA).

Methods

The patellar resection surface was simulated three-dimensionally using preoperative CT data of 54 patients (68 knees) who underwent TKA with varus knee osteoarthritis. The mediolateral position of the original patellar ridge was examined. The round and anatomical oval patellar components were aligned in the following cases: medial edge setting, patellar ridge setting, maximal size setting. The component ridge position from the medial edge and size in each case were examined.

Results

The original patellar ridge was located nearly 40% from the medial edge. In aligning the component to reproduce the original patellar ridge, the medial bone width uncovered with the component was nearly 4 mm in both designs. The component size was significantly smaller as the component was placed more medially. In selecting the maximal size, the round component was aligned more laterally than the original patellar ridge. In contrast, the anatomical oval component enabled to be concomitant with a more appropriate position and size.

Conclusion

The position where the medial bone width uncovered with the component was nearly 4 mm, not the medial edge, was found as the best place to reproduce the original patellar ridge in both round and anatomical oval components. Specifically, the anatomical oval component might be more favorable with respect to the component position and size.