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The wrist is the articulation between the distal forearm bones (radius and ulna) and eight carpal bones. The most common carpal instability is between the scaphoid and lunate, termed scapholunate instability. Complete scapholunate dissociation results in a gap between the scaphoid and lunate on posterior–anterior (PA) radiographic projections (scapholunate gap). On lateral radiographs, the scaphoid assumes a flexed posture and the lunate extends, resulting in increased scapholunate and radiolunate angles. The second most common carpal instability patters is between the triquetrum and lunate, termed lunotriquetral instability. Ulnar translocation of the carpus, also known as carpal translation, refers to medial displacement of the entire carpus on the forearm (radius and ulna) and is the most common radiocarpal instability. In the AMA Guides to the Evaluation of Permanent Impairment (AMA Guides), Sixth Edition, carpal instabilities are rated using Table 15-3, Wrist Regional Grid; the impairment class is determined using Table 15-9, Clinical Studies Adjustment: Upper Extremities. Measurements from plain radiographs are used in Table 15-9 to characterize the instability as mild, moderate, or severe; these characterizations, in turn, determine the class. The assessment of carpal instability using radiographic measurements has limitations, particularly that the radiographic parameters used to grade impairment are imprecise; angular measurements between individual bones are particularly variable, and carpal bone axes can be difficult to determine due to bony overlap on plain radiographs.

Wrist trauma can disrupt the ligamentous support between the carpal bones, leading to instability of the carpus and pain, loss of motion, and loss of function. The most common patter of wrist instability is scapholunate instability that results from a fall on the outstretched hand, possibly with twisting motion. The second most common carpal instability pattern is that between the triquetrum and the lunate, termed lunotriquetral instability. The AMA Guides to the Evaluation of Permanent Impairment directs physicians to use frontal and lateral roentgenographic projections of the wrist to evaluate carpal instabilities and to rate impairment as mild, moderate, or severe. Carpal height can be used to assess impairment. Carpal translation is a medial or lateral translation of the entire carpus on the forearm (radius and ulna). Arthritic changes also can impair wrist stability and are seen roentgenographically as loss of joint space in the wrist. The degree of carpal instability lies on a continuum of loss of carpal bone support and amount of collapse, and, although little absolute difference exists between a 28-degree radiolunate angle and a 31-degree measurement, these two measurements yield different impairment ratings. Also, some forms of instability (eg, dynamic carpal instability) appear roentgenographically if the wrist is stressed, and examiners have freedom to assign impairment without reproducible, objective measures.

Nicotine-dependent smokers exhibit craving and brain activation in the prefrontal and limbic regions when presented with cigarette-related cues. Bupropion hydrochloride treatment reduces cue-induced craving in cigarette smokers; however, the mechanism by which bupropion exerts this effect has not yet been described.To assess changes in regional brain activation in response to cigarette-related cues from before to after treatment with bupropion (vs placebo).Randomized, double-blind, before-after controlled trial.Academic brain imaging center.Thirty nicotine-dependent smokers (paid volunteers).Participants were randomly assigned to receive 8 weeks of treatment with either bupropion or a matching placebo pill (double-blind).Subjective cigarette craving ratings and regional brain activations (blood oxygen level-dependent response) in response to viewing cue videos.Bupropion-treated participants reported less craving and exhibited reduced activation in the left ventral striatum, right medial orbitofrontal cortex, and bilateral anterior cingulate cortex from before to after treatment when actively resisting craving compared with placebo-treated participants. When resisting craving, reduction in self-reported craving correlated with reduced regional brain activation in the bilateral medial orbitofrontal and left anterior cingulate cortices in all participants.Treatment with bupropion is associated with improved ability to resist cue-induced craving and a reduction in cue-induced activation of limbic and prefrontal brain regions, while a reduction in craving, regardless of treatment type, is associated with reduced activation in prefrontal brain regions.