A screw is a device that converts rotational motion into linear motion. It consists of structures such as a nut, threads, and a screw rod.

 

The classification methods of screws are numerous. They can be divided into cortical bone screws and cancellous bone screws according to their uses, semi-threaded screws and fully-threaded screws according to their thread types, and locking screws and Cannulated screws according to their designs. The ultimate goal is to achieve effective fixation. Since the advent of self-locking screws, all non-locking screws have been referred to as “common screws.”

 Common screws and locking screws

   

 Different types of screws: a. fully threaded cortical bone screw;  b. partially threaded cortical bone screw;  c. fully threaded cancellous bone screw;  d. partially threaded cancellous bone screw;  e. locking screw;  f. self-tapping locking screw.

Cannulated screw

Function of the screws

1.plate screw

Fastens the plate to the bone, producing pressure or friction.

 

2.Lag screw

Forms compression between the fracture fragments using sliding holes, achieving absolute stability fixation.

  

3.Position screw

Maintains the position of the fracture fragments without producing compression. Examples include tibiofibular screws, Lisfranc screws, etc.

 

4.Locking screw

The threads on the screw cap can match the opposite threads on the steel plate hole to achieve locking

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5.Interlocking screw

Used in conjunction with intramedullary nails to maintain bone length, alignment, and rotational stability.

 

6.Anchor screw

Serves as a fixation point for steel wire or suture.

 

7.Push-pull screw

Serves as a temporary fixation point for resetting fractures by traction/pressure method.

 

8. reset  screw

A common screw that is inserted through a steel plate hole and used to pull the fracture fragments closer to the plate for reduction. It can be replaced or removed after the fracture is reduced.

 

9.Blocking screw

Used as a fulcrum for intramedullary nails to change their direction.