Background:

There is evidence that the extent of vertebral bone marrow adiposity increases caudally along the vertebral column in children and adolescents. However, no studies have examined the lipid composition of bone marrow along the vertebral column, which may uniquely influence bone acquisition and metabolism during growth independent of the amount of bone marrow adipose tissue. The goal of this study was to characterize the pattern of lipid composition index measures from the thoracic to lumbar spine (T11-L4) among a sample of adolescents with idiopathic scoliosis (AIS) undergoing routine orthopedic surgical care for scoliosis correction.

Methods:

Adolescents between 14 and 18 years of age, with a confirmed diagnosis of AIS, and undergoing routine posterior spinal fusion surgery at our institution were initially included for this descriptive study. The surgery yielded transpedicular vertebral body marrow samples from T11 through L4; 11 participants had bone marrow samples from T11 through L2 and 4 of the 11 participants had marrow samples from T11 through L4. Lipid composition index measures, including the saturated, monounsaturated, and polyunsaturated index, were measured using a targeted lipidomics technique. Linear regression equation for the slope (m) and Pearson correlation coefficient (r) was computed to assess the pattern of lipid composition index measures along the vertebral column from T11 to L2 (n=11) and extended analysis to L4. Exploratory analyses were performed to examine the association between the pattern of lipid composition measures (individual slopes) and physical characteristics for T11-L2.

Results:

For T11-L2, the slope of the saturated index was near 0 (r=0.08; P=0.92), whereas the slopes of the unsaturated indices were approximately opposite of one another: the monounsaturated index exhibited a -0.55 change (r=0.58; P=0.42) per vertebra and the polyunsaturated index exhibited a 0.52 change (r=0.72; P=0.28) per vertebra in the caudal direction from T11-L2. For T11-L4, there were modest changes in slope for the saturated (m=0.12; r=0.30; P=0.57) and monounsaturated (m=-0.68; r=0.74; P=0.09) indices, while the polyunsaturated index slope remained similar (m=0.56; r=0.89; P=0.02). Age, sex, height, body mass, and BMI were not associated with the pattern of any of the lipid composition index measures.

Conclusions:

Study findings in this small sample of individuals with AIS suggest that the bone marrow saturated index may be relatively stable across T11-L4, while the monounsaturated index may decrease by 0.55-0.68% per vertebra and the polyunsaturated index may increase by 0.52-0.56% per vertebra in the caudal direction.