20 TREPHINING OF THE FRONTAL SINUSES 



directly through the skin, subcutem 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 

 the scalpel or bone chisel. Control the hemorrhage. 



With the center- bit of the trephine extended, place it accu- 

 rately 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- 

 bit should be retracted and the operation continued until 

 the disc of bone is detached, being careful to maintain the 

 trephine perpendicular 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 may turn back and forth. The pressure under 

 which the trephining is carried out must not be too great 

 or the instrument may become wedged and broken. 



When the bony plate which has been isolated begins to 

 loosen, remove the trephine and break or pry out the piece 

 of bone with the bone gouge or chisel. Smooth any uneven 

 edges of bone with a heavy scalpel or by re-inserting the 

 trephine and using it as a rasp. The abnormal contents of 

 the' sinus may now escape through the opening or be re- 

 moved with the curette, forceps or scissors, and the cavity 

 irrigated with an antiseptic fluid. 



I^eave the trephine wound entirely open and irrigate the 

 sinuses daily with antiseptics. 



The frontal being in free communication below with the 

 superior maxillary sinus, the irrigating fluid falls directly 

 into the latter until it becomes filled. The superior turbi- 

 nated bone of the same side, forming the median wall of 

 the frontal sinus, is commonly perforated by necrosis in 

 cases of serious disease, establishing a communication be- 

 tween the frontal and nasal cavities, through which pus 

 and irrigating fluids readily escape into the nostril. 



