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Diagram of Collateral Circulation after Ligatures of Arteries of Abdomen and
Lower Extremity. (Smith and Walsham.)
OPERATIONS ON THE OSSEOUS SYSTEM.
MANIPULATION OF THE SAW.
1. How to hold. Hold the saw in the full
of the hand, with the index-finger placed along the side.
2. How to use. Before a saw can be freely moved to and fro, a groove must be made in the bone to retain it in position.
In the case of a trephine, the central pin controls the movement of the crown until a groove is cut.
A chain-saw is conducted into position by a needle or probe, to which it is attached by a ligature. The chain should not be twisted, and its cutting-edge must be presented to the bone. The chain should be kept taut, and as nearly straight as the depth of the wound in the soft parts will allow. To keep the chain taut, the two arms of the operator must move in unison. Hold the handles in the palm, allowing the chain to pass between the middle and ring fingers.
The ordinary saw must be steadied, and a groove in the bone be established, by drawing the saw toward the operator. The left thumb-nail, applied just above the level of the teeth, will steady the instrument.
If the saw is moved rapidly, the heat, which would be excessive, must be prevented by irrigation. When the bone is nearly severed, the undivided por. tion bends and the track of the saw is narrowed, hence the saw should then be presented to the bone at a different angle.
Various instruments are used to cut bones, as saws, chisels, osteotomes, scoops, etc. The use of the osteotome, in making a section of the bone in this operation, must be considered a matter of choice.
EXAMPLE: Middle of the Tibia.—Place the subject on the back. Shave the part. Adjust a sandpillow under the limb at the site of the operation.
Select the subcutaneous portion of the tibia. Draw the skin upward so that the wound will be valvular. Make an incision in the long axis of the limb through all the tissues. There are no important structures to be avoided. The incision should be long enough to admit the osteotome, which should be inserted with its cutting edge in the axis of the wound until it touches the bone. Hold the osteotome at a right angle to the bone, and turn it so that its cutting edge is presented to the bone crosswise. Strike the head of the osteotome with a mallet, and then move the osteotome in the axis of its cutting edge to prevent its becoming wedged. When the section is deep and the osteotome is moved with difficulty, a narrower and thinner osteotome must be substituted. The smaller osteotome can be directed backward and outward and backward and inward in the wound made by the larger osteotome. When the