In vitro three dimensional morphometry of the lateral atlantoaxial articular surfaces.
METHODS
The present study verifies the 3-dimensional anatomic features of the lateral atlantoaxial joints with reference to a local reference frame using a direct in vitro approach.


OBJECTIVE
To study the concordance between the axial and atlantal articular surfaces.


BACKGROUND
Detailed information of joint-configurations is imperative for understanding the complex kinematics of the upper cervical joint. Data on the quantitative morphology of the human spinal facet joints has been published, but did not include the atlanto-occipital and atlantoaxial joints.


METHODS
In 20 fresh spine specimens, metal markers were implanted on the cranium, the atlas, and the axis. After registration of the intact specimens, the bony segments were separated and markers and anatomic landmarks were digitized. The size, shape, and orientation relative to the local reference frame of the axis were derived from the relative position data of the joint surface landmarks.


RESULTS
The diameters and surface areas of the inferior articular surfaces of the atlas are slightly smaller than the corresponding surfaces on the superior aspects of the axis (17.7 mm and 235 mm vs. 17.0 and 212 mm). In this sample of older-aged specimens, the curvature of the articulating surfaces is nearly flat. The absolute angle between the left and right surface areas is about 130 degrees and corresponds well between axis and atlas. The orientation of the joint surfaces of axis and atlas with respect to the sagittal plane of the axis indicates a good congruency.


CONCLUSIONS
There seems to be a strong relationship between the anatomic features of the lateral articulating surfaces of atlas and axis. Differences in the orientation of joint surfaces to the frontal plane may be related to deviations from the neutral position. This issue raises the problem of the definition of three-dimensional-neutral joint positions.
Cattrysse
Erik
E
Department of Experimental Anatomy, Arthrokinematics research group, Vrije Universiteit Brussel, Brussels, Belgium. ecattrys@vub.ac.be
Provyn
Steven
S
Gagey
Olivier
O
Kool
Patrick
P
Clarys
Jan Pieter
JP
Van Roy
Peter
P
D000368:Aged; D000369:Aged, 80 and over; D001268:Atlanto-Axial Joint / Q000033:anatomy & histology*; D001368:Axis, Cervical Vertebra / Q000033:anatomy & histology; D001696:Biomechanical Phenomena; D001270:Cervical Atlas / Q000033:anatomy & histology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular