Minimally Invasive Delivery System for Bone Graft Materials

Minimally Invasive Delivery System for Bone Graft Materials Lauren Burdock (BME) Jon Witten (BME) Frank Zhao (BME) Sponsor: Michael Voor Ph. D. University of Louisville Medical School

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

Bone composition and natural repair l Osteoblasts and osteoclasts mobilized l Reparative phase of healing l What is nonunion?

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

Current Bone Graft Insertion Procedures l 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. l Open surgery is more prone to contamination and infection than less invasive procedures.

Goal l We want to reduce morbidity associated with current bone grafting procedures l To do this, a minimally invasive technique would be needed to replace the procedures that are currently in place l This is a proof-of-concept project. We intend to construct a prototype that will deliver the bone graft “glue” developed at University of Louisville Medical School.

Market Potential Broken Tibia set with fixation device using bone screws l 300, 000 -600, 000 fractures per year exhibit delayed healing and/or non-union. l There is market potential for the device in industry, but we are designing it for testing in the orthopaedic lab. l Once the development of both the delivery device and material is completed, the process can be adopted by industry.

Target l Unstable fractures: l l Long bone fracture: l l Oblique Spiral Transverse Femur and the femoral head Bone Graft Material l Proprietary bone glue under development by the Orthopaedic Lab at University of Louisville

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

Design Concept l Hollow needle design l Diameter of lumen must allow passage of bone graft material l Can be attached to the external fixation device Pin will be inserted into this area to fill the gap with bone graft materials.

Surgical Procedure l We are shadowing Dr. Franklin Shuler, an orthopedic surgeon at VUMC to observe a surgery l We plan to obtain an operative report that will help us design a medical protocol.

General Pin Design

Types of Output Ports

Device Operation Lumen (inlet port) l The pin is inserted in or near the fracture site to serve as a conduit for the application of a bone graft material. l 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.

Testing l Phase I: Viscosity Determination l l l We are going to use the Materials Testing System to determine the maximum viscosity of the bone glue that can be passed through the lumen of the pin. Poiseuille’s Law: Phase II: Plug Creation l l Using the maximum viscosity that could be manually passed through the pin, we will test the pin’s ability to create the plug of bone graft. The target is a full size polycarbonate femur.

Testing Continued l Phase l II continued After plug formation we will examine the bone by x-ray imaging and manual sectioning. l Phase III: CT Scan Analysis The best delivery pin will be used on a porcine femur. l We will then examine the plug formation of the graft with a CT scan. l

Potential Problems l Contamination at l Viscosity of bone inlet port graft material change diameter of lumen l Clogging of output port experiment with size and position l Accurate delivery to fracture site experiment with pin placement l Pin material must be biocompatible

Progress l Work Accomplished Met with Dr. Voor and the Orthopedic lab on March 24 th. Discussed testing procedures and time. l The manufacturing of the pins have been completed and we have prototypes. l l Future Work We will test the device on April 14, 2006. l Shadow Dr. Shuler and obtain operative report. l