Introduction
Four-dimensional computed tomography (4DCT) is a novel imaging method for real-time motion analysis. In the last decade, several studies have investigated the possibilities of 4D-CT to detect joint related musculoskeletal pathologies. The main applications are the evaluation of entrapment, impingement and snapping, the assessment of intra-articular instability and complex motion analysis [1]. However, the ability of dynamic CT to detect small changes due to ligament insufficiency is still under investigation [2]. The purpose of this study was to investigate the capability of dynamic CT acquisition to detect kinematic changes induced by sequential sectioning of lateral ankle ligaments.

Methods
Dynamic CT acquisitions were performed on one fresh frozen ankle specimen during foot inversion. A 256-slice GE Revolution CT Scanner (80 kV, 25 mA, gantry rotation time 0.28 s, z-axis coverage 120 mm, scanning time 3.92 s) was used. The tibia was fixed on a custom-made device and the ankle joint was moved at a pace of 25 cycles/minute. After four separate dynamic acquisitions of the same motion with the ankle undamaged, three scenarios were considered for sequential ligament sectioning: 1) section of the the Anterior Talo-Fibular Ligament, 2) section of the Calcaneo-Fibular Ligament and 3) section the Posterior Talo-Fibular Ligament. Four distinct dynamic CT acquisitions were repeated for each scenario. 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 matrixes were derived. The technical frame (XYZ) of the CT scanner was used to described the 3D-motion. Joint kinematics of the talocrural joint and subtalar joint were defined as Cardan angles rotation calculated based on the composition sequence ZYX and ZXY respectively.

Results
Maximum detectable differences in bone rotation of the talocrural joint were 6.07˚, 5.46˚ and 9.83˚ between intact vs first cut, intact vs second cut and intact vs third cut respectively around the X-axis (flexion/extension), 5.12˚, 5.47˚ and 10.01˚ around the Y-axis (pro-supination), and 4.88˚, 5.47˚ and 6.93˚ around the Z-axis (abduction/adduction) (Figure 1). Regarding the subtalar joint, a maximal detectable difference of bone rotation was 0.37˚, 0.81˚ and 4.09˚ around the X-axis, 2.49˚, 3.28˚ and 7.82˚ around the Y-axis, and 1.33˚, 1.87˚ and 2.09˚ around the Z-axis. Each acquisition required a radiation dose (CTDIvol) of 1.9mGy.

Conclusion
We demonstrated that sequential sectioning of the lateral ankle ligaments progressively increased the angular motion in both the talocrural and subtalar joint, especially after the last ligament was sectioned. As such, this study demonstrated that minimal kinematics changes due to ligaments failure can be demonstrated with 4D-CT. However, it also showed that the amount of kinematic changes is related to the amount of ligament damage. Due to 4D-CT’s high temporal and spatial resolution it allows detailed acquisition in vivo situation and highlight the possibility of adopting such method to investigate joint kinematics when different pathological conditions are present. Quantifying the amount of lateral ankle ligament damage could help the clinician in choosing the optimal treatment with a very small radiation exposure for the patient.


1.Teixeira PAG et al., Semin Musculoskelet Radiol 2015;19(5):456–62.
2. Mat Jais IS,Tay SC, Clin Radiol 2017;72(9):794.e1-794.e9.

Original languageEnglish
Publication statusUnpublished - 2018
EventISEK 2018 - XXII Congress of theInternational Society of Electrophysiology and Kinesiology - Dublin
Duration: 30 Jun 20182 Jul 2018

Conference

ConferenceISEK 2018 - XXII Congress of theInternational Society of Electrophysiology and Kinesiology
Period30/06/182/07/18

ID: 43559509