Gradual-radius femoral component with s-curve post-cam provides stable kinematics at mid-flexion after total knee arthroplasty

Tetsuro Ushio, Satoshi Hamai, Ken Okazaki, Hirotaka Gondo, Satoru Ikebe, Hidehiko Higaki, Yasuharu Nakashima

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


Background: Mid-flexion instability is the one of the reasons for patient dissatisfaction after total knee arthroplasty (TKA). The purposes of this study were to evaluate in vivo knee kinematics and clinical outcomes using a novel TKA design with a gradual femoral radius component and s-curve post-cam, which are intended to prevent the instability initiated by sudden reductions in the femoral radius observed with conventional components. Methods: We used radiographic-based, image-matching techniques to analyze femorotibial anteroposterior translation, axial rotation, and anterior/posterior cam-post contact during two dynamic movements, squatting and stair climbing, in 20 knees that had undergone posterior-stabilized fixed-bearing TKA with an improved sagittal profiles of the femoral component and post-cam mechanism. We also evaluated patient-reported outcomes assessed by the 2011 Knee Society Score (KSS 2011). Results: Squatting and stair climbing produced a similar trend in anteroposterior translation and a relatively small standard deviation at mid-flexion. Although the rotation angles varied widely during squatting and stair climbing, the femoral component was consistently externally rotated. Anterior/posterior cam-post contact during squatting and stair climbing were observed in 0/17 knees and 0/0 knees, respectively. The “Symptoms”, “Satisfaction”, and “Functional activities” subscales of the KSS 2011 were significantly (P < 0.05) improved postoperatively compared to preoperatively (“Symptoms”, 10 to 21; “Satisfaction”, 15 to 26; “Functional activities”, 25 to 71). Conclusion: A gradual femoral radius component with an s-curve post-cam provided stable kinematics and favorable clinical results during squatting and stair climbing at 1 year after surgery.

Original languageEnglish
Pages (from-to)665-671
Number of pages7
JournalJournal of Orthopaedic Science
Issue number3
Publication statusPublished - May 2022

All Science Journal Classification (ASJC) codes

  • Surgery
  • Orthopedics and Sports Medicine


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