Which proximal row carpal bone is most commonly dislocated?

Which proximal row carpal bone is most commonly dislocated?

• A. Lunate
• B. Scaphoid
• C. Pisiform
• D. Capitate

Answer: (A)

When the wrist is forced into a hard extension, the sharp place where the radiocarpal ligaments are weaker, called the space of Poirier, becomes a vulnerable route. The lunate sits right in the middle of the proximal row and is held in place mainly by the dorsal ligaments, while the volar (palm-side) side is comparatively less reinforced. That combination makes the lunate more likely to slip out of alignment anteriorly into the carpal tunnel when the ligaments tear under stress. Scaphoid fractures are more common in this mechanism, because the scaphoid bears a lot of the load between the radius and the distal row, but it tends to break rather than dislocate. Pisiform and capitate are better stabilized by their ligament connections, so they’re less prone to dislocation. So the bone most commonly dislocated in the proximal row is the lunate.

When the wrist is forced into a hard extension, the sharp place where the radiocarpal ligaments are weaker, called the space of Poirier, becomes a vulnerable route. The lunate sits right in the middle of the proximal row and is held in place mainly by the dorsal ligaments, while the volar (palm-side) side is comparatively less reinforced. That combination makes the lunate more likely to slip out of alignment anteriorly into the carpal tunnel when the ligaments tear under stress. Scaphoid fractures are more common in this mechanism, because the scaphoid bears a lot of the load between the radius and the distal row, but it tends to break rather than dislocate. Pisiform and capitate are better stabilized by their ligament connections, so they’re less prone to dislocation. So the bone most commonly dislocated in the proximal row is the lunate.