Comparison of three anatomical structures as a distal landmark for extramedullary tibial alignment in total knee arthroplasty

Abstract

Objective To compare dorsal pedis artery, extensor hallucis longus tendon and extensor digitorum longus tendon as a distal landmark in terms of accuracy of extramedullary tibial alignment in total knee arthroplasty. Methods Color Doppler ultrasonography was used in 56 ankles of 56 patients undergoing total knee arthroplasty to locate the dorsal pedis artery, the extensor hallucis longus tendon and the extensor digitorum longus tendon at the ankle joint at 3 different positions (90° dorsal flexion with neutral rotation, 90° dorsal flexion with 30° external rotation and 90° dorsal flexion with 30° internal rotation). The distances between the ankle centre and 3 landmarks at 3 positions were measured and compared by analysis of variance with repeated measurements and one way analysis of variance. Results Analyses of variance with repeated measurements showed significant differences between the distances to the ankle center of the 3 landmarks at the 3 positions (P < 0.05). The dorsal pedis artery lay the closest to the ankle center (0.20±0.21 cm lateral), followed by the extensor hallucis longus tendon (0.46±0.36 cm medial) and the extensor digitorum longus tendon (0.63±0.30 cm lateral). One way analysis of variance showed significant differences in distance from each landmark to the ankle center at different ankle positions (P < 0.05). There were significant differences between 3 anatomical landmarks in distance to the ankle center at the same ankle position (P < 0.05). The dorsal pedis artery was the closest to the ankle center at all ankle positions. Conclusion Since the dorsal pedis artery lies closer to the ankle center than the extensor hallucis longus tendon and the extensor digitorum longus tendon at different ankle positions, it can be a reliable distal landmark for extramedullary tibial alignment in total knee arthroplasty. Key words: Arthroplasty, replacement, knee; Tibia; Alignment; Anatomical landmark