Errors in the identification of the distal femur transepicondylar and anterior posterior axes in minimal incision TKR and conventional incision TKR - A cadaveric study

Abstract

INTRODUCTION: Minimal incision surgery (MIS) total knee replacement (TKR) has become widespread in the past few years. However, because the exposure is limited in MIS TKR, there is a concern about the precision in the identification of the anatomical landmarks during the course of the TKR procedure, including those used for aligning the rotation of the femoral prosthesis. This study investigated the errors in the identification of the Transepicondylar-Axis (TEA) and Anterior-Posterior-Axis (Whiteside line) between a MIS and a conventional-incision-approach in four pieces of fresh frozen cadaveric knees. METHODS: The specimens were approached first with minimal-incision-approach and then conventional-incision-approach. Repeated identification of the TEA and Anterior-PosteriorAxis was sequentially performed twenty five times by each of the two orthopaedic surgeons in the same setting. The spatial orientations of these axes were recorded using an optical computer navigation system. The errors in aligning the prosthesis were compared with the reference TEA established by CT. RESULTS: It was found that the errors in identifying the Anterior-Posterior-Axis in MIS and conventional-incision-approach were 0°+/-5°and 1.8° internal-rotation+/-5°(p<0.001). The error in the i dentification of the TEA was significantly higher in the MIS-approach (4.5°inter nal-rotation+/-4°) when compared with the conventio nal-incision-approach (3°internalrotation+/-4°) (p<0.001). CONCLUSION: The precision in the identification of the Anterior-Posterior-Axis was not ostensibly jeopardized by the use of MIS-approach. On the other hand, the adoption of the minimal incision approach led to an increase in error in the identification of the TEA.