4D CT Images Show Ankle Joint Motion

Quantitative dynamic 4D CT may play a role in evaluating subtalar instability by providing a detailed analysis of joint motion, according to a study published in the American Journal of Roentgenology.

Researchers from France performed a small study to demonstrate the use of quantitative 4D CT for subtalar joint evaluation in healthy volunteers and cadavers.

Fifteen healthy volunteers with no history of subtalar joint trauma and three cadavers were recruited for the study and were prospectively evaluated with dynamic CT. The subtalar joint was evaluated during a pronosupination cycle. The researchers measured angles and distances between the talus and the calcaneus. Measurement variation was described in healthy volunteers and in cadavers, the latter before and after resection of the cervical and interosseous ligaments. The mean effective dose was below 0.1 mSv.

The results showed that the cadavers had mean increases in joint amplitude of over 19% and 22% were seen after partial ligament sectioning and after full ligament sectioning, respectively. The interobserver variability of the measurement ratios was considered to be excellent for three of the measurements made and moderate for the fourth. The normal range of joint motion in healthy volunteers is described, with joint amplitudes varying from 6.4% to 22.8%.

The researchers concluded that quantitative dynamic CT of the subtalar joint can provide a detailed analysis of joint motion, supporting its potential role in the evaluation of subtalar instability.