The terminal tendon of the digital extensor mechanism: Part I, anatomic study

The purpose of this study was to examine the anatomy of the terminal tendon (TT) and its relationship to adjacent structures.

The extensor tendons of 56 cadaveric digits (52 fresh-frozen and 4 formalin-preserved) underwent anatomic dissection.

The TT is a segment between the convergence of the lateral bands proximally and the bony insertion in the phalanx distally. The ulnar lateral bands were thicker than the radial bands. The average distance from the TT insertion to the germinal matrix of the nail bed was 1.4 mm. The triangular ligament (TL) is a thin layer of transverse fibers between the lateral bands proximal to the TT. The dimensions of the TT and the TL vary relative to the size of the digit with the largest often occurring in the middle, followed by the ring, index, and small finger. The transverse retinacular ligament (TRL) had a dorsal attachment to the lateral bands and was much more defined and distinct than the oblique retinacular ligament. The ulnar TRL often was thicker than the radial TRL.

The TT is the primary structure responsible for extending the distal interphalangeal (DIP) joint. The function of the adjacent retinacular structures is to provide stability to the TT. The thin nature and proximity of the TT to the nail matrix must be kept in mind during surgery. Knowledge of the TT anatomy is necessary for further study of its kinematics and pathology and for diagnosis and management of its disorders.