Anatomical landmarks of the distal femoral condyles are not always parallel to the tibial bone cut surface in flexion during total knee arthroplasty.
BACKGROUND
Soft tissue balancing is crucial to the success of total knee arthroplasty (TKA). To create a rectangular flexion joint gap, the rotation of the femoral component is important. The purpose of this study is to determine whether or not anatomical landmarks of the distal femoral condyles are parallel to the tibial bone cut surface in flexion.


METHODS
Forty-eight patients (three male and 45 female) with a mean age of 74years were examined. During the operation, we estimated the flexion joint gap with the following three techniques. 1) a three degree external cut to the posterior condylar line (MR1), 2) a parallel cut to the surgical transepicondylar axis (MR2), and 3) a parallel cut to the anatomical transepicondylar axis (MR3).


RESULTS
The flexion joint gap was 1.1±3.0° (mean±standard deviation (SD)) in internal rotation in the case of MR1, 0.9±3.4° in internal rotation in the case of MR2, and 2.1±3.4° in external rotation in the case of MR3. An outlier (flexion joint gap >3.0°) was observed in 12 cases (25%) in MR1, 13 cases (27%) in MR2, and 15 cases (31%) in MR3.


CONCLUSIONS
The anatomical landmarks of the distal femoral condyles are not always parallel to the tibial bone cut surface in flexion. To create a rectangular flexion joint gap, the rotation of the femoral component rotation is based not only on the anatomical landmarks but also on the ligament balance.
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Maki
M
Itokazu
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan. Electronic address: yminoda@msic.med.osaka-cu.ac.jp.
Yukihide
Y
Minoda
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Mitsuhiko
M
Ikebuchi
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Shigekazu
S
Mizokawa
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Yoichi
Y
Ohta
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka 545-8585, Japan.
Hiroaki
H
Nakamura
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D005260:Female; D005269:Femur / Q000033:anatomy & histology / Q000601:surgery*; D056305:Genu Varum / Q000601:surgery; D006801:Humans; D007717:Knee; D007719:Knee Joint / Q000601:surgery; D007720:Knee Prosthesis; D008297:Male; D020370:Osteoarthritis, Knee / Q000601:surgery*; D016059:Range of Motion, Articular; D013977:Tibia / Q000601:surgery*
Femoral component rotation; Flexion joint gap; Measured resection technique; Total knee arthroplasty