Anatomical Study of Position of the Rib Head for Placing Anterior Vertebral Body Screws in a Chinese Population.

Instrumentation of anterior vertebral body screws has become an important approach for treatment of unstable fracture or curvature of the spine, but little attention has been paid to the starting point of placing the screws and variability of the rib head position. We analyzed the variability of rib head position in a Chinese population in terms of the spinal canal and vertebral body using computed tomography (CT). Images from transverse CT scan of the T4-TI 2 vertebral bodies of 30 normal individuals were 3D reconstructed, and analyzed for measurement of parameters, which included: 1 ) distance between the left (or right) anterior border of the rib head and the posterior (or anterior) margin of the vertebral body [L(R )ARHP(A)VB], 2) left (or right) transverse dimension [L(R)TD], 3) left (or right) posterior (or anterior) safe angle [L(R)P(A)SA], and 4) distance between the inferior border of the left (or right) rib head and the superior (or inferior) end-plate in the sagittal plane [IL(R)RHS(1)EP]. The ARHPVB, PSA, and IRHIEP gradually decrease, but ARHAVB, TD, ASA, and IRHSEP gradually increase from T4 to TI2, indicating that the position of the rib head changes from a more anterior position to a more posterior position and from a more superior position to a more inferior position as the number of the vertebra increases. Our study has provided comprehensive reference guide for accurate and sate instrumentation of vertebral body screws in treating related spine diseases. [ABSTRACT FROM AUTHOR]