Multiple fluoroscopic views, including an external rotation-adduction view, are required to detect uncontained screws in the femoral neck

Abstract

Introduction: Peripheral screws in the femoral neck are often used for fixation of femoral neck fractures. The posterior-cranial screw can violate the femoral head blood supply if it is extra-osseous, and can be difficult to image intraoperatively. The purpose of this study was to identify whether any specific radiographic views were superior at detecting an uncontained screw in the femoral neck. Additionally, the external rotation-adduction view was defined and its efficacy at detecting an unsafe posterior cranial screw assessed. Methods: A radiographic study using three-dimensional (3D) computed tomography scanswas performed at a single institution academic hospital. Forty-six patients with normal CT scans of the pelvis were included. Cannulated screws were digitally templated on 3D renderings of the femoral neck in an inverted triangle configuration. Each screw was systematically moved to a position where it was uncontained. Ghost images were created, and the pelvis rotated to simulate obtaining various iterations of a lateral view of the proximal femur. The ability of a given radiographic view to detect an uncontained screw was determined. Results: A flat-lateral view detected 72% of unsafe anterior screw, while a neck-shaft colinear view detected 98%. The flat lateral view detected 61% of unsafe posterior cranial screws, while a new external rotation-adduction view identified 100% of unsafe posterior cranial screws. Conclusions: Multiple radiographic views should be obtained to assess screw safety when treating femoral neck fractures with peripherally placed screws. The external rotation-adduction view may be useful for detection of uncontained posterior cranial screws. Level of evidence: III