Lunate-triquetral and midcarpal joint instability.

Instability of the ulnar side of carpus centers around the triquetrum, which is suspended by the ulnar triquetral ligaments and supported proximally by the TFCC. The triquetrum guides the lunate by an interosseous membrane and stout palmar ligaments that provide a relatively rigid connection between the two bones. Disruption of the LT ligament is frequently associated with pathology in the ulnar carpal area and may progress to triquetral instability, VISI, and finally, degenerative arthritic changes on the ulnar side of the carpus. The diagnosis of LT injuries is made by stress radiographs, arthrography, video-fluoroscopy, and arthroscopy. Treatment is initially nonoperative, but if symptoms persist, surgery is warranted. Arthroscopic debridement and pinning the LT joint, ligament repair or reconstruction, and intercarpal arthrodesis have all been reported as successful treatments. For the chronic problem confined to the LT joint, a limited intercarpal arthrodesis of the joint is the most predictable procedure for relieving pain without causing any significant restrictions in wrist motions. When there is a dissociation pattern in addition to LT instability, a more extensive intercarpal arthrodesis is required. Midcarpal instability occurs at the triquetral-hamate joint and is characterized by a dynamic subluxation of the joint. During ulnar deviation, the joint undergoes an exaggerated shift from volar flexion to dorsiflexion. Supportive care is generally successful; although in chronic cases, a midcarpal joint arthrodesis is often required.