PROJECT SUMMARY/ABSTRACT Over 40,000 children in the US are hospitalized for musculoskeletal deformities each year. Abnormal and often diminished skeletal growth is the root cause of many of these conditions. For years, periosteal resection has been shown to accelerate longitudinal bone growth. Previous attempts to surgically exploit this phenomenon as a growth accelerating therapeutic modality have produced variable results that have not justified the procedures’ surgical morbidity and has been a major barrier to widespread clinical use. Recently, we have developed technology capable of performing these procedures non-invasively. However, the current technology lacks the necessary targeting and imaging capabilities to measure and ensure proper energy delivery at the bone surface. Furthermore, the exact portion of the periosteum that must be injured to accelerate growth is unclear. Thus, in the first aim we will determine the component of the periosteum injured during open surgical periosteal resection responsible for physeal growth acceleration and in the second aim we will integrate targeting capabilities into our system to allow precise placement of energy on the periosteum to minimize adjacent soft tissue injury. At the completion of the proposed work, we will have furthered our goal of developing a simple, non-invasive method to modulate skeletal growth.