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LARGE
ANIMAL SURGERY
Use of biomedical lasers in small-animal
orthopedics has been more limited than similar applications in
human or equine surgery for two reasons: Expensive arthroscopic
equipment is not always applicable or readily available, and
it is harder to use on the smaller joints of cats and dogs. Lasers
have not been effective thus far for ablation of bone, although
various wavelengths from the free electron laser are being evaluated.
Ablation with a CO2 laser of the synthetic polymer methylmethacrylate
during removal or revision of total hip prostheses from dogs
also has been evaluated recently.Surgical laser techniques for equine urogenital
and laryngeal procedures were intially reported in 1983.
Clinical
and histological evaluation of the CO2 laser's ability to prevent
the growth of painful nerve masses in a horse's forefoot after
surgery was introduced in 1984. Laparoscopic use of flexible,
hoolow fibers with the CO2 laser has been described as a clinical
possibility. Developing an economical transendoscopic system
to deliver higher powers from currently available CO2 lasers
might generate increased interest in their clinical use.The effectiveness of the CO2 laer for cutting
horse skin has also been compared with other incisional methods
and was found to produce adjacent thermal injury comparable to
that from an electrosurgical unit. Other uses of lasers in soft-tissue
procedures in large-animal surgery include excision and ablation
of tumors and excessive growths of scar tissue, known as proud
flesh in horses, with CO2, Nd:YAG, argon-ion, KTP, diode and
holmium lasers.
The CO2 and Nd:YAG lasers have proved to be the
most effective for rapid excision and vaporization when operated
at powers greater than 40 W.In addition, procedures that require meticulous
control of hemorrhaging such as excision of penile hematomas,
have been performed successfully using an Nd:YAG laser through
an optical fiber in contact mode. The CO2 laser's use for preparing
a wound bed for skin grafts (called a pinch graft) has found
favor among some surgeons since recipient pockets can easily
be created in a "no touch" mode that helps control
bleeding and can actually sterilize the wound. In addition, precise
tissue dissection in the equine abdominal cavity for laparoscopic
oophorectomy )removal of the ovary) was found to be safe and
effective using CO2 laser energy through a hollow waveguide.
Traditionally, laryngotomy has been used
to perform in the pharynx and larynx of horses, but the required
use of a general anesthetic often extends recovery time. For
the past 12 years, a few equine surgeons have used transendoscopic
laser techniques in both contact and noncontact modes. Transendoscopic
use of the Nd:YAG laser in the horse has been and continues to
be an effective method for treating certain upper airway obstructions.The advantages of approaching minimally
accessible lesions, the ability to perform procedures with local
rather than general anesthesia and the decrease in recovery time
have provided the motivation for continuing this successful effort.
Objective protocols have provided effective treatments for nasal
pharyngeal obstructions and laryngeal problems such as hyperplasia,
enlargement of lymph glands, epiglottic entrapment or dorsal
displacement of the soft palate.
Such methods make ventriculectomies possible
and have provided adjunctive therapy for diseases of the gutteral
pouches connected to the eustachian tubes of horses. Specifically,
transendoscopic delivery of Nd:YAG and diode laser energy has
provided treatment for endometrial cysts that cause infertility,
an otherwise hard-to-approach condition (Figure 4).
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