TREPHINING OF THE FRONTAL SINUSES. ' 23 



and periosteum down to the bone and remove in one piece 

 the entire mass of encircled soft tissues by seizing the skin 

 with a tenaculum and forcibly separating the periosteum, 

 from the bone with a scalpel or bone scraper. Control the 

 hemorrhage. With the centre extended place the trephine 

 accurately upon the denuded area perpendicular to the 

 surface of the bone and grasping the handle firmly turn it 

 to and fro until the bit has penetrated the bony plate and 

 the saw has cut a distinct groove to serve as a guide 

 when the center should be retracted and the operation con- 

 tinued until the disc of bone is detached, being careful to 

 maintain the trephine prependicular to the surface. The 

 operation is facilitated by grasping the- shaft of the trephine 

 between the thumb and fingers of one hand, constituting a 

 support in which it can glide back and forth. The pressure 

 under which the sawing is carried out must not be too great. 

 When the bony plate which has been isolated begins 

 to loosen, remove the trephine and insert the bone screw 

 into the centerbit opening and break aut the piece of bone 

 or pry it out with the bone gouge or chisel. Smooth any 

 uneven edges of bone with the lens-shaped knife. The ab- 

 normal contents of the frontal sinus can now escape through 

 the opening or be removed with the curette, forceps or scis- 

 sors, and the cavity irrigated with an antiseptic fluid. lyeave 

 the trephine wound entirely open and dress daily with anti- 

 septics. The frontal sinuses being in free communication 

 with the superior maxillary, and the superior turbinated 

 bone of the same side forming its median wall, indirectly 

 the irrigating fluid can escape through the nasal opening 

 by way of the former or by a perforation through the 



latter. 



In order to prevent the aspiration of the contents, which 

 are generally purulent, or may consist of blood or irri- 

 gating fluids, and to facilitate their escape, irrigation should 

 be carried out with the poll elevated and the head flexed. 



