Diagnostic performance of ultrasonography, bursography and standing magnetic resonance to detect navicular intrabursal pathology in horses with foot pain

Navicular intrabursal pathology is one of the most common causes of
forelimb lameness in horses. An accurate diagnosis of which structure is
involved is essential for therapy and prognosis. The study aimed
to compare the diagnostic performance of ultrasonography, bursography, and
standing magnetic resonance (MRI) imaging as diagnostic tools of the
proximal navicular intrabursal pathology using bursoscopy as the gold
standard. A total of 21 feet of 17 horses met the inclusion criteria. The
feet underwent ultrasonography, followed by MRI, and thereafter
bursography and bursoscopy. The images were interpreted blindly to
document the presence or absence of the podotrochlear lesions. The lesions
of interest were dorsal fibrillation and splits of the deep digital flexor
tendon (DDFT), adhesions, and fibrocartilage defect of the navicular bone.
The accuracy, specificity, sensitivity, positive predictive values, and
negative predictive values were calculated. Furthermore, the kappa test
was used to calculate the inter-observer agreement. The
bursoscopy revealed lesions in 95% (20/21) of the feet. Eighteen dorsal
fibrillation and eleven split lesions in the DDFT, nineteen fibrocartilage
defects, and eight adhesions were identified. MRI showed accuracy of 95%
(20/21) for dorsal fibrillation and 86% (9/21) for split lesions in the
DDFT, whereas the accuracy for fibrocartilage defects was 60% (14/21).
Adhesion formation with MRI was predicted correctly in only 57% (3/21) of
the feet. Bursography showed with MRI similar accuracy regarding the
adhesions. Moreover, bursography had an accuracy for fibrocartilage
defects of 67% (20/21), and DDFT lesions were detected in 86% (18/21) of
the feet. The ultrasound examination predicted DDFT lesions in 67% (14/21)
of the feet, whereas its accuracy for adhesion lesions was 33% (10/21).
(95% CI). The inter-observer agreement was the lowest for ultrasound
compared to MRI and bursography. A combination of ultrasonography and
bursography can be an alternative to standing MRI when the latter is not
an option or as a complementary test.