Study finds difference between Fixed vs Mobile Bearing PS TK
It has been hypothesized that the patella, working in conjunction with both medial and lateral femoral condyles, can influence kinematic parameters such as posterior femoral rollback and axial rotation. The objective of this study was to determine the in vivo kinematics of subjects implanted with a fixed bearing (FB) or mobile bearing (MB) posterior stabilized (PS) Total Knee Arthroplasty, with a specific focus on evaluating the impact that Anatomic and Medialized Dome patellar components have on tibiofemoral kinematic patterns.

Tibiofemoral kinematics were assessed for 40 subjects; 20 with an Anatomic patella and 20 with a Dome patella. Within these groups, 10 subjects received a FB PS TKA and 10 subjects received an MB PS TKA. All subjects were analyzed using fluoroscopy while performing a deep knee bend activity. Kinematics were collected during specific intervals to determine similarities and differences in regard to patella and bearing type.

--The greatest variation in kinematics was detected between the two Anatomic patellar groups.

--Specifically, the MB-Anatomic subjects experienced greater translation of the lateral condyle, the highest magnitude of axial rotation, and the highest range of motion compared to the FB-Anatomic subjects.

--Subjects with a Dome Patella displayed much variability amongst the average kinematics, with all parameters between FB and MB cohorts being similar.

The results of the study reveals that participants with an anatomical patellar component would have more normal movie patterns with an MB PS TKA compared with an FB PS TKA while subjects with a patellar Dome that could have equivalent cinematical results irrespective of the kind of TKA.