Page 161 - Manual of Equine Field Surgery

CHAPTER 26

Modified Forssell's Operation for Cribbing

David A. Wilson

INDICATIONS POSITIONING AND PREPARATION

The primary indication for this procedure is mod- This procedure is best performed under general

ification of cribbing behavior when nonsurgical anesthesia with the horse in dorsal recumbency

methods fail. and the head extended; however, with experience,

it can be accomplished in the standing sedated

horse with local anesthesia. Transecting the ster-

nohyoideus at the attachment to the hyoid appa-

ratus is difficult in the standing horse. The ventral

EQUIPMENT cervical region is clipped and prepared for aseptic

surgery.

Large Rochester-Carmalt, straight Rochester-Pean

or angiotribe forceps, and a Penrose drain are

used for this procedure. An Nd:YAG or diode laser
PROCEDURE

may be used to transect muscle.1

A 30-cm ventral midline incision is made starting

2 cm rostral to the larynx at the basihyoid bone

and extending caudally (Figure 26-1). The skin

ANATOMY is retracted laterally, and hemostasis is achieved

as needed in the subcutaneous tissue. A plane

The ventral branch of the accessory nerve ( CNXI) of dissection is established between the ornohy-

is located on the dorsomedial aspect of the ster- oideus and sternomandibularis muscles to expose

nomandibularis and enters the muscle about 5 cn1 the medial aspect of sternomandibularis 5 cm

from the musculotendinous junction. The paired caudal muscles to the musculotendinous junction.

sternothyrohyoideus muscles lie 011 the ventral The sternomandibularis muscle is gently retracted

aspect of the trachea. The tendon of insertion of and rolled slightly abaxial to expose the dorsal

the sternothyroideus muscle is on the caudal medial aspect. The nerve can be located by palpa-

border and abaxial surface of the thyroid cartilage tion of a slight indentation in the musculature

(see Figure 25-2). The larger sternohyoideus mus- where the nerve enters or by identifying the nerve

cle continues on midline to insert on the basihy- just caudal and ventral to a small arterial branch

oid bone. The paired omohyoideus muscle merges supplying the sternomandibularis muscle (Figures

with the sternohyoideus muscle in the proximal 26-2 through 26-4). In most cases, a small amount

third of the neck (see Figures 23-2 to 23-5). of fascia will need to be dissected from the ster-

157