Broken Coffin Bones Common in Warmblood Foals

A recent study of coffin bone (distal phalanx) fractures in foals found they were far from rare. In fact, all 20 of the Warmblood foals in the study (all foals on a particular farm in one season) had fractures at some point in their first year of life, for a whopping total of 61 fractures recorded.

At the 2009 American Association of Equine Practitioners convention, held Dec. 6-9 in Las Vegas, Nev., John J. Dascanio, VMD, Dipl. ACT, ABVP, associate professor of Large Animal Clinical Sciences at the Virginia-Maryland Regional College of Veterinary Medicine, discussed the incidence and healing of fractures of the palmar process of the coffin bone in this group of foals.

The palmar processes of the coffin bone within the hoof are slender extensions of bone that project rearward from the bone's main body. There are seven types of different fracture patterns in the coffin bone; fractures of these processes are classified as Type VII. Previous studies have found Type VII fractures in 19 to 77% of foals studied.

Fractured coffin bone

Radiographs show a large (left) and medium fracture of the coffin bone.

The current study found that nine of the 20 foals studied had large fractures (and sometimes medium and small ones, as well), seven had medium fractures (and sometimes small ones, too), and four had small fractures only. Sixteen foals had fractures in both forefeet, all had medial (inside) fractures on at least one foot, 18 foals had a lateral (outside) fracture, and nine had both medial and lateral fractures in both forefeet. Dascanio reported the small fractures tended to show up later, at an average of 4.2 months of age, while the larger ones occurred at an average of 2.6 months of age.

"Lameness was not evident with most foals," he noted. "Many of these fractures are, thus, likely to go unnoticed. Also, if the lameness is transient, it may not be noticed if the horse is at pasture."

The investigators found the best way to diagnose these fractures was via 60° dorsopalmar (front view, at a steep angle) radiographs, followed by dorsopalmar (straight front) views and lateral (side) views.

Small fractures unsurprisingly healed more quickly, requiring three months to heal versus 6.17 months for large fractures. Dascanio said no treatment--other than balanced trimming--was applied.

"The literature suggests that the pull of the deep digital flexor tendon, increasing weight of the foal, and concussion all contribute to these fractures," Dascanio commented. "We think they are due to torsional/shear forces on the bone, and it doesn't have time to remodel to handle the stress. The palmar process seems to have a period of vulnerability in the young foal that predisposes it to fracturing. These fractures seem to be a common occurrence in growing horses and seem to heal without complication in four to six months."

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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