Although degenerative problems associated with scapholunate dissociation are a very common cause of wrist arthritis, isolated lunotrique-tral arthritis is rare unless it is encountered as a result of a partial carpal coalition . Coalition of carpal bones is relatively common, and the lu-nate-triquetrum fusion is the most frequent carpal coalition [36,37]. This finding is almost always coincidental and asymptomatic (Fig. 5); however, when the coalition is incomplete, patients who have this problem may have ulnar-sided wrist pain  and arthritic changes in the remaining lu-notriquetral joint.
Clinical and radiologic evaluation
It is important to differentiate isolated luno-triquetral problems from other causes of ulnar sided wrist pain such as triangular fibrocartilage complex (TFCC) tears. After a complete physical examination, standard radiographs are obtained. There must be a true lateral radiograph to rule out a VISI deformity and a zero-rotation PA radiograph to assess ulnar variance. An arthrogram or magnetic resonance arthrogram may be a useful study because it is not uncommon to see TFCC and lunotriquetral pathology together.
As discussed earlier, isolated lunotriquetral arthritis is rare unless it is the result of a partial carpal coalition. This is one of the few clear indications for isolated lunotriquetral arthrodesis. Treatment of ligamentous injuries to the lunotri-quetral articulation is more controversial.
Lunotriquetral ligament injuries may result in a VISI deformity. For a VISI pattern to develop, there must be disruption of the dorsal and palmar lunotriquetral ligaments as well as the dorsal radiotriquetral and dorsal radioscaphotriquetral ligaments . Unotriquetral fusion or ligament reconstruction is recommended only if there is isolated lunotriquetral instability without a VISI deformity [40,41]. In addition, nonunion rates of lunotriquetral fusion are higher if the patient has positive ulnar variance. If there is a VISI deformity, isolated lunotriquetral arthrodesis is contra-indicated, because the static deformity will not be corrected. The hamate must be included in the lunotriquetral fusion or a four-bone fusion must be performed. If there is positive ulnar variance along with an isolated lunotriquetral ligament injury or lunotriquetral arthritis, the positive variance should be corrected at the time of lunotriquetral fusion.
Kirschenbaum and colleagues  reported on a series of lunotriquetral fusions in 14 patients. All patients had chronic LT instability and underwent lunotriquetral fusion. The follow-up period averaged 27 months. Radiographs were suggestive of fusion in 12 of the cases. One of the pseudarthro-ses required revision surgery, the other was asymptomatic. One patient had persistent wrist pain. Wrist motion compared with the contralateral side averaged 85%, 88%, 83% and 80%, respectively, for flexion, extension, ulnar deviation, and radial deviation. Grip strength compared with the contralateral side averaged 93%. The study authors concluded that LT fusion reliably relieves pain while maintaining functional wrist motion and grip strength .
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