Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

Introduction

Patients with adult idiopathic TL/L curves have been reported to have lower health-related quality of life (HRQOL) scores, related to Low Back Pain (LBP) and physical function, than patients with thoracic curves. In a previous study, it was suggested that lateral translation occurs in L3-L4 and that this correlates with back and radicular leg pain. The goal of this study was to identify early risks factors of lateral translation in patients with residual adolescent idiopathic scoliosis (AIS) with a thoracolumbar/lumbar curve.

Methods

We collected the complete radiographic and clinical data for consecutive preoperative AIS patients who have a TL/L Cobb angle >40^o. We included 50 patients (3 male, 47 female; age 41.5±17.2 years, TL/L Cobb angle 56.8°±10.2°). They were treated with corrective surgery using a posterior, or both anterior and posterior approaches, in our institute between June 2011 and January 2022. We measured L4 tilt using X-ray, and facet angle (FA), facet joint opening (FJO), facet vacuum (FJV), and vertebral bridging using CT. An intervertebral space with a slip of 6 mm or more on CT images was classified as a slipped vertebra. Student’s t-tests were used to compare the averages of continuous variables between groups with or without L3 slippage. Pearson correlation coefficients were calculated to determine the correlation between slip and bridging. A receiver operating characteristic (ROC) analysis was used to calculate the cutoff value for L4 tilt. Multivariate logistic regression analysis was performed to obtain risk factors for slip as the dependent variable.

Result

The total number of slipped vertebrae was 31, of which 4 were L1, 3 were L2, 21 were L3, and 11 were L4. As L3 slippage was the most common, the patients were divided into groups according to the presence or absence of L3 slippage. Of the total patient population, 21 out of 50 patients were classified into the slip group.

There was a significant difference between the slip and nonslip groups for ΔFA, FJO, and FJV. In the multivariate logistic regression analysis, FJO and FJV were significant risk factors for L3 slippage.

There was a significant difference between the two groups in L4 endplate tilt. Using ROC analysis, the cut-off value for L3 slippage based on L4 tilt was 20.5°.

There were significant correlations between vertebral slippage and vertebral bridging. The strongest correlation was between L3 slippage and L2/L3 bridging. The number of patients with L1/L2 bridging and L2/L3 bridging was significantly greater in the slip group than the nonslip group.

Discussion

Facet joint instability, L4 tilt>20.5°, and vertebral bridging of vertebrae cranial to L3 were associated with L3 slippage. If these characteristics are taken into consideration during outpatient care, it may be possible to identify cases that will lead to LBP and to identify patients with risks for advanced curve progression early so that surgery can proceed at an early stage of progression.