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Purpose. To investigate the effect of lag-screw positions in the femoral head on modes of fixation failure. Methods. 591 patients aged ≥65 years underwent sliding compression screw fixation for type A 1 (n=249) and type A 2 (n=342) intertrochanteric fractures of the femur after low-energy injuries. There were 18 cases of fixation failure; in 13 (group 1) the lag screw was placed in the central-central area, and in 5 (group 2) in the inferior 1/3-central area. Clinical variables of the 2 groups were compared. Results. All 18 cases of fixation failure were actually type A 23 and misinterpreted as type A 22 fractures. In 13 cases, failure was attributable to cut-out of the lag screws at the superolateral edge of the femoral head. In 3 cases, failure was attributable to telescoping and >2 cm shortening of the femur. In one case, failure was due to penetration of the lag screw into the acetabulum. In another case, failure was due to plate loosening with breakage of cortical screws. In the 13 cases with cut-out of the lag screw (group 1), the lag screw was placed in the central-central area (p<0.001). In the remaining 5 cases with no cut-out (group 2), the lag screw was placed in the inferior 1/3–central area (p<0.01). Complications occurred significantly earlier in group 1 than in group 2 patients (2.6 vs. 4.6 months, p=0.02). The tip-apex distance was significantly shorter in group 1 than in group 2 patients (19 vs. 30 mm, p<0.001). Conclusion. Misinterpretation of type A 23 fractures as type A 22 may lead to fixation failure. Operative treatment should not be delayed once complications occur. The positions of the lag screw may affect the mode of fixation failure.