Cannulated Drill

Cannulated Drill

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Cannulated Drill

Bone Fracture Fixation-Part 2

If the fracture is only experiencing a small level of force across its site then fixation pins or wires can be sufficient or can add appropriately to the fixation already provided by a fixator or plate. Fractures of the upper arm and shoulder, wrist, fingers and hands are the most commonly fixed with this method. Tension band wiring is Used for fractures of the elbow, knee-cap and ankle, with k-wiring sometimes used to add to stability. By using a percutaneous technique a pin can be inserted through the skin using x-ray guidance with an image intensifier.

Steinmann pins, often threaded and thicker than K-wires, have been routinely employed to engage and maintain skeletal traction predominantly in the bones of the leg. The pin is inserted through the bone and this is attached to a traction cord via a stirrup device, holding the bone in the correct position until enough healing callus has formed to allow removal. Modern techniques of fixing fractures sooner and more accurately have meant that the application of traction for long periods, with the risks of Bed rest, can now be avoided.

Fixation Screws

A basic tool in the armoury of managing orthopaedic and trauma injuries and conditions is the use of bone screws to effect fixation or to aid other techniques of fixation. Pre-drilling can be performed before insertion or a self tapping implant used. The amount of physical stress which can pull a screw out of the bone is affected by a series of matters of which the most influential is the density of the bone into which it is implanted. The surface area of contact between the bone and the screw threads determines a degree of the fixation achieved. Screw insertion is performed in a clockwise direction either along a drilled path or self tapped and produces force once the hard bone cortex is contacted by the head of the screw.

Bone is an active and dynamic body organ and can adapt to the stresses formed by the application of the screws, allowing a gradual reduction in fixation force with time. However, the fracture is usually healed before the fixation is likely to loosen. The two main kinds of screws available are cancellous and cortical bone screws, the denser bone of the cortex being fixed with cortical screws and the more honeycomb bone of the bone ends fixed with cancellous screws. The surface areas of contact between thread and bone are greater in cancellous screws, allowing cancellous screws to achieve purchase in less dense bone.

Tapping the hole or drilling it before insertion may not be necessary in cancellous bone as it can usually be easily screwed being relatively porous and low in density. Screwing a screw directly into the bone may be good as it may compress the local bone track and increase the density of the interface between the screw threads and the bone, allowing an increased hold for the screw. Plates can be held in position by positional screws which compress it against the bone, pilot holes being drilled beforehand and tapped or self tapping screws used.

A degree of compression can be produced by inserting lag screws across the line of a fracture to increase alignment and stability of a long bone fracture and to produce and maintain reduction of a fracture across a joint. To provide the greatest degree of stability requires the screw to be placed at right angles to the line of the break. It is unlikely that lag screws will give sufficient stability alone so they are often supplemented with added stability from an external fixator or a plate.

Cannulated screws are often used to fix hip fractures and can be inserted percutaneously without needing a Full open operative technique, inserting the screw along the track already identified by a guide wire and performed under x-ray control for positional control. To limit the potential damage to the soft tissues and the size of the operation, cannulated screws are employed in operations with limited open surgery. Modern screws are self tapping and self drilling as they are inserted and are much more costly than normal screws which are not cannulated.

About the Author

Jonathan Blood Smyth is the Superintendent of Physiotherapy at an NHS Hospital in the South-West of the UK. He writes articles about back pain, neck pain, and injury management. If you are looking for Physiotherapists in Bournemouthvisit his website.

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