Sensate scaffolds can reliably detect joint loading

Implantable sensor technology: measuring bone and joint biomechanics of daily life in vivo

Stresses and strains are major factors influencing growth, remodeling and repair of musculoskeletal tissues. Therefore, knowledge of forces and deformation within bones and joints is critical to gain insight into the complex behavior of these tissues during development, aging, and response to injury and disease. Sensors have been used in vivo to measure strains in bone, intraarticular cartilage contact pressures, and forces in the spine, shoulder, hip, and knee. Implantable sensors have a high impact on several clinical applications, including fracture fixation, spine fixation, and joint arthroplasty. This review summarizes the developments in strain-measurement-based implantable sensor technology for musculoskeletal research.

A novel biomimetic polymer scaffold design enhances bone ingrowth

There has been recent interest in treating large bone defects with polymer scaffolds because current modalities such as autographs and allographs have limitations. Additionally, polymer scaffolds are utilized in tissue engineering applications to implant and anchor tissues in place, promoting integration with surrounding native tissue. In both applications, rapid and increased bone growth is crucial to the success of the implant. Recent studies have shown that mimicking native bone tissue morphology leads to increased osteoblastic phenotype and more rapid mineralization. The purpose of this study was to compare bone ingrowth into polymer scaffolds created with a biomimetic porous architecture to those with a simple porous design. The biomimetic architecture was designed from the inverse structure of native trabecular bone and manufactured using solid free form fabrication. Histology and muCT analysis demonstrated a 500-600% increase in bone growth into and adjacent to the biomimetic scaffold at five months post-op. This is in agreement with previous studies in which biomimetic approaches accelerated bone formation. It also supports the applicability of polymer scaffolds for the treatment of large tissue defects when implanting tissue-engineering constructs. (c) 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009.

Sensate scaffolds coupled to telemetry can monitor in vivo loading from within a joint over extended periods of time

Polymer scaffolds have been used as a tool to provide growth and integration of engineered tissue substrates to repair damaged tissues in many organ systems including articular cartilage. Previous work has shown that "sensate" scaffolds, with integrated strain gauges have the potential for use as both a delivery vehicle for engineered cartilage as well as a device that can measure real time, in vivo joint loading. The purpose of this study was to use an implanted subminiature telemetry system to collect in vivo joint loading measurements over an extended period following placement of a "sensate" scaffold. Measurements were collected from seven of nine sensors that were implanted into the stifles of three canines. The limb loading rates and load distribution through gait were dependent on stride time but did not vary with time post op. The peak loads were not dependent on stride time but significantly increased with time post op. This demonstrated that peak loading measured with "sensate" scaffolds can be used to monitor healing. The portability of the "sensate" scaffolds coupled to telemetry systems highlights the potential use of this system in a clinical research setting to gather important information to improve tissue engineering and rehabilitation regimens.