Minimally Invasive Delivery System for Bone Graft Materials Lauren Burdock (BME) Jon Witten (BME) Frank Zhao (BME)

The physiology of bone Severe loading effects cause fractures Exploit the natural repair process Design Project: minimally invasive bone graft delivery device

Bone composition and natural repair Osteoblasts and osteoclasts mobilized Reparative phase of healing What is non-union?

Non-union and operative repair Non-union occurs when fragments fail to unite Introduce bone grafting material into fracture site Autograft Allograft Xenograft Synthetic compounds

Current Bone Graft Insertion Procedures Previous bone grafting techniques require incisions and manual application of bone pastes and putties into the fracture site, followed by closing of the surgical site. Open surgery is more prone to contamination and infection than less invasive procedures.

Goal We want to reduce morbidity associated with current bone grafting procedures To do this, a minimally invasive technique would be needed to replace the procedure that is currently in place This is a proof-of-concept project. We intend to construct a prototype that could then be adopted by the industry

Broken Tibia set with fixation device using bone screws Market Potential 6 million fractures per year in the US 1.5 million involves long bones Cost to society: 21 BILLION dollars 5-10% of fractures exhibit delayed healing and/or non-union Approximately six million fractures occur each year in the United States, of which 1.5 million involve long bones. These injuries produce considerable morbidity and impairment in individuals of both genders, all age groups and regardless of socioeconomic circumstances. On an annual basis, fractures account for over 36 million lost days from work, more than seven million days missed from school, approximately 6.4 million days of hospitalization, nearly 9.4 million visits to healthcare providers, and cost society an estimated $21 billion (Praemer, 1999). Among the most problematic and burdensome fractures are those 5-10% that demonstrate delayed healing or non-union (Connolly, 1991). Broken Tibia set with fixation device using bone screws

Intended Targets Unstable fractures: Long bone fracture: Oblique Comminuted Spiral Transverse Long bone fracture: Femur

Design Concept External fixation device holds bone sections together to allow proper healing and alignment

Design Concept Hollow needle design Diameter of lumen is determined by viscosity of bone graft material Potentially attached to the external fixation device Pin will be inserted into this area to fill the gap with bone graft materials.

Device Operation Lumen (inlet port) The pin is inserted in or near the fracture site to serve as a conduit for the application of a bone graft material. The bone graft will then solidify and the pin will be removed. Outlet port

Device Operation Bone graft material will flow through the lumen of the pin, exit into the medullary cavity of long bones, and subsequently moves into the fracture area.

Potential Problems Contamination at inlet port Viscosity of bone graft material  change diameter of lumen Clogging of output port  experiment with size and position Accurate delivery to fracture site  experiment with pin placement Pin material must be biocompatible Pin strength (a problem of lumen versus outer diameter size) The range for each allowable change to the system is contributed to by the nature of minimally invasive surgical procedures. The outer diameter of the pin must be no larger than 6mm to be feasible for use in current fixation devices. The outer diameter limits the lumen diameter due to the desired structural integrity of the pin. The size and shape of the exit port may vary to accommodate the consistency of the bone graft material.

Work Accomplished Started learning AutoCAD Discussed various designs and have made sketches Extensive preliminary research underway We are working with the Orthopaedic Lab at University of Louisville

Future Progress Meet to discuss preliminary design ideas before moving into the design process Use a QFD diagram to compare designs Having moved into the design process, we want to a full set of schematics for prototype production Initiate contact with the Department of Orthopedic Surgery at Vanderbilt University to discuss modern bone grafting techniques and surgical instruments involved