脛骨近位内側面接線と脛骨回旋軸のなす角度

抄録

Objective: Tibial rotational alignment in total knee arthroplasty (TKA) is generally determined in reference to the intraarticular structure. However, the determination is difficult in some cases. The purpose of this study was to ascertain whether angles involving the medial tangent of the proximal tibia and the anteroposterior axis can be useful in determining the tibial rotational alignment in TKA.

Methods: Preoperative computed tomography (CT) scanning was performed on 24 patients (7 men, 17 women ; 42 knees) with osteoarthritis (OA, 36 knees), rheumatoid arthritis (RA, 2 knees) or osteonecrosis (ON, 4 knees). The mean age was 75.7 years, the mean body height was 153.6 cm, the mean body weight was 60.6 kg, and the mean body mass index was 25.5. Using three dimensional template software (ZedKnee^®, LEXI, Japan), the angles between the medial tangent of the proximal tibia and Akagi’s line at three horizontal planes: at the distal edge of the tibial tubercle (A), at 5 cm distal to it (B), and at 10 cm further distally (C) were measured.

Results: The angles were 42.6±3.3° (mean±SD) at A, 39.8±5.0° at B, and 39.9±5.5° at C, respectively. Excluding men, patients with OA under 60-years-old, and patients with a higher or lower body height than mean height±SD, the angles were 42.8±2.7° at A, 40.0±4.3° at B, and 40.0±5.7° at C, respectively.

Conclusion: The angle between the medial tangent of the proximal tibia and Akagi’s line at the distal edge of the tibial tubercle (angle A) ranged from approximately 40 to 45°. As this angle is close to the surgical field and can be measured during TKA, it might be a suitable landmark in determining tibial rotational alignment during such procedures.