The Central Dislocation of Femoral Head in the Transverse and Both Column Acetabular Fractures: Is It Really Medialized?

PURPOSE We hypothesized that the central dislocation of the femoral head does generally not occur in transverse acetabular fractures, although it does usually occur in both column fractures. MATERIALS AND METHODS Fifty-two transverse and both column acetabular fracture cases were evaluated retrospectively. The distances between (a) the sciatic notch on the fracture side and the vertical axis of the pelvis (VA line) and (b) the contralateral intact sciatic notch and the VA line were measured. The a/b ratio corresponded to the superior iliac segment displacement or rotation. The ratio of the distance between the fracture side femoral head and the VA line (c) and the distance between the contralateral intact femoral head and the VA line (d) corresponded to the femoral head displacement. The width of ischium (e) on fractured side and (f) contralateral side were measured. The e/f ratio increment reflected ischiadic fragment mobility. RESULTS The median value of femoral head displacement (c/d) of the transverse fracture group (n=25) was 1.02 (1.000-1.07). Ischiadic fragment rotation (e/f ratio) of the transverse fracture group was 1.000. The median value of femoral head displacement (c/d) of the both column fractures (n=27) was 0.78 (0.64-0.85). Ischiadic fragment rotation (e/f ratio) of the both-column group was 1.15 (1.06-1.23). The differences between groups according to measurements were statistically significant. CONCLUSION In contrary to Letournel description, our findings showed no medialization of femoral head in transverse acetabular fractures in general. This might be an illusion resulting from external rotation of the superior iliac segment.