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Closed hand injuries, including dislocations of the interphalangeal (IP) joints of the fingers, are among the most common injuries encountered in the Emergency Department.1–3 Many finger dislocations are secondary to sports-related events. The proximal interphalangeal (PIP) joint is especially vulnerable in ball-handling activities.2,4 IP dislocations are second only to shoulder dislocations in incidence and are generally easy to reduce.4 IP joint dislocations may lead to chronic pain, swelling, stiffness, deformity, or early degenerative arthritis if not properly treated.1,5,6 Emergency Physicians must be capable diagnosing and managing IP joint dislocations.

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The PIP joint is a hinge joint with a bicondylar formation (Figure 70-1). It allows only for flexion and extension from 0 degrees to approximately 120 degrees.1,7,8 The convex proximal phalangeal head articulates with the concave base of the middle phalanx.4 This configuration provides the inherent static stability of the joint. Further stability, both static and dynamic, is provided by the surrounding ligaments and tendons that essentially form a box complex around the joint (Figure 70-2). The box complex supporting the articular surface is composed of the volar plate, the lateral and collateral accessory ligaments, and the extensor tendon. The volar plate is attached to the middle phalanx distally, where it is made of a dense, fibrous connective tissue. The volar plate thins proximally into a membranous portion that becomes continuous with the synovial reflection, allowing for folding with flexion of the digit. This configuration provides resistance against dorsal displacement of the middle phalanx.4 The extensor mechanism is composed of three slips: the central slip and two lateral slips (or bands) on the radial and ulnar sides (Figures 70-3 and 70-4). These slips provide dorsal support against dislocation of the joint. The lateral collateral ligaments bridge across the PIP joint on either side and stabilize it against lateral stress.3

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FIGURE 70-2
Graphic Jump Location

A schematic drawing of the box complex surrounding the PIP joint.

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FIGURE 70-3
Graphic Jump Location

Dorsal view of the extensor mechanism.

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FIGURE 70-4
Graphic Jump Location

Lateral view of the digit, demonstrating the anatomy and supporting structures. This support consists of the collateral ligaments and the volar plate, forming a box complex around the volar and lateral aspects of the joint. The extensor mechanism consists of the central and the lateral slips on the dorsal aspect of the digit.

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The distal interphalangeal (DIP) joint is a broad-based hinge joint that allows approximately 90 degrees of flexion.3 Like the PIP joint, the ...

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