The Variable Axis Knee Prosthesis

ABSTRACT: An important and often overlooked legacy and orthopaedic innovation of Dr. David G. Murray is the Variable Axis knee prosthesis. Conceptualized by Dr. Murray in 1972 and engineered over the ensuing 2 years, the unique "ball-in-socket" design of the prosthesis represented the first unconstrained cruciate-substituting knee prosthesis. Its metal-backed tibial component with modular polyethylene inserts of varying thicknesses and angular designs was also an innovative first and is a design feature that was incorporated into virtually all subsequent prosthetic knees. Released for clinical application in 1974, the Variable Axis knee prosthesis enjoyed over a decade of successful clinical use but was ultimately supplanted by the more anatomically configured Total Condylar-type designs.