Scaphopisocapitate alignment: criterion to establish a neutral lateral view of the wrist

To determine whether a "true" neutral lateral view of the wrist is necessary for accurate capitolunate angle measurement, to compare two standards of diagnostic adequacy for neutral lateral wrist views (distal radioulnar overlap [RUO] and scaphopisocapitate [SPC] relationship), and to confirm positional reproducibility and measurement precision of the SPC criterion.

Capitolunate angles were measured on neutral lateral and supine pisotriquetral views of 10 normal wrists. Two hundred neutral lateral wrist views were classified by each standard (RUO and SPC) as excellent, acceptable, or unacceptable. In two subgroups, capitolunate angles were measured on the lateral views to determine SPC practicality and sensitivity.

Compared with neutral lateral positioning, supinated off-lateral views showed an apparent increase in lunate dorsiflexion of up to 30 degrees. Diagnostically unacceptable, excellent, and acceptable pronosupination was present on 118, 22, and 60 of 200 views by using the RUO criterion and on 40, 79, and 81 of 200 views by using the SPC criterion, respectively. The capitolunate angle did not show a significant difference between each of the two subgroups (P > .05).

A true neutral lateral view of the wrist is necessary for accurate measurement of the capitolunate angle on the basis of a comparison with off-lateral views. SPC relationship provides a diagnostically reproducible standard for a neutral lateral wrist view and should reduce the need for repeat lateral radiographs.