Magnetic resonance imaging, ultrasonography and histology of the suspensory ligament origin: a comparative study of normal anatomy of warmblood horses

The Evolution of Lesions on Follow-Up Magnetic Resonance Imaging of the Proximal Metacarpal Region in Non-Racing Sport Horses That Returned to Work (2015-2023)

BACKGROUND

This study evaluates the change in an MRI of the proximal metacarpal region in a group of sport horses that returned to work. This retrospective analysis evaluated 18 limbs represented by 17 horses.

RESULTS

The hyperintense signal within the dorsal collagenous part of the proximal suspensory ligament (PSL) on T1W/T2*W GRE sequences decreased or stayed the same in the majority of cases. The hyperintense STIR signal within the dorsal collagenous part of the PSL resolved in the majority of the patients, and the third metacarpal bone (McIII) hyperintense STIR signal resolved in all patients. The dorsal margin irregularity of the PSL stayed the same, and McIII sclerosis and resorption of the palmar margin of McIII stayed the same in the majority of cases. McIII hyperintense STIR signal resolution carries a broad time range, with a mean of 94 days and a range of 47-202 days.

CONCLUSIONS

Complete normalization of the dorsal collagenous part of the PSL does not appear necessary for a return to soundness, but a resolution of the McIII hyperintense STIR signal is expected for horses returning to soundness. A rescan period of 120 days for the proximal metacarpal region is suggested. In addition, there was no significant change in the size of the PSL between the initial and final MRI.

The plantar proximal cortex of the third metatarsal bone shows raised longitudinal ridges at the suspensory ligament enthesis in normal equine isolated limbs - a radiographic, computed tomography, and MRI study

Introduction

Knowledge of normal radiographic appearance is essential to avoid misinterpretation of radiographs. This study aimed to assess the computed tomographic (CT) appearance of the plantar surface of the proximal metatarsus and evaluate the influence of the radiographic angle on the trabecular/cortical interface of the proximal plantar metatarsal cortex on lateromedial and slightly oblique radiographs.

Methods

Eight hindlimbs were collected from six horses with no known history of lameness and euthanized for reasons unrelated to the study. Limbs underwent computed tomographic (CT) and radiographic examination (dorsoplantar, lateromedial, and slightly oblique radiographic views obtained by angling the beam dorsally and plantarly from the plane used for the lateromedial projection). Standing magnetic resonance (MR) imaging and computed tomography (CT) were used to confirm normalcy. Images were compared side-by-side by two experienced readers.

Results

Limbs were normal at MR imaging. Longitudinal linear ridges were present on the proximal plantar metatarsal surface in all limbs (1-2 sagittal ridges and 1 ridge located at the medial or lateral margin of the suspensory ligament). Longitudinal ridges were positioned facing an adipose-muscular bundle of the suspensory ligament on CT images and were visible as linearly increased opacities on dorsoplantar radiographs. The delineation of the trabecular/cortical interface of the proximal metatarsus changed with radiographic projection and was the sharpest on the plantaro 85° lateral to the dorsomedial oblique view.

Conclusion

The proximal third metatarsal bone shows individual morphological variations, with longitudinal linear ridges that alter the bone homogeneity on dorsoplantar radiographs. An oblique plantaro 85° lateral to the dorsomedial view is suggested to better assess the presence of subcortical sclerosis when proximal suspensory enthesopathy is suspected.

Findings consistent with equine proximal suspensory desmitis can be reliably detected using computed tomography and differ between affected horses and controls

The objective of this retrospective, observational, controlled study was to evaluate bone and soft tissue window CT images of the proximoplantar metatarsus III region in twenty horses with pain localized to the proximal suspensory ligament (PSL) and 20 horses with findings nonrelated to tarsal pain. All horses underwent CT and radiographic examination. Images were reviewed by three independent observers who graded the severity and localization of findings. Bone-related categories as well as soft tissue-related categories were evaluated. For the comparison of imaging findings in horses with and without proximal suspensory desmitis (PSD), mixed linear regression was performed. The intraclass correlation coefficient (ICC) was calculated to assess intraobserver agreement, and kappa statistics were employed to evaluate interobserver agreement. CT examination identified significantly more abnormalities in the diseased group. The scores for osseous exostosis (p = .015) and PSL enlargement (p = .004) were notably higher in PSD horses compared to controls. Intraobserver agreement was overall high (ICC .82-1.0), and interobserver agreement was substantial for the detection of mineralization (kappa = .61) and moderate for sclerosis (kappa = .43), exostosis (kappa = .43), and PSL enlargement (kappa = .48/.51). Measurements in the soft tissue window were significantly smaller than those in the bone window. Findings concurrent with PSD including osseous proliferation and sclerosis as well as soft tissue enlargement, mineralization, and avulsion can be reliably detected using CT. Findings from the current study supported the use of CT for evaluating horses with suspected PSD where high-field MRI is not available.

Magnetic Resonance Imaging Measurements of the Proximal Palmar Cortex of the Third Metacarpal Bone and the Suspensory Ligament in Non-Lame Endurance Horses before and after Six Months of Training

Proximal metacarpal injury is common in endurance horses, yet exercise-induced changes in this region have not been described. This study aimed to document objective exercise-induced changes in the proximal palmar cortex of the third metacarpal bone (PcMcIII) and the suspensory ligament (SL). Low-field magnetic resonance (MR) images of both proximal metacarpal regions were obtained from six novice and six experienced horses, before and after six months of endurance training. Measurements were acquired in T1-weighted transverse MR images at four levels and included the thickness of the PcMcIII, the mediolateral width, and the dorsopalmar depth of the entire SL and its lobes. We used t-tests or their nonparametric equivalents to compare the measurements from the two examinations and both novice and experienced horses. The medial aspect of PcMcIII was significantly thicker in experienced horses than in novice horses at 2 and 3 cm distal to the carpometacarpal joint. This likely reflects the cumulative effect of long-term exercise and possibly age. The PcMcIII was significantly thicker medially than laterally. There was no significant difference between pre- and post-season measurements. Six months of endurance training were not sufficient to induce changes in the thickness of PcMcIII or the SL that are detectable in low-field MR images.

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.

Computed tomographic arthrography, gross anatomy and histology demonstrate a communication between synovial invaginations in the proximal aspect of the third interosseous muscle and the carpometacarpal joint in horses

This descriptive anatomical study investigates the relationship between the third interosseous muscle, also known as the suspensory ligament, and the carpometacarpal joint in forelimbs of horses, with the hypothesis that there was a direct synovial communication between these structures as shown by computed tomographic arthrography, histology, and gross anatomy sections. Computed tomography of the carpus and metacarpal region was performed on two groups. Group 1 consisted of eight cadaver limbs undergoing computed tomographic arthrography following injection of a mixture of positive contrast medium, saline, and color-pigmented fluid solution into the middle carpal joint. Group 2 consisted of eight forelimbs assessed using plain computed tomography. The images were interpreted subjectively for contrast medium distribution and objectively by comparing Hounsfield values of the proximal suspensory ligament at 0.5 cm intervals starting at the origin and extending 3 cm distal to the proximal subchondral bone plate of the third metacarpal bone. Of the 16 limbs, two were sectioned for gross anatomy and one was documented histologically. The proximal suspensory ligament was visualized with clear margins on computed tomography images. The positive contrast medium was found within the lateral and medial lobes of the suspensory ligament in all eight (100%) limbs. Hounsfield units within the suspensory ligament following contrast injection were significantly higher than in those in the plain CT group between 0.5 and 2.5 cm distal to the proximal subchondral bone plate of the third metacarpal bone (p < 0.05). The gross anatomy sections showed color pigmentation within the suspensory ligament correlating to the contrast medium distribution evident on computed tomography images. Histology confirmed a synovial lined cavity within the suspensory ligament. The demonstration of a direct synovial communication between the internal structure of the proximal suspensory ligament and the carpometacarpal joint in horses offers further explanation for commonly encountered interactions of diagnostic local anesthesia of the carpal and subcarpal regions. When performing diagnostic or therapeutic injections into the middle carpal joint, the likely effect on the proximal suspensory ligament should be considered. Furthermore, as the proximal suspensory ligament was identified clearly on CT images, further studies are needed to elucidate the utility of CT in clinical cases with suspected soft tissue pathology in the subcarpal region.

A Descriptive Study of the Carpal Joint of Healthy Donkeys Using Ultrasonography, Computed Tomography, and Magnetic Resonance Imaging

This study was conducted to establish a detailed anatomic reference for the carpal joint of apparently healthy donkeys using ultrasonography (US), computed tomographic (CT), and magnetic resonance imaging (MRI). Ten orthopedically sound adult donkeys were used for US examination of the carpal joint in each forelimb. Additionally, the carpi of ten donkey cadavers were subjected to CT and MRI examinations. The carpal joint was divided into four zones to simplify examination. US assessment of the carpal joint included transverse and longitudinal sonograms. CT was performed using three planes: axial, sagittal, and coronal. MRI was performed using axial and sagittal planes with two sequences: gradient-echo T1-weighted and proton density. The donkeys’ carpus US, CT, and MRI images were labeled and serially interpreted based on references and anatomical cross-sections. The anatomical characteristics of the carpal joint and the surrounding soft tissue structures were thoroughly described and precisely differentiated on US, CT, and MRI scans. It can be concluded that US, CT, and MRI are effective noninvasive diagnostic imaging tools for evaluating the carpal joint in donkeys. Moreover, these imaging modalities can aid in establishing a reference database for the carpal joint of donkeys, which differs from that of horses.

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.

Suspensory ligament or interosseous muscle? Histology of the interosseous muscle of South American Camelids

The interosseous muscles (IOM) have evolved to largely collagenized structures in many large grazers, including South American Camelids (SACs). SACs include lama (Lama glama), alpaca (Vicugna pacos), guanaco (Lama guanicoe) and vicuna (Vicugna vicugna). This study reports on a comparative histomorphological evaluation of the IOM in these four species. First, a descriptive qualitative analysis of the tissue composition within the physiological IOM clearly demonstrates that the IOM of all SAC species is predominantly tendinous. However, we can always find a small amount of striated muscle fibres supporting the claim that the term "interosseous muscle" should be preferred over the denomination "suspensory ligament". Second, we quantify the ratio of muscle tissue (MTr) occupying the cross-sectional area (CSA) of 80 limbs at three levels and examine it in relation to limb, sample localization and species. Values for MTr are highest at the middle level, ranging from 0.4% to 15.2% with a mean of 3.4% ± 3.2%. We also detect notable amounts of muscle tissue at the distal sample level in the area of the branches of the IOM. Of all SACs, alpacas present the highest MTr. Lamas have a significantly larger MTr than guanacos. These results suggest the influence of domestication and/or physical activity on the muscle tissue content of the IOM of SACs. Amounts and distribution of muscle, adipose and lose connective tissue vary greatly for each sample localization and within individuals of one species. This may complicate the interpretation of MRI images of SACs' IOM for diagnostic purposes.

Magnetic Resonance Imaging Findings of the Proximal Metacarpal Region in Warmblood Horses: 36 Lame and 26 Control Limbs (2015-2021)

Objectives: This study aims to evaluate the distribution and severity of bone and soft tissue lesions in the proximal metacarpal region of warmblood horses in lame and control groups. Correlation between lesions and ability to return to work was evaluated in the lame group.

Methods: This restrospective analysis evaluated 62 horses with MRI examination of the proximal metacarpal region between Sept 2015 and Feb 2021. There were 36 lame limbs and 26 control limbs. The control group included seven contralateral limbs.

Results: Proximal suspensory ligament (PSL) size was not different between the lame and control groups. Hyperintensity seen on T1W/T2^*W GRE images within the dorsal collagenous part of the PSL and hyperintense Short-TI Inversion Recovery (STIR) signal within the dorsal collagenous part of the PSL or within the McIII were only present within the lame group. Palmar cortical McIII resorption and dorsal margin irregularity of the PSL and McIII sclerosis were more severe within the lame limbs, but mild gradations were also seen in control limbs. Intermediate gradings for a subset of lesions were commonly seen in the non-lame contralateral to lame limbs. Return to work in the lame group is not statistically different for any measured observation(s), and 19/33 of the lame horses returned to work at similar or higher levels.

Conclusion and clinical importance: Fifty-eight percent in this group of warmblood horses returned to work within a variable time frame. The majority (81%) of lame limbs showed bone and soft tissue abnormalities, but no enlargement of the PSL was noted in lame horses, and no correlation was seen between the severity or type of lesions and the ability to return to work. The presence of STIR hyperintensity within the proximal McIII or dorsal collagenous part of the PSL and hyperintensity within the dorsal collagenous part of the PSL on T1W GRE and T2^*W GRE images, as well as significant palmar cortical McIII resorption are considered clinically relevant lesions. Contralateral limbs may not truly represent the normal condition, showing nonclinical variations and adaptive remodeling.

Effectiveness of Platelet-Rich Plasma and Bone Marrow Aspirate Concentrate as Treatments for Chronic Hindlimb Proximal Suspensory Desmopathy

This retrospective study aimed to evaluate the clinical effect of bone marrow aspirate concentrate (BMAC) and leukocyte rich PRP (LR-PRP) compared to horses undergoing controlled exercise alone in horses with >3 months proximal suspensory desmopathy in hindlimbs (HPSD). Nighty-three horses were divided into three groups according to the treatment: a control (n = 22), LR-PRP (n = 46), and BMAC (n = 25) group. Lameness and ultrasound scores were recorded before treatment (T0) and at 6 months (T1) post-treatment. Records horses considered sound at evaluation and level of performance were additionally registered at 12 months (T2) and 18 months (T3) after treatment. The BMAC cytology profiles from 22 horses were also analysed and compared to clinical outcomes. The results at T1 showed that 9% (2/22) of the horses in the control group were sound compared to 59% (25/46) and 84% (21/25) in the LR-PRP and BMAC groups, respectively. Additionally, ultrasound scores at T1 in the BMAC and LR-PRP groups were improved in comparison with the control group (p = 0.02). At T2, 68% of the horses in the BMAC group and 39% of the horses in the LR-PRP group had returned to the previous performance level. At T3, a significantly higher percentage of horses in the LR-PRP (43%) and BMAC (72%) group were sound when compared to the control (4.6%) group (p = 0.02). Similarly, at T3, significantly more horses of the BMAC (16/25) and of the LR-PRP (15/46) group had returned to the previous or a higher performance level compared to the control (1/22) group (p = 0.01). No correlation was found between long-term clinical outcome and cytology profiles in the BMAC group. In conclusion, long-term outcomes of treatment with LR-PRP or BMAC are significantly better than conventional treatment of the hindlimb chronic PSD in horses. Additionally, BMAC yielded better lameness scores than LR-PRP at short- and long-term follow-up.

Non-weight bearing ultrasonographic examination allows the diagnosis of longitudinal fiber disruption (split) in equine suspensory ligament branches not visible on weight bearing examination

When evaluating suspensory ligament branch splits, there is a discrepancy between high field MRI findings and weight bearing ultrasonographic imaging characteristics. In this descriptive and retrospective case series, ultrasonographic examination was performed on suspensory ligament branches with the limbs in weight bearing and non-weight bearing positions. Suspensory ligament branch splits were defined as linear regions of decreased echogenicity when imaged with the limb in a weight bearing position that increased in size and became anechoic with the limb in a non-weight bearing position. This appearance was considered an indication of pathologic change in the branch. A total of 62 suspensory ligament branches were included in the study from 37 horses, with 14 partial splits, 11 intrasubstance splits, and 14 complete splits of which two had extension of fetlock synovial fluid and synovial membrane through the split. Recheck ultrasonographic examinations performed in eight horses up to 14 months following the initial examination demonstrated persistence of the split in two horses, partial resolution in five horses, and complete resolution in one horse. Ultrasonographic examination using the non-weight bearing approach proved valuable for increasing the lesion conspicuity as compared to the weight bearing images. Certain abnormalities, such as longitudinal fiber disruption (split) in suspensory ligament branches may only be evident when imaged non-weight bearing. The use of this technique provides a more accurate representation of lesion severity and allows for monitoring over time. A longitudinal study is necessary to determine the clinical relevance of suspensory ligament branch splits.

Magnetic Resonance Imaging Findings in the Proximal Metacarpal Region of 359 Horses and Proximal Metatarsal Region of 64 Horses Acquired Under Standing Sedation

Standing magnetic resonance (MR) images of proximal metacarpal/metatarsal regions are increasingly being acquired. This study aimed at describing ranges of abnormalities detected in sport/racehorses, using retrospective evaluation of magnetic resonance imaging (MRI) reports from horses with lameness isolated to proximal metacarpal/metatarsal regions with images acquired standing. It was hypothesized that MRI features are different between metacarpal and metatarsal regions and between horses doing different sports. Reports from 359 forelimbs and 64 hindlimbs were included. Palmar/plantar metacarpal/metatarsal bone injury and suspensory desmopathy, which often occurred concurrently, were most frequently reported. Third metacarpal abnormalities were more likely at palmar/medial locations, including cortical (86.4%) and trabecular (38.2%) pathology with frequent thickening, irregularity, and periosteal/endosteal abnormalities. Fluid signal was reported in cortical (38.7%) and trabecular (22.6%) bone. Medial intermetacarpal articulation abnormalities were more frequently reported (52.5%) than lateral. Suspensory ligament pathology was reported in 83.8% forelimbs, frequently with cortical (74.1%) or trabecular (32.9%) pathology. Tarsal-joint abnormalities were significantly more likely than carpal-joint abnormalities. Third metatarsal cortical (57.8%) and trabecular (20.3%) pathology was most frequently plantar, but significantly more likely to be dorsal than forelimbs. Metatarsal fluid signal was significantly less likely than metacarpal. Lateral intermetatarsal articulation pathology (23.4%) was more frequent than medial; medial was significantly more likely in forelimbs. Suspensory ligament abnormalities were reported in 64.1% hindlimbs, 39.1% having concurrent cortical pathology. Metacarpal fluid signal was significantly more likely in endurance/racehorses than dressage/show jumping horses. Dressage was overrepresented in hindlimb suspensory origin pathology. These findings indicate different pathology patterns between forelimb/hindlimb and between different sports and may be useful for MRI interpretation.

Magnetic resonance imaging and histopathological evaluation of equine oblique sesamoidean ligaments

BACKGROUND

Pathology involving the oblique sesamoidean ligaments (OSLs) is commonly diagnosed during magnetic resonance imaging (MRI) of the equine distal limb. Presence of striations within the ligament and magic angle artefact can result in an incorrect diagnosis of pathological change. No studies have been performed using histopathology, the gold standard, to corroborate their imaging diagnosis.

OBJECTIVES

(a) To determine which MRI characteristics are associated with normal vs abnormal OSLs and (b) to evaluate the ability of MRI to correctly identify abnormal vs normal oblique sesamoidean ligaments using histopathology as the gold standard.

STUDY DESIGN

Observational, cross-sectional study.

METHODS

Cadaver limbs (n = 77) were obtained from horses (n = 21) subjected to euthanasia at the hospital. MRI and histopathology was performed on each of the limbs. MRI scoring was performed for multiple MRI characteristics, and each limb was deemed normal or abnormal. Histopathology scoring was performed to give an overall score of normal or abnormal. Mixed model logistic regression was performed to evaluate which MRI characteristics were associated with normal vs abnormal OSLs using backwards elimination and a significance level of <0.1. Sensitivity and specificity were also calculated.

RESULTS

The sensitivity and specificity of MRI to correctly identify abnormal OSLs was 81% (95% CI 54%-96%) and 90% (95% CI 79%-96%) respectively. Based on logistic regression, increased cross-sectional area at the origin (OR: 26.77, 95% CI 1.1-4640, P = .07), increased ligament hyperintensity (OR: 9.59, 95% CI 1.23-155; P = .04) and reduction in striations (increased hypointensity score) (OR: 7.8, 95% CI 0.72-218, P = .07) were associated with abnormal OSL.

MAIN LIMITATIONS

Lameness exam was not performed on any of the horses prior to euthanasia. Findings can only be applied to chronic, degenerative changes, rather than an acute injury.

CONCLUSIONS

Increased cross-sectional area and changes in the signal intensity are associated with pathology within the OSLs. Medial to lateral size asymmetry and striation pattern variation can occur in histologically normal OSLs and should be interpreted with caution if other signs of pathology are absent.

Prospective randomized comparison of platelet rich plasma to extracorporeal shockwave therapy for treatment of proximal suspensory pain in western performance horses

Proximal suspensory desmitis (PSD) is a frequent cause of lameness in the performance horse. Extracorporeal shockwave therapy (EST) and platelet rich plasma (PRP) have become common treatments for PSD yet clinical data on efficacy is limited. The main objective of this randomized, prospective clinical study was to compare long-term effectiveness of EST and PRP in Western performance horses. One hundred horses with lameness localized to the proximal suspensory ligament received treatment with either PRP or EST following baseline ultrasonographic evaluation. A veterinarian and agent evaluated the horses for lameness independently four days following the first treatment and long-term follow up was obtained from the agent at six and twelve months. Four days post treatment, horses treated with EST had significantly greater lameness improvement compared to PRP. At one-year horses with less severe baseline ultrasound changes (grades 0-1) appeared to respond better (degree of lameness) with EST treatment whereas horses with more severe ultrasound changes (grade 2) responded better to PRP. Horses with baseline lameness graded 1 or 2 were 5.1 times more likely to be back in work at 1 year compared to those presenting with grade 3 or 4. EST treatment was associated with going back to work 3.8 times more at one year compared to PRP independent of baseline ultrasound score. Both PRP and EST can be expected to yield favorable therapeutic responses in Western performance horses with lameness localized to the proximal suspensory region. Baseline ultrasound may guide treatment selection.

Comparison of Metzenbaum scissors and Y-shaped fasciotome for deep metatarsal fasciotomy for the treatment of proximal suspensory ligament desmopathy in horses

OBJECTIVE

To quantitate the iatrogenic injury associated with deep plantar metatarsal fasciotomy performed with Metzenbaum scissors compared with a Y-shaped fasciotome.

STUDY DESIGN

Experimental ex vivo surgical study.

STUDY POPULATION

Cadaveric hind limbs (n = 20) from 10 sound thoroughbred racehorses.

METHODS

A plantar metatarsal fasciotomy was performed, extending from the proximal extent of the deep metatarsal fascia, distally. Hind limbs were randomly assigned to 2 groups, undergoing fasciotomy with straight Metzenbaum scissors (n = 10) or a Y-shaped fasciotome (n = 10). Magnetic resonance imaging was performed before and after surgery to identify the maximal depth of any iatrogenic trauma. Gross examination of the surgical site included measuring the length of the incision in the deep metatarsal fascia and localizing iatrogenic trauma sustained by the plantar aspect of the proximal suspensory ligament (PSL) during the procedure.

RESULTS

Iatrogenic injury to the PSL was identified in 6 of 10 and 9 of 10 specimens prepared with the fasciotome and Metzenbaum scissors, respectively (P = .03), and was most commonly located in the distal third of the fascial incision. Differences between the length of incision (P = .02) and the maximal depth of signal (P = .03) for incisions created with Metzenbaum scissors or a fasciotome were identified.

CONCLUSION

The use of a fasciotome resulted in longer fascial incisions and less severe iatrogenic trauma to the PSL compared with using Metzenbaum scissors.

CLINICAL SIGNIFICANCE

A Y-shaped fasciotome may be the preferred surgical instrument for successful desmopathy of the PSL fasciotomy because a greater release of compartmental pressure is possible through a longer incision with minimal iatrogenic trauma to the underlying PSL.

Magnetic resonance imaging of plantar soft tissue structures of the tarsus and proximal metatarsus in foals and adult horses

Objectives: The object of this study was to describe previously defined soft tissue structures by using spin and gradient sequences in a 0.5 Tesla magnetic resonance system in order to improve the characterisation of tendon and ligaments at the plantar region of the equine tarsus and metatarsus while considering possible age-related variations.

Methods: Cadaveric hindlimbs from twenty-two Warmblood horses with an age range from one month to twenty-five years were examined in spin and gradient echoes. The proximal suspensory ligament from six limbs was dissected to assign the signal intensities histologically. For statistical analysis, horses were divided into two groups (≤3 years and >3 years) for evaluating signal intensity and homogeneity of the plantar tendons and ligaments.

Results: Focal increase of the signal intensity within the deep digital flexor tendon was significantly more present in horses older than three years. Signal alterations of the long plantar ligament were seen without a significant dependency to age. The accessory ligament of the deep digital flexor tendon could not be visualized on all images within the region of interest. The morphology of the proximal suspensory ligament was not affected by age-related changes.

Clinical relevance: Spin and gradient echoes in MRI were suitable to identify and assess soft tissue structures at the plantar aspect of the equine tarsus and proximal metatarsus. Age-related appearance must be considered when interpreting magnetic resonance images.

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.

Clinical findings, treatment, and outcome in 11 dairy heifers with breakdown injury due to interosseous medius muscle rupture

OBJECTIVE

To describe the diagnosis, treatment, and prognosis of fetlock breakdown due to interosseus medius muscle rupture in cattle.

STUDY DESIGN

Retrospective clinical study.

ANIMALS

Dairy heifers with unilateral or bilateral interosseus medius muscle rupture (n = 11).

METHODS

Breakdown injury due to rupture of the interosseus medius muscle was documented clinically, radiographically, and ultrasonographically. Breakdown was bilateral in 4 heifers (3 in forelimbs, 1 in hind limbs) and unilateral in 7 (all hind limbs). One heifer with severe bilateral hind limb breakdown was slaughtered and the remaining 10 were treated by transfixation pin cast (1 heifer), box rest (n = 2), and/or a cast and splint (7).

RESULTS

Hyperextension of the fetlock and hyperflexion of the proximal interphalangeal joints during weight bearing were characteristic for interosseus muscle breakdown. Ultrasonographically, the origin and body of the interosseus muscle and the branches to the sesamoid bones were primarily affected by the rupture. Conservative treatment was successful (used for their intended purpose) in 8 of 9 heifers with a median lifespan of 32 months after discharge from the clinic (range 6-83).

CONCLUSION

Rupture of the interosseus medius muscle in young cattle may be more common than previously suggested in the literature. Imaging with ultrasound allowed more detailed localization of lesions of the musculo-tendinous structure. Interosseus medius muscle rupture had a favorable prognosis when treated conservatively in these heifers.

Proximal suspensory desmopathy in hindlimbs: A correlative clinical, ultrasonographic, gross post mortem and histological study

REASONS FOR PERFORMING STUDY

It has been suggested that ultrasonography is unreliable for the detection of hindlimb proximal suspensory desmopathy (PSD) based on comparisons between ultrasonographic and magnetic resonance images.

OBJECTIVES

To compare ultrasonography with gross and histopathological post mortem examination in horses with PSD diagnosed based on ultrasonography and control horses.

STUDY DESIGN

Retrospective descriptive study.

METHODS

Part 1: 19 horses with hindlimb PSD and 10 control horses were humanely destroyed. Twenty control limbs and 37 lame limbs were examined grossly and 40 suspensory ligaments (SLs) were examined histologically and graded blindly. Part 2: 3 horses with recurrent lameness after surgical management of PSD and 4 with PSD were assessed ultrasonographically and by gross post mortem examination.

RESULTS

Part 1: ultrasonographic lesions were graded moderate in 31/38 (81.6%) and severe in 7/38 (18.4%) lame limbs; in 4/37 (10.8%) limbs adhesion formation between the proximal aspect of the SL and the accessory ligament of the deep digital flexor tendon was predicted. Gross post mortem and histological examinations of control limbs revealed no abnormalities. Gross post mortem examination revealed substantial adhesions between the proximal aspect of the SL and adjacent soft tissues in 10/37 (27.0%) lame limbs; in 10/37 (27.0%) limbs there were adhesions between the body of the SL and the mid plantar aspect of the third metatarsal bone, extending distally in 6 (16.2%) limbs. Histology revealed abnormalities (grades 1-3) of the collagenous tissue in 25/36 (69.4%) limbs; muscle was abnormal (grades 1-3) in 35/36 (97.2%) limbs and adipose tissue (grades 1-3) in 16/36 (44.4%) limbs. Part 2: adhesions between the SL and adjacent soft tissues were predicted ultrasonographically and confirmed post mortem.

CONCLUSIONS

Ultrasonography was reliable for the detection of SL pathology based on histology as the gold standard. Adhesions may be a reason for recurrent lameness after surgery.

Anatomic and histologic features and ultrasonographic appearance of the collateral ligaments of the metacarpophalangeal and metatarsophalangeal joints in cadaveric limbs from horses without lameness

OBJECTIVE

To describe the anatomic and histologic features of the collateral ligaments (CLs) of the metacarpophalangeal (MCP) and metatarsophalangeal (MTP) joints in cadaveric limbs obtained from nonlame horses and to compare the histologic findings with the ultrasonographic appearance of the CLs.

SAMPLE

Medial and lateral CLs of the MCP and MTP joints of 28 limbs (16 forelimbs and 12 hind limbs) from 9 adult nonlame horses euthanized for reasons unrelated to the study.

PROCEDURES

26 limbs of 8 horses were examined by ultrasonography immediately after euthanasia. Postmortem gross and histologic examinations were performed for all 28 limbs. Histologic and ultrasonographic images were graded and compared.

RESULTS

Ultrasonographically, the mean ± SD depth and width of the superficial CL were 5.1 ± 0.7 mm and 20.5 ± 1.7 mm, respectively. On histologic examination, only 125 of 319 (39%) specimens obtained from 56 medial and lateral CLs appeared normal. Histopathologic findings varied from mild changes in cellular density and collagen fiber orientation to severe fibrocartilaginous metaplasia. The degree of CL lesion severity increased distally, and the lateral CL was affected more frequently than was the medial CL. Ultrasonographically detectable abnormalities were not correlated with the histologic findings.

CONCLUSIONS AND CLINICAL RELEVANCE

In horses, histologic abnormalities within the CLs of the MCP and MTP joints may be an adaptive response to joint hyperextension and compression and might predispose horses to desmopathy and ligament failure in the event of trauma. Ultrasonography did not detect morphologic changes of the CL matrix. For an accurate diagnosis of subclinical lesions, more sensitive imaging techniques (eg, MRI) should be considered.

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.

Comparison between standard ultrasonography, angle contrast ultrasonography, and magnetic resonance imaging characteristics of the normal equine proximal suspensory ligament

Previous studies have proposed that standard ultrasonography may not adequately represent the pertinent anatomic characteristics of the equine proximal suspensory ligament. The purpose of the study was to compare the use of standard ultrasonography, angle contrast ultrasonography, MRI, and histology for identification of the anatomic characteristics of the normal equine suspensory ligament in the forelimb. Horses free from forelimb lameness with no palpable abnormalities in the region of the suspensory ligament were included in the study. The proximal suspensory ligaments in 20 forelimbs were examined using the standard ultrasound technique, angle contrast ultrasound technique, and MRI, followed by histologic evaluation. Total transverse (cross-sectional) area of the proximal suspensory ligament was estimated using the standard ultrasound and the angle contrast ultrasound techniques, MRI, and histologic sections for the following parameters: total area of the ligament, ligament fibers, muscle, and fat. The proximal suspensory ligament lobe size and tissue distribution were compared and subjectively graded (0-4) for asymmetry. Subjectively, angle contrast ultrasound technique improved differentiation of fibers from the remaining tissue types and allowed identification of the peripheral ligament margin. There was no significant difference in asymmetry scores between modalities. The asymmetry scores of the right and left forelimbs were significantly different with both ultrasound and MRI, based on the level of measurement. The angle contrast ultrasound technique has limitations compared to MRI. However, it provides additional diagnostic information that is not available with the standard ultrasound technique.

Imaging of the equine proximal suspensory ligament

Injury to the suspensory ligament can result in significant lameness. Multiple imaging modalities may be required to fully characterize injury to the suspensory ligament. Ultrasonography of the suspensory ligament is challenging, due to the normal anatomy. This article describes imaging of the proximal suspensory ligament in the front and hind limbs of the horse.

Morphometric analyses of the body and the branches of the normal third interosseous muscle (suspensory ligament) in Standardbreds

The third interosseous muscle (suspensory ligament, TIOM) is composed of connective tissue (CT) with a variable proportion of muscle (MT) and adipose tissue (AT). The aim of our study is to quantify the CT, MT and AT within the body and the branches of right thoracic and pelvic limbs TIOM in sound horses to determine whether there are differences in CT, MT and AT between age, sex, limbs and levels. Right limbs from 11 sound horses were collected. Samples from 6 levels of the TIOM were embedded in paraffin or in Tissue-Tek(®) . Most of the paraffin sections were shredded. Using the cryosection, some artefacts appeared. Cryoprotection was carried out, which produced the best results. Hematoxylin-phloxine-saffron and Hematoxylin-eosin gave a good contrast of colours between the tissues observed allowing the use of an image analysis programme to calculate percentage of each tissue within the TIOM. The percentage of MT and AT decreased significantly (P < 0.0001), whereas the percentage of CT increased significantly (P < 0.0001) with age and when descending from the proximal to the distal level of the TIOM. The percentage of MT was significantly higher (P < 0.0001) in females than males, while the percentage of CT was significantly higher (P < 0.0001) in males than females. The percentage of AT was significantly higher (P = 0.0278) in pelvic limbs than in thoracic limbs. These results confirm the variation in tissue composition within the TIOM of sound horses.

Excision of the deep branch of the lateral palmar nerve of horses to resolve lameness caused by proximal suspensory desmitis

OBJECTIVE

To assess outcome after neurectomy of the deep branch of the lateral palmar nerve (DBLPaN) as a treatment for horses with persistent lameness associated with chronic proximal suspensory desmitis (PSD) of the thoracic limb.

STUDY DESIGN

Case series.

ANIMALS

Adult, mixed-breed horses (n = 4), weighing 510-585 kg, used for amateur show-jumping.

METHODS

Records of 4 horses chronically lame because of PSD of one or both thoracic limbs that were treated by neurectomy of the DBLPaN were reviewed. The site of pain causing lameness was localized using regional anesthesia. The proximal aspect of the suspensory ligament of the affected limb(s) of all horses were enlarged on ultrasonographic examination, but fiber disruption was not observed. All horses remained lame after conservative therapy. Neurectomy was performed with the horses anesthetized and positioned in dorsal recumbency.

RESULTS

All 4 horses were sound at 6 weeks and remained sound for at least 12 months after neurectomy.

CONCLUSION

Lameness in horses caused by chronic PSD can be resolved by neurectomy of the DBLPaN in horses that are refractory to conservative management.

The role of MRI in selected equine case management

Magnetic resonance imaging (MRI) allows for excellent evaluation of many types of soft tissue and osseous lesions. Using MRI as a diagnostic modality can help in developing an individualized treatment protocol. Case management can include both surgical and medical intervention. Various MRI findings and associated treatment protocols are described.

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

REASONS FOR PERFORMING STUDY

To evaluate intra- and interobserver variability in ultrasonographic measurements of the proximal aspect of the suspensory ligament (PSL) in the horse.

HYPOTHESIS

A minimum difference of ≥20% is required to differentiate reliably between physiological and pathological alterations related to dimensions.

MATERIALS AND METHODS

Two operators examined the PSL in all 4 limbs of 14 horses twice using different techniques and different probes with and without standoff pads. Measurements were taken from the longitudinal and transverse images. Inter- and intraoperator variability was evaluated using agreement indices (AI) and the 95% limits of agreement (LOA).

RESULTS

On the longitudinal scan the mean inter- and intraoperator AIs for dorsopalmar/-plantar thickness were both ≥0.89 and the 95% LOA were within target values for almost all intra- and interoperator comparisons. Similar mean AIs and 95% LOA were calculated for the dorsopalmar/-plantar thickness on the transverse image. For lateromedial width, cross-sectional area and circumference on the transverse scan, the mean inter- and intraoperator AIs ranged between 0.81 and 0.95 and the 95% LOA were higher than target values regardless of the imaging technique used. In general, better values for AIs and 95% LOA were achieved in the fore- compared with the hindlimb.

CONCLUSION AND CLINICAL RELEVANCE

Acceptable precision was identified within and between operators only for the dorsopalmar/-plantar thickness in longitudinal and in transverse scanning directions. For the lateromedial width, cross-sectional area and circumference, a relatively large variability was identified. This aspect has to be considered if these parameters are to be used for objective measurement of the PSL from the transverse ultrasound image.

Characterization of the origin and body of the normal equine rear suspensory ligament using ultrasonography, magnetic resonance imaging, and histology

The suspensory ligament is difficult to image accurately, partly because it contains ligamentous fibers, as well as noncollagenous adipose and muscle tissue in the normal horse. Our hypothesis was that magnetic resonance (MR) imaging would be more accurate than ultrasonography in identifying the size of the suspensory ligament and the presence and size of noncollagenous tissues within the ligament. Eleven horses were used for ultrasonographic and MR imaging and histologic evaluation of the rear suspensory ligament. The origin and body of the normal suspensory ligament had a heterogenous appearance on MR images with two separate islands of mixed signal intensity evident throughout its otherwise hypointense cross-sectional area. Histologically, there were isolated islands of muscle, adipose, loose connective tissue and dense collagenous partitions, organized in two separate bundles that extended through the full length of the suspensory ligament origin and body to the level of its bifurcation. Comparison of MR images with corresponding histologic sections confirmed that islands of heterogenous signal intensity in normal suspensory ligaments correlated well with these bundles. Using ultrasonography, it was impossible to distinguish these islands from surrounding dense collagenous tissue consistently. MR imaging determined the cross-sectional area of the suspensory ligament more accurately than ultrasonography. Based upon these results, MR imaging is superior to ultrasonography for assessment of the suspensory ligament. The appearance associated with normal ligament anatomy needs to be understood before MR signal variation can be considered as indicative of disease in the suspensory ligament.

Evaluation of experimentally induced injury to the superficial digital flexor tendon in horses by use of low-field magnetic resonance imaging and ultrasonography

OBJECTIVE

To evaluate tendon injuries in horses over a 16-week period by use of ultrasonography and low-field magnetic resonance imaging (MRI).

SAMPLE

Tendons of 8 young adult horses.

PROCEDURES

The percentage of experimentally induced tendon injury was evaluated in cross section at the maximal area of injury by use of ultrasonography and MRI at 3, 4, 6, 8, and 16 weeks after collagenase injection. The MRI signal intensities and histologic characteristics of each tendon were determined at the same time points.

RESULTS

At 4 weeks after collagenase injection, the area of maximal injury assessed on cross section was similar between ultrasonography and MRI. In lesions of > 4 weeks' duration, ultrasonography underestimated the area of maximal cross-sectional injury by approximately 18%, compared with results for MRI. Signal intensity of lesions on T1-weighted images was the most hyperintense of all the sequences, lesions on short tau inversion recovery images were slightly less hyperintense, and T2-weighted images were the most hypointense. Signal intensity of tendon lesions was significantly higher than the signal intensity for the unaltered deep digital flexor tendon. Histologically, there was a decrease in proteoglycan content, an increase in collagen content, and minimal change in fiber alignment during the 16 weeks of the study.

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasonography may underestimate the extent of tendon damage in tendons with long-term injury. Low-field MRI provided a more sensitive technique for evaluation of tendon injury and should be considered in horses with tendinitis of > 4 weeks' duration.

Management of hindlimb proximal suspensory desmopathy by neurectomy of the deep branch of the lateral plantar nerve and plantar fasciotomy: 155 horses (2003-2008)

REASONS FOR PERFORMING STUDY

Neurectomy of the deep branch of the lateral plantar nerve and plantar fasciotomy have become accepted as methods of treatment of proximal suspensory desmopathy (PSD), but there are limited long-term studies documenting the outcome.

OBJECTIVES

To describe long-term follow-up in horses with PSD alone or with other injuries contributing to lameness and poor performance, including complications, following neurectomy and fasciotomy.

METHODS

Follow-up information was acquired for 155 horses that had undergone neurectomy and fasciotomy for treatment of PSD between 2003 and 2008. Success was classified as a horse having been in full work for >1 year post operatively. Horses were divided into 3 groups on the basis of the results of clinical assessment and diagnostic analgesia. Horses in Group 1 had primary PSD and no other musculoskeletal problem. Horses in Group 2 had primary PSD in association with straight hock conformation and/or hyperextension of the metatarsophalangeal joint. Horses in Group 3 had PSD and other problems contributing to lameness or poor performance.

RESULTS

In Group 1, 70 of 90 horses (77.8%) had a successful outcome, whereas in Group 3, 23 of 52 horses (44.2%) returned to full function for >1 year. Complications included iatrogenic damage to the plantar aspect of the suspensory ligament, seroma formation, residual curb-like swellings and the development of white hairs. All horses in Group 2 remained lame.

CONCLUSIONS AND CLINICAL RELEVANCE

There is a role for neurectomy of the deep branch of the lateral plantar nerve and plantar fasciotomy for long-term management of hindlimb PSD, but a prerequisite for successful management requires recognition of risk factors for poor outcome including conformation features of straight hock or fetlock hyperextension.

Regional differences in biochemical, biomechanical and histomorphological characteristics of the equine suspensory ligament

REASONS FOR PERFORMING STUDY

Desmopathies of the suspensory ligament are relatively frequent and vary in prevalence over different anatomical regions. This variation may be because of regional differences in tissue characteristics.

OBJECTIVE

To characterise different regions of healthy forelimb suspensory ligaments (SLs) by means of biochemical, biomechanical and histomorphological techniques.

HYPOTHESIS

There is substantial topographical heterogeneity in the SL with respect to structural, compositional and functional characteristics.

METHODS

SLs were harvested from 38 limbs and used for biochemical (n = 20), biomechanical (n = 14) and histomorphological (n = 4) evaluation. Sulphated glycosaminoglycan (S-GAG), DNA and collagen content, degree of lysyl hydroxylation and numbers of enzymatic and nonenzymatic cross-links were determined in 7 regions of the SL: lateral and medial part of the origin (OM, OL), mid-body (MB), axial and abaxial parts of the lateral and medial branches (ILAX, ILAB, IMAX and IMAB, respectively). Passive resistance to tensile loading was measured in 5 regions of the SL (all except OL and OM).

RESULTS

DNA content was lower in OL and OM than in all other parts. GAG content was also lower in OL and OM and highest in ILAB and IMAB. Collagen content was lower in OL/OM and highest in ILAX/IMAX. Pentosidine levels were highest in OL and significantly lower in the lateral insertion (ILAX/ILAB). There were no differences in hydroxylysylpyridinoline (HP) cross-links or lysyl hydroxylation. Stiffness (P<0.01) and modulus of elasticity (P<0.01) were substantially higher in the MB region than in all other regions except for IMAB. Strain at failure was lower in the MB region (P<0.0001), resulting in a comparable force at rupture as in the other regions.

CONCLUSIONS

Matrix composition differs to a relatively limited extent between different regions of the SL. The mid-body of the ligament is stiffer than the branches, which have similar properties and relevance and mechanical differences between mid-body and branches/origin may explain some use-related differences in the prevalence of lesions.

Clinical, magnetic resonance, and sonographic imaging findings in horses with proximal plantar metatarsal pain

Sonography is commonly used for diagnosis of desmopathy of the proximal part of the suspensory ligament in horses. However, magnetic resonance (MR) imaging has been stated to be superior for detecting disease and localizing lesions. In this retrospective study of 39 horses or 46 hind limbs with lameness due to proximal plantar metatarsal pain, the clinical and diagnostic findings are discussed and sonography and MR imaging compared for examination of the proximal part of the suspensory ligament. With MR imaging interpreted as the clinical gold standard, desmopathy of the proximal part of the suspensory ligament was diagnosed in 21 hind limbs, proximal plantar metatarsal pain of unknown cause in 12, an osseous injury at the origin of the suspensory ligament in four and a condition unrelated to the suspensory ligament in nine. Based on these findings, sonography had a sensitivity of 0.77 and 0.66 and specificity of 0.33 and 0.31 for diagnosing proximal suspensory desmopathy and for accurately localizing lesions, respectively. MR imaging changes consistent with proximal suspensory desmopathy were signal hyperintensities and an increase in cross-sectional area compared with the contralateral limb. Anesthesia of the deep branch of the lateral plantar nerve is not specific neither for proximal suspensory desmopathy, as conditions unrelated to the suspensory ligament were diagnosed, nor for diagnosis of proximal plantar metatarsal pain, as conditions outside the proximal plantar metatarsal region were also diagnosed.

In search of clinical truths: equine and comparative studies of anatomy

The importance of correlating anatomical studies with diagnostic and therapeutic approaches in practice has long been recognised. Such studies in the horse have, until recently, lagged behind this discipline in human medicine and surgery. Clinical techniques by which this correlation is achieved include radiography, ultrasound, computed tomography and magnetic resonance imaging. This review presents published literature on the subject and, in addition, describes the part played by plastination, a recently developed technique for the preservation of biological specimens. In this, tissue fluids and part of the lipids are replaced by certain polymers yielding specimens that can be handled without gloves, do not smell or decay, and even retain microscopic properties of the original sample. The technique has proved to be a useful tool to correct previously presented anatomical descriptions and is one now favoured by human surgeons. Studies of the horse employing this technique include those of the temporomandibular joint and tarsus. The aim of the review is to stimulate further correlations of anatomical structure and equine medical and surgical procedures, thereby advancing knowledge and understanding in practice and teaching.