Design of Dynamic Stander for Immobilized Children to Increase Bone Mineral Density
Megan D. Damcott
New Jersey Institute of Technology
Newark, NJ
In recent years, osteoporosis has become a focus of much research. Many studies have concentrated on post-menopausal women and the elderly, however recently the prevalence of osteoporosis and associated diseases in immobilized children has begun to draw attention. Passive standing has been incorporated into therapy program of immobilized children nationwide as it is believed that the mechanical loading experienced by the bones increases the bone mineral density. However, research in bone mechanisms have suggested that the signals created by the reciprocal loading of the bone during walking is responsible for increasing osteoblast formation at a greater rate than constant mechanical loading. Furthermore, studies on post-menopausal women and adolescents have determined that a low-amplitude, high-frequency vibration has the potential to maintain or increase bone mineral density. With the latest findings, it is hypothesized that by incorporating a dynamic component, which mimics the walking gait, into the standers of immobilized children bone density increase will be greater than that resulting from the presently used passive standing therapies. The design considerations, process, solutions and verification of a dynamic stander are discussed. The dynamic stander is controlled by computer programmable pneumatic actuators and is capable of applying a reciprocating force that mimics the forces and timing the child would experience during normal walking. A three-month pilot study with four subjects between 3- and 8-years old, two in passive standers and two in the modified dynamic standers, is presently being conducted at Children’s Specialized Hospital in Mountainside, NJ. A dual-energy x-ray absorptiometry scan (DXA) will be done prior to the commencement of the study and at the conclusion in order to compare the pre- and post-study bone mineral densities.
KEYWORDS:
Standing; immobilized; children; bone mineral density; dynamic.
ACKNOWLEDGMENTS:
This study is being funded by the National Institute on Disability and Rehabilitation Research, RERC for Children with Orthopaedic Disabilities Grant # H133E050011.
I would also like to thank Dr. Richard Foulds, PhD, Sheila Blochlinger, PT and Dr. Bruno Mantilla, PhD, for their advisement and Luis Espina, MS, Diego Ramirez, MS, Katharine Swift, MS and Amanda Irving, MS for their help in various aspects of the design process.
AUTHOR CONTACT:
Megan Damcott; New Jersey Institute of Technology; 323 Martin Luther King Jr. Blvd.; Fenster Hall, 6th Floor; Newark, NJ 07102; Phone: (201) 428-1581; Email: mdd7@njit.edu