Mechanical wear analysis helps understand a mechanism of failure in retrieved magnetically controlled growing rods: a retrieval study

Abstract Background To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. Methods This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. Results Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p<0.05) and rods with longer time in situ (r=0.692, p<0.05). Conclusion We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice.

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Mechanical wear analysis helps understand a mechanism of failure in retrieved magnetically controlled growing rods: a retrieval study

10.21203/rs.3.rs-26280/v4 ◽

2020 ◽

Author(s):

Jack Z. Wei ◽

Harry S. Hothi ◽

Holly Morganti ◽

Sean Bergiers ◽

Elisabetta Dal Gal ◽

...

Keyword(s):

Material Loss ◽

Mechanical Wear ◽

Plain Radiographs ◽

Growing Rods ◽

Single Side ◽

Internal Mechanism ◽

Measuring Machine ◽

Magnetically Controlled Growing Rods ◽

Mechanism Of Failure

Abstract Background: To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. Methods: This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. Results: Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p<0.05) and rods with longer time in situ (r=0.692, p<0.05). Conclusions: We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice.

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Mechanical wear analysis helps understand a mechanism of failure in retrieved magnetically controlled growing rods: a retrieval study

10.21203/rs.3.rs-26280/v2 ◽

2020 ◽

Author(s):

Jack Z. Wei ◽

Harry S. Hothi ◽

Holly Morganti ◽

Sean Bergiers ◽

Elisabetta Dal Gal ◽

...

Keyword(s):

Material Loss ◽

Mechanical Wear ◽

Plain Radiographs ◽

Growing Rods ◽

Single Side ◽

Internal Mechanism ◽

Measuring Machine ◽

Magnetically Controlled Growing Rods ◽

Mechanism Of Failure

Abstract Background To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. Methods This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. Results Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p<0.05) and rods with longer time in situ (r=0.692, p<0.05). Conclusion We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice.

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Mechanical Wear Analysis Helps Understand a Mechanism of Failure in Retrieved Magnetically Controlled Growing Rods: A Retrieval Study

10.21203/rs.3.rs-26280/v1 ◽

2020 ◽

Author(s):

Jack Z. Wei ◽

Harry S. Hothi ◽

Holly Morganti ◽

Sean Bergiers ◽

Elisabetta Dal Gal ◽

...

Keyword(s):

Material Loss ◽

Mechanical Wear ◽

Plain Radiographs ◽

Growing Rods ◽

Single Side ◽

Internal Mechanism ◽

Measuring Machine ◽

Magnetically Controlled Growing Rods ◽

Mechanism Of Failure

Abstract Purpose: To assess the relationship between mechanical wear and the failure of the internal lengthening mechanism in retrieved MAGnetic Expansion Control (MAGEC) growing rods. Methods: This study included 34 MAGEC rods retrieved from 20 patients. The state of the internal mechanism and mechanical wear were assessed in all the rods using plain radiographs and visual inspection. Metrology was then performed to assess the topography and mechanical wear of the telescopic bars, using a Talyrond 365 (Taylor Hobson, Leicester, UK) roundness measuring machine. Results: Plain radiographs showed evidence of a broken internal mechanism in 29% of retrieved rods. Single-side wear marks were found in 97% of retrieved rods. Material loss was found to significantly increase in rods with a damaged internal mechanism (p<0.05) and rods with longer time in situ (r=0.692, p<0.05). Conclusion: We found an association between damage to the internal mechanism of the rods and (1) patterns of single-side longitudinal wear marks and (2) increased material loss. As the material loss was also found to increase over time of rod in situ, we emphasise the importance of early detection and revision of failed MAGEC rods in clinical practice.

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Magnet Fracture within a Magnetically Controlled Growing Rod: A Case Report of a New Mechanism of Failure

Journal of Orthopaedic Case Reports ◽

10.13107/jocr.2021.v11.i08.2342 ◽

2021 ◽

Vol 11 (8) ◽

Author(s):

Conor S Jones ◽

Paul Rushton ◽

Michael Hutton ◽

Oliver M Stokes

Keyword(s):

Risk Factors ◽

Case Report ◽

Device Failure ◽

Growing Rods ◽

Relative Paucity ◽

Modes Of Failure ◽

Magnetically Controlled Growing Rods ◽

Magnetically Controlled Growing Rod ◽

Mechanism Of Failure ◽

Functional Components

Introduction: Magnetically controlled growing rods (MCGRs) have been widely adopted in the management of early-onset scoliosis since they were first described in 2012. Recent reports have highlighted concerns around their safety. To date, little is understood about the risk factors and modes of failure in these devices. Case Report: We report a novel mechanism of device failure in a 14-year-old patient following multiple revisions of MCGRs. Clinically, there was no evidence of device failure and the MCGRs appeared radiologically intact. Explantation analysis revealed multiple compromised/non-functional components. A previously undocumented phenomenon of complete magnet fracture was also seen. Conclusion: The absence of clinical or radiological features of device failure in this case makes the findings of great concern. Given the relative paucity of high-quality evidence surrounding the use of MCGRs, we support calls for urgent comparative studies and further investigation of risk factors for device failure. Keywords: Spinal surgery, Scoliosis, Magnetically controlled growing rods, Implant.

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Effects of magnetically controlled growing rods surgery on pulmonary function in young subjects with spinal muscular atrophy type 2 and other neuromuscular scoliosis

Journal of Neurosurgical Sciences ◽

10.23736/s0390-5616.17.04052-8 ◽

2020 ◽

Vol 64 (3) ◽

Author(s):

Luca Colombo ◽

Carlotta Martini ◽

Chiara Bersanini ◽

Francesca Izzo ◽

Jorge H. Villafañe ◽

...

Keyword(s):

Pulmonary Function ◽

Spinal Muscular Atrophy ◽

Muscular Atrophy ◽

Neuromuscular Scoliosis ◽

Spinal Muscular Atrophy Type ◽

Growing Rods ◽

Young Subjects ◽

Magnetically Controlled Growing Rods

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Interactions between programmable shunt valves and magnetically controlled growing rods for scoliosis

Journal of Neurosurgery Pediatrics ◽

10.3171/2020.6.peds20299 ◽

2020 ◽

Vol 26 (6) ◽

pp. 667-670

Author(s):

Thomas Larrew ◽

Mohammed Alshareef ◽

Robert F. Murphy ◽

Ramin Eskandari ◽

Libby Kosnik Infinger

Keyword(s):

Remote Control ◽

Ex Vivo ◽

Shunt Valve ◽

Growing Rods ◽

Growing Rod ◽

Before And After ◽

Magnetically Controlled Growing Rods ◽

Ex Vivo Study

OBJECTIVEAlthough the advent of magnetic growing rod technology for scoliosis has provided a means to bypass multiple hardware lengthening operations, it is important to be aware that many of these same patients have a codiagnosis of hydrocephalus with magnet-sensitive programmable ventricular shunts. As the magnetic distraction of scoliosis rods has not previously been described to affect the shunt valve setting, the authors conducted an investigation to characterize the interaction between the two devices.METHODSIn this ex vivo study, the authors carried out 360 encounters between four different shunt valve types at varying distances from the magnetic external remote control (ERC) used to distract the growing rods. Valve settings were examined before and after every interaction with the remote control to determine if there was a change in the setting.RESULTSThe Medtronic Strata and Codman Hakim valves were found to have setting changes at distances of 3 and 6 inches but not at 12 inches. The Aesculap proGAV and Codman Certas valves, typically described as MRI-resistant, did not have any setting changes due to the magnetic ERC regardless of distance.CONCLUSIONSAlthough it is not necessary to check a shunt valve after every magnetic distraction of scoliosis growing rods, if there is concern that the magnetic ERC may have been within 12 inches (30 cm) of a programmable ventricular shunt valve, the valve should be checked at the bedside with a programmer or with a skull radiograph along with postdistraction scoliosis radiographs.

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