Understanding carpal instability: a radiographic perspective.

The wrist is disposed to a variety of instability patterns owing to its complex anatomical and biomechanical properties. Various classification schemes have been proposed to describe the different patterns of carpal instability, of which the Mayo classification is the most commonly used. Understanding the concepts and pertinent terminology of this classification scheme is important for the correct interpretation of images and optimal communication with referring physicians. Standard wrist radiographs are the first line of imaging in carpal instability. Additional information may be obtained with the use of stress radiographs and other imaging modalities.

Role of muscles in the stabilization of ligament-deficient wrists.

This article reviews the results of a series of cadaver investigations aimed at clarifying the role of muscles in the stabilization of ligament-deficient wrists. According to these studies, isometric contraction of some forearm muscles induces midcarpal (MC) supination (ie, the abductor pollicis longus, extensor carpi radialis longus, and flexor carpi ulnaris), whereas other muscles induce MC pronation (ie, the extensor carpi ulnaris). Because MC supination implies tightening of the volar scaphoid-distal row ligaments, the MC supination muscles are likely to prevent scaphoid collapse of wrists with scapholunate ligament insufficiency. MC pronator muscles, by contrast, would be beneficial in stabilizing wrists with ulnar-sided ligament deficiencies owing to their ability to tighten the triquetrum-distal row ligaments. Should these laboratory findings be validated by additional clinical research, proprioceptive reeducation of selected muscles could become an important tool for the treatment of dynamic carpal instabilities.

Isolated or predominant capitolunate osteoarthritis is the consequence of lunotriquetral dissociation. X-ray analysis of 22 consecutive cases.

Secondary osteoarthritis due to a scapholunate malalignment is well known, but is debatable in cases of lunotriquetral malalignment. It has been shown that lunotriquetral malalignment can lead to midcarpal osteoarthritis. The hypothesis of this retrospective study was that a relationship exists between the presence of midcarpal osteoarthritis and the presence of lunotriquetral malalignment. All patients with midcarpal osteoarthritis, isolated or predominant, treated between 1981 and 2013 were reviewed. Intracarpal angles were measured and the relative position of the carpal bones was analyzed by two examiners. Osteoarthritis of the wrist's joints was quantified in three stages. Diagnosis of static dissociative ligament lesion was made and correlated with the location of osteoarthritis. Twenty-two wrists in 20 patients (13 men and 7 women; mean age of 59 years) were included. The lunocapitate osteoarthritis was moderate in 6 cases and severe in 16 cases. The radioscaphoid osteoarthritis was moderate in 5 cases and severe in 1 case. Lunotriquetral malalignment was present in all cases; it was isolated in 8 cases and associated with scapholunate malalignment in 14 cases. In isolated lunotriquetral malalignment cases, midcarpal osteoarthritis was isolated or associated with degenerative lesions of lunotriquetral interval. Cases of perilunate instability in which the osteoarthritis is more severe in the midcarpal joint than in the radioscaphoid joint likely resulted from an injurying mechanism with ulnar beginning (ulnar-sided perilunate instability).