TFN Set Screw

Carl-Peter Cornelius, Paulo Barbosa, Diarmuid De Faoite, Sabine Goldhahn, Takeshi Sawaguchi, Clifford Turen, PFNA Asia Multicenter Study Group 

Fig 1: The TFN Set Screw with long tongue and grooves on the underside (a) allows the surgeon to lock the TFN head element to prevent sliding (b). 

The development of the TFN Set Screw (Fig 1) is a solution for helical blade or screw migration after fracture fixation in the proximal femur and subsequent postoperative collapse of the femoral head element.

Once the set screw is tightened with a torque limiting handle, the grooves on the underside of the TFN Set Screw engage with the helical blade or screw to prevent sliding. The Set Screw is available in 3 angles (125, 130 and 135) matching the CCD angle of the nails, and is made of TAN (alloy).

If a surgeon wants to prevent sliding, the scrub technician has to remove the TFN locking mechanism from inside the nail and replace it with the pre-assembled TFN Set Screw. The surgeon must make a conscious decision to replace the locking mechanism with the TFN Set Screw which helps to ensure that the surgeon does not unintentionally prevent sliding.

Self-retention between sub-components of the TFN Set Screw allows for ease of insertion. After the head element is inserted, the surgeon will use a torque limiting handle to tighten the set screw and prevent collapse. If the surgeon changes his or her mind and wants to allow sliding, the tang is long enough that the set screw can be backed off to allow sliding, while still preventing rotation. If sliding is permitted, however, an end cap must be used in conjunction with the set screw.

It is important to note that the TFN Set Screw should only be used for fixation in fractures where sliding of the head element is not desired. The addition of the locking feature expands the utility of the TFN system. While it should only be used in select cases, the new locking feature offers an alternative fixation option for certain difficult and complex fractures.

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