2023 ISAKOS Biennial Congress ePoster
In-Vivo Kinematic Analysis of Evolution® Medial-Pivot Total Knee Arthroplasty during Weight-Bearing Activity
Eiichi Nakamura, MD, PhD, Kashimashiki-Gun, Kumamoto JAPAN
Nobukazu Okamoto, MD, PhD, Kumamoto, Kumamoto JAPAN
Hitoshi Ito, MD, PhD, 熊本市中央区, 熊本県 JAPAN
Tetsurou Masuda, MD, PhD, Kumamoto, Kumamoto JAPAN
Satoshi Hisanaga, MD, PhD, Kumamoto, Kumamoto JAPAN
Yasunari Oniki, MD, PhD, Kamimashiki-Gun, Kumamoto JAPAN
Kumamoto Kaiseikai Hospital, Kumamoto University Hospital, Kumamoto, Kumamoto, JAPAN
FDA Status Cleared
Summary
The EVOLUTION® Medial-Pivot knee arthroplasty showed that, during flexion in weight-bearing, a medial pivot motion was seen at higher reproducibility, which is consistent with the implant design intent.
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Abstract
Introduction
Total knee arthroplasty (TKA) is the most effective surgical treatment for patients with severe osteoarthritis of the knee. The physiological motion of the normal knee joint shows a posterior sliding of the lateral femoral condyle on the tibial plateau while a pivoting movement on the medial compartment. One of the main goals of TKA implant design is to produce kinematics at least similar to such normal knee. The Medial-Pivot (MP) TKA has been developed to replicate the medial pivot motion seen in the normal knee by modifying the joint geometry. However, it is still somewhat controversial as to whether or not this MP implant can actually reliably reproduce such desired kinematics in vivo.
The purpose of the present study is to examine the three-dimensional in-vivo kinematics in the MP TKA during weight-bearing activity.
Materials And Methods
A total of 18 consecutive patients (10 women and 8 men) who required a unilateral TKA for severe medial knee osteoarthritis were enrolled in this study. All knees had been implanted with Evolution® Medial-Pivot Knee and cruciate-substituting insert (MicroPort Orthopedics Inc., Arlington, TN, USA). At one year after surgery, all patients were examined clinically and analyzed in-vivo kinematics during lunge and step-up activities using fluoroscopy. In kinematic analysis, anteroposterior movement of medial and lateral femoral condyles (MFC and LFC) on the tibial tray, tibial axial rotation relative to the femoral component, and center of rotation were measured using a 2D/3D registration technique.
Results
Postoperatively, all patients had pain relief and well-functioning knee in daily life. The average postoperative ROM was 120.6 ± 9.5°. During both activities, the amount of anterior movement of MFC was less than 0.5 mm showing a constant position on the medial tibial tray. On the other hand, LFC moved posteriorly up to 5 mm on the lateral tibial tray as flexion increased. The averaged tibial internal rotation angle was approximately 4° from extension to flexion. The femoral component showed a medial pivot pattern in 15 knees (83%) and 13 knees (72%) during lunge and step-up activities, respectively.
Conclusion
The knees implanted with EVOLUTION® MP knee arthroplasty showed at higher reproducibility, during flexion in weight-bearing, a medial pivot motion with a stable AP contact position of MFC and rollback of LFC. Such in-vivo kinematics is consistent with the implant design intent, in spite of the magnitude in tibial internal rotation less than the normal knee.
There are some limitations in the present study. First, this study is a study with small sample size in postoperative early phase. Further studies with larger samples in longer follow-up period are needed.