Correction loss following short-segment posterior fixation for traumatic thoracolumbar burst fractures related to endplate and intervertebral disc destruction

Abstract

Background: There has been widespread use of short-segment posterior fixation (SSPF) for traumatic thoracolumbar burst fractures. The relationship between the destruction of the vertebral endplate and adjacent disc and postoperative correction loss has been studied in only a few studies. This study investigated the risk factors for correction loss following SSPF.

Methods: Forty-eight patients (mean age 35.0 years) who underwent SSPF for thoracolumbar burst fractures were enrolled. The mean follow-up period was 25.7 months (12-98 months). The neurological status and postoperative back pain were assessed by the medical records. Segmental kyphotic angle (SKA) and anterior vertebral body height ratio (AVBHR) were measured radiographically to assess indirect vertebral body reduction and local kyphosis. Preoperative Sander's traumatic intervertebral disc lesion (TIDL) classification and AO classification were used to evaluate the severity of disc and vertebral endplate injury. The corrective loss was considered present if ΔSKA was ≥10°. A multivariate logistic regression analysis was performed to identify the risk factors associated with postoperative loss of correction.

Results: The fracture distribution was as follows: 10 at T12, 17 at L1, 10 at L2, 9 at L3, and 2 at L4. Vertebral fractures were classified in the following way: A3 in 13 patients, A4 in 11, B1 in 11, and B2 in 13. In 47 patients (98%), a union of the fractured vertebrae was achieved. SKA and AVBHR improved significantly after surgery from 11.6° to 3.5° and from 67.2 to 90.0%, respectively. However, the correction loss at follow-up was 10.4° and 9.7%, respectively. Twenty patients (42%) had severe TIDL (grade 3). Postoperative ΔSKA and ΔAVBHR were significantly higher in patients with TIDL grade 3 than with TIDL grade 0-2. The presence of cranial TIDL grade 3 and older age were significant risk factors for ΔSKA ≥10° on multivariate logistic regression analysis. All patients could walk at follow-up. TIDL grade 3 and ΔSKA ≥10° were associated with severe postoperative back pain.

Conclusions: Risk factors for loss of correction after SSPF for thoracolumbar burst fractures were severe disc and endplate destruction at the time of injury and older age.

Keywords: Correction loss; Endplate injury; Short-segment posterior fusion; Thoracolumbar burst fractures; Traumatic intervertebral disk lesion.

Fig. 1

Schematic diagrams of radiographic parameters. Segmental kyphotic angle (SKA) = θ, Anterior vertebral body height ratio (AVBHR) = c/(a + b)/2

Fig. 2

Classification of traumatic intervertebral disc lesion (TIDL). A case of AO type A3 fracture at L3. CT shows a fracture of the cranial endplate and MRI shows infraction of the disc into the vertebral body (white triangles) which means a TIDL grade 3. The caudal disc showed a TIDL grade 2

Fig. 3

A 39-year-old woman with L2 burst fracture (AO A3). CT (A) and MRI (B) showed severe damage of the cranial endplate and infraction of the disc into the vertebral body (TIDL grade 3). The fractured vertebra was reduced after surgery (C). At follow up, fractured vertebra showed bony union, however disruption of the vertebral endplate and degeneration of intervertebral disc resulted in correction loss and breakage of the pedicle screw (D, E). Panel E shows residual endplate deformity

Fig. 4

Preoperative and postoperative neurological status using the ASIA impairment scale