Recreating Fiber Recruitment With Fiber Recruitment Using Additive Manufacturing

Injured ligaments are often repaired with tendon grafts which may over or under constrain the joint; there is a need for an artificial graft option with the mechanical properties of a native ligament. Crimped fibers within ligaments allow for recruitment which means the viscoelastic properties of stress relaxation and creep are not inversely related. A feasibility study using ACLs and large-scale crimp models to study viscoelasticity, led to an in-depth analysis of the scapholunate interosseous ligament. Using the Modified Kelvin spring-dashpot model, for describing viscoelasticity with a variable stiffness property (time dependent fiber recruitment), we defined the relationship between creep and stress relaxation and verified its accuracy with experimental data. Seven biocompatible polymers, two additive manufacturing technologies, and three crimp types were evaluated for use in recreating an artificial ligament. Two crimp types were combined to successfully show an increase in stiffness under static axial load (recruitment) and an overall decrease in strain during cyclic loading. The data verifies successful creation of an artificial ligament sample with the recruitment properties found in native ligaments.