In Vivo Ankle Kinematics Revealed Through Biplane Radiography: Current Concepts, Recent Literature, and Future Directions

Abstract

Purpose of review: Lateral ligament repair, specifically the modified Broström-Gould (BG) procedure, has been described for patients with chronic ankle instability (CAI) after failure of nonoperative management. However, there is minimal data about native in vivo ankle bone kinematics and how repairs such as the BG procedure affect the kinematics. The objective of this review is to appraise existing literature that used biplane radiography to measure in vivo kinematics of the ankle in healthy, CAI, and BG populations.

Recent findings: Results showed that the tibiotalar joint contributes more to dorsi/plantarflexion, the subtalar joint contributes more to inversion/eversion and internal/external rotation, and that both joints are capable of complex three-dimensional (3D) motion. Preliminary data suggests that demanding activities (as opposed to walking) are necessary to elicit kinematic differences between healthy and CAI populations. Results also indicate that the BG procedure restores static kinematics and range of motion. All but one of the studies identified in this review collected static, quasi-stance, or partial gait capture data. The strength of our current knowledge is low given the small sample sizes, exploratory nature of previous work, and lack of rigorous experimental design in previous studies. Future directions include development of an improved protocol for establishing coordinate systems in the ankle bones, continued development of a database of normal kinematics during a variety of activities, and large-scale, longitudinal studies of CAI and BG patients.

Keywords: Ankle syndesmosis; Biplanar radiography; Broström-Gould; Chronic ankle instability; In vivo kinematics.

Fig. 1

Lateral ankle anatomy [24]

Fig. 2

Overview of the biplane radiography workflow for determining in vivo ankle joint kinematics. a The ankle joint is imaged during a dynamic activity such as walking. b Synchronized biplane radiographs are collected as the participant passes through the imaging system. c Three-dimensional models of the bone of interest are created by segmenting bone tissue from CT or MRI. d Coordinate systems are established in each bone to measure relative translation and rotation. e A registration process is carried out by positioning the bone model within the simulated imaging system and a simulated radiograph is generated. The correct position and orientation of the 3D bone model is identified when the simulated radiograph matches the synchronized biplane radiographs. f The matching process is repeated for each bone in every pair of synchronized radiographs, resulting in 3D bone position during the entire movement

Fig. 3

Images of the foot during gait at heel strike (t = 0.0 s), midstance (t = 0.35 s), and terminal stance (t = 0.70 s). Kinematic analysis started, on average, 0.02 ± 0.02 s before heel strike, and ended, on average 0.69 ± 0.09 s after heel strike