We wanted to assess the characteristics and clinical significance of screw migration after surgical treatment of femoral neck fractures.

We reviewed 44 hips (22 males, 22 females) that were treated with closed reduction and multiple cannulated screws between February 1998 and May 2005. The medical records and radiographs were analyzed retrospectively at a minimum of 18 months after surgery. 3 mm migration was arbitrarily chosen as the differentiating measure between the migration (27cases) and the nonmigration (17 cases) groups. The anatomical location of the fracture, Garden's classification, comminution, the screw position in the femoral head and the complications were statistically compared between the migration and nonmigration groups. The time sequence of events after surgery and the distance of migration were evaluated in the migration group.

No significant differences between the two groups were noted in regard to complications, the screw position in the femoral head, the degree of displacement of fractures with using Garden's classification and the anatomic location of the fracture. There was a statistically significant difference between the two groups with regard to comminution (p=.001). In the migration group, the screws started migrating from 1 month after the operation and this was remarkable at 3~6 months. The average migration was 6.51 mm with 4.23 mm migration occurring in the first 3 months.

For comminuted femur neck fractures that are treated with multiple cannulated screws, screw migration and shortening of the femoral neck can be anticipated to happen at 3 months after surgery.