Purpose of use determines the type of surgical screws selected for internal repair of bone fractures and breaks. Employed alone or in combination with surgical plates, bolts, rods or nails, surgical screws compress cracked and broken bones; this allows mending with new bone-cell growth. Some surgical screw designs work with specific types of fractures. Depending on the type of bone injury, various screws remain in the body permanently while others can be removed after the injury has healed.
Dynamic Hip Screw
A specialized surgical screw, the dynamic hip screw bridges fractures of the bony prominence near the end of the thighbone neck fitting into the hipbone socket. It is a collection of individual screws attached to two hinged plates. The dynamic compression hip screw brings the damaged bone together and allows femur movement within the hip socket, creating desirable dynamic stress with the expectation of normal fracture healing.
Designed with thin threads the full length of the screw, the cortical bone surgical screw grabs and anchors together damaged and diseased bones of the most-dense material in the human skeleton. The cortical screw holds together fractures and breaks in the compact, less-porous cortical bone found in such long bones as the leg femur and the humerus in the upper arm.
The holding strength of a surgical bone screw measures in ratio to the amount of metal-bone contact. Cancellous bone, unlike cortical, contains porous soft material requiring the specialized design of the cancellous screw with its coarser threading. This longer and more course thread of the cancellous screw equals the same quantity of metal-bone contact as the thinner cortical thread contact on the denser cortical bone, thus providing equal holding strength.
Used in reconstructive knee surgery, the interference surgical screw holds the repairing pieces of end bones that are attached to the ACL ligament and removed from a donor cadaver. The bone ends fit through a tunnel drilled in the thigh and calf bone, allowing the ACL ligament replacement. Placed along the two implanted blocks of bone, the interference surgical screw holds the transplant immobile.
Use of the Acutrak screw assists mending wrist or scaphoid fractures. Because wrist fractures and breaks have little surrounding bone tissue allowing typical surgical screw applications, the fully threaded headless Acutrak screw permits implantation below the surface of the bone. This screw improves holding strength for fractures or bone removal through osteotomy by allowing screw placement wherever the surgery site exists.
Preferred for its precision placement characteristics, the commonly used hollow-shafted or cannulated type surgical screw works with a guide wire or Kirschner (K) wire that the surgeon places in the damaged bone area through a pre-drilled hole. Securing the desired position of the K wire, the surgeon then puts the screw into the bone along the wire shaft. With the screw in position, the surgeon then removes the K wire.
Used when standard surgical screw use invades adjacent tissue, the hollow-shafted Herbert screw comes with both ends threaded and running in the same direction. The Herbert screw threading design secures fractured bones joined by ligaments, such as in the wrist, foot and jaw. The threading inserted closest to the bone moves through it more rapidly than the other screw end, causing the two bones to come together for mending.
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