Migration of the Tibial Component in Successful Unicompartmental Knee Arthroplasty: A Clinical, Radiographic and Roentgen Stereophotogrammetric Study

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Abstract
Migration of the tibial component in unicompartmental Marmor knee arthroplasty was measured by conventional radiography and roentgen stereophotogrammetry during a 2-year follow-up of six patients operated on for femoro-tibial arthrosis. the clinical course was satisfactory for all six patients. A radiolucent zone developed in all cases, the width of which was greater than 2 mm in one case. by radiography movements of two of the six prosthetic components could be detected. Roentgen stereophotogrammetry showed significant rotational and translatory movements in all six tibial components. in four cases these movements were small, not exceeding 1 mm for translation and 1.5o for rotation. the remaining two components showed larger migrations with maximum values of 2.7 mm for translation and 12.6o for rotation. Five of the components tilted backwards about the transverse axis, four tilted away from the centre of the knee about the sagittal axis, and four rotated with the anterior part away from the centre of the knee about the vertical axis. The small movements of the four tibial components may be due to a semi-rigid fixation by connective tissue in the bone-cement interface. Since all knees were asymptomatic, neither the zones nor the minor movements seemed to have any clinical significance within the follow-up period.