Causes of Femoral Component Radiologic Abnormality After Total Knee Arthroplasty Using Legacy Posterior Stabilized-Flex Prosthesis

Ko, Dong Oh; Lee, Song; Kim, Jin Hak; Kim, Dae Geun; Hong, Sung Won

Abstract

PURPOSE
We analyzed the causative factors of femoral component radiologic abnormality after total knee arthroplasty (TKA) using a Legacy Posterior Stabilized (LPS)-Flex prosthesis.
MATERIALS AND METHODS
140 cases of TKA using LPS-Flex and 140 cases of Vanguard from Jan 2008 to June 2010 were analyzed and radiographic abnormalities around the femoral stems were compared. Secondly, TKA using LPS-Flex was divided into two groups according to the posterior femoral cutting technique, which were single cutting method and additional cutting method. Accuracy of the femoral posterior resection was compared.
RESULTS
Radiographically, anterior radiolucent line was found in eight cases with LPS-Flex but no case with Vanguard. Posterior overhang more than 30% was found in ten cases in both groups. Posterior bone defect more than 50% was found in 23 and seven cases respectively. Anterior radiolucent line and posterior bone defect were observed significantly more in LPS-Flex. In the second study, we found femoral posterior bone defect in 20 cases with additional cutting method which was caused by flexion of the femoral box-cutting guide.
CONCLUSION
Posterior bone defect from LPS-Flex was caused by inappropriate resection due to flexion of the box cutting guide. Single cutting method should be adopted for more accurate posterior femoral cutting.