Finger Dislocation

Excerpt

Finger joint dislocations are common hand injuries that may occur at the metacarpophalangeal (MCP), proximal interphalangeal (PIP), or distal interphalangeal (DIP) joints, with varying frequency. The complex and extensive anatomy of the finger permits coordinated digital function. Each digit has 3 primary joints: the MCP, PIP, and DIP. The MCP joint is a condyloid articulation between the metacarpal and proximal phalanx. The PIP joint is a hinge joint between the proximal and middle phalanges. The DIP is also a hinge joint between the middle and distal phalanges.

The range of motion of these joints allows for flexion and extension, which provides grasping, pinching, clawing, and reaching functions of the fingers. The MCP joint typically achieves 90° of flexion; the PIP and DIP often reach 100° and 80°, respectively. While flexion and extension of the digit are possible at the MCP joint, this joint can also perform adduction, abduction, and circumduction. See Image. First Metacarpophalangeal (MCP) Joint Dorsal Dislocation.

The finger joints have important soft tissue stabilizers that provide necessary support during motion. These joint stabilizers are both static and dynamic. Static stabilizers consist of noncontractile tissues, including the radial and ulnar collateral ligaments, volar plate, dorsal capsule, and sagittal bands, which surround the MCP joint. The volar plate is a crucial stabilizer, as it reinforces the volar aspect of the joint capsule and maintains stability by preventing hyperextension of the finger joints. The collateral ligaments provide stabilization against radial and ulnar (lateral) deviation of the interphalangeal joints.

Sagittal bands encircle the MCP joint to keep the extensor tendon centralized. Dynamic stabilizers include extrinsic and intrinsic tendons and muscles, and 3 important dynamic stabilizers are the central slip, terminal tendon, and flexor tendons. The central slip is found dorsally and allows for PIP joint extension, while the terminal tendon inserts at the dorsal base of the distal phalanx and facilitates DIP joint extension. The flexor digitorum profundus and flexor digitorum superficialis tendons serve as additional restraints against hyperextension of the DIP and PIP joints, respectively.