To predict the feature and stability of intertrochanteric fractures with posterior fragment using preoperative 3D computed tomography and to investigate the importance of the posterior fragment in treatment of unstable intertrochanteric fracture.

15 cases of unstable fractures with posterior fragment which were treated with nail only between October 2006 to August 2007 were classified into 2 groups: study group (5 cases with cannulated screw fixation of posterior fragment) and control group (10 cases without cannulated screw fixation). The average difference of neck-shaft angle, neck screw sliding distance and the complications in the two groups were compared retrospectively after a follow up of at least 3 months.

The average difference of neck-shaft angle in study and control group was 3.8 and 7.5 degree (p>0.05), respectively. The average difference of neck screw sliding distance was 1.6 and 6.6 mm (p<0.05), respectively. Complication which required reoperation was not noted in study group and complications of 3 cases about neck screw lateral protrusion, proximal migration and Z-effect phenomenon were noted in control group.

The recognition and fixation of the posterior wall was found to be an important predictive factor in unstable intertrochanteric fracture treatment.