Fig. 6From: Compression-distraction reduction surgical verification and optimization to treat the basilar invagination and atlantoaxial dislocation: a finite element analysisDegrees of freedom constraints of the model. a Planar joint COP to U-shaped nail. b Planar joint U-shaped nail to titanium rod. c Fixed joint titanium rod to universal head. d Revolute joint screw to universal headBack to article page