Juan P Sardi1, Joe Iwanaga2, Cameron Schmidt3, Tarush Rustagi4, Jens R Chapman4, Rod J Oskouian5, R Shane Tubbs6. 1. Hospital Universitario San Ignacio, Bogotá, Colombia. 2. Seattle Science Foundation, Seattle, Washington, USA; Department of Anatomy, Kurume University School of Medicine, Kurume, Fukuoka, Japan; Dental and Oral Medical Center, Kurume University School of Medicine, Kurume, Fukuoka, Japan. Electronic address: joei@seattlesciencefoundation.org. 3. Seattle Science Foundation, Seattle, Washington, USA. 4. Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA. 5. Seattle Science Foundation, Seattle, Washington, USA; Swedish Neuroscience Institute, Swedish Medical Center, Seattle, Washington, USA. 6. Seattle Science Foundation, Seattle, Washington, USA; Department of Anatomical Sciences, St. George's University, St. George's, Grenada.
Abstract
OBJECTIVE: Various authors have described the morphology of the alar ligaments; however, there are no reports of a cadaveric study focusing on their attachments onto the dens. The purpose of this study was to use fresh cadaveric specimens to describe in detail different attachment patterns of the alar ligaments onto the dens. METHODS: This study used 22 sides from 11 fresh frozen cadaveric heads. Specimens were obtained from 8 men and 3 women who were 67-99 years old at death. Dissection of the exact attachment of the alar ligaments onto the dens was observed from posterior, superior, and anterior views under the surgical microscope. RESULTS: From a posterior view, 6 alar ligaments passed over the tip of the dens, and 16 alar ligaments attached onto the posterolateral part of the dens; the right and left ligaments had no continuity. From a superior view, the alar ligament was classified in 2 ways: depending on the covered area of the dens (entirely or posterior two thirds) and continuity of the alar ligament (transversely, separately, or combination). Fourteen alar ligaments covered the posterior two thirds of the dens. From an anterior view, in 1 specimen, the alar ligament extended to the anterior surface of the dens. CONCLUSIONS: Wide posterolateral anchoring to the dens coupled with the nearly horizontal trajectory explains the biomechanical advantage of the alar ligaments in undertaking a stabilizing function in limiting head rotation that would otherwise be ineffective in the case of weaker attachments or a more vertical orientation.
OBJECTIVE: Various authors have described the morphology of the alar ligaments; however, there are no reports of a cadaveric study focusing on their attachments onto the dens. The purpose of this study was to use fresh cadaveric specimens to describe in detail different attachment patterns of the alar ligaments onto the dens. METHODS: This study used 22 sides from 11 fresh frozen cadaveric heads. Specimens were obtained from 8 men and 3 women who were 67-99 years old at death. Dissection of the exact attachment of the alar ligaments onto the dens was observed from posterior, superior, and anterior views under the surgical microscope. RESULTS: From a posterior view, 6 alar ligaments passed over the tip of the dens, and 16 alar ligaments attached onto the posterolateral part of the dens; the right and left ligaments had no continuity. From a superior view, the alar ligament was classified in 2 ways: depending on the covered area of the dens (entirely or posterior two thirds) and continuity of the alar ligament (transversely, separately, or combination). Fourteen alar ligaments covered the posterior two thirds of the dens. From an anterior view, in 1 specimen, the alar ligament extended to the anterior surface of the dens. CONCLUSIONS: Wide posterolateral anchoring to the dens coupled with the nearly horizontal trajectory explains the biomechanical advantage of the alar ligaments in undertaking a stabilizing function in limiting head rotation that would otherwise be ineffective in the case of weaker attachments or a more vertical orientation.