[Imaging study of "shell" phenomenon of thoracolumbar fractures after posterior reduction]

To analyze the imaging characteristics of vertebral "shell" phenomenon of thoracolumbar fractures after posterior reduction and to explore the relationship between vertebral "shell" and fracture healing.

Between January 2013 and December 2015, the clinical data of 116 patients with thoracolumbar fractures treated with posterior pedicle screw-rod system reduction and internal fixation were analyzed retrospectively. There were 72 males and 44 females, aged 22-66 years (mean, 43 years). Injury causes were traffic accident in 24 cases, falling from height in 54 cases, bruise in 38 cases. Fracture segment located at T ₁₁ in 5 cases, T ₁₂ in 38 cases, L ₁ in 52 cases, L ₂ in 21 cases. There were 51 cases of compressive fracture and 65 cases of burst fracture. The sagittal Cobb angle ranged from 8 to 27°, with an average of 15°. Degree of preoperative spinal compression ranged from 20% to 75%, with an average of 44%. Bone density measurement showed that normal bone mass in 30 cases, bone loss in 40 cases, osteoporosis in 41 cases, and severe osteoporosis in 5 cases. The number, pathological characteristics, and imaging regularity of the vertebral "shell" phenomenon were observed and analyzed by logistic regression.

All patients were followed up 11-18 months with an average of 13 months. A total of 72 cases of vertebral "shell" phenomenon mainly located in the vertebral anterior column and the end plate near the weak area (54/72, 75.0%). Most of them were in the irregular shape (50/72, 69.5%). The vertebral fracture line was related to the shape of the vertebral body and the displacement of the vertebral body after reduction. The outcome of the "shell" can be divided into disappeared type, reduced type, and collapse type, the volume of vertebral "shell" and its outcome were the risk factors for vertebral fracture healing.

The incidence of vertebral "shell" and nonuion of thoracolumbar fractures after posterior reduction are high. The main influencing factors are vertebral "shell" outcome and size.