Relation analysis between coronal imbalance and spine-pelvic parameters in adult spinal deformity

English Keywords:Adult spinal deformity  Coronal imbalance  Radiological parameters  Coronal balance distance

English Abstract:

  【Abstract】 Objectives: To explore the prevalence of coronal imbalance, and to demonstrate the relationship between coronal imbalance and spine-pelvic parameters by investigating the pre-operative radiographic parameters in adult spinal deformity(ASD). Methods: A total of 161 patients with ASD in our hospital was reviewed. The radiographic parameters were measured on the pre-operative anteroposterior and lateral spinal radiographs. Parameters on coronal plane included curve angle(Cobb), compensatory angle(C-Cobb), types of curvature(left or right), the involved vertebrae and the subluxation degree of structural curvature, the degree of apical vertebra rotation(AR), coronal pelvic tilt angle(C-PT), coronal balance distance(CBD): the coronal offset between C7PL and the center of S1 endplate. Parameters on sagittal plane included thoracic kyphosis(TK), thoracolumbar kyphosis(TLK), lumbar lordosis(LL), sacral slope(SS), pelvic tilt(PT), pelvic incidence(PI), sagittal vertical axis(SVA). Patients were divided into two groups, group A(the imbalance group, CBD＞30.00mm) and group B(CBD<30.00mm). Radiographic parameters in imbalance and balance group were compared by using independent samples t-test. The ratio of gender, and the types of curve in the two groups were compared by using χ2-tset. Results: All the 161 patients were included in this study, 29 males(M) and 132 females(F), with the age ranging from 45 to 79 years(63.9±8.4 years). Among them, 106 patients had left side curve, and the other 55 patients had right side curve. Coronal imbalance occurred in 31 patients(M∶F, 8∶23), but did not occure in the other 130 patients(M∶F, 21∶109). The coronal imbalance rate was 19.25%(31/161). The age, gender, types of curve, TK, TLK, LL, SS, PT, PI and SVA in the two groups had no significant differences(P>0.05). The location of apical vertebra had significant difference between the two groups(χ2=12.692, P<0.001), the apical vertebrae were all located at L2 to L3 segments. Although the Cobb degree of the structural and the compensatory curvature in the two groups had no difference respectively(P＞0.05), the involved vertebrae were less in group A than those in group B(3.87±0.85 vs 4.36±0.95, t=2.639, P=0.009), and the degree of apical vertebra rotation in group A was much more than that in group B(2.81±0.60 vs 2.32±0.77, t=-3.796, P<0.001). The thoracolumbar kyphosis degrees in group A were much bigger than those in group B(t=-2.445, P=0.017). The 121 patients whose apical vertebra located at L2 to L3 segment were divided into two groups, group A′(the imbalance group, CBD＞30.00mm) including 31 patients and group B′(CBD<30.00mm) including 90 patients. The curve angle(Cobb), the compensatory angle(C-Cobb), the involved vertebrae and the subluxation degree of structural curvature, and the degree of apical vertebra rotation(AR) of the two groups were compared by using independent samples t-test respectively. The similar results were found: although the Cobb degree of the structural and the compensatory curvature had no significant difference respectively(P＞0.05), the involved vertebrae were less in group A′ than those in group B′(3.87±0.85 vs 4.23±0.85, t=2.052, P=0.04), and the degree of apical vertebra rotation in group A′ was much more than that in group B′(2.81±0.60 vs 2.27±0.68, t=-3.905, P<0.001). Conclusions: The prevalence of pre-operative coronal imbalance in ASD patients is about 20%. The　apical vertebrae of the structural curvatures locate at L2 to L3 segments. Ｔｈｅ　patients who have more rotation degrees, less involved vertebrae, may more easily suffer from coronal imbalance.