Injury Threshold of Rectus Capitis Muscles at the Atlanto-occipital Joint

Area of Science:

• Biomechanics
• Anatomy
• Orthopedics

Background:

• The rectus capitis (RC) muscles are key stabilizers of the atlanto-occipital joint.
• Their passive load-displacement properties, or stiffness, have not been previously quantified.

Purpose of the Study:

• To measure the passive stiffness of the four RC muscles.
• To elucidate the role of RC muscles in atlanto-occipital joint stabilization.

Main Methods:

• Passive length-force data were collected from RC muscles of three unembalmed head and neck specimens.
• A servo-controlled hydraulic test machine was utilized for data acquisition.
• Multivariate analysis of variance with Bonferroni correction was employed for statistical analysis.

Main Results:

• Rectus capitis lateralis (RCL) muscles demonstrated significantly higher failure loads and strains compared to other RC muscles.
• Both RCL and RC anterior muscles exhibited significantly greater passive stiffness than the other two RC muscle pairs.

Conclusions:

• The high passive stiffness and anatomical position of RCL muscles likely contribute to maintaining atlanto-occipital joint congruence.
• RC posterior minor muscles may be susceptible to strain injuries in rear-end collisions.
• Clinical protocols involving the upper cervical spine should account for patient factors to prevent RC muscle overstretching.