Lag Screw – A Novel Parameter to Guide Lag Screw Placement
Lag Screw is a type of fastener that has a hex head. They are typically used in projects requiring more torque than standard hex-headed bolts and screws. They can be installed with a drill or ratchet and are available in different materials such as steel/zinc, stainless steel, and silicon bronze for corrosion resistance.
Lag screws can be used to compress large fracture fragments of multifragmentary tibial plateau fractures in order to provide stability and support. It is crucial to use lag screws perpendicularly to the fracture line in order to achieve maximum compression and stability. This is easier to accomplish in the symphysis and angle regions than in the body region due to anatomic limitations.
Several parameters have been developed to guide lag screw placement, including Cleveland Zones, Parker’s ration in the AP and LAT views, Calcar referenced Tip Apex Distance (TAD), and Axis Blade Angle. However, none of them reflects the lag screw insertion depth and direction simultaneously [1] – ].
To address this issue, a novel parameter was created which takes into account the rotation of the lag screw and the lateralization of the tip. This modified TAD is superior to Parker’s ration in the AP view and Cleveland zones, and provides excellent sensitivity and specificity for predicting lag screw cut-out. This new tool may help clinicians select the correct lag screw in intertrochanteric fractures. It should be noted, however, that the results in this study were obtained on a simulated bone model rather than cadaveric bone.Lag Screw