Pins can be threaded or smooth. The terminology is not exact and refers more to the name that was originally given to the device than to its function. Steinmann pins are large caliber wires used for fracture fixation or as traction pins. They have pointed tips and are cut to the needed length.
Large Steinmann pins can be used for intramedullary fixation. Some types of pins are threaded and work as screws; others are smooth are used for intramedullary fixation, such as the Rush pin. Two types of pins are used with external fixation device: transfixing and unilateral pins. Usually two or more pins are placed in each major fragment below and above the fracture.
One-half or Unilateral pins enter the soft tissues on one side through a small incision and thread directly into the bone. They have threads at one end that engage a smooth shank and the cortex that connects with the external fixation frame. These pins are also referred to as Schanz screws. Many of these pins now have threads only at the tip so that the smooth shank also engages the near cortex. This reduces the soft-tissue irritation caused by the threads which are outside the bone and increases the strength and stiffness of the pin.
Transfixing wires and pins pass through the entire extremity and are supported on both ends by the fixation and traction frame. Transfixing pins used with Hoffman or bilateral type devices usually are threaded in the center of the pin, and ideally the threaded section should be equal to the diameter of the bone. Transfixing pins are also used with the ring-type or circular external fixation devices, such as the Ilizarov frame. They are more commonly called transfixing wires as they are unthreaded and small in diameter.
Several types of pins were developed for treating femoral neck farctures or for pinning slipped capital femoral epiphyses. These usually have a smooth shank with a threaded end. The smooth shank crosses the fracture line and permits dynamic compression. These pins include Hagie, Guffon, Knowles, and Deyerle. Many surgeons now use partially threaded cannulated screws rather than these pins.
Traction is a directional force applied to the extremities with transfixing pins or wires attached to the soft tissues on placed through the metaphysis, perpendicular to the long axis of bones. Traction is used for correcting deformities, immobilizing and reducing fractures, and evaluating extremities for the treatment of soft tissue injuries.
External fixation is mostly used with complex injuries, and, thus, complications are not uncommon. They include loosening, infection, or cutting out of the fixation wires or pins, and fracture distraction. Problems with fracture healing are mostly related more to the nature of the original injury than to the use of the external fixation device. Pin- track infection is the most common complication and is related to the care of the pin site, technique of pin insertion, and stresses on the pin bone interface. Both increased stress at this interface and infection can result in pin lossening. Incorrect pin placement can also result in injury to the soft tissues, especially the neurovascular bundle.
Pins can be obtained from the orthopedic instruments manufacturers. There are many other ortho implants orthopedic implants such as screws, plates, rods, nails etc.