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Heterotopic ossification (HO) is the abnormal formation of bone in soft tissue. Current diagnostics have low sensitivity or specificity to incremental progression of mineralization, especially at early time points. Without accurate and reliable early diagnosis and intervention, HO progression often results in incapacitating conditions of limited range of motion, nerve entrapment, and pain. We hypothesized that non-invasive near-infrared (NIR) optical imaging can detect HO at early time points and monitor heterotopic bone turnover longitudinally. C57BL6 mice received an Achilles tenotomy on their left hind limb in combination with a dorsal burn or sham procedure. A calcium-chelating tetracycline derivative (IRDye 680RD BoneTag) was injected bi-weekly and imaged via NIR to measure accumulative fluorescence for 11 wk and compared to in vivo microCT images. Percent retention of fluorescence was calculated longitudinally to assess temporal bone resorption. NIR detected HO as early as five days and revealed a temporal response in HO formation and turnover. MicroCT could not detect HO until 5 wk. Confocal microscopy confirmed fluorophore localization to areas of HO. These findings demonstrate the ability of a near-infrared optical imaging strategy to accurately and reliably detect and monitor HO in a murine model.

We analyze adverse selection in the used-car market using a new approach that considers a car as an assemblage of parts, some with symmetric information and others with asymmetric information. Using data from the Consumer Expenditure Survey and Consumer Reports, we examine turnover and repair patterns. We find evidence of adverse selection due to the conditions of the transmission, engine, and, during colder months, air-conditioning; and sorting due to the conditions of the vehicle body and, during warmer months, air-conditioning. Our quantification exercises indicate that adverse selection may have a meaningful effect on trade volume and quality in the secondhand market.