Distal border fragments and shape of the navicular bone: Radiological evaluation in lame horses and horses free from lameness

Abstract

The palmar cortex of the navicular bone was thicker in lame compared with sound horses. Distal border fragments were most frequent in horses with navicular pathology. Evaluation of changes in shape of the navicular bone may also be important for recognition of pathological abnormalities of the bone.

Distal Border Fragments of the Equine Navicular Bone: Association Between Magnetic Resonance Imaging Characteristics and Clinical Lameness

“…This prevalence was similar to a recent study of horses that underwent high‐field MRI in which fragments were observed in 13.6% of horses and 9.8% of feet . The prevalence was lower than several studies that reported distal border fragments in populations of horses diagnosed with clinical navicular syndrome . Of the horses that had osseous fragments at the distal border, 50% had unilateral fragments and 50% had bilateral fragments.…”

“…In a study looking at horses with chronic navicular syndrome with fragments in one limb only, fragments were associated with the lamest limb in 64% of the time . Similarly, fragments observed on radiological evaluation were more frequent in lame horses (8.7%) compared to sound horses (3.6%) . In the present study, no significant statistical association was found between the presence of a fragment and the likelihood of being classified as lame.…”

“…Proposed pathogenesis theories include avulsion fracture of the navicular bone, fracture of an enthesiophyte at the origin of the impar ligament, separate center of ossification, and dystrophic mineralization within the impar ligament or adjacent soft tissue structures . Fragments are typically located adjacent to a smooth, concave defect in the distal border of the navicular bone, supporting the theory of an avulsion fracture fragment associated with the impar ligament.…”

“…In contrast, 40% of middle‐aged horses with clinical navicular syndrome had an osseous fragment at the distal border of the navicular bone . Similarly, in a study of horses undergoing radiographs of the front feet, fragments were identified in 3.6% of sound horses, 8.7% of lame horses, and 24.1% of horses with navicular bone pathology, suggesting that distal border fragments are a significant finding in horses with navicular syndrome.…”

Magnetic resonance imaging and foot lameness. Problem solved? Or do we know we know less now that we know more?

“…Nowhere has this problem, the detection of lesions of uncertain significance, been more marked than distal border fragmentation of the navicular bone . This finding is clearly visible on MRI scans, and it has been shown that horses with distal border fragments are more likely to be lame than horses without . The presence of distal border fragments can be predicted by radiographic lucency of the lateral or medial angles of the distal border of the bone .…”