Medical records and radiographs of 52 patients were studied after incl
usion/exclusion criteria were met. The anatomical location of proximal
femoral fractures that involved the femoral neck were examined after
the primary fracture planes were drawn onto templates of the proximal
femur The AO classification is comprehensive and widely accepted. It h
as not been used in this injury combination in a large series of patie
nts. Therefore, me classified each fracture by the AO method and then
the AO classes were tabulated and analysed. Only three patterns of pro
ximal femoral fractures appeared. The inferior aspect of the fracture
line clustered in the inferomedial aspect of the femoral neck above an
intact lesser trochanter in each separate pattern: 55 per cer rf were
AO B2.1 (basilar); 35 per cent AO B2.3 (intracapsular); and 10 per ce
nt AO A1.2 (pertrochanteric) fractures). Eleven fractures (21 per cent
) were not detected initially. None of these were A1.2 eight were B2.1
and three were B2.3. Despite many proximal femoral fracture types rep
orted in the literature only three fracture patterns were noted in thi
s large study group. A new finding of clustering of these fractures in
the inferomedial femoral neck was noted. AO class B2.1 fractures were
the most common fractures missed at initial presentation and were the
most common type seen. (C) 1997 Elsevier Science Ltd.