Motion of the distal tibiofibular syndesmosis under different loading patterns: A biomechanical study

Abstract

The distal tibiofibular syndesmosis is an important structure for ankle stability. The objective of this study was to evaluate the motion of the syndesmosis under different loading patterns and determine the characteristics of the syndesmotic motion. Methods: Six fresh cadaveric lower extremity specimens with the knee reserved were tested in this study. The skin and muscles were removed with all ligaments around the syndesmosis and knee and ankle joint intact. An axial load of 600 N was applied to the specimens with the ankle joint in 10 dorsiflexion, neutral position, and 15 plantar flexion using a universal material testing machine. Then, with the ankle joint positioned neutrally, a combination of 600-N axial and 5-Nm torsional external rotation loading was applied to the specimens. The medial-lateral and anterior-posterior displacement and rotation of the distal fibula relative to the distal tibia were measured. Results: Under the axial loading, the distal fibula tended to move medially and anteriorly and rotate internally with the ankle positioned from the neutral position to 15 plantar flexion. Meanwhile, when the ankle was positioned from the neutral position to 10 dorsiflexion, the distal fibula tended to move laterally and posteriorly and rotate externally. Under the combined loading, with respect to the isolated axial loading, the distal fibula tended to move medially and posteriorly, and rotate externally relative to the distal tibia. Conclusion: Micro motion existed in the syndesmosis. The relative motion of the syndesmosis was correlated to the ankle position and loading patterns.

Biomechanics of the Distal Tibiofibular Syndesmosis: A Systematic Review of Cadaveric Studies

“…4,14 Six of the 12 included studies examined the biomechanics of the syndesmosis under compression and external rotational loading, and recorded fibular translation in the coronal and sagittal planes, and rotation of the fibula and foot. 6,8,15,19,25,27 Details of loading parameters for each study are included in Table 1. The largest measurements of fibular range of motion recorded in these studies were 2.53 mm of posterior translation (Markolf et al 19 ), 1.00 mm lateral translation (Xenos et al 27 ), 3.6 degrees of external rotation (Burssens et al 6 ), and 1.4 degrees of internal rotation (Clanton et al 8 ).…”

“…Three included studies evaluated individual syndesmotic ligament contributions to stabilizing translational and rotational loads by recording the force required to create diastasis and percentage reduction in forces and torques on sectioning of syndesmotic ligaments. 9,15,23 The results of these investigations are shown below in Table 2. Clanton et al 8 reported that sectioning of the AITFL resulted in the largest percentage decrease in torque required to cause external rotation displacement, whereas sectioning of the PITFL resulted in the largest percentage decrease in internal rotational torque to cause a similar internal rotation displacement.…”

“…Four of the 12 studies evaluated the normal range of excursion of the syndesmosis and the variation therein with loading and ankle position. 6,8,15,19 Although the IOL was the strongest and stiffest of the ligaments, the AITFL was found to be the largest contributor to resistance of external rotation forces, and the PITFL was the largest contributor to resistance to the internal rotation force. Not only do these findings provide a baseline for clinical and radiographic assessment for injury to the syndesmosis, but they provide a framework for which repairs and reconstructions can be designed to restore proper anatomic biomechanics to the syndesmosis following injury.…”

“…4,14 Results of sequential sectioning studies performed by Clanton et al, 8 Ogilvie-Harris et al, 23 and D'Hooghe et al 9 demonstrate significant variability in results based on the order in which ligaments were sectioned. 15 The considerable variability in individual ligament contributions to resistance identify a need for further standardized evaluation. Some variability can be explained by sequential cutting in the anteroposterior direction performed by D'Hooghe et al, 9 whereas Ogilvie-Harris et al 23 sectioned ligaments in random sequence avoiding bias incurred by synergistic resistance by combinations of ligaments.…”

Leave it or fix it? How fixation of a small posterior malleolar fragment neutralizes rotational forces in trimalleolar fractures

“…Different examinations analyzed the motion of the distal syndesmosis during the stance phase of the gait cycle. From heel strike to mid-stance, in these studies the fibula everted, externally rotated relative to the tibia, and then moved to the reverse direction from mid-stance to toe-off [4,18]. In our study, we aimed to mimic loading of an ankle under full weight bearing in different phases of the gait cycle.…”