Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Science

Program

Surgery

Supervisor

Bailey, Christopher S

2nd Supervisor

Zdero, Radovan

Co-Supervisor

3rd Supervisor

Rasoulinejad, Parham

Co-Supervisor

Abstract

Posterior approaches remain among the most used to perform lumbar interbody fusion (LIF) surgery. It happens because of the advantage of providing direct access to the neural elements in the lumbar spine and the surgeons' preference for the approach. But the interbody fusion devices (IFD) inserted using posterior approaches are of limited size, and implant subsidence remains the most common complication after LIF surgery. It can be catastrophic for the patient resulting in worse outcomes or even requiring revision surgery. Since increasing the cage's size is not possible in PLIF surgeries, this thesis will explore biomechanical strategies to increase the load distribution across the IFD and reduce the risk of subsidence. It will be done using patient-specific devices, matching the bony endplate anatomy, manufactured through rapid prototyping and exploring the role of the bone graft housed inside the cage to increase load sharing.

Summary for Lay Audience

Different techniques promote bone fusion between the vertebrae on the spine in posterior lumbar spine surgery. One of the most used methods is called interbody fusion, which involves removing the intervertebral body disc, meaning the soft material located between the bones of the spine. After this soft material is removed, a device containing a bone graft is usually inserted inside the disc space to promote bone fusion between the superior and the inferior vertebra of the spine. This device is referred to as "cage" and has different purposes, like increasing the space for the spine's neural elements (i.e. nerves) and promoting a better alignment for the lumbar spine. But one of the biggest problems after inserting those devices into the disc space is that they can sink into the vertebral body over time. This is called subsidence. When it occurs, it can trigger the new onset of leg pain and back pain for the patients, resulting in worse outcomes.

Usually, the cages are produced having a similar size and shape for all the patients. The present study proposes investigating if the development of a device that matches the bone geometry of the patient's own vertebra is better than using a "one size fits all" device that suits everyone and can reduce the risk for device subsidence. The purpose of the testing is to figure out which kind of device will subside more easily into the bone under compressive load. This biomechanical study involved using a mechanical loading frame to test the implants created to compare to commercial implants. Another goal for the study was to investigate if the bone graft inserted inside these devices can help prevent subsidence. We will use spine vertebrae from people that have donated their bodies for research. This research will be informative to spine surgeons with the first biomechanical evidence to date regarding this subject. The results of this study will draw the attention of the scientific community to an important topic regarding surgical complications that occurs in approximately 15% of surgeries and will present a possible solution to the problem.

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