Investigating Screw Fixation in Cervical Spinal Fusion Through Artificial Bone Modeling
Orthopaedic Innovation Centre
Cervical spinal fusion is a surgical procedure that joins two or more adjacent vertebrae in the neck region to treat severe pain, trauma, and other spinal disorders. A posterior fusion of the subaxial cervical vertebrae is routinely performed with screws implanted into the lateral mass regions of these vertebrae and joined with vertical rods.
The success of interbody fusion is greatly dependent on the degree of screw fixation. Screw fixation can be affected intraoperatively by implant design, path of screw trajectory, purchase depth, and bone quality. Achieving optimal screw fixation in the cervical spine presents several challenges due to the small footprint of the lateral mass region and its anatomic proximity to the vertebral arteries and nerve roots. The importance of screw fixation is critical, as screw-bone failure may result in catastrophic neurologic injury and major spinal revision surgery.
Engineers at the Orthopaedic Innovation Centre (Winnipeg, Canada) and surgeons and residents from the Department of Surgery at the University of Manitoba (Winnipeg, Canada) combined orthopaedic practice with biomechanical testing to determine optimal screw fixation in subaxial cervical spinal fusion. Screw design, trajectory angle, and purchase depth were investigated.
Improving Pedicle Screw Fixation in Lumbar Spinal Fusion
Orthopaedic Innovation Centre
Many people in North America suffer from severe back pain. To remedy, patients may undergo surgical intervention to immobilize the affected areas by means of spinal fusion. In spinal fusion, screws are implanted into neighbouring vertebrae and joined by rods to create a rigid construct, thereby promoting intervertebral fusion. Unfortunately, a reasonable portion of these procedures suffer from fusion failure.
To improve the success rate of spinal fusion, the Orthopaedic Innovation Centre (Winnipeg, Canada) has been working with orthopaedic surgeons and residents from the Health Sciences Centre (Winnipeg, Canada) to study pedicle screw fixation in lumbar spinal fusion.
Utilization of Radiostereometric Analysis (RSA) to Assess Quality of Spinal Fusion
Orthopaedic Innovation Centre
Spinal fusion is a surgical treatment to manage traumatic, degenerative, deformative and infectious diseases of the spine. Unfortunately, a portion of spinal fusions result in complications involving adjacent-segment degeneration and fusion failure.
The Orthopaedic Innovation Centre (OIC) is a research and engineering facility in Winnipeg, Manitoba, that dedicates 50 per cent of their work towards clinical RSA research studies. They have recently completed a phantom study that assessed the feasibility of RSA as a technique for diagnosing successful or failed spinal fusion.
Testing and Validation of a Patient-specific, Surface-guided Total Knee Replacement
Orthopaedic Innovation Centre
The white paper describes the extensive development of the technology as well as results of numerous validation tests performed on a surface-guided knee prototype. These works, which have been published in numerous peer-reviewed journals, demonstrate the superiority of the design in terms of:
- Guided, patient-specific knee kinematics with more precise implant fit
- High range of motion with up to 155° of flexion, up to 22° external rotation of the femur, and 12 mm of femoral rollback
- Joint stability without relying on ligaments
- Low articular surface pressure which reduces risk of polyethylene damage and lowers wear rate
Pilot Study: The Effect of Femoral Head Roughening Techniques on Polyethylene Wear in Total Hip Replacements
Orthopaedic Innovation Centre
Three different femoral head roughening techniques were selected in order to investigate their effect on polyethylene wear. We found that tumbling the femoral heads provided a consistent roughened surface finish. It was also shown to produce the most consistent wear rates. Wear rates generally increased when the lubricant protein concentration was increased from 17 g/L to 30 g/L. Surface roughness measurements from retrieved femoral heads showed that artificial roughening beyond an average roughness of 0.30 μm may not be clinically relevant, and that certain methods of artificial femoral head roughening can produce excessive wear. It is recommended that ensuring a consistent and repeatable method for artificial roughening will maintain the integrity of the surface finish and the wear test.