Correlation between the morphological characteristics of the facet joints and the ossification of ligamentum flavum in the lower thoracic spine

Abstract

Objective To investigate the correlation between the morphological characteristics of the facet joints and the ossification of ligamentum flavum in the lower thoracic spine. Methods 168 patients admitted at the First affiliated Hospital of Zhengzhou University who did the 64 layer CT scan in lower thoracic were chosen and divided into case group (88) and normal group (80). The PACS imaging system was applied to measure the angle of the bilateral articular surface of T8-T12 in the sagittal plane and axial plane. All the data were analyzed statistically. Results The difference of sex ratio between two group have no statistical significance (P=0.120); The average age of TOLF group is (50.61±12.13), and normal group is (50.49±10.83), there is no statistical significance between the two group (P=0.096). The angle of articular surfaces in the sagittal plane of TOLF group: T8 (75.60±3.31)° left, (75.42±3.59)° right; T9 (78.78±3.65)° left, (79.60±3.51)° right; T10 (83.40±2.94)° left, (84.64±3.32)° right; T11 (97.61±16.67)° left, (97.30±14.62)° right; T12 (124.13±12.36)° left, (131.50±11.13)° right. The angle of articular surfaces in the axial plane of TOLF group: T8 (78.00±3.21)° left, (77.53±3.14)° right; T9 (78.58±3.18)° left, (78.73±2.92)° right; T10 (84.21±4.00)° left, (83.70±3.40)° right; T11 (82.18±2.79)° left, (83.05±3.27)° right; T12 (77.13±3.81)° left, (78.20±4.05)° right. The angle of articular surfaces in the sagittal plane of normal group: T8 (72.96±2.98)° left, (72.39±3.22)° right; T9 (77.50±2.98)° left, (76.72±3.05)° right; T10 (81.71±3.54)° left, (81.36±2.83)° right; T11 (105.97±10.43)° left, (106.36±9.88)° right; T12 (131.85±20.78)° left, (135.80±16.27)° right. The angle of articular surfaces in the axial plane of normal group: T8 (75.75±2.66)° left, (75.07±2.90)° oright; T9 (76.82±3.02)° left, (77.24±2.88)° right; T10 (81.24±3.75)° left, (81.94±2.60)° right; T11 (77.64±3.28)° left, (78.69±3.10)° right; T12 (74.69±2.67)° left, (74.42±4.19)° right. There are statistical significance about the difference of the angle of articular surfaces in the sagittal plane in all the segment except the left side of T9 and the right side of T12 (P=0.000, 0.000, 0.088, 0.000, 0.007, 0.000, 0.007, 0.001, 0.037, 0.171). The difference of the angle of articular surfaces in the axial plane between the two groups all have statistical significance in all segments (P=0.000, 0.000, 0.008, 0.016, 0.000, 0.004, 0.000, 0.000, 0.001, 0.000). In the TOLF group, the angle of left or right side in the sagittal plane all have statistical significance exceptT8 and T9, T9 and T10 (P=0.000); the angle of left or right side in the axial plane all have statistical significance except T8 andT9, T8 and T12, T9 and T12, T11 and T12 (P=0.000). There are a phenomenon that the angle of left and right side in the sagittal plane in the same segment are asymmetry in both two groups, it is 12 in TOLF group, and 13 in normal group, we found that the differences between the two groups have statistical significance by chi square test (P=0.020). Conclusion Ossification of the ligamentum flavum most frequently occurred at T10 and T11 in the lower thoracic segments. The more the direction of the lower thoracic articualr surfaces is close to coronal plane, the higher the incidence of ossification of ligamentum flavum. There is a correlation between the asymmetry of the bilateral angles in the sagittal plane and the occurrence of Ossification of ligamentum flavum. Key words: Lower thoracic spine; Ossification of ligamentum flavum; Morphological characteristics of the facet joints