A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency
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 mecha...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
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SAGE Publishing
2021-09-01
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| Series: | Journal of Orthopaedic Surgery |
| Online Access: | https://doi.org/10.1177/23094990211042237 |
| _version_ | 1818969141163327488 |
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| author | Douglas C Wong Wanis Nafo William Weijia Lu Kenneth Man Chee Cheung |
| author_facet | Douglas C Wong Wanis Nafo William Weijia Lu Kenneth Man Chee Cheung |
| author_sort | Douglas C Wong |
| collection | DOAJ |
| description | 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. |
| first_indexed | 2024-12-20T14:15:52Z |
| format | Article |
| id | doaj.art-e42e3cd0bc3f4751b4800b4b75155fd2 |
| institution | Directory Open Access Journal |
| issn | 2309-4990 |
| language | English |
| last_indexed | 2024-12-20T14:15:52Z |
| publishDate | 2021-09-01 |
| publisher | SAGE Publishing |
| record_format | Article |
| series | Journal of Orthopaedic Surgery |
| spelling | doaj.art-e42e3cd0bc3f4751b4800b4b75155fd22022-12-21T19:38:03ZengSAGE PublishingJournal of Orthopaedic Surgery2309-49902021-09-012910.1177/23094990211042237A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequencyDouglas C WongWanis NafoWilliam Weijia LuKenneth Man Chee CheungPurpose: 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.https://doi.org/10.1177/23094990211042237 |
| spellingShingle | Douglas C Wong Wanis Nafo William Weijia Lu Kenneth Man Chee Cheung A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency Journal of Orthopaedic Surgery |
| title | A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency |
| title_full | A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency |
| title_fullStr | A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency |
| title_full_unstemmed | A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency |
| title_short | A biomechanical study on the effect of lengthening magnitude on spine off-loading in magnetically controlled growing rod surgery: Implications on lengthening frequency |
| title_sort | biomechanical study on the effect of lengthening magnitude on spine off loading in magnetically controlled growing rod surgery implications on lengthening frequency |
| url | https://doi.org/10.1177/23094990211042237 |
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