Review Question - QID 4436

Titanium implants have decreased tensile (ultimate) strength when compared to cobalt chrome.

Ultimate strength, or tensile strength, is the maximum stress a material can withstand before undergoing breakage or failure. The ranking of ultimate strength, from highest to lowest is: 1) cobalt chrome, 2)titanium, 3)stainless steel, and 4) cortical bone.

Young's modulus of elasticity is defined as the measure of stiffness of a material in the elastic zone. A higher Young's modulus indicates a stiffer material. While titanium is highly biocompatible with a low modulus of elasticity (Young's modulus), it has poor wear characteristics making it non-suitable for femoral heads in total hip arthroplasty.

Long et al. present a review on titanium implants with a focus on bio-mechanical properties. Their study supports previous data which showed high rates of ultra-high molecular weight polyethylene wear due to accelerated breakdown when in contact with a titanium surface.

Incorrect Answers:
Answer 1: Fatigue strength, or the maximum cyclic load (10 million cycles) that a standard sized metal can absorb before fracture, is lower in titanium compared to cobalt chrome.
Answer 2: Yield strength, or the maximal stress a material can take before permanent deformation, is decreased in titanium compared to cobalt chrome.
Answer 3: Endurance limit is another way of saying fatigue strength, which is discussed in incorrect answer 1.
Answer 4: Ductility, or the measure of how much strain a material can take before rupturing, is higher for titanium than cobalt chrome