RESUMEN
AIMS AND OBJECTIVES: The alignment of upper and lower cervical spine is presumed to be closely interrelated and the knowledge of this is mandatory when performing occipito-cervical and upper cervical fusions. The aim of this study was to establish standard values for upper and lower cervical spine alignment in the Indian population. MATERIALS AND METHODS: Five hundred eighteen asymptomatic volunteers (261 males and 257 females) between 12 and 80 years of age underwent lateral radiography with their neck in the neutral position. Angles for occipital to 2nd cervical (Oc-C2), 1st to 2nd cervical (C1-C2) and sagittal alignment of 2nd to 7th cervical vertebrae (C2-C7) were measured. Statistical analyses were performed using a statistical package SPSS 10 for windows and the students 't' test. RESULTS: The mean Oc-C2, C1-C2 and C2--C7 angles were 14.66+9.5 degrees , 25.6+7.9 degrees and 16.8+12.7 degrees in male, while same angles in female were 15.59+8.26 degrees, 26.9+6.8 degrees and 9.11+10.4 degrees respectively. Weak statistically significant negative correlation was observed between the measured angles of the upper (Oc-C2 and C1-C2) and lower (C2-C7) cervical spines, which means if the lordosis of the occiput and upper cervical spine increases (if the Oc-C2 angle increases), the alignment of lower cervical spine becomes kyphotic and vice versa. This negative correlation was stronger between the Oc-C2 and C2-C7 angles than between the C1-C2 and C2-C7 angles. CONCLUSIONS: Relationship between alignment of the upper and the lower cervical spine should be taken into consideration when performing cervical fusion.