Abstract
Hip spacers are temporary implants having a geometry similar to the femoral component of a hip prosthesis, and they are manufactured with antibiotic-impregnated bone cement. The use of spacers in two stage revisions is the most effective treatment to eradicate infections and to avoid limb shortening. The most frequent complication associated with spacers is fatigue failure, for which doctors recommend patients to stay at rest. In this work, several spacer designs are analyzed in order to determine the feasibility of doing activities like walking, standing up or sitting down while performing the antibiotics treatment. Designs combine both different neck diameters and the presence/absence of an internal, stainless steel reinforcement. By means of computational simulations based on the finite element method, stress fields are calculated for various hip spacer designs under several load and fixing conditions. For this purpose, a 3D model of human femur is generated by processing tomographic images with segmentation techniques and inverse engineering. The results allow us to estimate the life expectancy of each design, by considering the fatigue behavior of the bone cement. Only the introduction of a reinforcement with a proper diameter into the bone cement matrix could assure the integrity of the spacer along the treatment period.
Highlights
Total hip replacement is a successful solution to relieve pain and restore hip movement [1]
The results shown in this work, obtained from a model with several simplifications, allowed us to estimate the lifetime of different spacer designs under several loading conditions
A particular design (TNS10.2) meets the strength and durability requirements that enable patients both to complete the antibiotics treatment and to carry out basic daily activities that notoriously improve their quality of life
Summary
Total hip replacement is a successful solution to relieve pain and restore hip movement [1]. Despite the success achieved with hip prosthesis, hip arthroplasty could lead to several complications, among which infections are the most feared because available treatments are complex, expensive and not always effective [2, 3]. The most effective treatment to eradicate the infection involves the extraction of the implant, followed by the administration of antibiotics and the placement of a new implant after 2-6 months since the extraction surgery. In order to overcome these drawbacks, hip spacers are usually implanted during the time interval between the two surgeries, showing infection healing in more than 93% of the cases [2]. Hip spacers have a geometry similar to the femoral component of metallic prosthesis and are manufactured from antibiotic-impregnated bone cement. Mechanical failures are considered the most important complication among those associated with spacers
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