Optimization of extruded collagen fibers for ACL reconstruction

Collagen fibers used in a scaffolding device for ligament reconstruction must be thin, strong, and degradable. The purpose of this study was to determine the effects of fiber diameter (20, 50, or 90 microns), crosslinking agent (uncrosslinked, dehydrothermal-cyanamide, or glutaraldehyde), and hydration on the initial mechanical properties, biocompatibility, and subcutaneous degradation rates of fibers extruded from an acidic dispersion of insoluble type I collagen. The wet tensile strength of extruded collagen fibers was significantly improved by decreasing the fiber diameter. Low-diameter, crosslinked fibers had wet tensile strengths ranging from 75-110 MPa. In contrast, high diameter fibers had wet strength values of about 30 MPa. The degradation rate of the implanted fibers, in contrast, was not significantly prolonged by changing the initial fiber diameter. This result is important because prolonged degradation of the fibers can lead to implant encapsulation instead of neoligament formation. By minimizing the diameter, fiber strength can be increased without prolonging the fiber degradation rate. Low-diameter, dehydrothermal-cyanamide crosslinked fibers have greater tensile strength and a more rapid degradation rate than medium-diameter, glutaraldehyde crosslinked fibers, and are therefore more suitable for use in a degradable ligament reconstruction device.