Nonunion is a common complication of spinal fusion surgeries. Electrical stimulation technologies (ESTs)—namely, direct current stimulation (DCS), capacitive coupling stimulation (CCS), and inductive coupling stimulation (ICS)—have been suggested to improve fusion rates. However, the evidence to support their use is based solely on small trials. Here, the authors report the results of meta-analyses of the preclinical and clinical data from the literature to provide estimates of the overall effect of these therapies at large and in subgroups.
A systematic review of the English-language literature was performed using PubMed, Embase, and Web of Science databases. The query of these databases was designed to include all preclinical and clinical studies examining ESTs for spinal fusion. The primary endpoint was the fusion rate at the last follow-up. Meta-analyses were performed using a Freeman-Tukey double arcsine transformation followed by random-effects modeling.
A total of 33 articles (17 preclinical, 16 clinical) were identified, of which 11 preclinical studies (257 animals) and 13 clinical studies (2144 patients) were included in the meta-analysis. Among preclinical studies, the mean fusion rates were higher among EST-treated animals (OR 4.79, p < 0.001). Clinical studies similarly showed ESTs to increase fusion rates (OR 2.26, p < 0.001). Of EST modalities, only DCS improved fusion rates in both preclinical (OR 5.64, p < 0.001) and clinical (OR 2.13, p = 0.03) populations; ICS improved fusion in clinical studies only (OR 2.45, p = 0.014). CCS was not effective at increasing fusion, although only one clinical study was identified. A subanalysis of the clinical studies found that ESTs increased fusion rates in the following populations: patients with difficult-to-fuse spines, those who smoke, and those who underwent multilevel fusions.
The authors found that electrical stimulation devices may produce clinically significant increases in arthrodesis rates among patients undergoing spinal fusion. They also found that the pro-arthrodesis effects seen in preclinical studies are also found in clinical populations, suggesting that findings in animal studies are translatable. Additional research is needed to analyze the cost-effectiveness of these devices.