Comparative Mechanical Behavior of Stainless Steel and Titanium for Pectus Bar Applications

Abstract

Abstract. Stainless steel pectus bars are the go-to material for treating pectus excavatum (PE), a condition characterized by a sunken chest wall. However, 5% of patients develop metal allergies and skin rashes. This study aimed to assess whether titanium is a viable alternative material for these implants, considering its lower risk of allergic reactions and magnetic resonance imaging (MRI) compatibility. Stainless steel (316L) and titanium (CP-Ti) pectus bars were subjected to static and dynamic fatigue testing using MTS testing frame. The static test involved ramp-to-failure four-point bending, where the force was measured until 15 mm of midspan displacement was detected. In the fatigue test, a sinusoidal amplitude of peak (250 N±5 N) and valley (50 N±5 N) was applied to the bars for 1 × 106 cycles at 15 Hz in displacement control. In the static test, both materials showed similar maximum force (p = 0.81), but titanium displayed higher values in plastic deformation (p = 0.0142), total energy (p = 0.0051), and stiffness (p = 0.0051), with relative differences of 16.14%, 3.99%, and 9.44%, respectively. During the fatigue test, titanium showed higher stiffness at 50 N and 250 N, with relative differences of 9.03% and 1.1%, respectively. However, stainless steel had higher values for all other fatigue measurements. Importantly, neither material sustained any noticeable damage after 1 × 106 cyclic loads. The study concluded that both materials perform equally well, but titanium's reduced risk of allergic reactions and MRI compatibility make it a favorable option for patients with metal allergies.