Design of a novel anterior cruciate ligament prosthesis

Abstract

Injuries to the anterior cruciate ligament (ACL) are extremely common (approximately 100,000 every year in the US) and result in greatly reduced mobility; although several surgical procedures have been devised to address this condition, they are far from being completely satisfactory. The golden standard is currently represented by tendon autografts which, however, result in considerable donor site morbidity. An ideal solution would be to use effective, off-the-shelf permanent prostheses: however, all such devices proposed to date have proved highly disappointing, because of poor long term stability and biocompatibility, and unphysiological mechanical behavior. To address both concerns a novel prosthetic device has been developed, employing crimped NiTi superelastic wire bundles. To achieve near-physiological mechanical behavior, the fiber geometry resembles (on a much larger scale) that of the collagen fibrils that naturally make up the ligament, using as a starting point the Comninou-Yannas crimped-fiber model.

(cont.) NiTi (a superelastic alloy of titanium and nickel) has been tested and employed in a variety of biomedical settings and its excellent wear and biocompatibility characteristics make it a superior candidate for this application; the relevant literature has been reviewed and assessed. A detailed design for such prosthesis has been proposed, and a proof-of-principle model of the fiber geometry built and tested. The results obtained to date are encouraging and further testing, with a NiTi prototype should be carried out to validate our proposed design.