Surgical Methods for Angular Limb Deformities Assessed (AAEP 2010)

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Angular limb deformities (ALDs) of the carpus (knee) are a common problem in foals and yearlings, and researchers have narrowed the surgical treatment options down to the two that present the best results. Eric R. Carlson, DVM, an equine surgery resident at the University of Illinois' Veterinary Teaching Hospital, gave a presentation on these options at the 56^th Annual Convention of the American Association of Equine Practitioners held Dec. 4-8 in Baltimore, Md.

"ALDs are important because they affect how weight bearing is transferred through the lower limb, and they can have negative effects on performance and on sale value," said Carlson.

When one side of the limb grows faster from the growth plate than the other, an ALD arises. If the lateral aspect (outside) of the limb grows faster than the medial aspect (inside), then the limb deviates inward and is called a varus deformity. In contrast, a valgus deformity is caused by the medial aspect of the limb growing faster, causing the limb to deviate outwards away from midline .

The two standout surgical correction techniques that Carlson discussed were the screw and wire or the single transphyseal screw (STS) technique.

"The screw and wire technique works by placing a screw above and below the growth plate that is growing too quickly and using a wire to tighten the growth plate to slow the rate of growth," explained Carlson.

The STS technique uses a similar principle, but the screw is placed directly through the growth plate to slow the rate of growth and straighten the foal's limb.

To determine if one technique is better than the other, Carlson and colleagues reviewed the medical records of 568 Thoroughbred foals admitted to Rood & Riddle Equine Hospital, in Lexington, Ky., that were treated with either screws and wires (253 foals) or an STS (315 foals).

Key findings of the study:

• Lateral placement of the screws and/or wire for treatment of carpal varus was most common;
• Surgeons left STS in place for a shorter period of time than the screws and wire; and
• Complications such as inflammation of the growth plate (physitis) post-treatment and metaphyseal collapse (a collapse of the area between the growth plate and the shaft of the bone) were significantly more common in foals treated with STS than with screws and wires.

 "Both treatment options are viable for management of ALDs in yearlings," noted Scott Hopper, DVM, MS, Dipl. ACVS, of Rood & Riddle, and co-author on the study. "The primary benefit to using the screw and wire method is the decreased chance of physitis or metaphyseal collapse postoperatively. The primary benefits to using the STS are the ease of implantation and the shorter duration to correction."

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.

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