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Stand and Split
Standing medial patellar ligament splitting make good option for delayed patellar release.
Illustration courtesy of Dr. James
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A recent retrospective study of horses with delayed patellar release showed that standing medial patellar splitting may be a successful long-term surgical option with few complications and a relatively rapid return to work. Delayed patellar release is an acute inability to flex the hind limb. Upward fixation of the patella occurs when the medial patellar ligament and its parapatellar fibrocartilage remain hooked over the medial trochlear of the femur 4
Issue 10/2015 | ModernEquineVet.com
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and locks the reciprocal apparatus with the limb in extension. “There are a few variations of the syndrome, but the exact mechanism of the problem is unknown,” said Sarah James, DVM, DABVP, of the Steinbeck Country Equine Clinic in Salinas, Calif. “Anything that causes decreased or altered range-of-motion in the hind end can result in this problem.” Some predisposing factors include weak quadriceps or biceps femoris muscles, especially in debilitated horses or young, fit horses who are abruptly confined to a stall. Hind-end conformation is also important. A straight conformation or long-toe/low-heel conformation in the hind end has been associated with the condition, according to Dr. James. Trauma, most likely from hyperextension of the stifle, can also result in upward fixation of the patella. Conservative treatment is often the first step. Developing muscle mass and coordination through exercise, corrective trimming and shoeing, intramuscular administration of estrone sulfate, and/or direct injection of the middle and medial patellar ligaments with counter irritants are typically at the top of the list.
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“It’s important to give the young horses a little time to develop muscle mass and coordination,” Dr. James said. “They may end up fixing the problem on their own.” Surgical treatment is indicated for horses who do not respond to conservative therapy, who have recurring complete fixation, or who are developing lameness because of the problem. Patellar ligament desmotomy sometimes can provide a permanent cure, but literature shows the procedure can cause instability of the stifle joint, which can lead to fracture or fragmentation of the distal patella, chondromalacia of the patella, or osteoarthritis. Ultrasound-guided patellar ligament splitting has been shown to be fairly effective without short- or long-term complications, but it does come with the extra risk and expense associated with general anesthesia.
The Standing Option
Dr. James and her colleagues performed a retrospective study over a 9-year period. To be included in the study, horses needed to have a diagnosis of delayed patellar release, standard surgical and postoperative management, and be available for follow-up of at least 6 months.