Site of insertion of flexor digitorum profundus tendon and volar plate at the distal phalanx in relation to a volar spur - A radiological-anatomical study

Abstract

Background: This study aimed to differentiate between the attachment sites of the volar plate and the flexor digitorum profundus (FDP) tendon by specific measurements in lateral radiographs. Furthermore, their relation to a volar spur was assessed.

Methods: We dissected the attachments of the volar plate and the FDP tendon in 200 distal phalanges of male and female body donors. The margins of the attachments were marked with cannulas for subsequent radiological evaluation. The location of a not yet described volar spur at the base of the distal phalanx was assessed hypothesizing a potential correlation to the FDP tendon attachment.

Results: The analyzed phalanges were 16.8 ± 1.5 mm long and 5.6 ± 0.7 mm deep. The volar spur was identifiable in all specimens and was located 3.5 ± 0.6 mm from the volar articular line. The distances from the articular line to the volar spur and to the proximal margin of the FDP tendon showed strong correlation (0.560, p < 0.001). The proximal margin of the FDP tendon attachment was located at 47.4 % ± 10.6 % of the distance between the articular line and the volar spur.

Conclusion: The volar spur at the volar base of the distal phalanx facilitates the identification of the FDP tendon attachment and its differentiation from the volar plate attachment. This may be essential in the characterization of bony volar plate avulsion in the distal phalanx. Furthermore, the volar spur may serve intraoperatively as radiological reference of the centroid of the FDP tendon attachment facilitating correct repair placement in FDP tendon avulsions.

Keywords: Distal phalanx; FDP tendon; Flexor digitorum profundus; Radiological anatomy; Volar plate.