Special Article: Update on the Magnetically Controlled Growing Rod: Tips and Pitfalls

Abstract

Magnetically controlled growing rods (MCGR) have become an important treatment option in young patients with spinal deformities. This device allows for gradual lengthening on an outpatient setting with continuous neurological monitoring in an awake patient. With its growing popularity and interest, this study reports the tips, pitfalls, and complications of the MCGR for management of scoliosis. On 3 June 2015 at the University of Hong Kong, 32 participants from 16 regions shared their experience with MCGR. Current indications for surgery include early-onset scoliosis patients. Adolescent idiopathic scoliosis and congenital scoliosis patients have less favourable outcomes. The number of instrumented levels should be minimised, as all instrumented levels must be included in the definitive fusion surgery. Rod contouring is important and owing to the straight portion of the rod housing the magnet, there is limited proximal rod portion for proper contouring, which may predispose to proximal junctional kyphosis. There is currently no consensus on the rod configuration, timing, frequency, technique, and amount of distraction. Risk factors for distraction failure include larger patients, internal magnets too close to each other, and magnets too close to the apex of the major curve. Future studies should resolve the issues regarding the technique of distraction, optimal frequency and amount of distraction per session. More comprehensive cost analyses should be performed.

Analysing a mechanism of failure in retrieved magnetically controlled spinal rods

“…This is further supported by a 4 year follow-up study that included one case of a fractured pin within the rod [17]. This mechanical distraction failure was also noted in a special article for the device [18].…”

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

“…Out of all the planned revisions, 4 rods (rod 10,11,19,20) were found with structural damages. Although previous studies have suggested that 'clunking' or 'stalling' may occur during rod distractions due to the failure of internal mechanism [23], the clinical records of these rods did not show any evidence of structural damages in distraction clinics prior to the planned revisions. We suggest that the evidence of internal damages from retrieval analysis does not necessarily correspond to the functional changes of the rod in the clinic.…”

Device-Related Complications Associated with Magec Rod Usage for Distraction-Based Correction of Scoliosis

“…This benefit is realized by a drastic reduction in the number of consecutive surgeries, and in some cases, the possibility of reducing growth rod fracture and autofusion (caused due to gradual trauma to the spine via excessive distraction in traditional growth rod systems). [11][12][13][14][15][16] However, the failure of this attribute, noninvasive distraction mechanism, reduces the overall efficacy of the device with newer studies even questioning if there is a real quality-of-life difference with use of MAGEC rods. 17 The results of the current study show that the most frequent clinical problem associated with the MAGEC rod is the failure of noninvasive distraction mechanism, which leads to invasive revision surgeries required to replace the device.…”

“…This would also reduce tissue trauma and its effects, such as autofusion. [11][12][13][14][15][16] Other technical methods to reduce attrition could include ceramic coating at wear generating surfaces, also applicable for growth guidance techniques. [18][19][20] 20.…”