Relationship Between ground Surface and Tibial Posterior Slope at Erect Posture in Total Knee Arthroplasty

Yim, Soo Jae; Kim, Min Young; Cha, Joo Seok; Kim, Eung Ha; Shin, Byung Joon; Lee, Byung Il

Abstract

PURPOSE
To evaluate the perioperative changes of the relationship between tibial posterior slope and ground surface and the factors which influence the perioperative changes of the relationship between tibial posterior slope and ground surface following total knee arthroplasty.
MATERIALS AND METHODS
Between Sept. 2005 and Feb. 2006, 94 consecutive primary total knee arthroplasty with posterior cruciate ligament-retaining type performed in 50 patients by one surgeon. Posterior slope of the proximal tibia resection in extramedullary guide was fixed at 5degrees. All the retrieved patients wore a 90degrees ankle brace and stood on the ground during radiographic examination. We prospectively analyzed the measurement of tibial posterior slope angle, the angle between tibial posterior slope and ground surface and the angle between a midline from 1st metatarsal shaft to talus and ground surface on preoperative and postoperative 2-weeks radiographs.
RESULTS
On preoperative radiograph, average of tibial posterior slope angle is 11.3degrees and 11.5degrees in right and left knee, respectively. Angle between tibial posterior slope and ground surface is an average of 8.8degrees and 9.5degrees in right and left knee, respectively. On postoperative 2-weeks radiograph, tibial posterior slope angle is an average of 9.3degrees and 9.1degrees in right and left knee, respectively. Angle between tibial posterior slope and ground surface is an average of 6.2degrees and 6.4degrees in right and left knee. There are significant differences between tibial posterior slope angle and the angle between tibial posterior slope and ground surface on preoperative and postoperative 2-weeks radiograph (p<0.05).
CONCLUSION
According to ankle lateral angle, it is possible that tibial posterior slope associated with the ground surface may decrease at erect posture in total knee arthroplasty. This may lead to overly decrease tibial posterior slope associated with the ground surface at comfortable erect posture in total knee arthroplasty.