Quantifying the 'law of diminishing returns' in magnetically controlled growing rods.
Bone Joint J
; 99-B(12): 1658-1664, 2017 Dec.
Article
em En
| MEDLINE
| ID: mdl-29212690
ABSTRACT
AIMS:
Magnetically controlled growing rods (MCGRs) allow non-invasive correction of the spinal deformity in the treatment of early-onset scoliosis. Conventional growing rod systems (CGRS) need repeated surgical distractions these are associated with the effect of the 'law of diminishing returns'. The primary aim of this study was to quantify this effect in MCGRs over sequential distractions. PATIENTS ANDMETHODS:
A total of 35 patients with a maximum follow-up of 57 months were included in the study. There were 17 boys and 18 girls with a mean age of 7.4 years (2 to 14). True Distraction (TD) was determined by measuring the expansion gap on fluoroscopy. This was compared with Intended Distraction (ID) and expressed as the 'T/I' ratio. The T/I ratio and the Cobb angle were calculated at several time points during follow-up.RESULTS:
The mean follow-up was 30 months (6 to 57). There was a significant decrease in the mean T/I ratio over time (convex rod at 3 months 0.81, sd 0.58 vs 51 months 0.17, sd 0.16, p = 0.0001; concave rod at 3 months 0.93, sd 0.67 vs 51 months 0.18, sd 0.15, p = 0.0001). A linear decline of the mean T/I ratios was noted for both convex rods (r2 = 0.90, p = 0.004) and concave rods (r2 = 0.81, p = 0.015) over 51 months. At the 24-month follow-up stage, there was a significant negative correlation between the mean T/I ratio of the concave rod with weight (r = -0.59, p = 0.01), age (r = -0.59, p = 0.01), and BMI of the child (r = -0.54, p = 0.01).CONCLUSIONS:
The 'law of diminishing returns' is also seen after serial distraction using MCGR. Compared to previously published data for CGRS, there is a gradual linear decline rather than a rapid initial decline in lengthening. In older, heavier children a reduced distraction ratio in the concave rod of the MCGR device is noted over time. Cite this article Bone Joint J 2017;99-B1658-64.Palavras-chave
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Reoperação
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Escoliose
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Fusão Vertebral
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Coluna Vertebral
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Procedimentos Cirúrgicos Minimamente Invasivos
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Osteogênese por Distração
Tipo de estudo:
Observational_studies
/
Prognostic_studies
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Risk_factors_studies
Limite:
Adolescent
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Child
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Child, preschool
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Female
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Humans
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Male
Idioma:
En
Revista:
Bone Joint J
Ano de publicação:
2017
Tipo de documento:
Article