Validation of the extensor carpi ulnaris groove as a predictor for the recognition of standard posteroanterior radiographs of the wrist.

This study was designed to establish the extensor carpi ulnaris groove (ECUG) as a reliable radiographic criterion for recognition of true neutral posteroanterior (PA) radiographs and to verify precise measurements of ulnar variance in a large cohort of patients. In 197 patients 197 wrists were evaluated with a series of radiographic views obtained during routine wrist arthrography. Posteroanterior views were taken in all patients at 90 degrees, 45 degrees, and 0 degrees arm abduction and in 171 patients at 90 degrees elbow flexion and 90 degrees arm abduction with full elbow extension. The ECUG position was classified according to its profile with the ulnar styloid as excellent, acceptable, or unacceptable. Ulnar variance was measured on all x-ray films. Statistical analysis included interobserver reliability with 100 x-ray films measured by 2 evaluators. The ECUG was excellent or acceptable in 100% of the x-rays on standard PA views (arm abducted 90 degrees ), 87% excellent or acceptable and 13% unacceptable on 45 degrees arm abduction views, and 23% excellent or acceptable and 77% unacceptable on 0 degrees arm abduction (adducted) views (all with the elbow flexed at 90 degrees ). With the arm at 90 degrees abduction and full elbow extension the ECUG was excellent or acceptable in 91% of cases. These results show that the ECUG is a reliable criterion to verify arm position during PA wrist radiography and therefore provides a standard for making treatment decisions. The need for repeat radiographs should be reduced.