Risk of neurovascular injury with limited-open carpal tunnel release: defining the "safe-zone".

Limited-open carpal tunnel release was performed in ten cadaver arms using the "Safeguard" system. The "Safeguard" guide was intentionally placed off of the longitudinal middle/ring finger axis, either in 15 degrees of radial deviation or 15 degrees of ulnar deviation. Despite the errant placement, carpal tunnel release was performed without damage to any neurovascular structure. The proximity of neurovascular structures to the middle/ring finger axis was measured in all ten cadaver specimens. From this, a "safe-zone" was defined for endoscopic or limited-open carpal tunnel release. The "safe-zone" expands when surgery is performed from distal to proximal. The area of the "safe-zone" is greatest when a protective guide is placed between the bursal sac of the carpal canal and the flexor retinaculum.