Comparison between radiological and magnetic resonance imaging lesions in the distal border of the navicular bone with particular reference to distal border fragments and osseous cyst-like lesions.

ABSTRACT

REASONS FOR PERFORMING STUDY There are no data concerning the accuracy of conventional and computed or digital radiography for evaluation of the equine foot. OBJECTIVES: To compare conventional film-screen and computed radiography with magnetic resonance imaging (MRI) for detection of distal border fragments of the navicular bone; and to establish which type of fragment was more likely to be detected radiologically. METHODS: Horses were included if forelimb lameness was localised to the foot and both radiography and high-field MR images had been acquired. Horses were divided into 2 groups based on acquisition of conventional (Group A) or computed (Group B) radiographs. The presence of distal border fragments was recorded. From MR images, distal border fragments were graded based on their size and changes in signal intensity in the adjacent navicular bone. Sensitivity and specificity of conventional and computed radiography for detection of fragments were calculated using MRI as the gold standard. A Chi-squared test was used to test for associations between specific radiological and MRI findings in the distal border of the navicular bone. RESULTS: In Group A 46 and 18 fragments were identified on MR and radiographic images, respectively; in Group B 45 and 17 fragments were seen. There was no significant difference between computed and conventional radiography. Grades 4 and 5 fragments or large-sized fragments were identified most frequently; low-grade fragments were unlikely to be observed. There was a significant correlation between radiological and MRI abnormalities of the distal border of the navicular bone. CONCLUSIONS: Conventional and computed radiography had similar, rather low sensitivity for identification of distal border fragments of the navicular bone, but specificity was high. Large-sized and high-grade fragments were most likely to be identified radiologically. POTENTIAL RELEVANCE Fragments observed radiologically are likely to be associated with other pathological abnormalities of the distal border of the navicular bone.