CT measurements prior to computer-assisted total knee arthroplasty do not improve rotational placement of the femoral component.

PURPOSE: The aim of this study is to determine whether computer-assisted surgery (CAS) can gain more precision by utilizing information from pre-operative computed tomography (CT).
METHODS: Sixty-five patients undergoing total knee arthroplasty in 2008 were included. On pre- and post-operative CT, epicondylar and posterior condylar lines were drawn and the posterior condylar angle between these two lines measured. During the surgery, epicondylar and posterior condylar lines were also registered before and after CAS-guided cuts were made. CAS was used to fix the orientation of the cutting guide on the distal femur at 3° of external rotation from the posterior condylar line.
RESULTS: There was no correlation between CT measurements and CAS measurements. All orientations of the lines (relative to the horizontal) and angles measured using CT were significantly different (p < 0.05).
CONCLUSION: No relationship was found between pre-operative CT measurements and peri-operative CAS measurements used to orient the femoral component. Data obtained from CT cannot be used peri-operatively with CAS to improve rotational setting of the femoral component. LEVEL OF EVIDENCE: Therapeutic study, Level II.