220 
STERNAL SINUS. 
Prognosis. The sequestrum prevents healing; whether it can he 
removed depends on its size and position, and to ascertain this, opeiative 
interference is usually necessary. Prognosis is more favourable wheie 
the process is confined to the external surface of the rib; but where it 
extends to the inner surface the condition becomes chronic, and pleuiisy 
may supervene. The latter condition is indicated by the difficulty in 
breathing and the relatively copious discharge. But even with chronic 
necrosis of the outer surface, animals may remain useful foi a long 
time. 
Treatment. The direction and extent of the sinus has first to be 
discovered, bearing in mind that the middle point of the swelling is 
the spot beneath which the chief alterations exist. The sinus should be 
laid open freely, especially if it trends downwards, care being taken not 
to wound the external thoracic vessels. The exposed rib is scraped with 
a curette, the necrotic bone removed, and healing encouraged. In sinuses 
which cannot be laid open setons may be used, or they may be treated 
with antiseptics and astringents, such as liquor Villati , 1 carbolic, or 
sublimate solutions. When the sinus extends to the inner surface of 
the rib, non-irritant substances are selected. After removal of large 
pieces of bone, deep scars often remain in the chest wall. The resection 
of a piece of rib, although not easy, and involving danger of perforating 
the pleura, was effected in the horse by Ferguson fifty years ago, and 
may occasionally be necessary. In such case the necrotic portion is 
exposed by a long incision through the skin and subcutaneous tissues and 
periosteum. The periosteum is separated from the deep face of the rib, 
great care being taken not to perforate the pleura nor to injure the 
intercostal artery, which passes down the posterior face of the bone. The 
necrotic part is then removed by strong bone forceps. A drain is inserted 
in the lower part of the wound, which is sutured and covered with a 
dressing. 
III.—STERNAL SINUS AND FRACTURE OF THE 
STERNUM. 
Sternal sinus is a condition almost entirely confined to the horse, in 
which, however, it is not uncommon, and is due to suppuration dependent 
on local necrosis of the sternum. 
The sternum consists of a mass of spongy bone, and in horses is 
especially liable to be injured by falls on uneven hard ground, by the 
1 Liquor Villati or Villat’s solution consists of: 
Sulphate of copper.. 
1 part. 
1 part. 
2 parts. 
12 parts. 
,, 
Acetate of lead . 
Vinegar 
, zinc 
