Dr. McCarthy, MD, MHCM, serves as POSNA President

This year, Dr. McCarthy is serving as the president of the Pediatric Orthopaedic Society of North America (POSNA). POSNA is a not-for-profit professional organization of over 1200 surgeons, physicians, and allied health members passionately dedicated to advancing musculoskeletal care for children and adolescents through education, research, quality, safety and value initiatives, advocacy, and global outreach to children in underserved areas.

Additionally, Dr. McCarthy is the former chair of POSNA’s Quality, Safety and Value Initiative (QSVI) and successfully launched the group’s first performance measures. As president, Dr. McCarthy will continue focusing on the QSVI measures, as well as, work to initiate micro grants for members and implement the first ever combined POSNA and EPOS (European Paediatric Orthopaedic Society) annual research symposium.

Justifying Patellar Instability Treatment by Early Results

Dr. Shital Parikh received a combined $55,000 award from the Pediatric Orthopaedic Society of North America, and the Arthroscopy Association of North America, to create a study group aimed at analyzing the management and treatment results of patellar instability frequently seen in adolescents and young adults. Patellar instability can be a cause of significant morbidity and arthritis and management is currently controversial. JUPITER (Justifying Patellar Instability Treatment by Early Results) will be a multi-center, multi-armed, prospective cohort study to compare the safety and efficacy of (1) non-operative treatment, (2) isolated MPFL reconstruction, and (3) combined or ‘other’ surgical procedures for management of patellar instability. Recruitment will take place over one year at eight sports centers. Researchers will assess post-treatment outcomes at six, 12 and 24 months, including assessment of function, activity level, health-related quality of life and complications.

The Orthopaedic Biomechanics Lab

The Orthopaedic Biomechanics lab recently published two papers. The first described results from biomechanical feasibility testing of a novel material for spinal ‘growing rods.’ The second reported research in an in vivo model of knee joint injury of the bone-cartilage interface in growing joints. The purpose was to develop a preclinical model to determine causes and compare treatments.

Recent presentations include two at the Orthopaedic Research Society (ORS), and two at the International Research Society for Spinal Deformities (IRSSD). For the latter, an analysis of the effectiveness of magnetically-lengthened growing rods received an award nomination for measuring rod length increases using ultrasound.

Ongoing research includes exploring a novel material for bioresorbable intramedullary nails for fracture fixation in applications with relatively low load requirements and analyzing and testing aspects of growing rods explanted from early onset scoliosis patients. In addition, researched have finalized the second generation implant for the clinical trial of spine growth modulation for adolescent idiopathic scoliosis.

The Cornwall Lab in the Neuromuscular Development Group

The Cornwall lab focuses on investigating the pathophysiology of contracture formation following neonatal brachial plexus injury (NBPI). Using a surgical mouse model which recapitulates contracture formation in humans, we discovered that impaired postnatal skeletal muscle growth is the cause of contractures. We are using this model to elucidate the mechanisms by which neonatal denervation impairs muscle growth in order to develop novel medical strategies to prevent and treat neuromuscular contractures.

Our current work addresses two aspects of neuromuscular contractures. First, we seek to determine the fundamental aspects of muscle growth disturbed in neonatally denervated muscle, including myonuclear accretion and protein synthesis. We have identified, and characterized, deficiencies in the behavior of satellite cells-resident muscle stem cells thought to be critical for skeletal muscle growth through fusion with growing myofibers. In collaboration with the Millay lab, we are using transgenic mice to both track, and manipulate, the ability of satellite cells to fuse to growing muscle fibers in normal and denervated muscle. Our findings to date challenge existing assumptions about the importance of satellite cell fusion to neonatal muscle growth, and highlight novel mechanisms by which stem cells may regulate protein synthesis, and muscle growth.

Second, we seek to determine the precise neuromuscular circuitry required for normal muscle growth, as well as the specific circuitry perturbations required to impair muscle growth. We have identified that muscle growth can proceed without motor innervation, provided the preservation of afferent and/or sympathetic innervation. This finding highlights roles for afferent and sympathetic circuitry in muscle growth and development, which we are studying with surgical and chemical models to manipulate these circuits. Again, there is little known about the role of sympathetic innervation in normal muscle function, our hope is that our model will shed light on both contracture formation, and normal neuromuscular physiology.

The Osteochondral Tissue Engineering Lab

The osteochondral tissue engineering lab is a new lab within the Division of Pediatric Orthopaedics. The lab is working towards the improving care of large osteochondral (OC) injuries (≥2.5cm) by overcoming current barriers inherent to micro-fracture, autologous chondrocyte implantation and autologous osteochondral transfer. Our current project can be broadly divided into two major areas of study.

The first study assesses the chondroinductive ability of synthetic, biocompatible microspheres containing decellularized osteochondral matrix. We have successfully decellularized the osteochondral matrix and characterized the residual DNA, protein, growth factors and chemokines present after the decellularization process. Cell viability and chondrogenic/osteogenic differentiation of mesenchymal stem cells from bone marrow on plates coated with dOCM was observed in the laboratory with immunocytochemistry, biochemical analysis and rtPCR. Our present involvement is in incorporating the dOCM within the microspheres for 3D tissue culture.

The second study aims to combine the microspheres into a biphasic 3-d printed scaffold with dimensions equal to 2.5 cm in diameter and assess the ability of the biphasic scaffold to produce osteochondral differentiation and tissue formation in the presence of seeded mesenchymal precursor cells.

We are collaborating with Dr. James Lin from the University of Cincinnati. We are currently applying for various grants, and look forward to several publications and presentations at major tissue engineering conferences this academic year.