Reduced Lumbar Indentation Value, Vertebral Body Cross-Sectional Area, and Paralumbar Cross-Sectional Area Predicts Reduced Pelvic Tilt prior to Complex Adult Spinal Deformity Surgery

Introduction: Sarcopenia is a known risk factor for reduced perioperative outcomes following various spinal surgery procedures. Additionally, pelvic tilt angle is associated with risk of proximal junctional kyphosis. Available data on the relationship between preoperative muscle health and pelvic tilt is insufficient, making it challenging to identify potential cascading effect. The purpose of this study is to determine the relationship between sarcopenia and pelvic tilt angle among patients undergoing complex adult spinal deformity surgery.

Methods: Patients that underwent complex adult spinal deformity surgery was included in the study. Sarcopenia was analyzed by using the psoas, paralumbar and vertebral cross-sectional area (CSA) at the L3 and L4 mid-vertebral body, and the lumbar indentation value (LIV) L4/L5 intervertebral disk on preoperative magnetic resonance imaging (MRI). Intraclass Correlation Coefficient (ICC) was calculated for analyzing inter-rater reliability. Patients were grouped in sex-specific terciles for each measured muscle CSA and LIV. Patients within the lowest tercile were defined as having reduced muscle health. The primary outcome measure was the preoperative pelvic tilt angle.

Results: 113 patients (86 females, 27 males, mean age 66.0  10.4 years) were included in the study. ICC for L4 vertebral body CSA was 0.806 (95% CI: 0.575-0.918), LIV L4/5 intervertebral disc was 0.889 (95% CI: 0.777-0.953), L4 Left paralumbar CSA was 0.867 (CI: 0.746-940), L4 Right paralumbar CSA was 0.882 (CI: 0.772-0.947), and L4 Total Paralumbar CSA was 0.915 (CI: 0.832-0.963).
Both male and female patients with lower tercile LIV had significantly lower preoperative pelvic tilt angle (p=0.047, p= < 0.001). Male patients with lower L4 vertebral CSA had lower preoperative pelvic tilt (p=0.018). Female patients with reduced left, right and total L4 paralumbar CSA had lower preoperative pelvic tilt angle (p=0.012, p=0.022, p=0.002).

Conclusion : Reduced LIV at the L4/L5 intervertebral disc, reduced L4 vertebral CSA (male patients), and reduced L4 paralumbar muscle health (female patients) are associated with reduced pelvic tilt among patients undergoing complex adult spinal deformity.