Increased Lumbar Lordosis and Smaller Vertebral Cross-Sectional Area Are Associated With Spondylolysis.

STUDY DESIGN: A cross-sectional comparison of vertebral morphology and lumbar lordosis (LL) in adolescents with and without spondylolysis. OBJECTIVE: To test the hypothesis that in addition to LL, vertebral cross-sectional area (CSA) is also associated with spondylolysis. SUMMARY OF BACKGROUND DATA: Recent data indicate that the CSA of the vertebral body is a determinant of LL, which has been shown to be associated with spondylolysis. METHODS: Using magnetic resonance imaging, we compared the degree of LL from L1 to L5 and the CSA of the lumbar vertebrae in 35 adolescents (16 females and 19 males) with spondylolysis and 86 healthy controls (36 females and 50 males) of similar sex, age, height, and weight. RESULTS: There were no significant differences in age, height, weight, or vertebral height between subjects with and without spondylolysis, regardless of sex. In contrast, LL angle in spondylolysis patients was 57% and 51% greater in girls and boys with spondylolysis; 44.1 ±â€Š10.4° versus 28.1 ±â€Š9.8° and 34.8 ±â€Š5.9° versus 23.0 ±â€Š6.0° for girls and boys, respectively (both P's < 0.0001). Additionally, values for vertebral CSA were on average, 8% and 10% smaller in females and males with spondylolysis; 7.6 ±â€Š0.8 cmversus 8.3 ±â€Š1.1 cm and 8.4 ±â€Š1.6 versus 9.3 ±â€Š1.6 for girls and boys, respectively (both P's ≤ 0.039). Multiple linear and logistic regression analyses indicated that the CSA of the vertebral body was negatively associated with LL angle and an independent predictor of the presence of spondylolysis. This was true regardless of whether girls and boys were analyzed together or independently, and whether LL angle was measured from L1 to L5 or S1. CONCLUSION: We provide evidence that patients with spondylolysis have increased LL and smaller vertebral CSA. LEVEL OF EVIDENCE: 4.

Vertebral cross-sectional growth: A predictor of vertebral wedging in the immature skeleton.

The degree of vertebral wedging, a key structural characteristic of spinal curvatures, has recently been found to be negatively related to vertebral cross-sectional area (CSA). The purpose of this longitudinal study was to examine the relation between vertebral cross-sectional growth and vertebral wedging progression within the immature lumbar spine. Using magnetic resonance imaging (MRI), we analyzed the potential association between increases in lumbar vertebral CSA and changes in L5 vertebral wedging in 27 healthy adolescent girls (ages 9-13 years) twice within a two-year period. Vertebral CSA growth was negatively associated with changes in posteroanterior vertebral wedging (r = -0.61; p = 0.001). Multiple regression analysis showed that this relation was independent of gains in age, height, and weight. When compared to the 14 girls whose vertebral wedging progressed, the 13 subjects whose vertebral wedging decreased had significantly greater vertebral cross-sectional growth (0.39 ± 0.25 vs. 0.75 ± 0.23 cm2; p = 0.001); in contrast, there were no significant differences in increases in age, height, or weight between the two groups. Changes in posteroanterior vertebral wedging and the degree of lumbar lordosis (LL) positively correlated (r = 0.56, p = 0.002)-an association that persisted even after adjusting for gains in age, height, and weight. We concluded that in the immature skeleton, vertebral cross-sectional growth is an important determinant of the plasticity of the vertebral body; regression of L5 vertebral wedging is associated with greater lumbar vertebral cross-sectional growth, while progression is the consequence of lesser cross-sectional growth.

Association Between Vertebral Cross-sectional Area and Vertebral Wedging in Children and Adolescents: A Cross-sectional Analysis.

A small vertebral cross-sectional area (CSA) imparts a mechanical disadvantage that escalates the risk for vertebral fractures in elderly populations. We examined whether a small vertebral CSA is also associated with a greater degree of vertebral wedging in children. Measurements of vertebral CSA, lumbar lordosis (LL) or thoracic scoliosis angle, and vertebral wedging were obtained in 100 healthy adolescents (50 boys and 50 girls) and 25 girls with adolescent idiopathic scoliosis (AIS) using magnetic resonance imaging. Vertebral CSA of the lumbar vertebrae negatively correlated to the degree of posteroanterior vertebral wedging at L5 (r = -0.49; p < 0.0001); this was true whether all subjects were analyzed together or boys and girls independently. In contrast, we found a positive correlation between the degree of LL and vertebral wedging (r = 0.57; p < 0.0001). Multiple regression analysis showed that the association between vertebral CSA and wedging was independent of age and body mass index. In girls with AIS, vertebral CSA negatively correlated to the degree of lateral thoracic vertebral wedging (r = -0.66; p = 0.0004), an association that persisted even after accounting for age and body mass index. Additionally, Cobb angle positively correlated to lateral thoracic vertebral wedging (r = 0.46; p = 0.021). Our cross-sectional results support the hypothesis that smaller vertebral CSA is associated with greater vertebral deformity during growth, as in adulthood. © 2017 American Society for Bone and Mineral Research.

Biomechanical Modeling of Spine Flexibility and Its Relationship to Spinal Range of Motion and Idiopathic Scoliosis.

STUDY DESIGN: Cross-sectional. OBJECTIVE: To examine the relationships between spine morphology, spine flexibility, and idiopathic scoliosis. BACKGROUND: Girls have a higher incidence of clinically significant scoliosis than boys, along with smaller vertebrae and greater flexibility. Based on biomechanical modeling, we hypothesized that smaller vertebral width relative to intervertebral disc (IVD) height would be associated with both greater lateral flexibility of the spine and with idiopathic scoliosis. METHODS: Magnetic resonance imaging was used to measure IVD height, vertebral width, and paraspinous musculature in 22 girls with mild and moderate idiopathic scoliosis and 29 girls without scoliosis ages 9-13 years. Clinical measurement of maximum lateral bending was also performed in the girls without scoliosis. A simple biomechanical model was used to estimate bending angle from the ratio of IVD height to vertebral half-width for L1-L4. The average ratio (Ravg) and calculated total bending angle (αtot) for L1-L4 were compared to the clinical measurements of lateral bending flexibility in the control group. These measures were also compared between the scoliosis and control groups. RESULTS: There was a significant positive relationship between clinical flexibility and both Ravg (p = .041) and αtot (p = .042) adjusting for skeletal age, height, body mass index, and paraspinous muscle area as covariates. The ratio was significantly higher (Ravg = 0.45 vs. 0.38, p < .0001) and the bending angle was significantly greater (αtot = 107° vs. 89°, p < .0001) for girls with scoliosis compared with controls. CONCLUSION: These results suggest that differences in spine morphology and corresponding changes in spine flexibility may be related to idiopathic scoliosis. If these relationships can be corroborated in larger prospective studies, these easily measured morphologic traits may contribute to a better understanding of the etiology of idiopathic scoliosis and an improved ability to predict scoliosis progression. LEVEL OF EVIDENCE: Level III.

Association between vertebral cross-sectional area and lumbar lordosis angle in adolescents.

Lumbar lordosis (LL) is more prominent in women than in men, but the mechanisms responsible for this discrepancy are poorly defined. A recent study indicates that newborn girls have smaller vertebral cross-sectional area (CSA) when compared to boys-a difference that persists throughout life and is independent of body size. We determined the relations between vertebral cross-sectional area (CSA) and LL angle and whether sex differences in lumbar lordosis are related to sex differences in vertebral CSA. Using multi-planar magnetic resonance imaging (MRI), we measured vertebral cross-sectional area (CSA) and vertebral height of the spine of 40 healthy boys and 40 girls, ages 9-13 years. Measures of the CSA of the lumbar vertebrae significantly differed between sexes (9.38 ± 1.46 vs. 7.93 ± 0.69 in boys and girls, respectively; P < 0.0001), while the degree of LL was significantly greater in girls than in boys (23.7 ± 6.1 vs. 27.6 ± 8.0 in boys and girls, respectively; P = 0.02). When all subjects were analyzed together, values for LL angle were negatively correlated to vertebral CSA (r = -0.47; P < 0.0001); this was also true when boys and girls were analyzed separately. Multivariate regression analysis indicated that vertebral CSA was independently associated with LL, even after accounting for sex, age, height or vertebral height, and weight. Similar negative relations were present when thoracic vertebrae were analyzed (Model P < 0.0001, R2 = 0.37, thoracic vertebral CSA slope P < 0.0001), suggesting that deficient vertebral cross-sectional dimensions are not merely the consequence of the anterior lumbar curvature. We conclude that vertebral CSA is negatively associated with LL, and that the greater degree of LL in females could, at least in part, be due to smaller vertebral cross-sectional dimensions. Studies are needed to examine the potential relations between vertebral CSA and spinal conditions known to be associated with increased LL, such as spondylolysis and spondylolisthesis.

Small vertebral cross-sectional area and tall intervertebral disc in adolescent idiopathic scoliosis.

BACKGROUND: When compared to boys, girls have smaller vertebral cross-sectional area, which conveys a greater spinal flexibility, and a higher prevalence of adolescent idiopathic scoliosis. OBJECTIVE: To test the hypothesis that small vertebral cross-sectional area and tall intervertebral disc height are structural characteristics of patients with adolescent idiopathic scoliosis. MATERIALS AND METHODS: Using multiplanar imaging techniques, measures of vertebral cross-sectional area, vertebral height and intervertebral disc height in the lumbar spine were obtained in 35 pairs of girls and 11 pairs of boys with and without adolescent idiopathic scoliosis of the thoracic spine matched for age, height and weight. RESULTS: Compared to adolescents without spinal deformity, girls and boys with adolescent idiopathic scoliosis had, on average, 9.8% (6.68 ± 0.81 vs. 7.40 ± 0.99 cm(2); P = 0.0007) and 13.9% (8.22 ± 0.84 vs. 9.55 ± 1.61 cm(2); P = 0.009) smaller vertebral cross-sectional dimensions, respectively. Additionally, patients with adolescent idiopathic scoliosis had significantly greater values for intervertebral disc heights (9.06 ± 0.85 vs. 7.31 ± 0.62 mm and 9.09 ± 0.87 vs. 7.61 ± 1.00 mm for girls and boys respectively; both P ≤ 0.011). Multiple regression analysis indicated that the presence of scoliosis was negatively associated with vertebral cross-sectional area and positively with intervertebral disc height, independent of sex, age and body mass index. CONCLUSION: We provide new evidence that girls and boys with adolescent idiopathic scoliosis have significantly smaller vertebral cross-sectional area and taller intervertebral disc heights - two major structural determinants that influence trunk flexibility. With appropriate validation, these findings may have implications for the identification of children at the highest risk for developing scoliosis.

Changes in Brown Adipose Tissue and Muscle Development during Infancy.

OBJECTIVE: To examine the relationship between brown adipose tissue (BAT) and muscle development, two tissues that derive from a common cell lineage, during the first 6 months of postnatal life. STUDY DESIGN: Thirty healthy term infants (15 males and females) underwent whole-body magnetic resonance imaging examinations. Measurements of BAT in the supraclavicular area as well as measures of trunk musculature and subcutaneous adiposity were obtained at birth and at 6 months of age. RESULTS: Paraspinous musculature and subcutaneous white adipose tissue (WAT) increased, and the proportion of BAT in the supraclavicular area decreased during infancy. Although measures of BAT did not correlate with paraspinous musculature through the first 6 months of life (r = -0.35; P = .09), BAT was a significant predictor of paraspinous musculature after adjusting for weight, body length, and WAT (P = .002); infants with the smallest decreases in BAT had the greatest gains in musculature. In contrast, changes in BAT did not predict increases in subcutaneous WAT (P = .25) during infancy, which were primarily determined by body weight. CONCLUSIONS: Changes in BAT are associated with muscle development but not WAT accumulation in healthy infants. Studies are needed to determine the mechanism(s) by which BAT could facilitate muscle growth, and the degree to which decreased muscle mass, such as in preterm and low birth weight infants, is related to a deficiency of BAT.

Sexual Dimorphism in Newborn Vertebrae and Its Potential Implications.

OBJECTIVE: To examine whether the sex-related differences in vertebral cross-sectional area (CSA) found in children and at the timing of peak bone mass-a major determinant of osteoporosis and future fracture risk-are also present at birth. STUDY DESIGN: Vertebral CSA, vertebral height, and intervertebral disc height were measured using magnetic resonance imaging in 70 healthy full-term newborns (35 males and 35 females). The length and CSA of the humerus, musculature, and adiposity were measured as well. RESULTS: Weight, body length, and head and waist circumferences did not differ significantly between males and females (P ≥ .06 for all). Compared with newborn boys, girls had significantly smaller mean vertebral cross-sectional dimensions (1.47 ± 0.11 vs 1.31 ± 0.12; P < .0001). Multiple linear regression analysis identified sex as a predictor of vertebral CSA independent of gestational age, birth weight, and body length. In contrast, the sexes were monomorphic with regard to vertebral height, intervertebral disc height, and spinal length (P ≥ .11 for all). There were also no sex differences in the length or cross-sectional dimensions of the humerus or in measures of musculature and adiposity (P ≥ .10 for all). CONCLUSION: Factors related to sex influence fetal development of the axial skeleton. The smaller vertebral CSA in females is associated with greater flexibility of the spine, which could represent the human adaptation to fetal load. Unfortunately, it also imparts a mechanical disadvantage that increases stress within the vertebrae for all physical activities and increases the susceptibility to fragility fractures later in life.

Presence of brown adipose tissue in an adolescent with severe primary hypothyroidism.

CONTEXT: Brown adipose tissue (BAT) generates heat during adaptive thermogenesis in response to cold temperature. Thyroid hormone (TH) receptors, type 2 deiodinase, and TSH receptors are present on brown adipocytes, indicating that the thyroid axis regulates BAT. It is unknown whether absent TH in humans would down-regulate development of BAT and its thermogenic function. OBJECTIVE: The objective of the study was to examine BAT by magnetic resonance imaging (MRI) and infrared thermal imaging (IRT) in a pediatric patient with severe primary hypothyroidism before and after TH treatment. DESIGN/SETTING: This study was a case report with longitudinal follow-up in a tertiary center. MAIN OUTCOME MEASURES: BAT fat fraction (FF) by MRI and skin temperature by IRT were measured. RESULTS: An 11.5-year-old female was severely hypothyroid (TSH, 989 µIU/mL; free T4, 0.10 ng/dL; low thyroglobulin, 3.0 ng/mL). Low MRI measures of FF (56.1% ± 3.7%) indicated that BAT was abundantly present in the supraclavicular fossa. IRT showed higher supraclavicular temperature (36.0°C ±0.16°C) than the suprasternal area (34.3°C ± 0.19°C). After 2 months of TH replacement, she was euthyroid (TSH, 4.3 µIU/mL; free T4, 1.49 ng/dL; T3, 102 ng/dL) at which time supraclavicular BAT decreased (increased FF 60.7% ± 3.8%). IRT showed a higher, more homogeneous skin temperature throughout the upper thorax (supraclavicular, 37.1°C ± 0.23°C; suprasternal, 36.4°C ± 0.13°C). The overall size of the supraclavicular fat depot decreased from 84.79 cm(3) to 41.21 cm(3). CONCLUSIONS: These findings document the presence of BAT and thermogenesis in profound hypothyroidism and suggest a role for TSH and/or TRH as a potential regulator of BAT.

Brown adipose tissue in the buccal fat pad during infancy.

BACKGROUND: The buccal fat pad (BFP) is an encapsulated mass of adipose tissue thought to enhance the sucking capabilities of the masticatory muscles during infancy. To date, no conclusive evidence has been provided as to the composition of the BFP in early postnatal life. OBJECTIVE: The purpose of this study was to examine whether the BFP of neonates and infants is primarily composed of white adipose tissue (WAT) or brown adipose tissue (BAT). MATERIALS AND METHODS: The percentage of fat in the BFP in 32 full-term infants (16 boys and 16 girls), aged one day to 10.6 months, was measured using magnetic resonance imaging (MRI) determinations of fat fraction. RESULTS: BFP fat fraction increased with age (r = 0.67; P<.0001) and neonates had significantly lower values when compared to older infants; 72.6 ± 9.6 vs. 91.8 ± 2.4, P<.0001. Multiple regression analysis indicated that the age-dependent relationship persisted after accounting for gender, gestational age, and weight percentile (P = .001). Two subjects (aged one and six days) depicted a change in the MRI characteristics of the BFP from primarily BAT to WAT at follow-up examinations two to six weeks later, respectively. Histological post-mortem studies of a 3 day and 1.1 month old revealed predominantly BAT and WAT in the BFP, respectively. CONCLUSION: The BFP is primarily composed of BAT during the first weeks of life, but of WAT thereafter. Studies are needed to investigate the contributions of BAT in the BFP to infant feeding and how it is altered by postnatal nutrition.

Comparison of brown and white adipose tissues in infants and children with chemical-shift-encoded water-fat MRI.

PURPOSE: To compare fat-signal fractions (FFs) and T2* values between brown (BAT) and white (WAT) adipose tissue located within the supraclavicular fossa and subcutaneous depots, respectively. MATERIALS AND METHODS: Twelve infants and 39 children were studied. Children were divided into lean and overweight/obese subgroups. Chemical-shift-encoded water-fat magnetic resonance imaging (MRI) was used to quantify FFs and T2* metrics in the supraclavicular and adjacent subcutaneous adipose tissue depots. Linear regression and t-tests were performed. RESULTS: Infants had lower supraclavicular FFs than children (P < 0.01) but T2* values were similar (P = 0.5). Lean children exhibited lower supraclavicular FFs and T2* values than overweight children (P < 0.01). In each individual infant and child, supraclavicular FFs were consistently lower than adjacent subcutaneous FFs. Supraclavicular T2* values were consistently lower than subcutaneous T2* values in children, but not in infants. FFs in both depots were positively correlated with age and weight in infants (P < 0.01). In children, they were correlated with weight and body mass index (BMI) (P < 0.01), but not age. Correlations between T2* and anthropometric variables existed in children (P < 0.01), but were absent in infants. CONCLUSION: Cross-sectional comparisons suggest variations in FF and T2* values in the supraclavicular and subcutaneous depots of infants and children, which are potentially indicative of physiological differences in adipose tissue fat content, amount, and metabolic activity.

Brown adipose tissue and its relationship to bone structure in pediatric patients.

CONTEXT: Emerging evidence suggests a possible link between brown adipose tissue (BAT) and bone metabolism. OBJECTIVE: The objective of this study was to examine the relationships between BAT and bone cross-sectional dimensions in children and adolescents. DESIGN: This was a cross-sectional study. SETTING: The study was conducted at a pediatric referral center. PATIENTS: Patients included 40 children and teenagers (21 males and 19 females) successfully treated for pediatric malignancies. INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURES: The volume of BAT was determined by fluorodeoxyglucose-positron emission tomography/computed tomography. Measures of the cross-sectional area and cortical bone area and measures of thigh musculature and sc fat were determined at the midshaft of the femur. RESULTS: Regardless of sex, there were significant correlations seen between BAT volume and the cross-sectional dimensions of the bone (r values between 0.68 and 0.77; all P ≤ 0 .001). Multiple regression analyses indicated that the volume of BAT predicted femoral cross-sectional area and cortical bone area, even after accounting for height, weight, and gender. The addition of muscle as an independent variable increased the predictive power of the model but significantly decreased the contribution of BAT. CONCLUSIONS: The volume of BAT is positively associated with the amount of bone and the cross-sectional size of the femur in children and adolescents. This relation between BAT and bone structure could, at least in part, be mediated by muscle.