Allergic or Hypersensitivity Reactions to Orthopaedic Implants.

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Abstract

[Indexed for MEDLINE] 5. IEEE J Transl Eng Health Med. 2024 Feb 12;12:314-327. doi: 10.1109/JTEHM.2024.3365305. eCollection 2024. Compliant Intramedullary Stems for Joint Reconstruction. Mccullough JA(1), Peterson BT(2), Upfill-Brown AM(2), Hardin TJ(3), Hopkins JB(1), Soohoo NF(2), Clites TR(1)(4). Author information: (1)Department of Mechanical and Aerospace EngineeringUniversity of California Los Angeles Los Angeles CA 90095 USA. (2)David Geffen School of MedicineUniversity of California Los Angeles Los Angeles CA 90095 USA. (3)Material, Physical, and Chemical Sciences CenterSandia National Laboratories Albuquerque NM 87123 USA. (4)Department of Orthopaedic SurgeryUniversity of California Los Angeles Los Angeles CA 90095 USA. The longevity of current joint replacements is limited by aseptic loosening, which is the primary cause of non-infectious failure for hip, knee, and ankle arthroplasty. Aseptic loosening is typically caused either by osteolysis from particulate wear, or by high shear stresses at the bone-implant interface from over-constraint. Our objective was to demonstrate feasibility of a compliant intramedullary stem that eliminates over-constraint without generating particulate wear. The compliant stem is built around a compliant mechanism that permits rotation about a single axis. We first established several models to understand the relationship between mechanism geometry and implant performance under a given angular displacement and compressive load. We then used a neural network to identify a design space of geometries that would support an expected 100-year fatigue life inside the body. We additively manufactured one representative mechanism for each of three anatomic locations, and evaluated these prototypes on a KR-210 robot. The neural network predicts maximum stress and torsional stiffness with 2.69% and 4.08% error respectively, relative to finite element analysis data. We identified feasible design spaces for all three of the anatomic locations. Simulated peak stresses for the three stem prototypes were below the fatigue limit. Benchtop performance of all three prototypes was within design specifications. Our results demonstrate the feasibility of designing patient- and joint-specific compliant stems that address the root causes of aseptic loosening. Guided by these results, we expect the use of compliant intramedullary stems in joint reconstruction technology to increase implant lifetime. © 2024 The Authors. DOI: 10.1109/JTEHM.2024.3365305 PMCID: PMC10939320