A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency.
J Orthop Surg (Hong Kong)
; 29(3): 23094990211042237, 2021.
Article
em En
| MEDLINE
| ID: mdl-34592859
ABSTRACT
Purpose:
To assess whether the magnitude of lengthening in magnetically controlled growing rod (MCGR) surgeries has an immediate or delayed effect on spinal off-loading.Methods:
9 whole porcine spines were instrumented using two standard MCGRs from T9 to L5. Static compression testing using a mechanical testing system (MTS) was performed at three MCGR lengthening stages (0 mm, 2 mm, and 6 mm) in each spine. At each stage, five cycles of compression at 175N with 25 min of relaxation was carried out. Off-loading was derived by comparing the load sustained by the spine with force applied by the MTS to the spine. Micro-CT imaging was subsequently performed.Results:
The mean load sustained by the vertebral body before lengthening was 39.69N, and immediately after lengthening was 25.12N and 19.91N at 2 mm and 6 mm lengthening, respectively; decreasing to 10.07N, 8.31N, and 8.17N after 25 minutes of relaxation, at 0 mm, 2 mm, and 6 mm lengthening stages, respectively. There was no significant difference in off-loading between 2 mm and 6 mm lengthening stages, either instantaneously (p = 0.395) or after viscoelastic relaxation (p = 0.958). CT images showed fractures/separations at the level of pedicle screws in six spines and in the vertebral body's growth zone in five spines after 6 mm MCGR lengthening.Conclusion:
This study demonstrated MCGRs cause significant off-loading of the spine leading to stress shielding. 6 mm of lengthening caused tissue damage and microfractures in some spines. There was no significant difference in spine off-loading between 2 mm and 6 mm MCGR lengthening, either immediately after lengthening or after viscoelastic relaxation.Palavras-chave
Texto completo:
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Coleções:
01-internacional
Base de dados:
MEDLINE
Limite:
Animals
Idioma:
En
Ano de publicação:
2021
Tipo de documento:
Article