4D CT is a promising technique for the detection of alteration in joint kinematics induced by pathology [1-2].
The aim of the study was to investigate the ability of 4D-CT to detect changes of the talocrural and subtalar joint after sequential sectioning of ankle lateral compartment ligaments.
A 256-slice GE Revolution CT Scanner (80kV, 25 mA, gantry rotation time 0.28 s, z-axis coverage 120mm, scanning time 3.92 s) was adapted to perform dynamic imaging acquisition on a fresh frozen ankle/foot. The tibia was fixed on a custom-made device and the ankle joint was moved at a pace of 25 cycles/minute. After obtaining four dynamic motion acquisitions, the Anterior Talo-Fibular Ligament (first scenario), the Calcaneo-Fibular Ligament (second scenario) and the Posterior Talo-Fibular Ligament (third scenario) were sequentially cut. Four separate 4D acquisitions were performed for each of the three cut scenarios. Using mutual information as the similarity metric, the talus and the tibia of the dynamic sequences were rigidly registered to a reference image dataset of the foot at rest and transformation matrices were derived. The predefined technical frame (XYZ) of the CT scanner was used to describe the 3D-motion. Joint kinematic of the talocrural joint was described as the displacement of a point located on the centre of the articular surface of the talus, while the movement of the calcaneus was described as displacement of the centroid.
Maximum detectable differences observed regarding displacement of the talocrural joint were 0.56 mm, 0.78 mm and 0.21 mm between intact vs first cut, intact vs second cut and intact vs third cut respectively, along the X-axis (medio-lateral displacement); 1.54 mm, 2.37 mm and 2.73 mm along the Y-axis (anterior-posterior displacement) and 2.61 mm, 2.41 mm and 3.85 mm along the Z-axis (caudo-cranial displacement) (Figure 1). For the subtalar joint, the differences between different scenarios were 0.98 mm, 0.51 mm and 1.63 mm along the X-axis, 0.28 mm, 0.09 mm and 0.38 mm along the Y-axis, and 1.05 mm, 0.96 mm and 1.34 mm along the Z-axis. Each acquisition required a radiation dose (CTDIvol) of 1.9mGy.
Except for the X axis where the movement was minimal, the results show clear differences between the four scenarios, especially along the axis perpendicular to the gantry (Z-axis). This confirms the fact that 4D-CT may be able to detect minimal changes in joint kinematics due to ligaments failure. It also highlights the potential of 4D-CT as a tool to detect musculoskeletal pathologies that occur only during the motion and that are not detectable at the extremes joint positions or in with static examinations using minimal radiation exposure for the patient.
1. Mat Jais IS, Tay SC. Clinical radiology. 2017;72(9):794.e1-.e9.
2. Gondim Teixeira et al., AJR Am J Roentgenol. 2017;208(1):150-8.
|Publication status||Unpublished - 2018|
|Event||8th World Congress of Biomechanics - Dublin, Ireland|
Duration: 8 Jul 2018 → 12 Jul 2018
|Conference||8th World Congress of Biomechanics|
|Period||8/07/18 → 12/07/18|