Fracture of the Femoral Component in Total Knee Arthroplasty Using Whiteside Ortholoc Prosthesis with Cement - Metallurgical Study by SEM and EDS

Chun, Churl Hong; Song, Jeong In; Nam, Kee Suk; Lee, Jong Soo

Abstract

The present study reports two cases of femoral component fracture using Whiteside Ortholoc prosthesis(Dow Corning Wright, Arlington, Tennessee) with cement. The causes of the fracture were investigated by radiological findings, prosthetic design and metallurgical study using scanning electron microscope(SEM) and energy dispersive spectrometer(EDS). Respectively, the findings from this study are summarized as follows. In X-ray study, one case had valgus 3 mechanical axis(normal: valgus 7 axis) while the other case had 10 tibial anterior slope(normal: 10 posterior slope). The medial side of femoral component fractured in both cases. The fracture site was in the junction between the posterior bevel and distal surface of the medial side of femoral component. The analysis of the prosthetic design showed that the Whiteside Ortholoc femoral stem was thinner, and shorter at the site of posterior bevel surface of the femoral stem than other TKA(Total Knee Arthroplasty) system. The metallurgical study by SEM showed that the crack was developed initially near the inner surface of fractured femoral component and was extended to the outer surface. Carbon particles were detected in the fractured femoral component by EDS. The findings imply that operating technique is very important especially during bone cutting and soft tissue balance in TKA. It is also proposed from this study that a minor design modification such as a thicker and longer Whiteside Ortholoc femoral component would be better and that the cast-iron ware of TKA system has to he produced by careful metallurgical process, that precludes the incorporation of any foreign material such as carbon particles.