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The purpose of this systematic review was to assess the currently available evidence for the use of external stimulation to modulate neural activity and promote peripheral nerve regeneration. The most common external stimulations are electrical stimulation (ES), optogenetic stimulation (OS), and magnetic stimulation (MS). Understanding the comparative effectiveness of these stimulation methods is pivotal in advancing therapeutic interventions for peripheral nerve injuries. This systematic review focused on these three external stimulation modalities as potential strategies to enhance peripheral nerve repair (PNR). We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses framework to systematically evaluate and compare the efficiency of ES, OS, and MS in PNR. The review included studies published between 2018 and 2023 using ES, OS, or MS for PNR focused on enhancing recovery of peripheral nerve injuries in rodent models identified through PubMed and Google Scholar. The search strategies and inclusion criteria identified 19 studies (13 ES, 4 OS, and 2 MS) for detailed analysis, focusing on critical parameters such as functional recovery, histological outcomes, and electrophysiological data. Although ES demonstrated a consistent improvement in all the analyses, high-frequency repetitive MS (HFr-MS) emerged as a promising modality. HFr-MS demonstrated accelerated PNR, as histological and electrophysiological evidence indicated. In contrast, OS exhibited superior functional recovery outcomes. Notable limitations include constrained MS and OS data sets and the challenge of comparing relative improvements because of methodological diversity in evaluation techniques. Our findings underscore the potential of HFr-MS and OS in PNR while emphasizing the critical need for standardized testing protocols to facilitate meaningful cross-study comparisons. External stimulations have the potential to improve functional recovery in patients with nerve injury.

Background:. Although extensive research shows an association between distal radius fractures and the development of median nerve related pathologies such as carpal tunnel syndrome, none directly track how the resulting angular deformity relates to likelihood of development of median nerve pathology. Methods:. Median nerve strain was measured with a custom-built system using a camera, optical markers, and a proprietary segmentation algorithm. After initial validation of the system in a cadaver model, our system was used to assess strain in 10 cadaver arms with a simulated distal radius fracture and increasing dorsal angulation. The measured strain at each angle was then analyzed using a linear regression model. Results:. The linear regression model in the validation experiment demonstrated a regression coefficient of 1.00067 (P < 0.0001) with r2 = 0.899, thus validating the use of the optical tracking system. The average strain at maximum dorsal angulation (50 degrees) across all specimens was −0.2%. Linear regression analysis of the effect of increasing dorsal angulation on strain in the osteotomy model yielded a regression coefficient of −0.000048 (P = 0.714), r2 = 0.00129, suggesting no significant correlation between increasing dorsal tilt and median nerve strain. Conclusions:. Increases in median nerve strain at the wrist are negligible with increasing dorsal tilt in a distal radius fracture model. It is therefore likely that other factors, such as increased pressure within the carpal tunnel, are the primary cause of median neuropathy in distal radius malunions. Therefore, correction of dorsal tilt may not be required to improve neurologic symptoms.