To investigate the effect of lateral buttress on the fracture healing of Jensen type 4 intertrochanteric fracture of the femur treated by dynamic compression hip screw (DCS) in elderly patients, retrospectively.

From March 1999 to February 2003, 54 patients, older than 65 years, of Jensen type 4 intertrochanteric fractures of the femur treated by DCS were included. The relationship between the structual integrity of lateral buttress measured by proximal-medial fragment angle (PMFA) and postoperative neck-shaft angle, penetrating length of lag screw, the sliding length and incidence of fixation loss were evaluated.

Among 38 patients of group II (PMFA above 50 degree), 6 cases (15.8%) including 4 cases of cutting out of lag screw from femoral head, 1 case of nonunion and 1 case of excessive extrusion of lag screw failed radiologically. But there was no fixation loss case in 16 cases of group I (PMFA 50 and below 50). The neck-shaft angle in last follow-up was 138.1 degree in group I and 132.1 in group II. The sliding length of lag screw was 7.0 mm in group I and 12. 5 mm in group II (p<0.05).

Preoperative evaluation of intactness of lateral buttress measured by proximal-medial fragmentary angle is an useful method in treatment of Jensen type 4 intertrochanteric fractures treated by DCS in elderly patients.