The Biomechanical Influence of Defected Cartilage on the Progression of Osteochondral Lesions of the Talus: A Three-dimensional Finite Element Analysis

Abstract

Objectives: Osteochondral lesions of the talus (OLTs) are common injuries in the general population. Abnormal mechanical conditions applied to defected cartilage are believed to be the culprits to deteriorating OLTs. This study aims to investigate the biomechanical effects of defect size of talar cartilage on OLTs during ankle movements.

Methods: A finite element model of the ankle joint was created based on the computed tomography images of a healthy male volunteer. Different defect sizes (S = 0.25, 0.5, 0.75, 1.0, 1.25, 1.5, 1.75, and 2.0 cm² ) of talar cartilage were modeled to simulate the progression of OLTs. Mechanical moments were applied to the model to generate different ankle movements, including dorsiflexion, plantarflexion, inversion, and eversion. The effects of varying defect sizes on peak stress and its location were evaluated.

Results: The maximum stress on the talar cartilage increased as the area of the defect enlarged. Additionally, as the defect size of OLTs increased, the areas with peak stress on talar cartilage tended to move closer to where the injury was located. High stresses were present in the medial and lateral areas of the talus at the neutral position of the ankle joint. The concentrated stresses were mainly located in the anterior and posterior defect areas. The peak stress in the medial region was higher than on the lateral side. The order of peak stress from highest to lowest was dorsiflexion, internal rotation, inversion, external rotation, plantar flexion, and eversion.

Conclusions: Osteochondral defect size and ankle joint movements significantly modulate the biomechanical features of the articular cartilage in osteochondral lesions of the talus. The progression of osteochondral lesions in a talus deteriorates the biomechanical well-being of the bone tissues of the talus.

Keywords: Ankle movements; Biomechanical; Defect size; Finite element analysis; Osteochondral lesions; Talus.

Fig. 1

Modeling process: (A) Image segmentation of ankle bones in CT images; (B) The models of cartilages created in the tibiotalar joint; (C) Assembly of the ankle joint with ligaments; (D) Meshed model and detail; (E) The load we set in different times of weight in the neutral position; (F) Center of rotation and the moments we simulated.

Fig. 2

Mark the position of peak stress of talar cartilage: (A) Obtain the position of peak stress and record the coordinates; (B) Circles located in zone 4 represent eight types of defect size of osteochondral lesions, which can be identified by serial numbers 1–8; (C) Superimpose (B) on (A) according to the coordinates; (D) Reserve the position of peak stress of talar cartilage and identify it by serial number; (E) Repeat the procedure to mark the peak stress positions of nine types of defect sizes in the neutral position.

Fig. 3

Method to divide the area near the defect into nine grids. The three grids covering medial cartilage were marked as M zone. L, A, and P zones represented lateral, anterior, and posterior cartilage, respectively.

Fig. 4

Stress of intact talar cartilage with different ankle movements.

Fig. 5

Peak stress of different defect areas at each moment.

Fig. 6

Locations of the peak stresses in different defect sizes and ankle movements under the same moment are marked in the cartilage plane.

Fig. 7

Development of the defect area (even though the primary injury was a circle shape): (A) Primary injury; (B) Predicted shape of defected cartilage progression based on stress distribution. Significantly, the medial cartilage was worn out; (C) Real defect shape.