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  • Title: Kinematics of three variations of the Freeman-Samuelson total knee prosthesis.
    Author: Saari T, Uvehammer J, Carlsson LV, Herberts P, Regnér L, Kärrholm J.
    Journal: Clin Orthop Relat Res; 2003 May; (410):235-47. PubMed ID: 12771835.
    Abstract:
    The effect of changes in the articulating surfaces on the kinematics of the Freeman-Samuelson total knee replacement was evaluated. Twenty-two patients (22 knees) (median age, 69 years) were randomized to a standard design with a fixed polyethylene bearing, a design with a mobile bearing, or a new design with a spherical medial femoral condyle with a fixed bearing. The patients were studied with radiostereometry and film-exchangers at 0 degrees nonweightbearing and during active weightbearing extension from 45 degrees to 15 degrees. The center of the tibial tray with a mobile-bearing prosthesis occupied a more anterior position than observed in the designs with a fixed bearing. The medial femoral condyle center had a more posterior position in the standard design than in the design with a spherical medial condyle. From a distally displaced position at 45 degrees, the medial condylar center displaced a mean of 1.8 mm proximally during extension in the standard design and had a constant position in the meniscal design. In the spherical design the medial condyle was displaced proximally at 45 degrees and displaced a mean of 1.6 mm distally during extension. The reduced anteroposterior and proximodistal translations in the meniscal design are compatible with improved congruency between the components. The design with a spherical medial condyle stabilized anteroposterior motions, but showed more pronounced proximodistal displacement medially than did the other two designs.
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