A study published ahead of print in Spine indicated that paediatric patients have abnormally elevated serum titanium and niobium levels up to 12 months after receiving titanium-based implants, which raises the issue of the long-term consequences of metal debris from spinal instrumentation given that the instrumentation is likely to remain in a paediatric patient for the rest of their life.
Thomas Cundy, School of Paediatrics and Reproductive Health, Faculty of Heath Sciences, The University of Adelaide, South Australia, and others reported that serum metal levels of paediatric patients with titanium-based spinal implants has not been reported and the short-, medium-, and long-term sequelae of implant-derived systemic metal dissemination is unknown. They added that there is a “theoretical risk” associated with metal debris following spinal instrumentation and this risk is particularly concerning in paediatric patients with scoliosis or kyphosis, who “have a longer exposure time and larger volume of metal implanted compared to adult populations undergoing shorter length spinal fusions.”
In their study, the authors evaluated the serum metal levels in 32 paediatric patients (mean age at surgery 14.7 years; 25 females and seven males) who had undergone spinal arthrodesis for scoliosis or kyphosis. All patients received Ti6 A17 Nb instrumentation (Synthes Universal Spine System, Synthes) and autologous bone graft. Cundy et al obtained blood samples, to assess serum levels of titanium, niobium, and aluminium, preoperatively (on day of surgery), one week postoperatively, one month postoperatively, six months postoperatively, and 12 months postoperatively.
According to the results, both titanium and niobium levels were at their lowest preoperatively and then significantly increased during the first week after surgery and remained relatively constant over the 12 months of the study period. However, the aluminium levels were lowest at 12 months. Cundy et al reported: “When time since surgery was considered as a continuous variable following log transformation of results, postoperative serum titanium concentration was found to increase by 6.5% per 100 days (p=0.0003).”
They added that 95% of postoperative samples were found to contain abnormally elevated serum levels of titanium, 99% of samples contained abnormally elevated levels of niobium, and 5% had abnormally elevated serum levels of aluminium.
Cundy et al commented that elevated serum titanium levels are not considered to be toxic. However, they wrote: “Conjectural risks persist and thresholds of potential harm or toxicity have not defined.” They added: “In this paediatric cohort, our principle concern is the potential for long-term deposition of metal debris in organs. Deposition of metal debris in organs is understood to be cumulative and paediatric patients with spinal instrumentation may experience around 60 years of potentially harmful exposure given normal life expectancy.”
Other than a heightened awareness of this “nascent concern” being indicated as a result of their study, Cundy et al did not advise any major change in clinical practice. However, they wrote that consideration should be given to routine measurement of preoperative baseline serum metal levels for reference for future monitoring; informed consent discussions including the possibility of elevation in serum metal levels and the associated theoretical effects; and having intraoperative irrigation and washout before wound closure to remove metal debris that may have been generated at time of implantation.