[Incorrect classification of extra-articular distal radius fractures by conventional X-rays. Comparison between biplanar radiologic diagnostics and CT assessment of fracture morphology]. / Fehlklassifikation extraartikulärer distaler Radiusfrakturen in konventionellen Röntgenaufnahmen. Vergleichende Untersuchung der Frakturmorphologie zwischen biplanarer Röntgendiagnostik und CT.

Thirty-five displaced fractures of the distal radius, classified by standard radiographs as extra-articular type A2 and A3 fractures according to the AO classification, were investigated before operative treatment by computed tomography. The comparative analysis surprisingly revealed an involvement of the articular surface of the distal radius in 57%. The intra-articular fractures were classified after CT as C1 in 15%, C2 in 65%, and C3 in 20%. The distal radioulnar joint was involved in 80% of the type C injuries and showed a dorsal subluxation in 17% of all cases. Similar to the results of type A2 and A3 fractures, type B and C fractures of the distal radius also may be underestimated in standard radiographs. This concerns important components such as the involvement of the radiocarpal joint surface and concomitant injuries of the distal radioulnar joint. Since joint congruency is an important predictor of outcome, CT scanning should be used more generously for planning and controlling surgical therapy.