The use of sonoelastography to assess the recovery of stiffness after equine superficial digital flexor tendon injuries: A preliminary prospective longitudinal study of the healing process.

BACKGROUND: The objective assessment of the mechanical properties of the superficial digital flexor tendon (SDFT) could provide useful information for the rehabilitation of horses with SDFT injuries. Assessment of strain ratio (the strain of a standard reference divided by that of lesions) is a quantitative method in sonoelastography for evaluating tissue stiffness in vivo. As yet, no longitudinal studies have used strain ratio to evaluate the progression of stiffness in SDFT injuries. OBJECTIVES: To test the hypothesis that strain ratio can evaluate the recovery of stiffness during the healing of SDFT injuries. STUDY DESIGN: Prospective and longitudinal study with observer-blinded evaluation. METHODS: Ultrasonography, including sonoelastography, was performed in seven Thoroughbred horses with naturally occurring SDFT injuries at five time points: within 20 days of the injury, and at 2, 3, 6 and 9 months after the injury. Blinded sonoelastographic images were independently evaluated by two veterinarians to assess interobserver agreement. The recovery of stiffness and echogenicity in lesions were evaluated using the strain ratio and grey-scale ratio (echogenicity of lesions divided by that of the surrounding area), respectively. RESULTS: Interobserver agreement was assessed as 'almost perfect'. Strain ratios were significantly higher at 9 months after injury than at the other time points (all P<0.05). Strain ratios at 6 months after injury were significantly higher than those at earlier time points (P<0.05). Grey-scale ratios within 20 days of injury were significantly lower than those at the other time points (all P<0.05). MAIN LIMITATIONS: Validations of SDFT status were evaluated only by recovery of the echogenicity in lesions and not by histopathological examination. CONCLUSIONS: Although further studies are needed to validate the relationships between injured SDFT status and sonoelastographic findings, this preliminary study shows that strain ratio may provide a means to monitor the recovery of stiffness in lesions during rehabilitation, even when the grey-scale ratio remains unchanged from a few months after SDFT injury. The Summary is available in Chinese - see Supporting Information.

Application of sonoelastography for evaluating the stiffness of equine superficial digital flexor tendon during healing.

Sonoelastography can assess the inner stiffness of tissues. Sonoelastographic evaluation of injured equine superficial digital flexor tendons (SDFTs) is considered to be useful for assessing the stiffness of a lesion even during late-stage rehabilitation. The purpose of this study was to investigate and compare the sonoelastographic appearance of injured SDFTs over time from the onset of the injury. Eighteen horses were classified into three groups according to the length of time from injury onset: group A, within two weeks after injury; group B, approximately five months after injury; and group C, approximately nine months after injury. Longitudinal and transverse images of all injured SDFTs were obtained using grey-scale ultrasonography and sonoelastography. Grey-scale and sonoelastographic images were evaluated by two observers using echogenicity-grading and colour-grading systems, respectively. The authors evaluated the interobserver agreement and compared the grades among the three groups. The results indicated almost perfect interobserver agreement. Significant differences were found in the sonoelastography among the three groups, whereas no significant difference was found in the grey-scale ultrasonography between groups B and C. Sonoelastography is a feasible and useful modality to evaluate the equine injured SDFTs in vivo and to distinguish between them among the different phases even during the chronic phase.

Three-dimensional ultrasound imaging of the equine fetus.

The objective was to assess the optimal procedure for real-time, three-dimensional (3D) ultrasound (US) imaging for assessing the equine fetus during the first half of gestation and the possibility of using 3D US imaging of the equine fetus in clinical applications. Seventeen pregnant mares were examined by 3D US between Days 35 and 180 of gestation. Abdominal and endo-vaginal real-time 3D transducers used in human medicine were used for transrectal and transvaginal examinations, respectively. Images were recorded by both 3D stationary and real-time movies. In a comparison of four methods, transrectal examination with a bulb-shaped abdominal 3D transducer enabled the equine fetus to be clearly visualized, and did not require sedation of the mare. Therefore, this approach was the most suitable procedure for examining equine fetuses during the first half of gestation. Each scan required only a few seconds and an entire examination took <10 min in total. The 3D volume image was easy to restore after the examination and could be rotated to any angle the examiner desired. Fetal surface structures, including the head, body, limbs, and genital tubercle, were observed as 3D images which enabled fetal development to be characterized. For early (Days 60-70), but not later (Days 90-150) periods, 3D ultrasonography was not able to evaluate fetal structure in detail as well as conventional 2D ultrasonography. In conclusion, 3D ultrasonography of the equine fetus was a valuable adjunct to 2D ultrasonography and a convenient modality for more detailed assessment of fetal structures.