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Background: In the posterior cervical spine approach, the form of the cervical spinous process tip is one important landmark for level determination. However, it is still controversial whether the most caudal level of the bifurcated spinous process is C5 or C6 in previous reports., Methods: The study samples consisted of 47 bleached bones and 3 fixed bodies for anatomical practice. According to the classification of Okuwa, patients who showed remarkable bifurcation of the spinous process tip were regarded to have "remarkable bifurcation", those who showed unclear indentation in the spinous process tip to have "slight bifurcation", and those who showed no bifurcation and no indentation to have "lack of bifurcation"., Results: The spinous process tips from C2 to C5 bifurcated in 26 out of 50 cervical spines (52%), and those from C2 to C6 in 20 (40%). There was no significant difference in the frequency of bifurcation of the spinous process tip between males and females., Conclusion: The results of the present study indicate that it does not seem useful to use bifurcation of the cervical spinous processes for anatomical landmarks.

The aims of this study were to investigate the relationships between the cranial base and maxillofacial morphology in Japanese crania, and to examine the differences between Class I and Class II samples. Data were obtained from 46 male Japanese crania from the collection of the Jikei University School of Medicine (Tokyo). The sample represents populations which would have lived during the last 100 years. A principal component analysis of linear and angular measurements showed that the anterior and posterior cranial base, and the cranial base angle were associated in different ways with different aspects of maxillofacial morphology. Variation in the anterior cranial base was associated with differences in facial height, lower facial height, bicondylar breadth, ramal height, and ramal width, while posterior cranial base length was correlated with bizygomatic breadth. The cranial base angle was negatively correlated with SNA (r = -0.46) and SNB (r = -0.59), and positively correlated with the palatal and occlusal plane angles. There were significant differences between Class I and Class II specimens in palatal width, SNA, ANB, and the palatal plane angle, but no significant difference in cranial base length or angle. The evidence suggested that cranial base shape and size was related to facial length, inclination of the maxilla, and both maxillary and mandibular prognathism.

A total of thirty-six Japanese adult subjects (consisting of eighteen men and eighteen women) with normal occlusion and harmonious facial features were subjected to cephalographic examination for the purpose of studying their soft tissues. Out of this group, twenty were selected and compared with twenty Class II, Division 1 and twenty Class III patients for the purpose of establishing an appropriate diagnostic guide for the Tweed triangle. These are our conclusions: 1. The Z angle of the Japanese subjects with normal occlusion was 69.70 degrees for the men and 71.75 degrees for the women. There is no significant difference between the sexes. 2. Although there are no significant differences between the sexes for the integumental and total chins, there is slight sexual difference for the upper lip measurement. 3. As compared to the subjects with normal occlusion, there is a significant difference for the Z angle of Class II, Division 1 and Class III patients. 4. In this study, the measurements of the Tweed triangle were FMA 27.28 degrees, IMPA 95.50 degrees, and FMIA 57.22 degrees. On the basis of this study and the reports of other Japanese investigators, we would like to suggest an FMIA of 57 degrees as being the most suitable basis for the diagnosis of Japanese patients, but this should be modified according to the FMA value.