Abstract
Objectives/background: Flexion Stability and Patella tracking after Total Knee Replacement is mainly influenced from the rotational alignment of the femoral component. Different implant philosophies use different landmarks for rotational alignment, as the epicondylar line, the posterior condyles or the anteroposterior line. An individual variation of the different landmarks is known from manual implantation an cadaver and CT studies.
The purpose of this study was to measure the variation of three different lines for femoral rotational alignment to show the possible difference and check the so far used values in manual instrumentation technique.
Design/methods: Using the Navitrack Navigation system we performed 100 consecutive TKRs. The landmarks for the 3 most common lines for rotational alignment of the femoral component has been probed.
The software calculated the position of the lines and the 3-dimensional ankle between the lines. Intraoperative snapshots were taken to postoperative data analysis of the numeric data.
Results: The mean difference between the ECL and the PCL was –0,96 (SD 3,64; range −10.7 − 5,9). In varus knees −0,2 (−6 −4,5) in valgus knees 1,4 (–10,7 – 5,9). ECL to the APC was in mean 88,83 (SD 7,23; range 100,8 – 71,9). In varus knees 91,3 (99 – 76,2) in valgus knees 83,8 (100,8 – 71,9).
Conclusions: Using a navigation system it is easy to perform an individual, intraoperative measurement of the relationship of different anatomical landmarks for rotational alignment of the femoral component. But the range of values shows that in the manual technique with fixed rotational alignment given by the instruments, there is a high risk for femoral rotational malalignment. The results depended on preoperative deformity could only be seen as a bias for higher variance in valgus knees. For the navigation procedures there is not one universal landmark which can be used. Furthermore the systems must be developed for intraoperative functional analysis, with integration of soft tissue balancing, to improve functional and long-term outcome in TKR.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
