[Craniometric studies on the functional morphology of the atlanto-occipital joint in man. Part II. Data and...

Metric and statistical methods were used on a series of skulls (n = 100) to examine the relationship of size and shape parameters of the occipital condyles with other skull variables, which might contribute to an understanding of the morphological variability of occipital condyles and the functional importance of the cranio-vertebral joint (occipital-atlantal-joint) in man. A total of 67 metric variables were included which could be classified into three groups: a) linear measurements, indices and angles of the size and position of the condyles (length, breadth, height and size of the condyles surfaces; length-breadth, length-height and breadth-height indices of the condyles; distance measurements and inclination angles of condyles in the horizontal frontal planes). The size of the condylar surfaces was determined using the printing method of Stofft and Müller. b) Length and breadth measurements and angles of the occipital bone on which the condyles are situated; c) Size circumference, weight and volume measurements of the cranium. The variables of groups b) and c) were mostly taken according to the metrical scheme of Martin. Statistical analysis of the material includes measures of frequency distributions (means, variances, skewness and kurtorsis) and intercorrelations of the variables. Most of the metrical characters of the condyles show high intercorrelations. Similarily, to a large extent highly significant correlations were found between variables of the condyles and length and breadth measurements of pars basilaris and lateralis of the occiput, while little or no statistical association was observed with the size variables of squama occipitalis. The same is true of the correlations between metrical characteristics of the condyles and most of the measurements of the cranium. Likewise cranial capacity and weight of the cranium show little correlation with condylar measurements. Therefore the present study does not support the existence of a relationship between cranial weight or the pressure on the cranio-vertebral joint, and the size and position of occipital condyles as supposed by zoologists on the basis of research work on different species of mammals. However the size and distance measures of the condyles show significant correlations with skull height (basi-bregmatic height) and the length of the skull base (basi-nasal length). The highest correlation coefficient values (r = 0.5) were observed between skull height and the size of the surface of the condyles and the length of the condyles. Somewhat smaller but statistically significant r values were found between basi-bregmatic height of skull and the distance measurement between the condyles. The correlation coefficients demonstrate that skull of greater height possess the condyles which are not only larger and longer but show increased distance between the condyles as well, resulting in a larger supporting area for the skull...