BP-C2 Angle Measurement And Its Integration In Occipitocervical Surgery Applications

Background:Occipital-cervical fusion surgery was first reported by Foerster in1927, occipital-cervical fusion surgery was considered as a effective method to cure the Occipital-cervical and upper cervical spine congenital malformations, traumatic fracture dislocation and other disorders caused by the Occipital-cervical or cervical spine instability later. It was essential to measure the Occipito-cervical angle that would be used to guide the head and neck fixed in a suitable location in intraoperative. At present, there is limited number of the literatures which concerned about the Occipito-cervical angle measurement and clinical application.Objective:By taking the cervical flexion, neutral and extension lateral X-ray film as well as head from the healthy subjects to measure the hard palate-C2angle (BP-C2) in order to determine the normal range of the occipito-cervical neutral position BP-C2angle and guide the treatment of occipital-cervical fusion surgery.Material and methods:Collecting50cases of healthy subjects, including24males and26females and had them taken the cervical flexion, neutral and extension lateral X-ray films as well as the head, the materials of X-ray films were used to measure the angle formed by the hard palate parallel lines with the C2vertebral body perpendicular in X-ray to the lower edge of the tangent (BP-C2)(Figure2) to determine the normal range of BP-C2angle. Then BP-C2angle was applied to our hospital’s17patients of Chiari malformation (including Chiari I type15cases, Chiari II type2patients) and a patient with fractures of the atlas(Jefferson fracture) in occipital-cervical fusion surgery in patients to determine the location of the head and neck and study the preoperative and postoperative measured values.Results:1. The BP-C2angle of50cases of healthy subjects measured in flexion was91.3°±5.6°, the neutral position measured BP-C2angle was100.0°±5.6°,the extension position measured BP-C2angle was115.3°±7.3°;24healthy male subjects measured in flexion position BP-C2angle was89.9°±5.9°, the neutral position measured BP-C2angle was99.8°±5.9°, the extension position measured BP-C2angle was116.2°±7.5°;26female healthy subjects measured in flexion position BP-C2angle was92.5°±5.1°, the neutral position measured BP-C2angle was100.2°±5.4°, the extension position measured BP-C2angle was114.5°±7.2°, the BP-C2angle in male and female healthy subjects in flexion position、 neutral position、 extension position which via two independent samples t-test analysis were of no significant difference (P>0.05).2. A case of atlas fracture patient postoperative neutral position of the BP-C2angle was97.5°, within the range of healthy neutral position BP-C2angle.3.17cases of Chiari malformation patients with preoperative flexion position measured BP-C2average angle was80.8°±12.3°, the neutral position measured BP-C2average angle was84.5°±12.5°, the extension position measured BP-C2average angle was91.1°±9.4°;17cases of Chiari malformation patients postoperative neutral position measured BP-C2average angle was87.8°±9.7°. Healthy subjects in flexion position with Chiari malformation patients with preoperative flexion position of the BP-C2angle, via two independent samples t-test, the difference was of statistically significant (P=0.000). Healthy subjects in neutral position with Chiari malformation patients with preoperative neutral position of the BP-C2angle, via two independent samples t-test, the difference was of statistically significant (P=0.000). Healthy subjects in extension position with Chiari malformation patients with preoperative extension position of BP-C2angle, via two independent samples t-test, the difference was of statistically significant (P=0.000).Chiari malformation patients with preoperative flexion position and the neutral position BP-C2angle, via two independent samples t-test, the difference was not statistically significant (P=0.395). Chiari malformation patients with preoperative neutral position and the extension position BP-C2angle, via two independent samples t-test, the difference was not statistically significant (P=0.092). Chiari malformation patients with preoperative neutral position and postoperative neutral position BP-C2angle, via two independent samples t-test, the difference was not statistically significant (P=0.398).Conclusions:1.50cases of healthy subjects in flexion position was91.3°±5.6°,the neutral position was100.0°±5.6°, the extension position was115.3°±7.3°.2. If did not obtain preoperative normal BP-C2angle for the non-deformity Occipito-cervical disorders which had to operate occipito-cervical fusion, according to healthy subjects BP-C2angle to guide the occipital-cervical fusion.3.17cases of Chiari malformation BP-C2angle in flexion position was80.8°±12.3°, the neutral position was84.5°±12.5°, the extension position was91.1°±9.4°, the BP-C2angle decreases compared with healthy subjects, with the significant of diagnosis.4. Chiari malformation patients who had Occipital-cervical joint stiffness, limited mobility, during operating Occipital-cervical fusion surgery, the adjustment of BP-C2angle in intraoperative should be decided according to the preoperative angle.