Design Considerations for Supplemental Implants with Electrical Stimulation

Abstract

After a severe fracture or damage to bone, many patients have a long road of recovery. In healthy patients, successful fusion can take 3 to 6 months, and even longer for high risk demographics. [1] Depending on the break most fractures are stabilized with fixation instrumentation such as, posterior rods, screws, or bone plates. This study looks into the application of pedicle screws and posterior rods for lumbar spinal fusion. To help decrease the risk of failure, surgeons will implement spinal fusion instrumentation to help provide increased stability as the bone heals. Instrumented spinal fusion has several advantages, such as no external immobilization, an early ambulation, along with improved rates of fusion. [2] Even with the advancements of medical devices lumbar fixation surgeries have a relatively high failure rate. It has been noticed that bone fusion can be benefited through electrical stimulation. Current electrical stimulation devices implement harmful batteries that need to be removed after they have run out of power. Piezoelectric material is a safe alternative power source that can be permanently implanted inside the body. Piezoelectric material has the capability to produce electric energy when stimulated through mechanical loading. Therefore, this study looks into the idea of utilizing piezoelectric ceramics to hone the mechanical loading produced in the body to generate beneficial electrical stimulation. Using finite element analysis (FEA), this study investigates the mechanical stresses transferred from the lumbar spine to fixation devices. With a better understanding of the stress distribution during everyday movements, we hope to use the compressive forces to promote healthy bone growth through electrical stimulation. The overall goal of this study is to show that, even with minimal force and low frequency applications, piezoelectric material can be strategically implemented onto already existing posterior rods and other orthopedic devices to promote faster and improved healing through clip-on devices.