Total knee arthroplasty in-vivo kinematics changes after insert replacement for posterior cruciate ligament deficiency: a case report

In cruciate-retaining (CR) total knee arthroplasty (TKA) the preservation of the posterior cruciate ligament (PCL) provides joint stability and drives knee kinematics. No previous studies described in-vivo knee kinematics of PCL-deficient CR TKA. In the present case report it's described the in-vivo kinematic pattern change in a patient with post-operative PCL failure before and after insert replacement to a cruciate substituting (CS) design. In-vivo fluoroscopic analysis showed that PCL-deficient TKA showed more anterior translation of the lateral femoral condyle with respect to a cohort  of patients operated of CR-TKA with intact PCL, undergoing fluoroscopic analysis. The replacement to a CS design provided more external rotation of the femoral component and less anterior motion of the lateral condyle. The antero-posterior translation of the medial condyle was similar in PCL-deficient knee, CS TKA and controls. TKA with PCL deficiency showed more antero-posterior motion compared to TKAs with intact PCL and this can be source the of instability and a potential factor for patient's dissatisfaction. For this reason surgeons should attentively verify PCL integrity when performing a cruciate-sparing TKA.