Surface characteristics following tibial preparation during total knee arthroplasty

A clinical study, where flatness of the cut surface was quantified, was performed during 26 tibial bone cuts prepared for noncemented endoprosthetic components. Using sterilized dental imprint material and measured by the Zeiss Universal Measuring Centres (UMC) 850 (Oberkochen, Germany), the characteristics of the cut surface were defined. A clinically "flat" surface was found to be uneven with a maximum roughness of 1.71 mm (range, 1.06-2.57 mm), and defined as the distance between the uppermost and lowermost points. The flatness, defined as the standard deviation of the measuring points, was 0.26 mm (range, 0.16-0.38 min). This lack of smoothness creates gaps between the bone and prosthesis that are large enough to prevent direct bone contact when using noncemented fixation. This may be one reason why bony ingrowth is found inconsistently. The surface prepared by a 2-mm thick prototype saw blade was inferior to that created by a 1-mm blade.