Anatomic Association of the Proximal Fingernail Matrix to the Extensor Pollicis Longus Tendon: A Morphological and Histological Study

Patricia Palomo-López,Manuel Herrera-Lara,Ricardo Becerro-De-Bengoa-Vallejo,Marta Losa-Iglesias,Daniel López-López,Jorge Murillo-González,César Calvo-Lobo

doi:10.3390/jcm7120465

Abstract

Background: Extensor tendon disorders may cause severe functional impairments, and there is a lack of knowledge about their anatomic associations with the proximal fingernail matrix. Objective: To delineate the association between the distal extensor pollicis longus tendon (EPLT) insertion and the limit of the fingernail matrix in the thumb. Methods: The limit of the fingernail matrix and the distal bony insertion of the EPLT were identified in five thumbs from fresh-frozen human cadavers. An additional five thumbs were fixed and the longitudinal thumb sections were histologically analyzed. Results: The terminal limit of the matrix and fingernail was dorsal and overlapped to the EPL tendon, which was located between the fingernail matrix and the phalanx, and extended dorsally to the distal section of the terminal phalanx in all ten thumb bodies. Conclusion: The fingernail matrix is not directly inserted into the periosteum of the dorsal section of the base to the distal phalanx, because this anatomic relationship is separated by the deep fibers of the EPLT.

Highlights

Thumb extension is carried out by the abductor pollicis longus (APL), extensor pollicis longus tendon (EPLT), and extensor pollicis brevis muscles (EPB) [1]
We found that the EPLT is localized between the fingernail matrix and the phalange, and that the tendon’s superficial fibers extend dorsally to the distal area of the distal phalange
We demonstrate that the thumb’s fingernail matrix is not enclosed to the periosteum of the dorsal area of the base of distal phalange, as it was previously reported, because the deep lamina of the EPLT is directly below the fingernail matrix and dorsal to the bone

Summary

Introduction

Thumb extension is carried out by the abductor pollicis longus (APL), extensor pollicis longus tendon (EPLT), and extensor pollicis brevis muscles (EPB) [1]. Extensor tendon (ET) injuries may cause a severe functional impairment [4], and these conditions may often involve the thumb tip and the functionally integrated nail matrix, plate, and bed [5,6]. Surgery on these areas and the distal phalanx after trauma or other conditions, including infection, tumors, iatrogenic injury, and degenerative conditions, may require a detailed understanding of the anatomy and of the association between the fingernail and its surrounding tissue. Objective: To delineate the association between the distal extensor pollicis longus tendon (EPLT) insertion and the limit of the fingernail matrix in the thumb. Conclusion: The fingernail matrix is not directly inserted into the periosteum of the dorsal section of the base to the distal phalanx, because this anatomic relationship is separated by the deep fibers of the EPLT

Objectives

Methods

Discussion

Conclusion