Measurement and clinical significance of occipito-C2 angle and posterior occipitocervical angle in 150 healthy adults

English Keywords:Healthy adults  Occipito-C2 angle  Posterior occipitocervical angle  Correlation  Clinical significance

English Abstract:

  【Abstract】 Objectives: To measure the occipito-C2 angle(OC2A) and the posterior occipitocervical angle(POCA) in healthy Chinese adults and analyze their differences and clinical significance with regard to sex and age, so as to provide the oretical guidance and reference for the posterior occipitocervical fusion. Methods: A total of 150 healthy subjects without cervical spine disease(healthy group) was recruited(male:female=1:1). Each gender group was furtherly evenly divided into 5 groups according to the age, 20-29 year-old group, 30-39 year-old group, 40-49 year-old group, 50-59 year-old group, 60-69 year-old group. 3 spine surgeons measured the OC2A and POCA of the subjects twice respectively. The intraobserver and interobserver reliabilities were evaluated by the intra-class correlation coefficient. Statistical analysis was done to compare the OC2A and POCA between different gender and age group respectively. Results: The value of OC2A and POCA in 150 subjects was 14.14°±3.70° and 108.53°±7.80°, respectively. The 95% confidence intervals(CI) were 6.89°-21.39° and 93.24°-123.82°, respectively. The value of OC2A and POCA in male was 14.63°±3.10° and 108.05°±7.48°, and 13.66°±4.18° and 109.01°±8.14° were measured in female. There was no significant difference of OC2A between each gender or age group[male P=0.129, female P=0.160, One-Way ANOVA(LSD)]. In male, POCA in 60-69 year-old group was less than 20-29 and 50-59 year-old groups. But in female, POCA decreased with age after 30 year-old, and the 60-69 year-old group was significantly less than the 20-49 year-old group with regard to POCA. Pearson correlation analysis showed that there was a negative correlation(r=-0.386, P<0.001) between OC2A and POCA. The correlation coefficients(ICC) of intraobserver measurement of OC2A and POCA were 0.933 and 0.971 respectively, and the ICCs of interobserver were 0.916 and 0.935 respectively， P＜0.001. Conclusions: There is no significant difference of OC2A or POCA between male and female in heathy Chinese adults. The OC2A value is approximately the same among all age groups, while the POCA value decreases with age. Spine surgeons can consider the age of the patientsand refer to the CI value and negative correlation of the two parameters, thus to make better choice of the OC2A and POCA angles selection in posterior occipitocervical fusion.