AAEP Convention 2005: How-To Henderson Castration Instrument

Possibly one of the most talked-about presentations at the 2005 AAEP Convention, held Dec. 3-7 in Seattle, Wash., discussed the proper usage of the power-drill-mounted Henderson castration instrument in horses. Mark Reilly, DVM, of the South Shore Equine Clinic in Plympton, Mass., discussed his clinic's experience removing approximately 150 testicles with this device over the last two years with no complications.

"Castration is one of the most commonly performed surgical procedures in horses," he began. "Additionally, castration complications are the most common cause of malpractice claims against equine practitioners. Complications include hemorrhage (excessive bleeding), edema (fluid swelling), pain, evisceration (protrusion of the intestines through the surgical site), septic funiculitis (infection of the spermatic cord), hydrocele (accumulation of fluid within the vaginal tunic), peritonitis (inflammation of the body cavity's lining), and penile damage (from misapplication of emasculators)."

However, the Henderson instrument (which costs about $200) greatly minimizes these complications, Reilly reported. Also, it cuts eight to 30 minutes off the surgical time required to castrate an animal, depending on the procdure, which can be very helpful.

"The goal is to minimize complications with a simple, applicable technique," he said.

The Henderson instrument "uses a twisting action to effectively sever and seal the severed (spermatic) cord, which minimizes blood loss and risk of hemorrhage via the severed cord," he explained. This also helps minimize post-castration swelling, infection, and pain.

The instrument was originally designed for bulls and has been redesigned with a wider opening for use on stallions, he noted. It is intended to be used with a typical 14.4-volt variable speed drill with a three-eighths-inch chuck. Although he has heard of people using it in standing animals rather than under general anesthesia, he did not recommend that to the audience as this might result in more risk of complications.

How Do You Use It?

Following the standard pre-castration examination to identify two descended testicles and any complicating factors, the patient is put under general anesthesia and a 2-3-cm strip of skin is removed over the surgical site. This reduces the likelihood that the instrument will snag a piece of skin when it is applied. Once the testes are brought outside the scrotum and the fascia removed, the pliers of the Henderson instrument are clamped onto the stripped spermatic cord.
The practitioner then rotates the drill slowly in a clockwise direction, maintaining slight tension on the cord, but not pulling on it. The cord will shorten initially as it twists, then lengthen as it fatigues and nears severance. After about 15-25 turns, the cord will sever, leaving behind the tightly coiled and sealed end of the spermatic cord. The procedure is repeated for the other testicle, and the surgical site is stitched or left open as desired.

"This is very quick, with no bleeding," Reilly said. "The minimal expected post-operative swelling is effectively controlled with the administration of pre-operative non-steroidal anti-inflammatory drugs (NSAIDs) and using post-operative NSAIDs as needed."

Possible Problems

The potential downsides or problems Reilly reported with this method are the following:

• In very young, small breeds, the spermatic cords will often slip through the pliers. The smaller bull clamp might be an option for these horses, he said;
• It is not recommended for retained testicles;
• Dead drill batteries can be problematic;
• If the clamp is not secure in the drill, it can't be used;
• Infection is a risk, as with any other surgery;
• The spermatic cord can be torn if the practitioner places extreme tension on the cord; and
• Bleeding from large scrotal or skin vessels (more often seen in older males) is a potential complication of any castration, Reilly noted; cross-clamping the skin prior to removing it minimizes bleeding. Also, cross-clamping and removing the skin piece allows only one surgical site compared to two (one over each testicle) with other methods.

"It is the authors’ opinion that the use of this instrument provides advantages over emasculators by minimizing complications, particularly hemorrhage, and it is easy to incorporate into any practice," Reilly noted. "I think this method is very safe, easy to perform, and economical."

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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