Anterior cervical discectomy and fusion (ACDF) is a common type of neck surgery that involves removing a damaged disc to relieve pressure on the spinal cord or nerve root and thus relieve associated pain, numbness, weakness or tingling. The damaged disc is removed from between two vertebral bones along with simultaneous fusion surgery. Fusion involves placing a bone graft or “cage” and/or implants in place of the original disc to stabilize and strengthen the area.
The use of ACDF cages is important after surgery to align the cervical spine and maintain intervertebral disc elevation. However, few studies have examined the effect of the cancellous or “cancellous” core bone connection in relation to handling large loads from the cage. Furthermore, it remains unclear whether a cage with or without studs is the best choice for long-range incorporation since precise movement, slip-and-fall distance or penetration into the cage still occurs frequently.
Researchers from Florida Atlantic University’s College of Engineering and Computer Science, in collaboration with Frank Freones, MD, first author of the study and director of the Marcus Institute of Neurosciences, part of Baptist Health; And Professor of Surgery, FAU Schmidt School of Medicine, are the first to evaluate the effect of range of motion and cage migration and landing using variable-angle screws. The Marcus Neuroscience Center is located on the campus of Boca Raton Regional Hospital and affiliated sites at Bethesda Hospital in Boynton Beach and Deerfield Beach.
For the study, the researchers developed five finite element models of the cervical spine model. The first model was an intact spine model, and the second model was a modified model with the introduction of a cage and a two-tier fixed plate. The other three models have been changed with the same cage insertion and a two-tier dynamic panel. They compared ACDF cages with and without screws on the biomechanical properties of the human spine, implant cage, and associated devices by comparing micro-motion and landing.
The results of the study published in spine magazine, the magazine Neurosurgery in the world And Asian Spine Magazinedemonstrated that the screw cage-and-front coating combination model has promising potential to reduce the risks of micromotility and landing of cages implanted in two or more levels of ACDFs. This method can increase the rigidity of the structure and reduce the incidence of clinical failure and fusion after ACDF, which in turn can reduce the need for revision surgeries or complementary posterior realignment.
“Anterior cervical discectomy and fusion are widely used to treat patients with spinal disorders, where the cage is a critical component of satisfactory fusion outcomes. Risk factors for cage migration are multifactorial and include patient factors, radiological characteristics, surgical techniques, and postoperative factors,” said Freones. “Our results showed that the plate used in our study provided orientation stability and had excellent fusion, indicating promising clinical outcomes for patients with degenerative cervical spine disease.”
Vrionis further explains that due to the biomechanical stability of the existing structure, a rigid cervical collar, which is commonly used by other surgeons, was not needed.
“In addition, with more than 100 clinical cases, there was no evidence of pseudoarthrosis or hypofusion, a treated complication of anterior cervical disc surgery,” Freones said.
The lower helix rotation angle resulted in superior biomechanical performance and a lower ratio of migration and subsidence compared to a higher rotation angle in multi-level applications, regardless of loading. The researchers believe that the underlying mechanism may be due to the threaded cage attached to the bone and the restrictive lower portion of the C5 vertebra making it stiffer.
“Our research aims to develop a platform for the next generation of patient-specific spine surgery by combining intelligent image process, AI/machine learning technology, finite element simulation, and 3D printing to help surgeons design a surgery plan for each patient,” Chi Tai Tsai, Ph. Study Associate and Professor, FAU Department of Mechanical and Ocean Engineering, and Director of the FAU Backbone Laboratory of Biomechanics.
The researchers showed that a screw cage was able to prevent subsidence in all loading scenarios better than a cage without screws.
“Our clinical and biomechanical data showed that the results with the rigid fixed lamina are very good. The main reason may be that there is more contact area between the cortical bone and the cancellous bone in the spiral cage than in the unconstrained cage structures.” Tsai.
ACDF is one of the most common spine surgeries in the United States with an average of 137,000 procedures performed each year.
“The new methodology developed by our researchers in collaboration with Dr. Freones and O’Connor of the Marcus Institute of Neurosciences holds great promise for enhancing anterior cervical discectomy and fusion and ultimately helping to relieve the pain and discomfort experienced by patients with various disorders of the spine,” said Stella Batalama, Ph.D., Dean. Faculty of Engineering and Computer Science FAU.
The study’s other co-authors are Eric Ingberg, Ph.D., Professor, FAU Department of Oceanography and Mechanical Engineering. Maohua Lin, Ph.D., Research Scientist, FAU Department of Oceanography and Mechanical Engineering; Stephen Z. Shapiro, MD, a neurosurgeon in residence at Louisiana State University; James Dolgiris, Ph.D., both in the Department of Neurosurgery, Marcus Institute of Neurosciences, Boca Raton Regional Hospital, part of Baptist Health; Rudy Paul, Ph.D., FAU Department of Oceanic and Mechanical Engineering; and Timothy E. O’Connor, Ph.D., Department of Neurosurgery, Marcus Institute of Neurosciences.
The research was funded by the Boca Raton Regional Hospital Foundation which was awarded to Tsai, the principal investigator.