Reliability of ultrasonographic measurements of bovine sole structures in relation to sole horn thickness, measured by computed tomography, and sole horn hardness

Abstract

The goal of the present study was to determine the effect of sole horn thickness (SHT) and sole horn hardness (SHD) on ultrasonographic visualization of sole structures in the inner and outer claws of 150 Holstein-Friesian cows, and to evaluate different ultrasound frequencies for this purpose. Ultrasonographic views of the sole structure were considered complete when 3 echogenic lines, representing the ventral surface of the sole horn, the borders of the sole horn and soft-tissue layer, and the ventral surface of the distal phalanx, were seen. The proportion of complete ultrasonographic views of the sole structures, designated as the ultrasonographic visualization proportion (UVP), and the measurement errors of SHT were evaluated by comparing images from computed tomography (CT) and ultrasonography. The latter images were generated using 3 different probes, frequencies of 6.5 and 5.0 MHz, and 2 different ultrasound machines (#1 and #2) to assess the apex, middle, and heel regions of the claws. The UVP were 60.8 to 77.9% for the 6.5-MHz probe in ultrasound machine #1 (probe A), which were lower than those (>90%) for both the 5.0-MHz probe in ultrasound machine #1 (probe B) and the 5.0-MHz probe in ultrasound machine #2 (probe C). The UVP was significantly lower in claws with an SHD ≥50 units than in claws with an SHD <40 or 40 to <50 units (UVP: 77.1% compared with 93.7 and 91.4%, respectively) when measured with probe B. In claws with an SHT <10 mm, the UVP was significantly lower when SHD was ≥50 units compared with <40 or 40 to >50 units; the values were 69.0% versus 91.3 and 85.9%, respectively, for probe A, and 89.7% versus 100 and 100%, respectively, for probe B. When SHT were measured by either probes A or B in ultrasound machine #1, the proportions of claws in which ultrasonographic values were within a ±1 mm range compared with the values obtained by CT were 84.9 to 91.3% for CT-determined SHT <5 mm, 66.7 to 71.9% for CT-determined SHT 5 to <7 mm, 28.9 to 51.2% for CT-determined SHT 7 to <10 mm, and 6.2 to 19.7% for CT-determined SHT ≥10 mm. The data indicated that increased SHT was associated with a decrease in ultrasonographic measurement accuracy. In claws with an SHT <5 mm, the high proportion of ultrasonographic values that were accurate within a ±1 mm range suggests that this imaging modality would be useful in cows with thin soles.

Ultrasonographic changes associated with the healing process in a fracture of the distal phalanx in a cow

“…Currently, ultrasonography is used to measure the thickness of the sole horn and the soft tissue layers [7] and to diagnose fractures in the extensor process of the distal phalanx in lame cattle [6]. However, there have been no previous reports describing ultrasonographic findings of a typical fracture of the distal phalanx affecting the area distal to the distal interphalangeal joint in cattle.…”

“…It is possible to perform the examination at any time, in any place, and to obtain images in real-time, although a degree of forced restriction is required. Prior to the application of ultrasonography for bovine sole horn, the claw should be trimmed slightly to ensure the sole surface is flat, enabling good visualization of sole structures [7]. Trimming decreases the width of the sole horn, which is recommended to be less than 10 mm; a sole horn thickness of more than 10 mm can lead to poor visualization of the sole structures in an ultrasonogram [7].…”

“…However, diagnosis using a lateral radiogram has the disadvantage of superimposition of the inner and outer claws, therefore use of the oblique view is recommended for diagnosis of this type of fracture [ 5 , 6 ]. Currently, ultrasonography is used to measure the thickness of the sole horn and the soft tissue layers [ 7 ] and to diagnose fractures in the extensor process of the distal phalanx in lame cattle [ 6 ]. However, there have been no previous reports describing ultrasonographic findings of a typical fracture of the distal phalanx affecting the area distal to the distal interphalangeal joint in cattle.…”

“…Prior to the application of ultrasonography for bovine sole horn, the claw should be trimmed slightly to ensure the sole surface is flat, enabling good visualization of sole structures [ 7 ]. Trimming decreases the width of the sole horn, which is recommended to be less than 10 mm; a sole horn thickness of more than 10 mm can lead to poor visualization of the sole structures in an ultrasonogram [ 7 ]. In addition, the use of a 5-MHz transducer allows increased visualization of sole structures characterized by three echogenic lines of the line of the sole surface, the borderline between the sole horn and the soft tissue layers, and the DP line, compared with the visualization obtained using a 6.5-MHz transducer, although a slightly better image quality can be obtained with the latter [ 7 ].…”

“…Trimming decreases the width of the sole horn, which is recommended to be less than 10 mm; a sole horn thickness of more than 10 mm can lead to poor visualization of the sole structures in an ultrasonogram [ 7 ]. In addition, the use of a 5-MHz transducer allows increased visualization of sole structures characterized by three echogenic lines of the line of the sole surface, the borderline between the sole horn and the soft tissue layers, and the DP line, compared with the visualization obtained using a 6.5-MHz transducer, although a slightly better image quality can be obtained with the latter [ 7 ]. The use of a lower frequency transducer is recommended for the observation of pathological osseous changes in the bovine claws, because it provides a rough but more hyperechoic image of the DP line [ 7 ].…”