Abstract
Despite the overall successful outcomes following primary total knee arthroplasty
(TKA) and the concept that a well-balanced TKA yields a more successful result, concerns
still remain in the reported literature regarding the patellofemoral joint. Diminished
outcomes have been associated with poorly balanced or placed patella implants. The
effect of different techniques to achieve flexion–extension balance and the use of
posterior stabilized (PS) versus cruciate retaining (CR) implant designs on patellofemoral
balancing has not been previously studied. The purpose of this study is to utilize
a validated computational analysis software to simulate the effects of varying implant
positions and sizes of femoral components. The patellofemoral retinaculum (PFR) load
was significantly affected by some conditions, while others did not reach significance.
The proximal-distal implant position with knee flexion angle (p < 0.001), the implant size (p < 0.001), and the implant bearing type (CR/PS) (p < 0.05) were significant. For the proximal-distal implant position and knee flexion
angle, a more proximal implant position (elevating the joint line) increased the PFR
load from 15 to 30°, and a more proximal implant position reduced retinaculum load
from 60 to 135°. However, at 45°, implant position does not affect retinaculum load.
Achieving the appropriate balance between the dynamic nature of both the tibiofemoral
and the patellofemoral interaction in TKA has proven to be complex and challenging
to manage. Balancing of a TKA is essential to the proper functioning and overall longevity
of the implant. These results demonstrate that patellofemoral balance is affected
by implant size and position during flexion–extension gap balancing.
Keywords
total knee arthroplasty - patellofemoral balance - computer analysis
