ABSTRACT
Objective To explore the orientation relationships and changing rules of pedicle screw entry point (PSEP) on the posterior bony landmarks in middle-upper thoracic vertebrae in adults by measuring parameters of 3-D reconstruction CT images. Methods CT images of the middle-upper thoracic vertebrae from 30 healthy adults were used for 3-D reconstruction to observe the anatomical characteristics of posterior bony landmarks, including transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina. The following basic parameters, including PSEP-to-midline distance (PMD), transverse process-lamina concave-to-midline distance (CMD) and half lamina width (HLW), and target parameters, including PSEP-to-transverse process-lamina concave distance (PCD), entry point location ratio (EPLR) and PSEP-to-superior ridge of transverse process distance (PRD) were determined on reconstructed CT images from T1 to T10. The differences of bilateral measurements of all parameters and the differences of basic parameters were analyzed, and the changing rules of target parameters measurements from T1 to T10 were summarized. Results The transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina of middle-upper thoracic vertebral characterized by obvious and constant anatomical marks with less proliferative. The left and right PMD, CMD, HLW, PCD, EPLR, and PRD were (14.14±2.63) mm and (14.59±2.58) mm, (10.45±2.12) mm and (10.51±2.02) mm, (16.30±1.48) mm and (16.39±1.61) mm, (4.56±1.03) mm and (4.47±0.94) mm, 0.35±0.26 and 0.33±0.30, and (-1.62±1.90) mm and (-1.63±1.44) mm, respectively. There was no significant difference in the measured values between the two sides of the above parameters (P>0.05). Except that the difference between PMD and HLW in T2 was not significant (P>0.05), the differences between basic parameters in the other segments were statistically significant (P<0.05). PCD of T1 to T10 showed a trend of decrease first and then significant increases in T1, T2, T9, and T10 compared with in T3-T8 (P<0.05). EPLR of T1-T10 showed a trend of increase first and then decrease, in which EPLR in T1, T2 and T3 were significantly lower than in the following any segments (P<0.01), and in the T4-T6 and T10 were significantly lower than in T7-T9 (P<0.01). PRD of T1-T10 showed a trend of increase first and then decrease, in which the PRD in T1, T2 and T3 were significantly lower than in the following any segments, and in the T4-T6 were lower than T7-T10 (P<0.01). Conclusion There is constant orientation relationship and changing rules of PSEP in the middle-upper thoracic vertebrae on the posterior bony landmarks, such as transverse process-lamina concave, superior ridge of transverse process and outer edge of the lamina, and it can serve as a new clinical choice.