Fig. 1

Schematic drawing to show the inferior cortical apposition pattern after manual reduction in displaced femoral neck fractures. a The displaced femoral neck fracture. b Anatomic cortical apposition with smooth inferior cortex apposition. c Negative cortical apposition lost calcar support. d Positive cortical apposition obtained calcar support. The proximal head-neck fragment is slightly superiorly displaced intentionally (less than one cortex thickness or 4 mm) to the distal fragment (red arrow), so that the inferior cortex of the proximal head-neck fragment (red color) can be buttressed by the calcar cortex of the distal neck fragment (blue color). After screw fixation, the femoral head-neck is dual supported by the fixation screw and the calcar cortex, and a sustainable stability is restored