Background: The purpose of this study was to evaluate the risk of peri-prosthetic fracture of constructs made with cephalomedullary (CM) long and short nails. The nails were made with titanium alloy (Ti-6Al-4V) and stainless steel (SS 316L). Methods: Biomechanical evaluation of CM nail constructs was carried out with regard to post-primary healing to determine the risk of peri-implant/peri-prosthetic fractures. Therefore, this research comprised of, non-fractured, twenty-eight pairs of cadaveric femora that were randomized and implanted with four types of fixation CM nails resulting in four groups. These constructs were cyclically tested in bi-axial mode for up to 30,000 cycles. All the samples were then loaded to failure to measure failure loads. Three frameworks were carried out through this investigation, Michaelis-Menten, phenomenological, and probabilistic Monte Carlo simulation to model and predict damage accumulation. Findings: Damage accumulation resulting from bi-axial cyclic loading in terms of construct stiffness was represented by Michaelis-Menten equation, and the statistical analysis demonstrated that one model can explain the damage accumulation during cyclic load for all four groups of constructs (P > 0.05). A two-stage stiffness drop was observed. The short stainless steel had a significantly higher average damage (0.94) than the short titanium nails (0.90, P < 0.05). Long titanium nail group did not differ substantially from the short stainless steel nails (P > 0.05). Results showed gender had a significant effect on load to failure in both torsional and bending tests (P < 0.05 and P < 0.001, respectively). Interpretation: Kaplan-Meier survival analysis supports the use of short titanium CM nail. We recommend that clinical decisions should take age and gender into consideration in the selection of implants.

Left ventricle leads are designed for the purpose of long-term pacing in the left ventricle. This study investigated the leads that use polyurethane as an outer insulator and SI-polyimide as an inner insulator. Polyurethane is commonly used for the outer insulation of cardiac leads due to its flexibility and biocompatibility. SI-polyimide (SI-PI) is a high-performance material known for its electrical insulation properties and is used for the inner insulation to maintain the integrity of the electrical pathways within the lead. Ten leads were received from the Wright State University Anatomical Gift Program. The duration of in vivo implantation varied for each lead, from less than a month to 108 months, with an average in vivo duration of 41 ± 31 months. We used the Test Resources Q series system for conducting our tests, as well as samples prepared to ensure compliance with the ASTM Standard D 1708-02a and the ASTM Standard D 412-06a. During the test, the load was applied to the intact lead. Before conducting individual tests, each lead was carefully inspected for surface defects. After conducting the tests, the load to failure, percentage of elongation, percentage of elongation at 5 N, ultimate tensile strength, and modulus of elasticity were calculated. There was no significant difference in load to failure, the percentage of elongation to failure, ultimate tensile strength, and modulus of elasticity (p-value = 0.82, p-value = 0.62, p-value = 0.82, and p-value = 0.12), respectively, when compared to in vivo exposure time. On the other hand, the percentage of elongation at 5 N force showed a significant difference (p-value = 0.0066) after 60 months in an in vivo environment. As the duration of in vivo exposure increased, the load to failure, percentage of elongation, ultimate tensile strength, and modulus of elasticity decreased insignificantly. The residual properties of these left ventricle leads remained relatively stable after 108 months of in vivo exposure duration, with no statistically significant degradation or changes in performance.