biomechanical analysis of the anterior displacement of tibial tuberosity (maquet operation): a computer model study

computer model of the patellofemoral joint was developed and the effects on the anterior displacement of the tibial tuberosity were investigated. the input geometrical and verification data for the model were obtained form an experimental study on a cadaver knee, mounted in an instron machine. the computer program found the configuration of the patellofemoral joint which satified both the geometrical and force equilibrium conditions, simultaneously, using a trial graphical approach.verification of the model was achieved by determining the patellar sagittal plane motion and patellofemoral contact locations and comparing the results with the experimental results of the same specimen and published data. simulation of the anterior displacement of the tibial tuberosity by the model showed that the location of contact area migrates distally on the femur and proximally on the patella following operation. the contact force of the patellofemoral joint decreased significantly by 70% at full extension, 30% at 30 degrees flexion and around 15% at higher flexion angles for a 1 cm anterior displacement of the tibial tuberosity and nearly doubled for a 2cm anterior displacement. the change of the effective moment are of the quadriceps was not considerable. the results suggest that the major effect of the maquet operation on the contact force appears in extension and mid-flexion rather than deep flexion amgles. further displacement of the tuberosity enhances the reduction of the contact force, however, the total reduction is less than what was predicted by maquet. the change of the contact location relieves pain in short term but causes hyperpressure in the proximal retropatellar surface which might be detrimental in long term