Ultrasonographic characteristics (cross-sectional area and relative echogenicity) of the digital flexor tendons and ligaments of the metacarpal region in Purebred Spanish horses

Equine tendon mechanical behaviour: Prospects for repair and regeneration applications

Tendons are dense connective tissues that play an important role in the biomechanical function of the musculoskeletal system. The mechanical forces have been implicated in every aspect of tendon biology. Tendon injuries are frequently occurring and their response to treatments is often unsatisfactory. A better understanding of tendon biomechanics and mechanobiology can help develop treatment options to improve clinical outcomes. Recently, tendon tissue engineering has gained more attention as an alternative treatment due to its potential to overcome the limitations of current treatments. This review first provides a summary of tendon mechanical properties, focusing on recent findings of tendon mechanobiological responses. In the next step, we highlight the biomechanical parameters of equine energy-storing and positional tendons. The final section is devoted to how mechanical loading contributes to tenogenic differentiation using bioreactor systems. This study may help develop novel strategies for tendon injury prevention or accelerate and improve tendon healing.

Ultrasound Morphometry and Mean Echogenicity of Digital Flexor Tendons, Suspensory Ligament, and Accessory Ligament of Digital Deep Flexor Tendon in Gaited Horses

The objective of this study was to evaluate and compare the sonographic characteristics of the digital flexor tendons and ligaments of the palmar/plantar of the metacarpal and metatarsal regions in gaited horses, as well as to establish normal reference ultrasound values for Mangalarga Marchador (MM) and Campeiro breeds. Transverse sonographic images were obtained of 50 adult and healthy horses from the MM (n = 25) and Campeiro (n = 25) breeds. The images were taken in six metacarpal/metatarsal zones, and the following measurements were taken: transverse area, circumference, dorsopalmar/plantar length, lateromedial length, and mean echogenicity. Differences were observed between breeds in the fore- and hindlimbs, and, even when not significant, the Campeiro breed tended to have higher values for most variables and structures. Variations between zones and between structures in the same zone followed a similar trend in both breeds for all variables. In addition, the dimensions and variations between zones and structures were different between the fore- and hindlimbs, highlighting the need for specific values for the digital flexor tendons and ligaments of the metatarsal plantar region. In conclusion, the digital flexor tendons, suspensory ligaments, and accessory ligaments of the digital deep flexor tendon are influenced by the breed factor in gaited horses, and they are different between the fore- and hindlimbs.

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.

Response of the Thoroughbred forelimb to perturbations caused by a change in ground surface

Thoroughbred racehorses are often affected by musculoskeletal injuries, leading to involuntary rest, early retirement or death. Hardness and consistency of the track surface have been implicated as major risk factors for limb injury. The purpose was to test the utility of a preliminary AnyBody musculoskeletal model of the equine forelimb for its responses on two perturbing surfaces. A musculoskeletal model was developed using CT, muscle, tendon and ligament properties, and kinematic data were applied from ridden trials using five Thoroughbred horses. Horses were ridden at trot and canter on a baseline sand surface, and through two perturbation pits containing a harder and a softer surface for one stance phase. In response to the hard perturbation, the proximal limb was more compliant at trot and canter, as measured by increased shoulder flexion in the perturbed stance phase and increased elbow and carpal flexion in the subsequent swing phase. The suspensory ligaments and muscle-tendon units were less strained while lacertus fibrosus was more strained. In response to the soft perturbation, the coffin joint was more flexed and the elbow was more extended in the acute stance phase at trot, resulting in increased strain to the DDF, extensor branches and lacertus fibrosus. At canter, the coffin was more flexed, the fetlock less hyperextended and so the suspensory structures were less strained in the perturbed stance phase, but more strained in the second stance phase. Changes in ground surface affect both the perturbed stance phase, and the following stance phase.

The influence of the metacarpophalangeal joint angle on the transversal area and mean echogenicity of the superficial digital flexor tendon and suspensory ligament in gaited horses

The objective of this study was to assess the influence of the metacarpophalangeal (MCP) joint angle on the transversal area (TA) and mean echogenicity (ME) of the superficial digital flexor tendon (SDFT) and suspensory ligament (SL) in gaited horses. Ultrasound images were obtained from 50 healthy adult horses of the Mangalarga Marchador (MM; n=25) and Campeiro (n=25) breeds. Static and dynamic angles of the MCP joint were measured from photographs and video recordings. Higher ME values were evinced for the SL only in the group with the smaller dynamic angles of the MCP joint in the MM horses, in addition to weak negative correlation between the dynamic angle and ME. Moreover, weak negative correlation was also observed between the static angle and TA of the lateral branch of the SL and between the static angle and the ME of the SDFT. However, the difference observed in the group of MM horses, as well as the weak correlation, was not considered sufficient to support the hypothesis that a smaller angle of the MCP joint (greater extension) is associated with larger TA and ME values for the structures. The results also suggest that the static and dynamic angles of the MCP joint do not influence the TA and ME values of the SDFT and SL in gaited horses.

Ultrasound evaluation of digital flexor tendons of jumping horses undergoing treadmill training

This study aimed to perform ultrasonographic evaluation of the digital flexor tendons of jumping horses undergoing complementary training on a treadmill. Fifteen Brazilian Sport horses were divided into two groups: Group I with 7 animals in physical training complementary to the standard training at the Brazilian Army's Riding School; and Group II with 8 animals in standard training used in the Brazilian Army's Riding School. Complementary training was performed on a treadmill on an inclined plane. Ultrasonographic images were taken at the beginning and at the end of training. The left thoracic and pelvic limbs of horses were evaluated for echogenicity values and cross-sectional areas of the superficial digital flexor tendons (SDFTs) and deep digital flexor tendons (DDFTs) in zones IA, IIB, and IIIB. The mean areas of the SDFT were 93.7 mm² and 95.8 mm² at the beginning and the end of training, respectively. The cross-sectional area of DDFT increased from 124.6 mm² at the beginning of training to 136.8 mm² at the end of training. The echogenicity values of both tendons were between 0 and 1 as expected, concluding that clinically, the animals showed adaptation to the exercise protocol with no signs of tendon injury being detected, implying that traditional training and complementary training are safe.

Equine flexor tendon imaging part 1: Recent developments in ultrasonography, with focus on the superficial digital flexor tendon

Flexor tendon injuries are a major cause of lameness in performance horses and have considerable impact on equine welfare and the wider horse industry. Ageing and repetitive strain frequently cause varying degrees of tendon micro-damage prior to the recognition of clinical tendinopathy. Whilst B-mode ultrasonography is most commonly utilised for detection and monitoring of tendon lesions at the metacarpal/metatarsal level, the emphasis of recent research has focused on the identification of subclinical tendon damage in order to prevent further tendon injury and improve outcomes. The introduction of elastography, acoustoelastography and ultrasound tissue characterisation in the field of equine orthopaedics shows promising results and might find wider use in equine practice as clinical development continues. Based on the substantial number of research studies on tendon imaging published over the past decade this literature review aims to examine the currently used ultrasonographic imaging techniques and their limitations, and to introduce and critically appraise new modalities that could potentially change the clinical approach to equine flexor tendon imaging.

Development of An Anybody Musculoskeletal Model of The Thoroughbred Forelimb

Musculoskeletal injuries in horses are the main cause of retirement, rest, and death. To understand these injuries, it is necessary to study loads in muscles, tendons and ligaments. A musculoskeletal model makes it possible to consider all structures simultaneously and avoids invasive measurements. At present, most computational models of the equine limb described in the literature have been limited to the distal limb. The aim of this study was to create a preliminary musculoskeletal model of the whole equine forelimb and to run it with kinematic data collected during gait. The model was developed with the AnyBody Modelling System. It includes six limb segments, 11 muscle groups and 17 ligaments. Kinematic data were collected from the right forelimb of four Thoroughbreds at trot, right and left lead canter, and were then used in the model to compute sagittal plane joint excursions and ligament and tendon strains. The modelled joint excursions were in reasonable agreement with previous reports in the literature despite breed, gait and surface differences. Strain patterns of the tendons of the suspensory apparatus agreed with the literature, with maxima in mid-stance or at the end of stance. Strains in the distal palmar ligaments peaked in mid-stance, while strain in lacertus fibrosus peaked at the stance-swing transition. Tendon and ligament strains at canter were greatest when the measured forelimb was the trailing limb. Strain amplitudes varied against earlier models and these differences are discussed in relation to variations in methods, and especially in relation to attachment points of tendons and ligaments.

Influence of morphometric parameters on the size of collateral ligaments of the distal interphalangeal joint of equines

The physiological measurements of collateral ligaments of distal interphalangeal joint (CL-DIPJ) differ in the literature. The factors that influence these differences are not well described. The aims of this study are to compare CL-DIPJ sizes in equines with different withers height, as well as to correlate body weight and hoof size to the size of these ligaments. In total, 52 horses were used in the study. They were divided into two groups according to wither height: Group 1 (G1) - 21 animals with up to 147 cm - and group 2 (G2) - 21 animals with greater than 148 cm. CL-DIPJ was ultrasonographically measured in order to find the mean of dorso-palmar (DPD) and latero-medial (LMD) diameters and the cross-sectional area (CSA). Hoof width and length were measured, and the results were used to calculate the hoof surface area. Withers height and body weight were also measured. Groups were statistically compared by Student's t test and Pearson's correlation application to each group. Groups were different in body size, HS and CL-DIPJ size when p < .05, except for the LMD of the medial collateral ligament of left thoracic limb. Withers height and body weight did not show significant correlations to CL-DIPJ size in G1, but they had little influence on the size of CL-DIPJ on G2. No correlation between the hoof size and the CL-DIPJ was noted in any of the two groups. In conclusion, the CL-DIPJ were larger in taller horses and their sizes were correlated to their height and weight, but they were not correlated to hoof size.

Acoustic Radiation Force Impulse (ARFI) elastography imaging of equine distal forelimb flexor structures

ABSTRACT This study set out to determine normal values for acoustic radiation force impulse (ARFI) elastography of the superficial digital flexor tendon, deep digital flexor tendon, accessory ligament of the deep digital flexor tendon and suspensory ligament in horses. Twenty-four horses were submitted to conventional sonographic assessment and elastography imaging (quantitative ARFI method) of distal forelimb tendons and ligaments at nine anatomical regions. Elastograms depicted tendons and ligaments in orange to red tones consistent with greater stiffness. Shear wave velocity was higher in the longitudinal compared to the cross-sectional plane but did not differ significantly between the left and right forelimbs. The suspensory ligament was stiffer compared to remaining structures in the cross-sectional plane. Ligaments were stiffer than tendons and the deep digital flexor tendon was stiffer than the superficial digital flexor tendon in the longitudinal plane. Target structures were stiffer in male compared to female horses and stiffness tended to increase with age. ARFI elastography proved to be a feasible and reproducible imaging modality for assessment of distal forelimb tendons and ligaments in horses. Qualitative features derived from stiffness quantification in these structures can be applied to horses with musculoskeletal disorders, as well as to other animal species.

Subclinical Ultrasonographic Abnormalities of the Suspensory Ligament Branches Are Common in Elite Showjumping Warmblood Horses

Background: There is limited information concerning the ultrasonographic appearance of suspensory ligament branches (SLB) in sports horses. Publications exist on clinical injuries that lead to loss of training days and retirement, but not on the appearance of SLBs in high level showjumping Warmbloods.

Objectives: To demonstrate the prevalence of subclinical SLB abnormalities in regularly competing high-level showjumpers; to grade each branch 0–3; compare forelimb vs. hindlimb and medial vs. lateral SLBs; subjectively assess periligamentous fibrosis; measure cross sectional area (CSA) and to gather competition follow-up data.

Study Design: Prospective cross-sectional study using ultrasonograms.

Methods: Sixty elite showjumping Warmbloods without recent history or clinical signs of SLB desmopathy were examined ultrasonographically. Eight static images of each SLB were acquired in transverse and longitudinal sections, anonymised and stored. Images were then assessed and graded by two experienced blinded clinicians based on a published ordinal scale (grade 0–3). A branch score was assigned based on the most severe grade of any image slice in each branch series. SLB cross-sectional area measurement was obtained from each SLB using the transverse image proximal to insertion.

Results: The frequency of grade 2 (moderate) ultrasonographic abnormalities was high. Combined data showed a prevalence of 58% (554/960) grade 2 SLBs. Interobserver agreement was good (kappa = 0.65). Periligamentous fibrosis was over represented in hindlimbs (64%). Combined observer data showed there was no statistical difference in branch scores based on limb or laterality. Follow-up over 12 months revealed only two horses were excluded from competition due to SLB injury.

Main Limitations: Sample size was small. Images were obtained in static mode, limbs were not clipped of hair, lameness evaluation was under FEI veterinary inspection and not performed by the authors and follow-up evaluation was from FEI competition records and communication only, and was limited to 1 year.

Conclusions: Regularly competing elite showjumping Warmbloods have a high prevalence of subclinical SLB ultrasongraphic abnormalities, which may not contribute to causing lameness, poor-performance or be viewed entirely negatively at prepurchase examination. Judicious interpretation of moderate severity SLB abnormalities is advised due the low incidence of clinical injury demonstrated during the 1 year follow-up.

Relative Echogenicity of Tendons and Ligaments of the Palmar Metacarpal Region in Foals from Birth to 4 Months of Age: A Longitudinal Study

The objective of this study was to evaluate relative echogenicity of superficial and deep digital flexor tendons, the accessory ligament of the deep digital flexor tendon and interosseous muscle of the metacarpal region in foals ages 1 week to 4 months; and assess the association between echogenicity and sex or side/laterality. Seven Standardbred trotter foals were examined. Right and left metacarpal regions (palmar surface) were ultrasonographically investigated, and four regions of interest were assessed. A significant increase in echogenicity was seen in superficial and deep digital flexor tendons, accessory ligament of deep digital flexor tendon, and interosseous muscle during growth from 1 week to 4 months of age. Echogenicity of examined tendons and ligaments was not influenced by gender nor laterality. Reference values for tendon and ligament echogenicity could function as a tool to discriminate between physiological and abnormal conditions such as congenital contractural conditions.

Evaluation of mean echogenicity of tendons and ligaments of the metacarpal region in neonatal foals: A preliminary study

The aims of this research were to evaluate mean echogenicity (ME) of the deep and superficial digital flexor tendons (DDFT and SDFT), the interosseous muscle (IM), and the accessory ligament of the deep digital flexor tendon (ALDDFT) of the metacarpal region in neonatal foals, and determine the effect of sex, side and body weight on this quantitative ultrasonographic evaluation. Thirteen orthopedically sound neonatal foals were examined. Four areas of study (1A, 1B, 2A, 2B) were identified. Transverse scans of the DDFT, SDFT, IM and ALDDFT were obtained, recorded, and analyzed. The most echogenic structures were the ALDDFT and DDFT, while the SDFT was significantly less echogenic than all other structures (P<0.05). No influence of sex, forelimb, or body weight was observed. The echogenicity of the tenodesmic structures of foals partially overlapped that reported in the metacarpal region in adult horses, except for IM.

Ultrasonographic assessment of the equine palmar tendons

Aim:

The present study was conducted to evaluate the equine palmar tendon by ultrasonography (USG) in standing the position.

Materials and Methods:

USG of palmar tendons was performed in 40 adult horses using linear transducer having frequency of 10-18 MHz (e-soate, My Lab FIVE) and L52 linear array transducer (Titan, SonoSite) with frequencies ranging from 8 to 10 MHz. Palmar tendon was divided into 7 levels from distal to accessory carpal bone up to ergot in transverse scanning and 3 levels in longitudinal scanning.

Results:

The USG evaluation was very useful for diagnosis of affections of the conditions such as chronic bowed tendon, suspensory ligament desmitis, carpal sheath tenosynovitis and digital sheath effusions. The mean cross-sectional area (cm²) of affected tendons was significantly increased in affected than normal tendons. The echogenicity was also found reduced in affected tendons and ligaments along with disorganization of fiber alignment depending on the severity of lesion and injury.

Conclusion:

USG proved ideal diagnostic tool for diagnosis and post-treatment healing assessment of tendon injuries in horses.

Cross sectional area of forelimb metacarpal region flexor tendons in horses of different breeds and age

There are few studies on the effects of age within breeds on cross sectional area (CSA) of flexor tendons in horses. This study was designed to evaluate the relationship between age and the CSA of the superficial flexor tendon (SDFT), the deep digital flexor tendon (DDFT) and its accessory ligament (AL-DDFT) of both forelimbs in horses utilising ultrasound. Ages of the horses ranged from 2 years to aged, and the breeds evaluated were Thoroughbred (TB), Standardbred (SB), Quarterhorse (QH) and German Warmblood Riding horse (WB). CSAs were measured with ultrasound at 4 cm intervals, starting 4 cm from the distal border of the accessory carpal bone down to the metacarpophalangeal joint. The CSA of the SDFT in 3-year-old and older TB, QH and WBs was smaller than in the 2-year-olds (all P<0.001) and did not differ between 3-year-olds and older horses (P≯0.05). In comparison, the CSA of the SDFT in 2-year-old and 3-year-old SBs was smaller than in the horses older than 3 years (P<0.05 among age groups). The 2-year-olds had larger CSA of the DDFTs than the 3-year-olds (P<0.01), and the CSA was also larger in the older horses of all breeds (P<0.01). However, the 3-year-old QH and SBs had smaller CSAs of the DDFT than the horses older than 3 years of age, (P<0.001), but interestingly the CSA was not different in the TB and WBs based on age (P≯0.05). The CSA of the AL-DDFT in the left forelimb was smaller than in the right forelimb (P<0.01) of all horses. The results of this study show that differential effects exist between age and within breeds on the CSA of the SDFT, DDFT and AL-DDFT, indicating that training and management may play a role, in addition to genetics, in the CSA of the metacarpal region flexor tendons of horses. The data on the CSAs of the SDFT, DDFT and AL-DDFT in WB, QH and SBs provides additional physiological references for these breeds to compliment the CSA data previously published for other breeds.

Cross-sectional area and mean echogenicity of shoulder and elbow tendons in adult German Shepherd dogs

The aim of this study was to describe the cross-sectional area and mean echogenicity of the main tendons of the shoulder and elbow joints in adult German Shepherd dogs and to determine the effects of sex, weight, and age on these parameters. No previous publications in the veterinary literature have reported information regarding quantitative ultrasonographic tendon measurements in dogs. Thirty German Shepherd dogs were examined: 13 males and 17 females. The cross-sectional area was significantly higher in males than in females (p <0.05) for the distal tendon of the triceps brachii muscle and the tendons of the flexor carpi ulnaris and common digital extensor muscles. The influence of sex on mean echogenicity was not significant. According to age, mean echogenicity was higher in older dogs, while the cross-sectional areas were similar in the two groups. Cross-sectional area and mean echogenicity of the tendons showed a direct increase with an increase in body weight. The data gained from this study can help support the clinician to discriminate between normal and pathological conditions.

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.

Ultrasonograph and clinical quantitative characterization of tendinopathy by modified splitting in a goat model

A tendinopathy is a clinical condition characterized by activity-related pain, focal tendons tenderness, and intratendinous imaging changes. This study characterizes a surgically induced tendinopathy in a goat model with a noninvasive in vivo longitudinal followup based on physical examination and US. Cross-sectional area (CSA) is the most objective feature for the evaluation of tendinopathy in correlation with clinical findings. The deep digital flexor tendon (DDFT) of the left hind limb of six goats was isolated and scarified by a modified splitting. Pain and lameness at walk and trot were evaluated. External width and thickness of tendon region were measured by calipers. CSA and the ratio lesion/tendon CSA were obtained at days 0, 7, 21, 42, and 84 by US. The highest value of global functional score was obtained at day 7, then decreased until day 40 and was not significantly different from day 0 at the end of the study. The external width recovered a normal value at the end of the study, but the external thickness was still significantly increased (P < 0.05). Peritendinous oedema was observed at day 7, but intratendinous lesions were visible only at day 21 as a focal hypo to anechoic area. At day 84, two tendons still presented visible lesions. US examination was reproducible, specific, and provided complementary information to the global functional score. A standardized focal tendinopathy was induced in goats. This experimental model of focal tendinopathy could be used to study the effect of different treatments.

Cross-sectional area of the tendons of the tarsal region in Standardbred trotter horses

REASONS FOR PERFORMING STUDY

The assessment of a normal range for cross-sectional area (CSA) of tendons in the tarsal region is important in order to use them as reference values in the identification of pathological changes of dimensions.

OBJECTIVES

To provide normal reference values for the CSA of the tendons of the tarsus of Standardbred trotter horses (STH) by means of ultrasonography.

METHODS

Transverse echographic images of the tendons were obtained at different levels proximodistally; these images were digitised and CSA values (mean ± s.d.) were obtained for each structure.

RESULTS

The largest structure corresponded with the lateral digital flexor/caudal tibial tendon complex at Level 1 and the smallest was the medial digital flexor tendon at Level 4. Almost all tendons showed a slight decreasing in their CSA when crossing the tarsus.

CONCLUSIONS

The normal CSA values of tendinous structures in the tarsal region of the STH are reported. These data could be used as anatomical references.

POTENTIAL RELEVANCE

The establishment of reference values could serve as a tool to discriminate between normal and abnormal dimensions of tarsal tendons in STH. Other horse breeds should need their own reference values.

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.

Ultrasonographic morphometric measurements of digital flexor tendons and ligaments of the palmar metacarpal region in Haflinger horses

The aim of the study was to determine morphometric values of the superficial and deep digital flexor tendon, the inferior check ligament and the suspensory ligament in the palmar metacarpal region of sound Haflinger horses using ultrasonography and to assess the influence of different factors on them. The findings were compared with the literature. A total of 30 sound Haflinger mares aged 4-20 years were used. Transverse ultrasound images were obtained with an 8-10 linear MHz transducer and the cross-sectional area, the circumference and the dorsopalmar and lateromedial width were determined for each structure at six regions of interest (ROI) in both forelimbs. The coefficient of variation was <3%. The structures were compared between each other and the values of each structure at the ROIs. Age, height at the withers, body mass index, diameter of the Os metacarpale III and the circumference of the mid-metacarpal region showed significant influences on some of the parameters. Reference values for the tendons and ligaments in the palmar metacarpal region in sound Haflinger mares were obtained and the influence of different factors was tested. Description of the dimensional relationship between the structures and comparison of the data with the literature provide knowledge required for adequate veterinary care.