Comparison of the Outcomes between AO Type B2 Thoracolumbar Fracture with and without Disc Injury after Posterior Surgery

Abstract

Objective: The type AO B2 thoracolumbar fracture is a kind of flexion-distraction injury and the effect of disc injury on treatment results of patients with B2 fracture remains unclear. The objective of the current study was to compare and analyze the outcomes in AO Type B2 thoracolumbar fracture patients with and without disc injuries in terms of the Cobb angle of kyphosis, the incidence of complication, and the rate of implant failure.

Methods: This is a retrospective study. Of the 486 patients with thoracolumbar fractures who underwent posterior fixation, 38 patients with AO type B2 injuries were included. All the patients were divided into two groups according to changes in the adjoining discs. Disc injury group A included 17 patients and no disc injury group included 21 patients. Clinical and radiologic parameters were evaluated before surgery, after surgery, and at follow-up. Clinical outcomes included visual analogue scale (VAS) scores, incidence of complications, and incidence of implant failure. Radiologic assessment was accomplished with the Cobb angle (CA), local kyphosis (LK), percentage of anterior vertebral height (AVBH%), intervertebral disc height, and intervertebral disc angle. Fisher's precision probability tests were employed and chi square test were used to compare categorical variables. Paired sample t tests and independent-sample t tests were used to compare continuous data.

Results: Disc injury mainly involved the cranial disc (15/19, 78.9%). The mean follow-up period for the patients was 30.2 ± 20.1 months. No neurologic deterioration was reported in the patients at the last follow-up. Radiological outcomes at the last follow-up showed significant differences in the CA (18.59° ± 13.74° vs 8.16° ± 9.99°, P = 0.008), LK (12.74° ± 8.00° vs 6.55° ± 4.89°, P = 0.006), and %AVBH (77.16% vs 90.83%, P = 0.01) between the two groups.Implant failure occurred after posterior fixation in five patients with disc injury who did not undergo interbody fusion during the initial surgery. Additionally, in the subgroup analysis, interbody fusion in the implant failure group were significantly different than in the no implant failure group (0% vs 75%, P = 0.009).

Conclusions: AO B2 fracture patients with disc injury have higher risk of complications, especially implant failure after posterior surgery. Interbody fusion should be considered in AO type B2 fracture patients with disc injury.

Keywords: Disc injury; Flexion distraction injury; Posterior surgery; Thoracolumbar fracture.

Fig. 1

Classification of traumatic intervertebral disc lesions in B2 injuries: Photographs of discs showing (A) grade 0 (cranial), (B) grade 1 (cranial), (C) grade 2 (caudal), and (D) grade 3 (cranial)

Fig. 2

Radiological measurement using plain lateral radiography. AVBH = [2AVH0/(AVH1 + AVH2) × 100]. UIDH = (a1 + a2 + a3)/3, LIDH = (b1 + b2 + b3)/3. CA, Cobb angle; LK, Local kyphosis; AVBH, anterior vertebral body height; UIDA, upper intervertebral disc angle; LIDA, lower intervertebral disc angle

Fig. 3

The flow chart of the study

Fig. 4

A 19‐year‐old male who presented with an AO Type B2 fracture at L1‐L2 and severe back pain. (A, B) CT scan of the lumbar spine showed an L2 fracture involving the vertebral body and extending through the bilateral pedicle posteriorly. (C) Preoperative MRI revealed disruption of the posterior ligamentous complex, including ligamentum flavum and supraspinous ligament, but the adjacent discs were intact. (D) The patient underwent posterior long pedicle screw fixation without arthrodesis. Postoperative lateral radiograph showed satisfactory restoration of the spinal alignment and the L2 anterior vertebral body height. (E) CT scan showing internal fixation with pedicle screws in situ at 18 months postoperatively, without loss of correction. (F) After implant removal, the patient denied any lower back pain, and the lateral radiograph showed healing of the fracture in the vertebral body at L2

Fig. 5

A 64‐year‐old male with a T12 chance fracture (AO B2) caused by a fall from height. (A) Preoperative sagittal CT images show transosseous failure of the posterior column at T12 with an inferior endplate fracture in the vertebral body. (B) MR image showing a signal increase in the T12/L1 disc, indicating edema of the disc. (C) The patient underwent posterior long percutaneous pedicle screw fixation without fusion. Postoperative lateral radiograph showed correction of kyphosis from 16° to 13°. (D) After 6 months, the X‐rays showed pedicle screw failure at T11, and T12 had kyphosis (Cobb angle 31°). (E) Lateral radiographs taken at 15 months after the surgery show loosening of the implant. The Cobb angle was increased to 38° in the thoracolumbar junction. (F) MRI depicts an intraosseous herniation in the fractured vertebra

Fig. 6

A 46‐year‐old female patient who had a fall from a height. She suffered a L1 B2 with L1 A3 fracture according to the AO Classification. (A) Sagittal CT scans show the flexion‐distraction fracture of L1. (B) Preoperative MRI showing hyperintense appearances in the T12/L1 disc (arrow). (C) Postoperative X‐ray lateral plain showed the Cobb angle was corrected from 20° to 10°. (D) 8 months after the initial operation, the patient complained of severe back pain. Lateral plain radiograph showed rod breakage (arrow) and recurrent kyphosis (Cobb angle = 29°) (E) The patient underwent revision surgery and interbody fusion atT11‐L3, the sagittal alignment was restored (Cobb angle = 1°). (F) At the 2‐year follow‐up after the revision surgery, lateral X‐ray showed solid fusion at T12/L1, and no loss of correction. (Cobb angle = 3°)

Fig. 7

A 48‐year‐old male patient who had a vehicle accident. He suffered a L1‐L2 B2 with L2 A4 fracture according to the AO Classification. (A) Preoperative MRI showing abnormal shapes in the cranial and caudal discs near the L2 vertebral body, with appearances in the T12/L1 disc (arrows). (B) Sagittal CT scans show a flexion‐distraction fracture at L1‐L2. (C) After posterior short‐segment fixation, postoperative lateral plain X‐ray showed that kyphosis was corrected from 28° to 20°. (D) 17 months after the operation, kyphosis was increased, but the patient denied any pain in the back. Lateral plain showed the upper pedicle screws were inserted into the intervertebral space (arrow); the cobb angle was 36°. (E) The patient underwent revision surgery and interbody fusion at T12‐L4. Postoperative lateral standing radiographs show satisfactory sagittal alignment (Cobb angle 16°). (F) 3 months after the revision surgery, the lateral X‐ray did not show implant failure or loss of correction (Cobb angle = 19°)