A Mechanism-Based Classification and Review of Endoscopic and Ultrasound-Guided Carpal Tunnel Release

Background: Minimally invasive carpal tunnel release (CTR) approaches, including endoscopic and ultrasound-guided, encompass a range of distinct techniques. These approaches have been increasingly adopted across both surgical and non-surgical specialties. However, the literature frequently groups the techniques into broad categories, obscuring clinically meaningful differences in transection mechanism, safety profile, and learning curve. Methods: This narrative review organizes minimally invasive CTR into eight distinct techniques, two endoscopic and six ultrasound-guided, classified by their primary transection mechanism. Results: Single-portal endoscopic CTR has the largest evidence base, with network meta-analysis data demonstrating significant early functional advantages over open CTR. Among ultrasound-guided techniques, the retractable retrograde blade is the most widely adopted, with randomized trial data supporting comparable outcomes to mini-open CTR. Hook-knife retrograde and thread-loop techniques have demonstrated feasibility and durable outcomes, though experience is concentrated among a few high-volume operators. The antegrade cutting, pinhole scalpel, and needle-knife have more limited evidence. Earlier return to work is the most reproducible benefit across all minimally invasive approaches. Endoscopic CTR carries a modestly higher revision rate, while long-term data for ultrasound-guided techniques remain lacking. Conclusions: This mechanism-based classification highlights important differences between techniques in safety features, evidence maturity, and learning curves. Head-to-head trials comparing endoscopic and ultrasound-guided techniques and device-specific registries with standardized outcome reporting are needed to inform evidence-based adoption.