RESUMEN
Objective To explore the differences and correlation of imaging parameters of occipital-C2 angle (OC2A) and posterior occipitocervical angle (POCA) between sex and age, so as to provide theoretical reference for fixing the position of head and neck in occipitocervical fusion. Methods The imaging data of 473 cases (339 males and 134 females) were collected and divided into 2 groups according to sex. Each group was subdivided into 6 groups according to age: ≤29 year-old, 30-39 year-old, 40-49 year-old, 50-59 year-old, 60-69 year-old and ≥70 year-old. OC2A and POCA were measured in Mimics software, and their differences with sex and age were statistically analyzed. Results There was no significant difference in OC2A and POCA between sexes (P0.05); There were significant differences in POCA between the male group of 30-39 year-old and ≤29 year-old (P<0.05), but between the group of 40-49 year-old and each group (P<0.05). In the female group, there was significant difference between the group of ≤29 year-old and all age groups (P<0.05), but there was no significant difference among the other groups (P<0.05). Pearson correlation analysis showed that there was a positive correlation between OC2A and POCA (r= 0.038, P<0.05), that is, there was no correlation between them. Conclusion There is no difference in OC2A and POCA values between sexes; there are differences in OC2A and POCA values in males among different age groups, suggesting that clinical attention should be paid to the age differences in males, while there is no difference in OC2A values in females, but POCA is different in different age groups. The changes of OC2A and POCA values in different age groups and sex provide a parameter basis for fixing the anatomical reduction angle of head and neck in occipitocervical fusion.
RESUMEN
BACKGROUND: For patients with basilar invagination under occipitocervical fusion, the unreasonable choice of fixed angle in the occipitocervical region will reduce the clinical efficacy and accelerate the degeneration of subaxial cervical spine OBJECTIVE: To measure the Occipito-C2 angle (OC2A) and the posterior occipitocervical angle (POCA) in healthy subjects, and to analyze the influence of OC2A and POCA selection on the clinical efficacy and the loss of cervical spinal angle (CSA) of subaxial cervical spine in the occipitocervical fusion of basilar invagination. METHODS: 150 healthy subjects (healthy group) were grouped by gender and age, with 75 males and 75 females divided into five age groups ranging from 20 to 69 years old. OC2A and POCA of each healthy subject were measured by three spine surgeons. The intraclass correlation coefficient analysis was performed on the two parameters to prove their consistency. The mean of the two parameters and 95% confidence interval (95% CI) were obtained. Clinical data from 42 patients (malformation group) with basilar invagination who underwent occipitocervical fusion from January 2012 to January 2017 were analyzed retrospectively. These patients were divided into ideal angle subgroup and non-ideal angle subgroup, according to whether their OC2A and POCA immediately after postoperative ambulation were at 95% CI of the healthy group or not. OC2A, POCA, and CSA angles were measured preoperatively, immediately after postoperative ambulation, and at the final follow-up visit. The preoperative and final follow-up visual analog scale (VAS) score, Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and the loss of CSA from immediately after postoperative ambulation to the final follow-up (dCSA) were recorded. RESULTS AND CONCLUSION: The values of OC2A and POCA were (14.5±3.7)° and (108.2±8.1)° in the healthy group, respectively, and the respective 95% CI values were 7.2° -21.8° and 92.3° -124.0° as the normal range. There was a negative correlation between OC2A and POCA (r=-0.386, P < 0.001). The preoperative value of OC2A [(5.6±4.3)°] in the malformation group was smaller than that in the healthy group (P < 0.001); however, the preoperative values of POCA [(123.9±10.4)°] and CSA [(25.7±9.5)°] in the malformation group were larger than those in the healthy group (P < 0.001). In the 42 basilar invagination patients, 26 patients (ideal angle subgroup) were fixed in the ideal angle range immediately after postoperative ambulation (95% CI of the healthy group); 16 patients (non-ideal angle subgroup) were not fixed in the 95% CI of the healthy group, of which 14 patients (87.5%) had OC=A lower than 7.2° (lower limit of 95% CI of the healthy group), and 2 patients (12.5%) had POCA higher than 124.0° (upper limit of 95% CI in healthy group). The VAS score, JOA score and NDI of patients in the two subgroups were significantly improved compared with those before operation (P < 0.05). The VAS score and NDI of the ideal angle subgroup were higher than those of the non-ideal angle subgroup, but JOA score was lower than that of the non-ideal angle subgroup (P < 0.05). At the same time, dCSA [(4.0±6.8)°] in the ideal angle subgroup was significantly higher than that in the non-ideal angle subgroup [(-1.6±3.9)°; P < 0.05]. To conclude, the biomechanical balance between the occipitocervical region and subaxial cervical spine in patients with basilar invagination is different from that of normal healthy people. Therefore, it is not recommended to force OC2A and POCA to be fixed in the normal reference range during occipitocervical fusion for basilar invagination. Fixation of OC2A and POCA in the normal reference range will reduce the clinical efficacy of patients and accelerate the dCSA.