RESUMEN
PURPOSE: To elucidate whether specific spinopelvic morphologies affect the subsequent spinal sagittal alignments and determine the alignment patterns. METHODS: Whole-spine standing radiographs of 244 patients were analyzed. Sagittal alignment parameters were compared according to the three types of pelvic version: anteverted pelvis (AP), neutral pelvis, and retroverted pelvis (RP), grouped per the amount of pelvic tilt (PT) and the ratio of sacral slope to pelvic incidence (PI). Incidence angles of inflection points (IAIPs) were defined as the angle between a line from the center of the femoral heads through the midpoint of the sacral superior endplate and a line perpendicular to each L1, T1 superior endplate, C2 inferior endplate, and the C1 ring, respectively. RESULTS: C1 incidence equaled to the geometrical sum from the pelvis to the C1 vertebra; it also equaled the sum of the C1 slope and PT (p < 0.001). Moving from the AP group to the RP group, there were progressive increases in PT, PI, and IAIPs and decreases in LL, and SS/PI (p < 0.001). Negative correlation was observed between the pelvic anteversion and the IAIPs, and a significant positive correlation was observed between the pelvic retroversion and the IAIPs. CONCLUSION: IAIPs are novel PI-relevant radiographic parameters reflecting the relationship between the pelvis and the spinal alignment. An anteverted pelvis requires more lumbar lordosis than pelvic incidence and aligns with low IAIPs, and a retroverted pelvis requires less lumbar lordosis than pelvic incidence and aligns with high IAIPs. These slides can be retrieved under Electronic Supplementary Material.
Asunto(s)
Lordosis , Adulto , Anciano , Humanos , Lordosis/diagnóstico por imagen , Vértebras Lumbares , Persona de Mediana Edad , Pelvis/diagnóstico por imagen , Postura , Radiografía , Sacro/diagnóstico por imagen , Adulto JovenRESUMEN
OBJECTIVE: To analyze the correlation between C2 incidence (C2I) and cervical and thoracolumbar sagittal parameters and determine the effectiveness of C2I for evaluating global spinopelvic sagittal alignment. METHODS: Whole spine standing lateral radiographs of 226 patients (mean age, 47.8 ± 11.3 years; 63% women) were analyzed. Spinopelvic parameters and incidence angles of inflection point were evaluated. The correlation between each parameter was analyzed using Pearson correlation coefficient and linear regression. Using C2I quartiles, 3 groups were compared to distinguish different alignment patterns by analysis of variance. RESULTS: C2I correlated significantly with C0-2 lordosis (C02L), C2-7 lordosis (C27L), C0-7 lordosis , C2 slope (C2S), T1 slope-C27L, C2-7 sagittal vertical axis, and chin brow vertical angle (CBVA) in cervical parameters (r = -0.378, r = 0.533, r = 0.251, r = 0.688, r = 0.681, r = 0.278, and r = 0.351, respectively; P < 0.01) and with T1 incidence (T1I), pelvic incidence-lumbar lordosis mismatch, L1 incidence (L1I), pelvic tilt (PT), and pelvic incidence (PI) (r = 0.480, r = 0.516, r = 0.518, r = 0.635, and r = 0.392, respectively; P < 0.01) in thoracolumbar alignment parameters. C2I was estimated by the 2 following equations: C2I = 1.0C2S + 1.0PT and C2I = 0.98PI - 0.99LL + 0.98 thoracic kyphosis - 1.0C27L (R2 = 0.97, P < 0.001, respectively), with an excellent coefficient of determination. PI, PT, L1I, T1I, and C2S were increased significantly between groups using C2I quartiles. In the high C2I group, C27L and C0-7 lordosis had less lordosis; however, C02L had more lordosis and C2-7 sagittal vertical axis and CBVA showed higher than low C2I group. CONCLUSIONS: C2I was significantly correlated with both cervical and thoracolumbar sagittal parameters, and different sagittal alignment patterns were presented regarding the amount of C2I. As the geometric summation from the pelvis to C2 vertebra, C2I would be a beneficial clue to connect correlation chains of spinal sagittal alignment.