Optimizing patellar positioning during total knee arthroplasty: an anatomical and clinical study

Optimal positioning of the patellar component is crucial for the success of a total knee arthroplasty (TKA). Usually, the patellar component is placed empirically over the presumed centre of the patellar cut. Medialization of the prosthetic patella has been recommended; however, no evidence-based guidelines have been reported.

This anatomical study aims to quantify a pre-defined optimal location for positioning of the patellar component with regard to the centre of the patellar cut. Intra-operative measurements of the patellar cut of a series of 129 TKA were conducted in order to measure the distance between the optimal centre of prosthetic patella (OCPP) and the centre of the patellar cut, and that over the vertical (proximal-distal) axis and the horizontal axis (medial-lateral).

Our results demonstrated that, (a) a significant morphological difference of the patellar cut exists between men and women (P < 0.0001), and (b) with reference to centre of the patellar cut, the OCPP lies superiorly and medially in 89%, inferiorly and medially in 9.4%, laterally and superiorly in 1.6%, and in no case laterally and inferiorly. No anterior pain, dislocation episode or patellar revision has been encountered during a follow-up of 4.5 years.

The placement of the patellar component during TKA differs from one patella to another. Thus, by defining the OCPP on a patient-by-patient basis, the surgeon should be able to reproduce the functional anatomy of the native patella.