Joint-specific distance thresholds for patient-specific approximations of articular cartilage modeling in the first ray of the foot

Abstract

The addition of cartilage elements in a finite element model prevents bone-on-bone articulation during simulation, thus providing more accurate information about joint kinematics. We present a semi-automated method for identifying joint articulation surfaces and creating volumetric articular cartilage elements based on patient-specific bone information. The approach identifies contact surfaces based on a joint-specific, user-specified distance threshold criterion applied to a polygonized set of bones. Volumetric cartilage elements are generated using half of the minimum inter-joint distance. We present the method and then apply it to the first ray of the human foot, which includes the medial cuneiform, first metatarsal, and first proximal and distal phalanges. Distance thresholds for the first ray ranged from 3.0 to 4.25 mm depending on the joint and the desired contact surface coverage. Inter-joint distances were found and applied to the contact surfaces to generate uniformly thick cartilage models. Average inter-joint distances of 0.46, 0.72 and 0.51 mm were found for the first interphalangeal, metatarsophalangeal, and cuneometatarsal joints, respectively. The values cited are one half of the minimum inter-joint difference, as identified by the proximity algorithm. This is taken to represent the (uniform) cartilage thickness at each joint.

Biomechanical behavior of valgus foot in children with cerebral palsy: A comparative study

“…To simulate the covering layers of articular cartilages, compressive properties resembling the cartilaginous structure were prescribed between each pair of joint contact surfaces. Interface-joint distance was measured as described in the literature (Marchelli et al, 2014). All the bony, heel fat pad, ligamentous, and cartilaginous structures were embedded entirely in a volume of soft tissues.…”

“…The thickness of the cartilage between the contact surface coverage was also measured as described in the literature (Marchelli et al, 2014). The encapsulated soft tissue (Lemmon et al, 1997) was defined as a hyperelastic material.…”

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“…However, due to inter-patient variance in cartilage thickness values, a 1 mm uniform projection from both the acetabular and femoral subchondral bone caused the articulating surfaces to intersect in areas where the interbone distance was less than 2 mm. To account for this, a method similar to one used by Marchelli, et al [90] was implemented in MATLAB in which cartilage was projected half the inter-bone distance in areas with inter-bone distance less than 2 mm.…”