The proximal aspect of the suspensory ligament in the horse: How precise are ultrasonographic measurements?

Ultrasonographic anatomy of the distal flexor structures of the thoracic members of rodeo bulls

The veterinarian is responsible for monitoring and inspecting rodeos, thus ensuring the welfare of the animals. Clinical follow-up is of great importance in animal athletes, and ultrasound has become an important, widely used complementary diagnostic method in the evaluation of these animals. In equine medicine and dairy cattle, there are several studies that describe tendon injuries through ultrasonography. However, in athlete bulls, there are still no studies using this tool as a diagnostic aid for these injuries. The first objective of the present study is to describe the ultrasound anatomy of the distal flexor structures of the thoracic limbs of healthy rodeo bulls and their measurements. The second objective is to report sonographic findings referring to changes found in the studied region of these animals. Forty-two bulls from a farm specialized in breeding and training high-performance animals were evaluated. Physical evaluation and measurements of external parameters were performed to verify possible correlations. For the ultrasound examination, a 10 MHz linear probe was used. Measurements were taken of the tendons of the flexor digit muscles, branch of the interosseous muscle for the tendon of the superficial digital flexor muscle and interosseous muscle. 42 animals were evaluated, but two were excluded from the statistical analysis because they had a history of lameness or excessive effort in the preceding six months, and their cases are described in this study. Based on knowledge of ultrasound and anatomy, greater reliability is obtained in the diagnosis and prognosis of these animals.

Ultrasonographic Evaluation of the Suspensory Ligament in Quarter Horses Used for Cutting

Ultrasound remains a mainstay in proximal suspensory ligament (PSL) evaluation. Despite recent improvements facilitating earlier diagnosis/treatment, needs exist for (1) characterization of normal ultrasonographic PSL cross-sectional area (CSA) in specific breeds/disciplines, (2) improved detection of early/subtle changes in the PSL, and (3) an understanding of suspensory ligament (SL) morphology change from work-related stress. The objectives of this study were to establish normal PSL CSA in Quarter Horses (QH) used for cutting via angle contrast ultrasonography, ultrasonographically monitor SL morphology as horses progress through training, and assess the impact of PSL disease on performance (Lifetime Earnings - $LTE). One hundred ten 2-year-old cutting horses had PSL ultrasound examination on all limbs, and examinations were repeated 2 years later on 51 remaining horses. PSL CSA at select locations was compared between time points and entire examinations subjectively graded by an equine radiologist. $LTE was obtained from the National Cutting Horse Association for each horse and analyzed by abnormality number, location, and development over time. A total of 267 PSL ultrasound examinations across both times points were measured and graded. Normal CSA was established by zone for forelimbs and hindlimbs. The prevalence of abnormal limbs increased between the 2-year-old and 4-year-old years, forelimb abnormalities were statistically more prevalent than hindlimb abnormalities at both time points, and osseous attachment abnormalities were statistically more prevalent than ligament abnormalities at both times points. No significant differences in PSL CSA change over time were seen in any group and there was no significant difference in $LTE among or between groups.

Suspensory ligament size does not change after plantar fasciotomy and neurectomy of the deep branch of the lateral plantar nerve by ultrasonographic assessment

Objective

To determine the short‐term effect of plantar fasciotomy and neurectomy (PFN) of the deep branch of the lateral plantar nerve on the proximal suspensory ligament (PSL) cross‐sectional area (CSA) in horses with hindlimb proximal suspensory desmopathy (PSD).

Study design

Analytical, observational, cohort study.

Sample population

Twenty‐one horses.

Methods

Records of horses with chronic PSD treated by PFN were included if a preoperative ultrasonographic examination was available and at least one postoperative ultrasonographic examination. One masked observer measured the ultrasonographic cross‐sectional area (CSA) of the PSL. Intraobserver reliability was determined by repeatedly measuring a subset of ultrasonographic images (n = 127). Two masked observers measured the cross‐sectional area of the proximal suspensory ligament (PSL‐CSA) on preoperative proton density (PD)‐weighted transverse high field magnetic resonance images (n = 19 horses) . Agreements for PSL‐CSA between preoperative ultrasonographic and MRI measures and between the two magnetic resonance imaging (MRI) observers were assessed. Follow up considered the horses’ ability to return to exercise and their owners’ satisfaction.

Results

The reliability of the ultrasonographic measurement of the PSL‐CSA was excellent. Agreement between ultrasonographic assessment and MRI assessment of PSL‐CSA was good. No difference was detected between preoperative (median, interquartile range; oblique‐incidence, 2.07, 1.72‐2.55; on‐incidence, 2.23, 1.98‐2.65) and postoperative (oblique‐incidence, 2.08, 1.80‐2.74; on‐incidence, 2.28, 2.01‐2.74) PSL‐CSAs. At a median of 12 months (4‐33 months), 16/20 (80%) owners reported the horse was “better” and 15/20 (75%) functioned at or above preoperative levels.

Conclusion

Ultrasonographic measurement of the PSL‐CSA was reproducible and in good agreement with MRI measurement. The PSL‐CSA was not influenced by PFN.

Clinical significance

The PSL‐CSA cannot be used to guide return to function.

Signal changes in standing magnetic resonance imaging of osseous injury at the origin of the suspensory ligament in four Thoroughbred racehorses under tiludronic acid treatment

Problems associated with the proximal metacarpal region, such as an osseous injury associated with tearing of Sharpey’s fibers or an avulsion fracture of the origin of the suspensory ligament (OISL), are important causes of lameness in racehorses. In the present study, four Thoroughbred racehorses (age range, 2–4 years) were diagnosed as having forelimb OISL and assessed over time by using standing magnetic resonance imaging (sMRI). At the first sMRI examination, all horses had 3 characteristic findings, including low signal intensity within the trabecular bone of the third metacarpus on T1-weighted images, intermediate-to-high signal intensity surrounded by a hypointense rim on T2*-weighted images, and high signal intensity on fat-suppressed images. Following the sMRI examination, all horses received 50 mg of tiludronic acid by intravenous regional limb perfusion once weekly for 3 weeks. Attenuation of the high signal intensity on T2*-weighted and fat-suppressed images was observed on follow-up sMRI in 3 horses. Following rest and rehabilitation, these 3 horses successfully returned to racing. In contrast, the other horse that did not show attenuation of the high signal intensity failed to return to racing. To our knowledge, this is the first report of OISL in Thoroughbred racehorses assessed over time by sMRI under tiludronic acid treatment. Our findings support the use of sMRI for examining lameness originating from the proximal metacarpal region to refine the timing of returning to exercise based on follow-up examinations during the recuperation period.

The cross-sectional area changes in digital flexor tendons and suspensory ligament in foals by ultrasonographic examination

REASONS FOR PERFORMING STUDY

Flexural deformities are common conditions of growing horses and are suggested to have a relationship with the contraction of musculotendinous units. However, limited studies have documented the changes in each tendon and ligament in the metacarpal region with age.

OBJECTIVES

To investigate the changes in the cross-sectional area (CSA) of each tendon and ligament in the metacarpal region with age by ultrasonographic examination.

STUDY DESIGN

Longitudinal study of foals from Day 1 to age 24 months.

METHODS

The CSA of the superficial digital flexor tendon, deep digital flexor tendon, accessory ligament of the deep digital flexor tendon and suspensory ligament was measured by ultrasonographic examination at monthly intervals from Day 1 to age 24 months in 7 Thoroughbred foals.

RESULTS

Changes in superficial digital flexor CSA in all regions were larger than those of other structures from 10 months to 15 months. The suspensory ligament CSA was significantly larger than those of other structures on Day 1 in both the region of suspensory origin (RSO) and region of suspensory body (RSBO). This condition continued until 2 months in the RSO and until 5 months in the RSBO. The changes in deep digital flexor CSA were larger than those of other structures from 2 to 5 months in both the RSO and RSBO.

CONCLUSIONS

The rate of change in each structure varies with age. Thus, the functional adaptation with age that takes place may differ among structures because the primary function of each structure differs.