To discriminate the characteristics between reverse obliquity fractures in the elderly and that of young adults using three-dimensional computed tomography (3D CT).

Eighteen patients who had reverse obliquity intertrochanteric fractures were enrolled from January 2007 to March 2012. The fracture pattern was analyzed using the 3D CT. The area showing low density (bone defect) of trochanter and femoral neck region was measured. Patients were divided into two groups: Group I, less than 65 years old and Group 2, 65 years and over.

In all 9 cases of group 1, the proximal fragment had a 'V' shape with an average of 5.6 cm below the vastus ridge; however, the fracture of 8 cases (88.97%) in group 2 had a 'Λ' shape of the distal fragment at the level of vastus ridge and an additional fracture line extending to the greater trochanter tip. The bone defect volume of the trochanter and femoral neck region was larger significantly in group 2 than in group 1.

Reverse obliquity intertrochanteric fracture in the elderly demonstrated a pattern of bursting fracture with 4 parts, which had different patterns from that of young patients. We believe that the larger volume of bone defects resulted in the difference of fracture patterns between the two groups.