Kinematic Comparison between Medially Congruent and Posterior-Stabilized Third-Generation TKA Designs.

Background: This study compares knee kinematics in two groups of patients who have undergone primary total knee arthroplasty (TKA) using two different modern designs: medially congruent (MC) and posterior-stabilized (PS). The aim of the study is to demonstrate only minimal differences between the groups. Methods: Ten TKA patients (4 PS, 6 MC) with successful clinical outcomes were evaluated through 3D knee kinematics analysis performed using a multicamera optoelectronic system and a force platform. Extracted kinematic data included knee flexion angle at heel-strike (KFH), peak midstance knee flexion angle (MSKFA), maximum and minimum knee adduction angle (KAA), and knee rotational angle at heel-strike. Data were compared with a group of healthy controls. Results: There were no differences in preferred walking speed between MC and PS groups, but we found consistent differences in knee function. At heel-strike, the knee tended to be more flexed in the PS group compared to the MC group; the MSKFA tended to be higher in the PS group compared to the MC group. There was a significant fluctuation in KAA during the swing phase in the PS group compared to the MC group, PS patients showed a higher peak knee flexion moment compared to MC patients, and the PS group had significantly less peak internal rotation moments than the MC group. Conclusions: Modern, third-generation TKA designs failed to reproduce normal knee kinematics. MC knees tended to reproduce a more natural kinematic pattern at heel-strike and during axial rotation, while PS knees showed better kinematics during mid-flexion.

Atypical periprosthetic femur fracture on an underestimated atypical femoral pattern. A case report.

CASE: Atypical fracture patterns, especially to the femur midshaft, have begun emerging since long-term bisphosphonate use was introduced. The same fracture pattern could arise around prosthetic hip implant, but the literature reports few cases regarding atypical periprosthetic femur fracture on previous total hip arthroplasty implant in patients on long-term bisphosphonate therapy. To our knowledge we report here the first case of atypical periprosthetic femur fracture arising after total hip arthroplasty implant on a previously identified but underestimated atypical femur pattern. CONCLUSION: Surgeons should never underestimate an atypical femur pattern on x-rays and always relate groin and thigh pain to hip pathology before performing total hip arthroplasty.