Optimization of skeletal configuration: Studies of scoliosis correction biomechanics

Wynarsky, George T.; Schultz, Albert B.

doi:10.1016/0021-9290(91)90336-l

Cited by 50 publications

(45 citation statements)

References 50 publications

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“…It may serve as a prompt for the subjects to move the back and spine away from the applied pressure and hence, may result in active correction of the curve. This hypothesis is in accordance with prior research that indicates that there are both passive and active mechanisms which work to produce the corrective forces in bracing treatment (Wynarsky and Shultz 1991;Perie et al 2003).…”

Section: Daytime Findingssupporting

confidence: 92%

The effect of time on qualitative compliance in brace treatment for AIS

Mak

Lou²,

Raso

et al. 2008

Prosthetics &Amp; Orthotics International

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Brace treatment is the most commonly used non-surgical treatment method for adolescent idiopathic scoliosis (AIS). This study is to determine the force changes exerted by a brace over time during both day and night-time wear and to explore correlations between force changes to bracing outcomes. Twenty subjects (three male, 17 female) diagnosed with idiopathic scoliosis who had worn their braces for six months participated into this study. However, due to non-continuous brace wear and exclusion of subjects with large curves (Cobb angle 4408), only nine subjects were included into the day-time analysis and 11 subjects were included into night-time analysis. All subjects used a load monitor system from four days up to 14 days with Boston braces. Cobb angle measurements were taken at initiation of brace treatment as well as after weaning upon completion of the treatment. After the monitoring period, the data was extracted and analyzed. Forces were compared between hours 1, 2, and 5 for the day and night groups, and the correlation of force changes to bracing outcomes were analyzed. In daytime wear, a significant decrease in force over time was found. Most of the decrease occurred within hours 1 and 2 of brace wear. There was no significant decrease during night wear. There were no significant correlations between force decline and outcome.

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Section: Daytime Findingssupporting

confidence: 92%

The effect of time on qualitative compliance in brace treatment for AIS

Mak

Lou²,

Raso

et al. 2008

Prosthetics &Amp; Orthotics International

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“…Wynarsky and Schultz [31] suggest that two different mechanisms might contribute to achieving correction of scoliosis. They are as follows: (1) active mechanisms, such as muscle control to shift the trunk away from the pressure areas; (2) passive mechanisms, such as external forces applied by the brace pads.…”

Section: Discussionmentioning

confidence: 99%

Evolution of the curve patterns during brace treatment for adolescent idiopathic scoliosis

et al. 2012

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Summary of background data The curve pattern of idiopathic scoliosis is important for making decisions concerning bracing. However, whether the curve pattern changes during brace treatment have not been fully documented. The aim of this study was to investigate the changes of curve pattern during brace treatment in skeletally immature patients with adolescent idiopathic scoliosis (AIS). MethodsFrom January 2002 to January 2011, AIS patients treated with a Boston or Milwaukee brace were recruited after meeting the following inclusion criteria: older than 10 years of age at initiation of bracing; having a Cobb angle of 25°-40°; with a Risser sign 0-2; being regularly followed until the weaning of brace or the necessity of surgical treatment; and without history of previous treatment. A total of 130 female and 11 male AIS patients were included. The mean age was 12.9 years at initiation of bracing, and the female patients were, on average, 2.7 months past menarche. The mean follow-up period was 2.6 years (range 1.0-5.5 years). The definitions of changes in curve patterns were divided into four categories as follows: (1) shift of the apex of the main curve; (2) change in the curve span of more than two vertebrae; (3) change in the main curve type with regard to the apex location; and (4) change of curve direction. The patients were divided into two groups. Group A was comprised of patients who had experienced one or more categories of curve pattern changes, and Group B was comprised of those who had not. Results Of these 39 patients, 14 had apex shifting, 2 underwent curve span changes, 22 experienced changes in the main curve type, and one female had both changes in the apex and curve span. At the initiation of bracing, patients in Group A demonstrated significantly lower menarchal status (P = 0.018) and lower Risser grade (P = 0.025) than those in Group B. The difference in the percentage of patients who underwent Boston bracing between the two groups was statistically significant (41.5 % for Group A vs. 24.0 % for Group B, P = 0.023). Conclusion Changes in curve pattern can occur during brace treatment. Patients with less skeletal maturity and those treated with a Boston brace are more susceptible to this phenomenon.

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“…In indeterminant biomechanical analyses, it is usually assumed that the CNS control of trunk muscle activation strategy is in some way optimal, compatible with equilibrium and other constraints (Dul et al, 1984). In optimization models, several different physiological cost functions have been proposed, including to minimize intervertebral forces, minimize muscle forces (Bean et al, 1988;Crowninshield and Brand, 1981;Hughes et al, 1994;Schultz, 1990), minimize the total of muscle and joint forces (Yettram and Jackman, 1982) or optimize spinal displacements (Skogland and Miller, 1980;Wynarsky and Schultz, 1991). If more than one variable is entered into the cost function, then weighting factors must be assigned to each component.…”

Section: Introductionmentioning

confidence: 99%

Lumbar spinal muscle activation synergies predicted by multi-criteria cost function

Stokes

Gardner‐Morse

2001

Journal of Biomechanics

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The hypothesis that control of lumbar spinal muscle synergies is biomechanically optimized was studied by comparing EMG data with an analytical model with a multi-component cost function that could include (1) trunk displacements, (2) intervertebral displacements, (3) intervertebral forces; (4) sum of cubed muscle stresses, and (5) eigenvalues for the first two spinal buckling modes. The model's independent variables were 180 muscle forces. The 36 displacements of 6 vertebrae were calculated from muscle forces and the spinal stiffness. Calculated muscle activation was compared with EMG data from 14 healthy human subjects who performed isometric voluntary ramped maximum efforts at angles of 08, 458, 908, 1358 and 1808 to the right from the anterior direction. Muscle activation at each angle was quantified as the linear regression slope of the RMS EMG versus external force relationship, normalized by the maximum observed EMG.There was good agreement between the analytical model and EMG data for the dorsal muscles when the model included either minimization of intervertebral displacements or minimization of intervertebral forces in its cost function, but the model did not predict a realistic level of abdominal muscles activation. Agreement with EMG data was improved with the sum of the cubed muscle stresses added to the cost function. Addition of a cost function component to maximize the trunk stability produced higher levels of antagonistic muscle activation at low efforts than at greater efforts. It was concluded that the muscle activation strategy efficiently limits intervertebral forces and displacements, and that costs of higher muscle stresses are taken into account, but stability does not appear to be maximized. Trunk muscles are apparently not controlled solely to optimize any one of the biomechanical costs considered here. #

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Optimization of skeletal configuration: Studies of scoliosis correction biomechanics

Cited by 50 publications

References 50 publications

The effect of time on qualitative compliance in brace treatment for AIS

The effect of time on qualitative compliance in brace treatment for AIS

Evolution of the curve patterns during brace treatment for adolescent idiopathic scoliosis

Lumbar spinal muscle activation synergies predicted by multi-criteria cost function

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