The dorsal tangent line - A new approach in the radiological analysis of metacarpal fractures.

Abstract Traditionally, the angle between the intersecting central axes (lateral projection intersecting central axes - LCA) of the proximal and distal fragments of metacarpal fractures is measured on radiographs. We recommend using the angle between the intersecting dorsal tangent lines instead (lateral projection intersecting dorsal tangent lines - LDT). We analyzed radiographs of 25 fractures of the fifth metacarpal bone shaft in three planes. Intraclass correlation coefficients (ICC) were used to estimate inter-rater and intra-rater reliability. Mean palmar tilt was 35.6° ± 12.5° according to LCA and 27.6° ± 12.0° according to LDT. There were no differences during repeated measurements. Intra-rater reliability was high: ICC (95% CI) for LDT was 0.82 (0.74–0.88) and for LCA it was 0.71 (0.51–0.83). Mean values of palmar tilt using LCA exceeded those using LDT by 8.0° ± 7.7° (p