Lag Screw

Lag screw are heavy duty fasteners used to connect materials that bear a strenuous load. They are typically made from low carbon steel and may be coated with zinc or hot dipped galvanized to prevent corrosion. They can be ordered in a variety of lengths and have threaded ends that engage with lag shields. In general, lag screws are placed at an angle perpendicular to the fracture plane but can be placed at other angles for specific applications.

Lag screws are a widely used method of fixation for intertrochanteric fractures in the geriatric population. A helical blade implant system offers advantages with respect to tip-apex distance and cut-out complications compared with conventional lag screws. However, these advantages must be weighed against the increased difficulty with which the screw is placed and tightened.

Lag screws are usually predrilled with a pilot hole to avoid splitting or snapping during installation. They can be installed with a nut driver or ratchet and are compatible with a number of different head types depending on the drive type. Unlike wood screws, sheet metal screws or self-tapping screws, lag screws come with hex heads. This is because hex headed fasteners are better able to hold up to high levels of torque. In addition to hex headed screws, silicon bronze and stainless steel lag bolts are available to handle special circumstances or marine environments. These bolts are generally placed at a slight angle to reduce the risk of screw cut-out due to high loads on the screws and bone interface. Lag screw