Hamstring graft tibial fixation: biomechanical properties of different linkage systems

This biomechanical study analyzed the mechanical properties of different linkage systems commonly used in hamstring tendon ACL reconstruction. Two kinds of tapes, 5-mm braided polyester (Mersilene) and 3-mm woven polyester (Orthotape), were connected to a particular staple in bovine bone sections in single- and double-loop constructs with five replicates of each. These constructs underwent straight pull tensile tests, residual tensile tests, and fatigue tests at a loading regime of 540,000 cycles at 25 Hz frequency, using an Instron tensile test machine. Protrusion heights of the constructs were measured. The double-loop Mersilene-Fastlok construct was weaker than either single-loop or double-loop Orthotape-Fastlok construct. The mean failure strength of double-loop Orthotape-Fastlok was 93% higher and its mean stiffness was 40% greater at failure than that of Mersilene-Fastlok. At a 150-N load Mersilene-Fastlok was stiffer, while at 300 N Orthotape-Fastlok was stiffer. The thickness of Orthotape-Fastlok resulted in 1 mm more device protrusion. In hamstring tendon ACL reconstructions with indirect fixation we advocate the use of woven polyester (Orthotape) with Fastlok as a linkage material over braided polyester (Mersilene) with Fastlok because of its superior strength and stiffness.