Comparison of in vivo hindfoot joints motion changes during stance phase between non-flatfoot and stage II adult acquired flatfoot

Abstract

Background: To compare the kinematic characteristics of hindfoot joints in stage II adult acquired flatfoot deformity (AAFD) with those of non-flatfoot through the 3D-to-2D registration technology and single fluoroscopic imaging system.

Methods: Eight volunteers with stage II AAFD and seven volunteers without stage II AAFD were recruited and CT scans were performed bilateral for both groups in neutral positions. Their lateral dynamic X-ray data during the stance phase, including 14 non-flatfeet and 10 flatfeet, was collected. A computer-aided simulated light source for 3D CT model was applied to obtain the virtual images, which were matched with the dynamic X-ray images to register in the "Fluo" software, so that the spatial changes during the stance phase could be calculated.

Results: During the early-stance phase, the calcaneous was more dorsiflexed, everted, and externally-rotated relative to the talus in flatfoot compared with that in non-flatfoot (p < 0.05). During the mid-stance phase, the calcaneous was more dorsiflexed and everted relative to the talus in flatfoot compared with that in non-flatfoot (p < 0.05); however, the rotation did not differ significantly between the two groups (p > 0.05). During the late-stance phase, the calcaneous was more plantarflexed, but less inverted and internally-rotated, relative to the talus in flatfoot compared with that in non-flatfoot (p < 0.05). During the early- and mid-stance phase, the navicular was more dorsiflexed, everted, and externally-rotated relative to the talus in flatfoot compared with that in non-flatfoot (p < 0.05). During the late-stance phase, the navicular was more plantarflexed, but less inverted and internally-rotated, relative to the talus in flatfoot compared with that in non-flatfoot (p < 0.05). There was no difference in the motion of cuboid between the two groups during the whole stance phase (p > 0.05).

Conclusions: During the early- and mid-stance phase, excessive motion was observed in the subtalar and talonavicular joints in stage II AAFD. During the late-stance phase, the motion of subtalar and talonavicular joints appeared to be in the dysfunction state. The current study helps better understanding the biomechanics of the hindfoot during non-flatfoot and flatfoot condition which is critical to the intervention to the AAFD using conservative treatment such as insole or surgical treatment for joint hypermotion.

Keywords: Adult acquired flatfoot deformity; Hindfoot joint; In vivo; Movement.

Fig. 1

CT image of the ankle joint in coronal (A), sagittal (B) and transverse (C) views. (D) Setting of talus coordinate axis

Fig. 2

A X-ray later imaging of the ankle joint from plantar flexion to dorsiflexion of the specimen with tantalum beads implanted. B Matching of tantalum beads by software

Fig. 3

Macro view and X-ray of Stage II AAFD. A, D Forefoot abduction deformity. B, E Medial arch collapse. (C, F) Hindfoot valgus

Fig. 4

Key gait postures in the non-flatfoot and stage II AAFD

Fig. 5

3D-to-2D matching of subtalar joint (A-S), talonavicular joint (B-T) and calcaneocuboid joint (C-U) in the 7 postures

Fig. 6

Rotation trend of subtalar joint, talonavicular joint, and calcaneocuboid joint of all non-flatfoot and flatfoot volunteers from the first posture to the seventh posture around X-, Y- and Z-axes

Fig. 7

ROM changes of ankle joints of non-flatfoot and stage II AAFD (motiondata represents motion data; motionaxis represents motion axis; motion31, motion53 and motion75 represent the first to the third posture, the third to the fifth posture, and the fifth to the seventh posture respectively). A Subtalar joint. B Talonavicular joint. C Calcaneocuboid joint