Page 133 - Manual of Equine Field Surgery

Sinus Trephination 129

......-~~ Nasolacrimal duct

~..:.,..- lnfraorbital canal

Dorsal, middle, and

ventral nasal meatus

~-~c.,,.-ft:,v.~,..

Figure 21-3 Transverse section through the skull at level of M2 (between the medial canthus and the facial

tubercle).

Site of penetration are palpable and should be avoided when creating

of intramedullary pin portals for the maxillary sinuses.

For diagnostic trephination, a I-cm stab

incision is made through the skin and periosteum.

A Steinmann intramedullary pin is used to pene-

trate the bone. The pin should be positioned in

1/2
the chuck such that a maximum of inch of the

pin length is protruding (Figure 21-4). The goal is

to penetrate the bone without damaging deeper
•

structures. Excess pin length protruding from the

handle of the pin chuck should be guarded to

protect the surgeon. This size portal provides

access for aspiration or for placement of a lavage

catheter, biopsy instruments, or a 4-mm arthro-

scope for inspection of the sinuses.

Occasionally, there is a need for a larger portal

Facial into the sinuses. Commercial trephine instru-

crest
Facial ments are available up to 2.5 cm i11 diameter,

tubercle which is large enough to allow digital palpation

Figure 21-4 Identification of the limits of potential of the sinuses if necessary. A circular incision,

trephine sites in the maxillary and frontal sinuses. The slightly larger than the size of the trephine, is

diagonal dotted line is the approximate site of the

septum between the rostral and caudal maxillary made and the skin is discarded. Alternatively, a

•
sinuses. cross-incision can be made through skin and
periosteum. The four resultant flaps are elevated