Ankle and subtalar joint axes of rotation and center of rotation during walking and running in healthy individuals measured using dynamic biplane radiography

Toward subtalar joint axis-driven computer-aided design and computer-aided manufacturing foot orthoses: Reliability of a noninvasive clinical scanning protocol

BACKGROUND

The subtalar joint axis (STJA) occupies a key role in the dynamics of the lower limb kinetic chain, and its location has a wide interindividual variability. It has been suggested that considering the STJA location when designing foot orthoses may help to apply the required mechanical dose. However, the evidence is more anecdotal than empirical.

OBJECTIVE

This study aimed to evaluate the reliability of the STJA digitization, a procedure combining the clinical determination of the functional STJA location and its subsequent 3-dimensional (3D) scanning.

STUDY DESIGN

Two examiners identified the posterior and anterior exit points of the functional STJA on the skin of 15 healthy participants using a clinical method in a repeated-measure design.

METHODS

A handheld 3D scanner was used to scan the feet and the skin markers. The 3D coordinates of the skin markers were subsequently quantified and (1) STJA digitization intratester within-session, (2) STJA digitization intratester between-session, and (3) STJA digitization intertester between-session reliabilities were evaluated.

RESULTS

When pooling all skin marker 3D coordinates, intraclass correlation coefficients (ICCs) for the STJA intratester within-session reliability ranged from 0.74 to 0.98. ICCs for the STJA digitization intratester between-session reliability ranged from 0.58 to 0.94. ICCs for the STJA digitization intertester reliability ranged from 0.56 to 0.81. Standard error of measurement for the mediolateral position of the talus marker (anterior exit point of the STJA) was substantially higher than that for the other coordinates.

CONCLUSIONS

Overall, the STJA digitization demonstrated a good intratester between-session reliability and may be used in a computer-aided design and computer-aided manufacturing workflow to create foot orthoses. However, further efforts should be considered to improve the scanning process and intertester reliability.

Human in vivo talocrural contributions to ankle joint complex kinematics during walking, running, and hopping

The human ankle joint complex, consisting of calcaneus, talus, and tibia, is often simplified as a single functional ankle joint, neglecting the motion of the talus. Understanding the individual contributions of the talus and calcaneus is crucial for comprehending ankle joint complex function in healthy populations, and alterations in function that may exist in clinical conditions. To achieve accurate bone kinematics, high-resolution biplanar videoradiography was used with participants engaged in walking and running (n = 9) and hopping (n = 9) with no overlap in participants. The rotation axes for the calcaneus and talus were analysed relative to the tibia over the ankle joint dorsi-/plantar flexion phases. Contributions of the talocrural joint to overall ankle joint complex function were measured by comparing the range of motion (talus relative to calcaneus). Most of the sagittal plane motion in the ankle joint complex (80%) occurred in the talocrural joint, with the subtalar joint contributing 20%. Rotation of the calcaneus about the tibia dominated frontal and transverse plane motion during hopping. Although surprisingly large ranges of talus motion were also observed in these planes (>5deg), indicating notable inter-subject variability and that the talocrural joint is not a simple hinge joint. The study highlights the importance of directly quantifying talus motion to understand ankle joint complex function. The results showed opposing talus and calcaneus movements for many participants during different locomotor tasks, which may influence the magnitude and distribution of subtalar joint loading. In addition, the large out-of-sagittal plane movements and inter-subject variability in talus and calcaneus motion may further emphasize the need for personalised models to investigate treatments for ankle pathologies.