Fig. 7.

Visualized on the left is the characteristic deformity and fracture of the TFNa set screw that occurs if the lock prong is damaged during implant extraction. Failure to fully elevate the set screw prior to helical blade removal will cause the lock prong to deform and fracture more distally toward its tip. The fractured lock prong in this case remained within the patient as a retained foreign body visible on X-ray marked by the arrow in the image to the right