Effect of Patellofemoral Geometry and Simulated Tibial Tubercle Osteotomy on Patellar Stability

Abstract

Articular geometry is known to affect joint function and be correlated with pathology; however, its effect on treatment outcomes is not well understood. The influence of trochlear groove depth on lateral patella stability following simulated tibial tubercle osteotomy was investigated. A statistical shape model was used to produce knee models with trochlear groove geometries ranging from shallow to deep. A Monte Carlo approach was used and 750 musculoskeletal models were generated with varying trochlear groove depths and patellar tendon medial and anterior transfer distances. An overground walking trial was simulated for each model using the COMAK routine and a 200N lateral perturbation force was applied to the patella during early stance. The lateral displacement of the patella resulting from this perturbation was used as a measure of patellar stability. In knees with deep trochlear grooves, patella displacement due to the perturbation decreased with increased medial patellar tendon transfer, indicating increasing stability. However, in knees with shallow trochlear grooves, stability was maximized at ~1 mm of medial patellar tendon transfer, but decreased for patellar tendon insertions medial or lateral of this point. Additionally, the medial patellofemoral ligament was more important to maintaining joint stability for larger patellar tendon transfer distances in knees with shallow trochlear grooves. These results emphasize the importance of considering joint geometry in surgical planning.