Anatomic variations of the midcarpal joint.

Area of Science:

• Orthopedic anatomy
• Wrist biomechanics
• Radiographic analysis

Background:

• The midcarpal joint's complex anatomy influences wrist function.
• Understanding its variations is crucial for diagnosing pathologies.
• Previous classifications may not fully capture specific structural differences.

Purpose of the Study:

• To identify and describe distinct anatomic variations of the human midcarpal joint.
• To correlate these variations with specific degenerative changes and ligamentous injuries.
• To enhance diagnostic accuracy for midcarpal joint pathologies.

Main Methods:

• Anatomical dissection and radiographic analysis of human cadaveric wrists.
• Detailed examination of the articulation between the triquetrum, hamate, capitate, and lunate.
• Histopathological correlation of observed degenerative changes.

Main Results:

• Two distinct types of midcarpal joint anatomy were identified.
• Type I: Smooth oblique plane between triquetrohamate and capitolunate joints.
• Type II: Concave transition facet separating triquetrohamate from capitolunate joints, associated with proximal hamate and lunate facet degeneration, and lunotriquetral interosseous ligament tears.

Conclusions:

• The human midcarpal joint exhibits at least two distinct anatomic variations.
• Type 2 joints, characterized by a transition facet, are predisposed to specific degenerative changes.
• These degenerative changes and lunotriquetral ligament tears are key indicators of a Type 2 midcarpal joint configuration.