Cervical Alignment of Patients with Basilar Invagination: A Radiological Study

OBJECTIVE: To investigate the cervical alignment and the relative range of motion (ROM) in patients with basilar invagination (BI). METHODS: A total of 40 BI cases (38.1 years old ± 17.9 years old, 19 male and 21 female) and 80 asymptomatic individuals (33.8 years old ± 10.8 years old, 40 male and 40 female) were included. The Skull‐C(2)/Skull‐BV, Skull‐C(7), C(2)‐C(7)/BV‐C(7) wall angles, C(0)‐C(2)/C(0)‐BV, C(0)‐C(7), C(1)‐C(7), and C(2)‐C(7)/BV‐C(7) angles were measured in dynamic X‐ray images (including neutral, extension, and flexion positions). Correlation between the upper and lower cervical curvatures were analyzed. The total, extension, and flexion ROMs of these angles were calculated, respectively. RESULTS: The BI patients had a smaller C(0)‐C(2)/C(0)‐BV angle (18.2° ± 16.4° vs 30.9° ± 9.3°), but larger C(2)‐C(7)/BV‐C(7) (32.2° ± 16.1° vs 19.4° ± 10.6°) and C(2)‐C(7)/BV‐C(7) wall angles (37.8° ± 17.2° vs 23.6° ± 10.2°) than the control group in neutral position. The upper and lower curvatures correlated negatively in neutral (r = −0.371), extension (r = −0.429), and flexion (r = −0.648) positions among BI patients, as well as in extension position (r = −0.317) among control group. The BI patients presented smaller total ROMs in Skull‐C(2)/Skull‐BV (12.3° ± 16.6° vs 19.7° ± 10.9°), C(0)‐C(2)/C(0)‐BV (8.1° ± 11.1° vs 17.6° ± 10.5°), and C(0)‐C(7) angles (57.8° ± 14.2° vs 78.3° ± 17.9°), but a larger total ROM in C(2)‐C(7)/BV‐C(7) wall angle (52.8° ± 13.9° vs 27.0° ± 16.1°) than the control group. The BI patients also presented smaller extension ROMs in Skull‐C(2)/Skull‐BV (6.9° ± 9.4° vs 12.5° ± 9.3°), Skull‐C(7) (24.5° ± 10.9° vs 30.7° ± 12.5°), and C(0)‐C(2)/C(0)‐BV angles (4.4° ± 7.8° vs 9.9° ± 8.6°) than the control group. Moreover, the BI patients showed smaller absolute values of flexion ROMs in Skull‐C(2)/Skull‐BV (−5.2° ± 9.4° vs −7.3° ± 8.0°), C(0)‐C(2)/C(0)‐BV (−3.2° ± 8.8° vs −7.7° ± 8.7°), and C(0)‐C(7) angles (−33.2° ± 13.0° vs −52.8° ± 19.2°), but a larger absolute value of flexion ROM in C(2)‐C(7)/BV‐C(7) wall angle (−33.9° ± 14.8° vs −8.2° ± 15.1°). CONCLUSION: The cervical spine was stiffer in BI patients than the asymptomatic individuals, especially in the upper cervical curvature. The negative correlation between upper and lower cervical curvatures was more obvious in BI patients.