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Lower-limb amputees experience many gait impairments and limitations. Some of these impairments can be attributed to the lack of a functioning biarticular gastrocnemius (GAS) muscle. We propose a transtibial prosthesis that implements a quasi-passive spring mechanism to replicate GAS function. A prototype biarticular prosthesis (BP) was designed, built, and tested on one subject with a transtibial amputation. They walked on an instrumented treadmill with motion capture under three different biarticular spring stiffness conditions. A custom-developed OpenSim musculoskeletal model, which included the BP, was used to calculate the work performed and torque applied by the BP spring on the knee and ankle joints. The BP functioned as expected, generating forces with similar timing to GAS. Work transfer occurred from the ankle to the knee, with stiffer springs transferring more energy. Driven mostly by kinematics, the quasi-passive design of the BP consumed very low power (5.15 W average) and could lend itself well to future lightweight, low-power designs.

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Critical-sized defects of irregular bones requiring bone grafting, such as in craniofacial reconstruction, are particularly challenging to repair. With bone-grafting procedures growing in number annually, there is a reciprocal growing interest in bone graft substitutes to meet the demand. Autogenous osteo(myo)cutaneous grafts harvested from a secondary surgical site are the gold standard for reconstruction but are associated with donor-site morbidity and are in limited supply. We developed a bone graft strategy for irregular bone-involved reconstruction that is customizable to defect geometry and patient anatomy, is free of synthetic materials, is cellularized, and has an outer pre-vascularized tissue layer to enhance engraftment and promote osteogenesis. The graft, comprised of bioprinted human-derived demineralized bone matrix blended with native matrix proteins containing human mesenchymal stromal cells and encased in a simple tissue shell containing isolated, human adipose microvessels, ossifies when implanted in rats. Ossification follows robust vascularization within and around the graft, including the formation of a vascular leash, and develops mechanical strength. These results demonstrate an early feasibility animal study of a biofabrication strategy to manufacture a 3D printed patient-matched, osteoconductive, tissue-banked, bone graft without synthetic materials for use in craniofacial reconstruction. The bone fabrication workflow is designed to be performed within the hospital near the Point of Care.