TREPHINING OF THE FRONTAL SINUSES. 19 - 



3. TREPHINING OF THE FRONTAL SINUSES. 

 Pi,ate;s III- VIII. 



Uses. Fracture of the bony walls, necrosis, tumors. 



The ample communication below with the superior 

 maxillary sinuses prevents the accumulation of pus or fluids' 

 in the frontal cavities even if formed therein unless' the 

 former become filled and the conteilts back up into the 

 latter. In the case of empyema of the frontal sinus, trephin- 

 ing does not generally give full relief but calls for d re- 

 petition of the operation on the maxillary sinuses also. 



Instruments. Razor, scissors, convex scalpels, artery 

 forceps, tenacula, probe, trephine, curette, gouge, I^uer's 

 sharp bone forceps (rongeur forceps), hammer, chisel, bone 

 screw, lens-shaped bone knife, probe-pointed bistoury, 

 dressing forceps, disinfecting and dressing materials. 



Technic. The operation may be performed upon the 

 standing animal with the aid of local anaesthesia of the 

 skin, the bone having virtually no sensation. Restless 

 animals may be further secured with the twitch, in the 

 stocks, upon the operating table or by casting on the sound 

 side. Clip and shave the hair from the region of the front- 

 al bone on a level with the superior bprder of the orbital 

 cavity as indicated in Plate III or at any point below on a 

 line extending from F toward a point midway between N 

 and I M down to a level with the dotted line, S M, and dis- 

 infect the area carefully. F represents the highest point 

 at which the frontal sinus can be penetrated without injury 

 to the cranium. Within the shaved and disinfected area 

 locate the point for trephining, F, Plate III so that the in- ■ 

 ferior border of the opening on a medium sized horse will 

 be not higher than on a level with the superior border of - 

 the orbital cavity at the dotted line below F and the inner a 

 margin about i cm. from the median line of the face. With 

 a heavy convex scalpel make a circular incision as large as 

 the area of the trephine, directly through the skin, subcutem 



