gms | German Medical Science

Objectives: The objective of this ongoing study was to compare in vivo kinematics of posterior stabilized (PS) total knee arthroplasty (TKA) subjects implanted with either a traditional, patient sized off-the-shelf (OTS), TKA or a customized-individually-made (CIM) TKA replicating individual femur and tibia geometries.

Methods: In vivo kinematics for 20 clinically successful patients, 5 CIM-PS-TKA, and 15 OTS-PS-TKA, were assessed using mobile fluoroscopy and a 2D-3D registration process during weight-bearing deep-knee-bend (DKB), level-ground gait and stepping up and down.

Results and Conclusion: During DKB, CIM patients experienced between 14.56mm and 20.87mm of lateral condyle posterior translation compared to an average 4.70mm for the OTS subjects. The CIM-TKAs also demonstrated between 5.53° and 19.92° of external rotation compared to an average of 1.04° for the OTS-PCR-TKAs. On average, CIM subjects experienced greater weight-bearing flexion with an average of 106.5° verses 94.2° for OTS-TKA designs.

During DKB, CIM subjects experienced greater magnitudes of lateral condyle rollback and axial rotation compared to OTS subjects leading to an improved approximation of normal kinematics. The magnitudes of these kinematics were attenuated compared to the normal joint. This is a recurrent trend across all activities. The kinematics for both PS-TKA variants produced more normal kinematics than their respective cruciate-retaining designs.

Subjects having a CIM-PS-TKA demonstrate more normal kinematic patterns more closely approaching that of the normal knee. Additional subjects are being analyzed and early results show personalization of PS-TKA designs may provide a kinematic benefit to arthroplasty patients.