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Variations in the Anatomy of the Third Common Digital Nerve and Landmarks to Avoid Injury to the Third Common Digital Nerve with Carpal Tunnel Release
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ABSTRACT
Injury to the third common digital nerve was described as the most commonly injured digital nerve with carpal tunnel release. Anatomic variations in the origin and course of the third common digital nerve from the median nerve may place this structure at risk. Anatomic landmarks may be useful to predict the location of this third common digital nerve to minimize the risk for injury with carpal tunnel release.
Seventeen cadaver hands were used to determine the origin and course of the third common digital nerve. The origin of the third common digital nerve from the median nerve was identified in relation to the transverse carpal ligament, cardinal line, and superficial palmar arch. The course of the third common digital nerve was inspected in relation to the scaphoid tubercle and ring finger.
Three anatomic variations for the origin of the third common digital nerve were identified: type 1, originating proximal to distal edge of transverse carpal ligament (1/17); type 2, distal to the transverse carpal ligament but proximal to the superficial palmar arch (13/17); type 3, at or distal to superficial palmar arch (3/17). The origin of the third common digital nerve was measured an average of 5±1.2 mm distal to the cardinal line. The third common digital nerve coursed along an oblique vector from the scaphoid tubercle to the mid-point of the palmar digital crease of the ring finger for type 2 and type 3. The oblique course of the third common digital nerve passes across the longitudinal vector used for carpal tunnel release near the cardinal line. Distal to the cardinal line the third common digital nerve passed under the superficial palmar arch in all 17 dissections.
The anatomic landmarks of the center middle finger, cardinal line, and scaphoid tubercle to the midpoint of the palmar digital ring finger crease can be used to predict the origin and course of the third common digital nerve. However, a type 1 origin of the third common digital nerve may increase the risk of injury with carpal tunnel release.