Load response of an osseointegrated implant used in the treatment of unilateral transfemoral amputation: An early implant loosening case study |
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| Institution: | 1. School of Applied Physiology, Center for Human Movement Science, Georgia Institute of Technology, Atlanta, GA, USA;2. Georgia Hand, Shoulder & Elbow, Atlanta, GA, USA;3. Tufts University School of Medicine, Boston, MA, USA;4. Poly-Orth International, Sharon, MA, USA;1. U.S. Food and Drug Administration, Center for Devices and Radiological Health, Office of Science and Engineering Laboratories, Division of Applied Mechanics;2. U.S. Food and Drug Administration, Center for Devices and Radiological Health, Office of Clinical Evidence and Analysis, Division of Clinical Evidence and Analysis 2;1. Queen Elizabeth Hospital Birmingham, Royal Centre for Defence Medicine, Birmingham, UK;2. Institute of Naval Medicine, Defence Medical Services, Gosport, UK;3. Centre for Blast Injury Studies, Imperial College London, London, UK;4. Academic Department of Military Surgery and Trauma, Defence Medical Services, Birmingham, UK;5. Defence Medical Rehabilitation Centre, Stanford Hall, Loughborough, UK;6. Trauma and Orthopaedic Department, Victoria Hospital Kirkcaldy, NHS Fife, Kirkcaldy, Scotland, UK;7. Oncology Service, The Royal Orthopaedic Hospital NHS Foundation Trust, Birmingham, UK |
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| Abstract: | BackgroundOsseointegrated implants for transfemoral amputees facilitate direct load transfer between the prosthetic limb and femur; however, implant loosening is a common complication, and the associated implant-bone loads remain poorly understood. This case study aimed to use patient-specific computational modeling to evaluate bone-implant interface loading during standing and walking in a transfemoral amputee with an osseointegrated implant prior to prosthesis loosening and revision surgery.MethodsOne male transfemoral amputee with an osseointegrated implant was recruited (age: 59-yrs, weight: 83 kg) and computed tomography (CT) performed on the residual limb approximately 3 months prior to implant failure. Gait analyses were performed, and the CT images used to develop a finite element model of the patient's implant and surrounding bone. Simulations of static weight bearing, and over-ground walking were then performed.FindingsDuring standing, maximum and minimum principal strains in trabecular bone adjacent to the implant were 0.26% and −0.30%, respectively. Strains generated at the instant of contralateral toe-off and contralateral heel strike during walking were substantially higher and resulted in local trabecular bone yielding. Specifically, the maximum and minimum principal strains in the thin layer of trabecular bone surrounding the distal end of the implant were 1.15% and −0.98%, respectively.InterpretationLocalised yielding of trabecular bone at the interface between the femur and implant in transfemoral amputee osseointegrated prosthesis recipients may present a risk of implant loosening due to periprosthetic bone fracture during walking. Rehabilitation exercises should aim to produce implant-bone loading that stimulates bone remodelling to provide effective bone conditioning prior to ambulation. |
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