Base Of A Middle Phalanx, Anterior View

Description

Base of the middle phalanx (phalanx media) occupies the frame in anterior (volar) orientation, centered on the proximal articular surface that receives the head of the proximal phalanx at the proximal interphalangeal (PIP) joint. The socket-like contour is defined by paired concavities separated by a low central ridge, a configuration that matches the bicondylar form of the proximal phalangeal head. Along the volar margin, the articular rim transitions into nonarticular cortical bone where the volar plate anchors, while the collateral ligament attachment sites sit more laterally at the margins of the base, just beyond the articular cartilage boundary. Small details matter. PIP joint stability and fracture patterns hinge on this geometry: a dorsal PIP dislocation commonly fails through the volar plate insertion, producing a volar lip avulsion fracture from the base of the middle phalanx, and the size of that fragment guides decisions about extension-block splinting versus operative fixation. For intra-articular fractures, congruity between the central ridge and adjacent concavities determines whether the joint will track smoothly or develop post-traumatic stiffness and arthrosis. The fixed anterior perspective keeps the volar rim and the articular “gutter” readable in one glance, which is exactly where clinicians look when correlating surface anatomy with plain radiographs and CT reconstructions. Hand anatomy courses and osteology labs can pair this illustration with proximal phalanx and PIP ligamentous images to teach joint congruence, collateral ligament function, and volar plate mechanics. It also fits naturally into orthopedic and hand surgery texts discussing PIP fracture-dislocations, volar plate avulsion, and small-joint arthroplasty planning where precise bony landmarks must be communicated without ambiguity. Anatomical accuracy verified by SciePro's Medical Advisory Board.