The Impact of Navicular Bone Shape and Fragments in Horses

Navicular disease is not always straightforward for veterinarians to diagnose and treat, but new study findings that focus on the shape of the navicular bone (NB) and fragments found near it could help veterinarians better understand this disease in horses.

"The significance of distal border fragments of the navicular bone is not well understood," the researchers noted in the study. "There are also no objective data about changes in thickness and proximal (upper) and distal (lower) extension of the palmar cortex (rear-facing outer layer) of the navicular bone."

A recent retrospective study performed by Marianna Biggi, DVM, PhD, and Sue Dyson VetMB, PhD, at the Centre for Equine Studies at The Animal Health Trust, in Suffolk, England, examined the significance of fragments along the lower border of the NB, as well as the differences in thickness of the palmar cortex of the NB in 55 sound horses and 377 lame horses. The team hoped to better understand the distribution of distal border fragments and their association with radiological abnormalities of the NB, and to evaluate differences in the shape of the navicular bone in sound and lame horses and horses.

The sound horses used in the study had all undergone a prepurchase examination including radiographs of their front feet. The lame horses had foot-related pain and had undergone radiographic examination of at least one foot between January 2005 and December 2009. Horses used in the study were of varying breeds, disciplines, and genders. All radiographs were analyzed to determine the thickness of the palmar cortex and to measure upper or lower extensions of the palmar cortex.

Upon reviewing their findings, the researchers noted:

  • Horses with radiological signs consistent with navicular disease had a higher frequency of fragments along the lower border of the NB than sound horses;
  • Lame horses generally had a thicker palmar cortex; and
  • Lame horses more commonly had a larger upper extension of the NB than did the sound horses.

The authors concluded that there were significant differences in NB shape between the two groups of horses and that "fragments were also associated with primary navicular pathology, suggesting distal border fragments may be a part of navicular disease."

The team added that the evaluation of changes in shape of the navicular bone could also be important for researchers as they further their recognition and understanding of pathological (anatomic and physiological deviations from the normal state) abnormalities of the bone.

The study, "Distal border fragments and shape of the navicular bone: Radiological evaluation in lame horses and horses free from lameness," was published in July in Equine Veterinary Journal. The abstract is available online.

About the Author

Casie Bazay, NBCAAM

Casie Bazay holds a bachelor of science degree in education from Oklahoma State University. She taught middle school for ten years, but now is a nationally certified equine acupressure practitioner and freelance writer. She has owned Quarter Horses nearly her entire life and has participated in a variety of horse events including Western and English pleasure, trail riding, and speed events. She was a competitive barrel racer for many years and hopes to pursue the sport again soon.

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