What are sport-specific biomechanics of phalangeal fractures?

Updated: Jan 18, 2018
  • Author: Jay E Bowen, DO; Chief Editor: Craig C Young, MD  more...
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Answer

The PIP joint is the most commonly injured area in the hand. There is both anatomic and functional complexity to this joint, which consists of the articulation of the proximal end of the middle phalanx and the distal end of the proximal phalanx. It is a hinge joint with range of motion from 0 º to 120 º in the extension-flexion plane, with the bulk of static and dynamic stability provided by the surrounding ligaments and tendons.

The capsule surrounding the articular surface is composed of the volar plate, thick collateral ligaments, and the extensor tendon dorsally, which divides into 3 slips as it passes over the proximal phalanx. The central slip of the extensor tendon passes directly over the joint and inserts on the dorsal base of the middle phalanx. The lateral bands of the extensor tendon combine distally with the tendons of the intrinsic hand muscles (the retinacular ligaments) to form the extensor tendon that attach to the distal phalanx.

The thick ulnar and radial collateral ligaments of the PIP joint combine with the volar plate to provide lateral stability. The volar plate, a thick fibrocartilaginous structure, forms a sturdy attachment to the middle phalanx where it becomes continuous with the articular cartilage. This limits extension of the PIP joint beyond 0 º.

Proximally, the volar plate forms a thin continuous attachment with the synovial reflection. The lateral margins remain thick strong ligaments. This results in a cul-de-sac between the proximal half of the volar plate and the head of the proximal phalanx, which allows the base of the middle phalanx to glide along the articular surface of the proximal phalanx as the finger flexes. Thus, the volar plate becomes both a static stabilizer limiting hyperextension beyond 0 º and a dynamic stabilizer that influences the position of the flexor tendons at initiation of PIP joint flexion.


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