Direct Observations of Coastally Generated Near-Inertial Waves During a Wind Event.

Wind over the ocean generates near-inertial velocities. In the open ocean, horizontal variability in the inertial frequency and mesoscale vorticity generate internal waves that transport energy laterally and drive diapcynal mixing in remote locations. In the coastal ocean, horizontal variability is produced by the coastline.

Wave-slope soaring of the brown pelican.

Background: From the laboratory at Scripps Institution of Oceanography, it is common to see the brown pelican (Pelecanus occidentalis) traveling along the crests of ocean waves just offshore of the surf-zone. When flying in this manner, the birds can travel long distances without flapping, centimeters above the ocean's surface. Here we derive a theoretical framework for assessing the energetic savings related to this behavior, 'wave-slope soaring,' in which an organism in flight takes advantage of localized updrafts caused by traveling ocean surface gravity waves.

Adolescent idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is the most common form of structural spinal deformities that have a radiological lateral Cobb angle - a measure of spinal curvature - of ≥10(°). AIS affects between 1% and 4% of adolescents in the early stages of puberty and is more common in young women than in young men. The condition occurs in otherwise healthy individuals and currently has no recognizable cause.

Metabolic Effects of Angulation, Compression, and Reduced Mobility on Annulus Fibrosis in a Model of Altered Mechanical Environment in Scoliosis.

Study Design: Comparison of disc tissue from rat tails in 6 groups with different mechanical conditions imposed.

Objectives: To identify disc annulus changes associated with the supposed altered biomechanical environment in a spine with scoliosis deformity using an immature rat model that produces disc narrowing and wedging.

Background: Intervertebral discs become wedged and narrowed in a scoliosis curve, probably partly because of an altered biomechanical environment.

Contributions of Remodeling and Asymmetrical Growth to Vertebral Wedging in a Scoliosis Model.

Study Design: We performed a laboratory study of rats of 3 different ages with imposed angulation and compressive loading to caudal vertebrae to determine causes of vertebral wedging.

Objectives: The purpose was to determine the percentage of total vertebral wedging that was caused by asymmetric growth, vertebral body, and epiphyseal wedging. Approval from the Institutional Animal Care and Use Committee, the University of Vermont, was obtained for the live animal procedures used in this study.

Intervertebral disc changes with angulation, compression and reduced mobility simulating altered mechanical environment in scoliosis.

Purpose: The intervertebral discs become wedged and narrowed in scoliosis, and this may result from altered biomechanical environment. The effects of four permutations of disc compression, angulation and reduced mobility were studied to identify possible causes of progressive disc deformity in scoliosis. The purpose of this study was to document morphological and biomechanical changes in four different models of altered mechanical environment in intervertebral discs of growing rats and in a sham and control groups.

Abdominal muscle activation increases lumbar spinal stability: analysis of contributions of different muscle groups.

Background: Antagonistic activation of abdominal muscles and increased intra-abdominal pressure are associated with both spinal unloading and spinal stabilization. Rehabilitation regimens have been proposed to improve spinal stability via selective recruitment of certain trunk muscle groups. This biomechanical analytical study addressed whether lumbar spinal stability is increased by such selective activation.

Nonfusion treatment of adolescent idiopathic scoliosis by growth modulation and remodeling.

Background: Adolescent idiopathic scoliosis (AIS) is a common disorder in which the spine gradually develops a curvature that is first detected in patients between 11 and 17 years of age. The only accepted treatment methods are bracing and surgery. Whether brace treatment alters the natural history is being questioned, and patient compliance is low.

Terminology - glossary including acronyms and quotations in use for the conservative spinal deformities treatment: 8th SOSORT consensus paper.

Background: This report is the SOSORT Consensus Paper on Terminology for use in the treatment of conservative spinal deformities. Figures are provided and relevant literature is cited where appropriate.

Methods: The Delphi method was used to reach a preliminary consensus before the meeting, where the terms that still needed further clarification were discussed.

Refinement of elastic, poroelastic, and osmotic tissue properties of intervertebral disks to analyze behavior in compression.

Intervertebral disks support compressive forces because of their elastic stiffness as well as the fluid pressures resulting from poroelasticity and the osmotic (swelling) effects. Analytical methods can quantify the relative contributions, but only if correct material properties are used. To identify appropriate tissue properties, an experimental study and finite element analytical simulation of poroelastic and osmotic behavior of intervertebral disks were combined to refine published values of disk and endplate properties to optimize model fit to experimental data.

Intra-abdominal pressure and abdominal wall muscular function: Spinal unloading mechanism.

Background: The roles of antagonistic activation of abdominal muscles and of intra-abdominal pressurization remain enigmatic, but are thought to be associated with both spinal unloading and spinal stabilization in activities such as lifting. Biomechanical analyses are needed to understand the function of intra-abdominal pressurization because of the anatomical and physiological complexity, but prior analyses have been over-simplified.

Methods: To test whether increased intra-abdominal pressure was associated with reduced spinal compression forces for efforts that generated moments about each of the principal axis directions, a previously published biomechanical model of the spine and its musculature was modified by the addition of anatomically realistic three-layers of curved abdominal musculature connected by fascia to the spine.

The role of remodeling and asymmetric growth in vertebral wedging.

Background: Scoliosis with vertebral wedging is thought to be caused by asymmetric growth (Hueter-Volkmann law), but vertebral diaphyseal remodeling (Wolff's law) may also contribute to the deformity. We investigated whether vertebral wedging in scoliosis might involve both mechanisms.

Methods: An external fixator was used to impose a 30 degrees scoliosis and compression of 0.

The central hip vertical axis: a reference axis for the Scoliosis Research Society three-dimensional classification of idiopathic scoliosis.

Study Design: Reliability comparison of 2 radiographic axis systems by inter- and intraobserver variability.

Objective: To determine whether the central hip vertical axis (CHVA) provides a more reliable reference axis for the evaluation of scoliosis.

Summary Of Background Data: Current practices in the evaluation of the scoliotic spine use the central sacral vertical line (CSVL), a true vertical drawn upward from the middle of S1, to assess the spinal deformity.

Limitation of finite element analysis of poroelastic behavior of biological tissues undergoing rapid loading.

The finite element method is used in biomechanics to provide numerical solutions to simulations of structures having complex geometry and spatially differing material properties. Time-varying load deformation behaviors can result from solid viscoelasticity as well as viscous fluid flow through porous materials. Finite element poroelastic analysis of rapidly loaded slow-draining materials may be ill-conditioned, but this problem is not widely known in the biomechanics field.

Cobb angle progression in adolescent scoliosis begins at the intervertebral disc.

Study Design: Longitudinal radiographic study of patients with progressive idiopathic scoliosis.

Objective: To determine the relative contributions of vertebral and disc wedging to the increase in Cobb angle during 3 phases of adolescent skeletal growth and maturation.

Summary Of Background Data: Both disc wedging and vertebral body wedging are found in progressive scoliosis, but their relative contribution to curve progression over time is unknown.

Interobserver and intraobserver variability in the identification of the Lenke classification lumbar modifier in adolescent idiopathic scoliosis.

Study Design: Interobserver and intraobserver reliability study for the identification of the Lenke classification lumbar modifier by a panel of experts compared with a computer algorithm.

Objectives: To measure the variability of the Lenke classification lumbar modifier and determine if computer assistance using 3-dimensional spine models can improve the reliability of classification.

Summary Of Background Data: The lumbar modifier has been proposed to subclassify Lenke scoliotic curve types into A, B, and C on the basis of the relationship between the central sacral vertical line (CSVL) and the apical lumbar vertebra.

Growth plate mechanics and mechanobiology. A survey of present understanding.

The longitudinal growth of long bones occurs in growth plates where chondrocytes synthesize cartilage that is subsequently ossified. Altered growth and subsequent deformity resulting from abnormal mechanical loading is often referred to as mechanical modulation of bone growth. This phenomenon has key implications in the progression of infant and juvenile musculoskeletal deformities, such as adolescent idiopathic scoliosis, hyperkyphosis, genu varus/valgus and tibia vara/valga, as well as neuromuscular diseases.

Classification of scoliosis deformity three-dimensional spinal shape by cluster analysis.

Study Design: Cluster analysis of existing database of spinal shape of patients attending a scoliosis clinic.

Objective: To determine whether patients with scoliosis can be classified into distinct groups by 3-dimensional curve shape.

Summary Of Background Data: Subjective or semiquantitative methods can be used to classify curve types in scoliosis, with the goal of rationalizing surgical planning.

Spatially resolved streaming potentials of human intervertebral disk motion segments under dynamic axial compression.

Intervertebral disk degeneration results in alterations in the mechanical, chemical, and electrical properties of the disk tissue. The purpose of this study is to record spatially resolved streaming potential measurements across intervertebral disks exposed to cyclic compressive loading. We hypothesize that the streaming potential profile across the disk will vary with radial position and frequency and is proportional to applied load amplitude, according to the presumed fluid-solid relative velocity and measured glycosaminoglycan content.

Three-dimensional classification of thoracic scoliotic curves.

Study Design: Three-dimensional (3D) characterization of the thoracic scoliotic spine (cross-sectional study).

Objectives: To investigate the presence of subgroups within Lenke type-1 curves by evaluating the thoracic segment indices extracted from 3D reconstructions of the spine, and to propose a new clinically relevant means (the daVinci representation) to report 3D spinal deformities.

Summary Of Background Data: Although scoliosis is recognized to be a 3D deformity of the spine its measurement and classification have predominantly been based on radiographs which are 2D projections in the coronal and sagittal planes.

A three-dimensional retrospective analysis of the evolution of spinal instrumentation for the correction of adolescent idiopathic scoliosis.

This is a clinical radiographic study, spanning over three decades, analyzing the three-dimensional (3-D) changes in spine geometry after corrective surgery for adolescent idiopathic scoliosis (AIS) using four generations of instrumentation systems. The objective of this study was to retrospectively evaluate the evolution of spinal instrumentation over time by measuring the 3-D changes of spinal shape before and after surgical correction of subjects with AIS using Harrington/Harrington-Luque (H/HL) instrumentation, original and recent generations of Cotrel-Dubousset Instrumentation (CDI) with rod rotation maneuvers, as well as third generation systems using thoracic pedicle screws and direct vertebral derotation (DVD) manoeuver in order to determine if the claims for improved 3-D correction from generation to next generation could be substantiated. The 3-D shape of the thoracic and lumbar spine was recorded from a pair of standing radiographs using a novel 3-D reconstruction technique from uncalibrated radiographs in 128 adolescents with AIS undergoing surgery by a posterior approach.