Noninvasive electrical stimulation as an adjunct to fusion procedures: a systematic review and meta-analysis

Objective:
Noninvasive electrical stimulation represents a distinct group of devices used to augment fusion rates. However, data regarding outcomes of noninvasive electrical stimulation have come from a small number of studies. The goal of this systematic review and meta-analysis was to determine outcomes of noninvasive electrical stimulation used as an adjunct to fusion procedures to improve rates of successful fusion.

Methods:
PubMed, Embase, and the Cochrane Clinical Trials database were searched according to search strategy and PRISMA guidelines. Random-effects meta-analyses of fusion rates with the three main modalities of noninvasive electrical stimulation, capacitively coupled stimulation (CCS), pulsed electromagnetic fields (PEMFs), and combined magnetic fields (CMFs), were conducted using R version 4.1.0 (The R Foundation for Statistical Computing). Both retrospective studies and clinical trials were included. Animal studies were excluded. Risk-of-bias analysis was performed with the Risk of Bias 2 (RoB 2) and Risk of Bias in Nonrandomized Studies of Interventions (ROBINS-I) tools.

Results:
Searches of PubMed, Embase, and the Cochrane Clinical Trials database identified 8 articles with 1216 participants meeting criteria from 213 initial results. There was a high overall risk of bias identified for the majority of randomized studies. No meta-analysis could be performed for CCS as only 1 study was identified. Meta-analysis of 6 studies of fusion rates in PEMF did not find any difference between treatment and control groups (OR 1.89, 95% CI 0.36-9.80, p = 0.449). Meta-analysis of 2 studies of CMF found no difference in fusion rates between control and treatment groups (OR 0.90, 95% CI 0.07-11.93, p = 0.939). Subgroup analysis of PEMF was limited given the small number of studies and patients, although significantly increased fusion rates were seen in some subgroups.

Conclusions:
This meta-analysis of clinical outcomes and fusion rates in noninvasive electrical stimulation compared to no stimulation did not identify any increases in fusion rates for any modality. A high degree of heterogeneity between studies was noted. Although subgroup analysis identified significant differences in fusion rates in certain groups, these findings were based on a small number of studies and further research is needed. This analysis does not support routine use of these devices to augment fusion rates, although the data are limited by a high risk of bias and a small number of available studies.

Keywords: arthrodesis; capacitive coupling; combined magnetic fields; electrical stimulation; fusion; pulsed electromagnetic fields.

PMID: 35090134 DOI: 10.3171/2021.11.SPINE211098