Purpose. To radiographically assess the level of the umbilicus (i.e. latitude) relative to the anterior lumbar spine based on varying pelvic incidence (PI) magnitudes.

 

Methods. Pediatric patients (ages 10-18 years) at a single institution with a previously obtained CT abdomen/pelvis were identified and reviewed. Excluded were patients with prior spine surgery, spinal deformity, and/or underlying lumbar spinal degenerative pathology. On the CT’s sagittal images, two radiologists independently recorded the vertebral level/disc space that corresponded to the latitude of the umbilicus. On the CT’s scout lateral image, two spine surgeons measured the PI. The spinal level corresponding to the umbilicus’ latitude was compared between 3 groups based on PI magnitude: low (<45°), middle (45°-65°), and high (≥65°).

 

Results. One-hundred seven patients (average age=14.8±2.0 years; 62.6% female) met inclusion criteria. Of all patients, the umbilicus’ level ranged from the L3-4 disc to the L5 vertebral body with the L4-5 disc (36.4%) and L4 vertebral body (29.0%) being the most common levels. Average PI was 47.2° ± 11.9° (Low PI – 41.1%; Middle PI – 46.7%; High PI – 12.1%). The umbilicus’ level relative to the spine significantly varied based on PI magnitude (p<0.001). In Low PI, the majority’s umbilicus corresponded to the L4-5 disc (50%) or L5 vertebral body (18.2%). In Middle PI, the majority’s umbilicus was at the L4 vertebral body (34.0%) and L4-5 disc (34.0%). In High PI, the majority’s umbilicus corresponded to the L3-4 disc (38.5%) or L4 vertebral body (46.2%).