PFI:AIR-TT: Self-adaptive growing rod for the treatment of pediatric scoliosis

Texas A&M Engineering Experiment Station, College Station TX

Investigators

Abstract

This PFI:AIR Technology Translation project focuses on translating a novel titanium alloy to address the need for improving the outcome and reducing implant-related complications during growing rod treatment of adolescent scoliosis. The adaptive growing rod is important because of its potential to reduce the high incidence of implant loosening and failure, which are the primary sources of complications in the treatment of severe early-onset scoliosis in children and often necessitate costly and painful revision surgeries. The project will result in a working prototype of an adaptive growing rod and demonstrate its feasibility in a standardized biomechanics model. This device has the unique features of simultaneous high strength and ultra-low stiffness matching that of human bone, and the ability to vary its stiffness depending on location. When compared to the leading competing growing rods based on the Harrington rods system in this market, these features reduce the number of revision procedures required by reducing a leading source of complications, facilitating healthy development of the spine from better load sharing, and improving the overall efficacy for treatment of severe scoliosis in children. This project addresses the following technology gaps as it translates from research discovery toward commercial application: there is a current lack of quantitative understanding of how stress at the bone-screw interface is affected by implant stiffness in growing rod constructs. This is important because high stress at the bone-screw interface is believed to be responsible for implant loosening and pull-outs. Furthermore, it is not known how location-dependent implant stiffness modifies such stress. The project seeks to bridge these gaps by quantitatively monitoring how stress at the bone-screw interface is affected by variations in the implant stiffness introduced by microstructural engineering and thermo-mechanical training in a Ti-Nb alloy. Experiments are performed using a modified ASTM standard model that accounts for the changing stiffness of the growing spine. In addition, personnel involved in this project, including a Ph.D. level graduate student and undergraduate researchers, will receive entrepreneurship and technology translation experiences through direct involvement in the customer development process. Students will participate in all conversations with surgeons, hospital officials, regulatory personnel, and medical devices manufacturers. Students will be asked to make customer contacts independently, and receive training of the lean-startup strategy central to the NSF I-Corps program. The project engages pediatric orthopedic surgeons and a medical devices manufacturer to ensure a clear and current understanding of clinical needs and challenges, as well as regulatory and reimbursement hurdles of this technology translation effort from research discovery toward commercial reality.