Nondestructive mechanical testing of human knee meniscus allografts using MSSER ultrasound: A feasibility study

Researchers have begun to investigate novel meniscus graft construction with donor cell replacement through decellularization and host stem cell seeding. In these techniques, there is an unmet need for a nondestructive mechanical testing platform that can monitor changing mechanical properties of the seeded graft over time. In this study, Monitored Steady-State Excitation and Recovery (MSSER) ultrasound, which exploits multiple successive acoustic radiation force excitations interspersed with tracking lines to mimic a materials creep test, was used to nondestructively test the mechanical stiffness of meniscus grafts. Four human meniscus samples were evaluated ex vivo using MSSER: two chemically decellularized samples and two intact samples. MSSER testing measured a median stiffness difference of 37% between intact and decellularized samples, which agreed well with the 35% difference measured by destructive compression testing. Volumetric MSSER scanning showed highly heterogeneous stiffness throughout the samples. This demonstration substantiates the use of MSSER as a relevant nondestructive testing tool in tissue engineering applications.