INTRODUCTION: Whether the operating microscope provides superior functional outcomes compared with surgical loupes for peripheral nerve repair remains debated. No randomized controlled trial has addressed this question. We critically appraised all studies directly comparing these two magnification modalities for upper limb nerve repair.
METHODS: A narrative review following SANRA guidelines was conducted across four databases (1980-2026). Only studies with a direct microscope versus loupes comparison or testing magnification as a predictive variable were included. Experimental models (nerve and vascular, animal and synthetic), cadaveric studies, and clinical series were eligible.
RESULTS: Eleven studies met inclusion criteria: four experimental, one cadaveric with practice survey, five clinical series, and one individual-patient-data meta-analysis. Experimental and cadaveric evidence consistently demonstrated microscope superiority for structures below 1.5 mm. None of the five clinical comparisons, totaling 2610 patients with follow-up from 2 to 20 years, demonstrated any significant functional difference. The largest propensity score-matched cohort study (2416 patients) and the largest meta-analysis (623 cases) confirmed that age, delay, and nerve type are the dominant prognostic determinants.
CONCLUSION: No currently available clinical study has demonstrated a detectable functional superiority of microscope-assisted repair over loupe-assisted repair, explained by the modest amplitude of the precision difference, caliber-dependent saturation above 1.5 mm, and the dominance of biological factors. High-quality loupes (≥×4.5) may be reasonable in selected emergency and resource-limited settings, but formal non-inferiority to the microscope remains unproven. A standardized in vivo experimental study with histological endpoints is the essential next step before considering a multicenter clinical trial.
LEVEL OF EVIDENCE: IV (narrative review of predominantly Level IV studies).
Read the article: PubMed · Publisher (DOI)