Titanium wear from magnetically controlled growing rods (MCGRs) for the treatment of spinal deformities in children

Abstract

Magnetically controlled growing rods (MCGRs) are an effective treatment method for early-onset scoliosis (EOS). In recent years, increasing titanium wear was observed in tissue adjacent to implants and in blood samples of these patients. This study aims to investigate the potential correlation between amount of metal loss and titanium levels in blood during MCGR treatment as well as influencing factors for metal wear. In total, 44 MCGRs (n = 23 patients) were retrieved after an average of 2.6 years of implantation and analyzed using a tactile measurement instrument and subsequent metal loss calculation. Titanium plasma levels (n = 23) were obtained using inductively coupled plasma-mass spectrometry (ICP-MS). The correlation of both parameters as well as influencing factors were analyzed. Titanium abrasion on MCGRs was observed in the majority of implants. There was no correlation of metal implant wear or titanium plasma values to the duration of MCGR implantation time, number of external lengthening procedures, patient’s ambulatory status, gender, weight or height. Material loss on the MCGRs showed a positive correlation to titanium blood plasma values. The present study is one of the first studies to analyze retrieved MCGRs using high-precision metrological techniques and compare these results with ICP-MS analyses determining blood titanium values.

The Evaluation of Serum Metal Ion Levels and Metallosis in Graduated Patients With Magnetically Controlled Growing Rods

“…This lack of correlation with time and distraction is interesting and potentially indicates the metallic wear debris may be generated early after implantation due to bearing surface “run-in” which is long understood characteristic of metal-on-metal bearing surfaces. Similar results were found in a recent study by Lüders et al 22 in which a positive correlation was found between material loss on the retrieved MCGR and titanium blood plasma values.…”

“…There is a significant discrepancy among normal reference ranges, units of measurement, and environmental exposure based on geographic region, 6 and still there is a lack of comparability of results across laboratories and guidelines regarding normal or abnormal blood values. 22 Moreover, the potential contribution of the oral intake of titanium is unknown. 23 In the form of titanium dioxide or E171, it has been used as an additive to enhance the white color and brightness of food products (ie, candy, coffee creamer, fine bakery wares, and sauces), but also as a white pigment in toothpaste.…”

“…Finally, the paucity of available data on particle size estimation and standard reference range for serum metals are major limitations. There is a significant discrepancy among normal reference ranges, units of measurement, and environmental exposure based on geographic region, 6 and still there is a lack of comparability of results across laboratories and guidelines regarding normal or abnormal blood values 22 . Moreover, the potential contribution of the oral intake of titanium is unknown 23 .…”

Atomic spectrometry update: review of advances in the analysis of clinical and biological materials, foods and beverages

“…6.6.10 Titanium. Luders et al 174 investigated potential associations between plasma Ti concentrations and metal abrasion from magnetically controlled growing rods used in the treatment of early-onset scoliosis. This is the rst study to evaluate material loss from the retrieved rods (n = 44 in 23 patients) in relation to plasma Ti quantied by ICP-MS, but results were relatively inconclusive.…”

The magnetic field strength and the force distance dependency of the magnetically controlled growing rods used for early onset scoliosis

“…However, an increasing number of MCGR failure mechanisms have been observed [8][9][10][11] , and approximately 10% of patients undergo unplanned revisions 12 most often because of anchor failure, failure of the distraction mechanism 13,14 , fracture of the internal magnet 15 or a non-functioning MCGR 16 . Titanium wear has raised concerns 17 . The forces elicited by the MCGR depends on the distance between the MCGR and the ERC (implant depth) and has not so far been quantified.…”