Deep Digital Flexor Research Articles

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

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. To investigate the changes in the cross-sectional area (CSA) of each tendon and ligament in the metacarpal region with age by ultrasonographic examination. Longitudinal study of foals from Day 1 to age 24 months. 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. 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. 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.

Musculoskeletal lesions and lameness in 121 horses with carpal sheath effusion (1999-2010).

Equine carpal sheath effusion has multiple etiologies. The purpose of this retrospective study was to describe the prevalence of distinct musculoskeletal lesions lameness in a sample of horses with a clinical diagnosis of carpal sheath effusion. A total of 121 horses met inclusion criteria. Seventy-four percent (89/121) of horses were lame at presentation; middle-aged (9-18 years, 80%) and older (> 18 years, 85%) horses were lame more frequently than young horses (< 9 years, 44%). Ninety-three percent (113/121) were diagnosed with osseous and/or soft tissue abnormalities. Of these 113 horses, 10 exhibited osseous abnormalities, whereas 111 were diagnosed with soft tissue lesions. Eighty-four percent (93/111) of the soft tissue injuries extended from the caudodistal antebrachium to the palmar metacarpus. The superficial digital flexor tendon (98/111; 88%) and accessory ligament of the superficial digital flexor tendon (64/111; 58%) were the most commonly injured structures, with both structures affected in 41 (41/111; 37%) horses. Injuries within the caudodistal antebrachium included the superficial digital flexor musculotendinous junction (66), the accessory ligament of the superficial digital flexor tendon (64), and deep digital flexor muscle (21), in isolation or in combination with other structures. Increased echogenicity in the medial superficial digital flexor musculotendinous junction was detected in 40 horses and was significantly associated with increasing age (middle-aged, 19/40; old, 18/40). Findings from this study indicated that age should be taken into consideration for horses presented with carpal sheath effusion and that adjacent structures within the caudodistal antebrachium should be included in evaluations.

Is there an association between clinical features, response to diagnostic analgesia and radiological findings in horses with a magnetic resonance imaging diagnosis of navicular disease or other injuries of the podotrochlear apparatus?

Previous descriptions of the clinical features of navicular disease occurred before the widespread use of magnetic resonance imaging (MRI) allowed a more definitive diagnosis of foot pain. The objective of this study was to compare the clinical features of horses with lesions of the podotrochlear apparatus with those with other causes of foot pain. It was hypothesised that primary navicular bone disease would be associated with more advanced radiological findings than other diagnoses. A retrospective study was performed of all horses examined at a referral centre with a definitive diagnosis of foot pain based on MRI ± post-mortem examination. Clinical examination findings, response to diagnostic analgesia and radiological grading of the navicular bone were compared among five diagnosis groups: (1) primary navicular bone pathology (NB); (2) lesions of the collateral sesamoidean ligament and/or distal sesamoidean impar ligament (CSL + DSIL); (3) primary deep digital flexor tendon injury (DDFT); (4) navicular bone pathology and other lesions of the podotrochlear apparatus ± DDFT (PTA) and (5) Other.There were 702 horses (NB, 62; CSL + DSIL, 180; DDFT, 69; PTA, 92; Other, 299). Horses with PTA injuries were more frequently unilaterally lame than other groups (P = 0.04). Horses with DDFT injury were more likely to exhibit pain on turning than other groups (P < 0.01). There were no associations between response to diagnostic analgesia and diagnostic group, and no association between radiological grade and diagnostic group. Clinical examination findings generally did not discriminate between diseases of the PTA and other causes of foot pain. Overall radiological scores of the navicular bone did not accurately predict navicular bone pathology.

Computed Tomographic Tenography of Normal Equine Digital Flexor Tendon Sheath: An Ex Vivo Study.

Aim of this study was to document the normal computed tomographic tenography findings of digital flexor tendon sheath. Six ex vivo normal equine forelimbs were used. An axial approach was used to inject 185 mg/mL of iopamidol in a total volume of 60 mL into the digital flexor tendon sheaths. Single-slice helical scans, with 5 mm thickness, spaced every 3 mm, for a pitch of 0.6, and with bone algorithm reconstruction, were performed before and after injections of contrast medium. To obtain better image quality for multiplanar reconstruction and 3D reformatting, postprocessing retroreconstruction was performed to reduce the images to submillimetre thickness. Computed tomographic tenography of digital flexor tendon sheaths could visualize the following main tendon structures for every forelimb in contrast-enhanced images as low densities surrounded by high densities: superficial digital flexor tendon, deep digital flexor tendon, manica flexoria, mesotendons, and synovial recess. Results of this study suggest that computed tomographic tenography can be used with accuracy and sensitivity to evaluate the common disorders of the equine digital flexor tendon sheath and the intrathecal structures.

Mechanical strength of four allograft fixation techniques for ruptured cranial cruciate ligament repair in dogs.

To test ex vivo mechanical properties of 4 allograft fixation techniques for cranial cruciate ligament (CCL) replacement. 30 stifle joints from canine cadavers. CCL-deficient stifle joints repaired by 1 of 4 techniques (n = 6/group) and CCL-intact stifle joints (control group; 6) were mechanically tested. Three repair techniques involved a patella-patella ligament segment (PPL) allograft: a tibial and femoral interference screw (PPL-2S), a femoral interference screw and the patella seated in a tapering bone tunnel in the tibia (PPL-1S), or addition of a suture and a bone anchor to the PPL-1S (PPL-SL). The fourth technique involved a deep digital flexor tendon (DDFT) allograft secured with transverse femoral fixation and stabilized with a tibial interference screw and 2 spiked washers on the tibia (DDFT-TF). The tibia was axially loaded at a joint angle of 135°. Loads to induce 3, 5, and 10 mm of femoral-tibia translation; stiffness; and load at ultimate failure with the corresponding displacement were calculated. Group means were compared with a multivariate ANOVA. Mean ± SD load for the intact (control) CCL was 520.0 ± 51.3 N and did not differ significantly from the load needed to induce 3 mm of femoral-tibial translation for fixation techniques PPL-SL (422.4 ± 46.3 N) and DDFT-TF (654.2 ± 117.7 N). Results for the DDFT-TF were similar to those of the intact CCL for all outcome measures. The DDFT-TF yielded mechanical properties similar to those of intact CCLs and may be a viable technique to test in vivo.

Do low field magnetic resonance imaging abnormalities correlate with macroscopical and histological changes within the equine deep digital flexor tendon?

Correlating magnetic resonance (MR) imaging and histopathological findings is essential to validate low field MR imaging in lame horses. This study aimed to compare signal changes in the deep digital flexor tendon (DDFT) of the distal limb on low field MR imaging with macroscopical and histological findings. Cadaver limbs from lame horses with DDFT lesions were selected. The DDFT MR imaging findings and histopathological results were graded, and macroscopical abnormalities were recorded. There was a strong correlation between MR imaging and histopathology grades (rs = 0.76, p < 0.001) in the foot. There was moderate agreement (Kappa statistic 0.52) between the MR and histopathology grades; agreement was superior further proximal in the foot. The presence and severity of pathology in the DDFT are well represented by the presence and severity of MR imaging signal changes. The study supports the use of low field MR imaging for diagnosis of equine distal limb DDFT lesions.

Comparison of high resolution gradient echo, XBONE T1, XBONE T2, Spin Echo T1 and 3D SST1 magnetic resonance imaging sequences for imagining the canine elbow.

Twenty canine elbows were examined by low-field MRI. The objective of this study was to compare five magnetic resonance sequences: High Resolution Gradient Echo in the sagittal plane, XBONE T2 in the sagittal plane, Spin Echo T1 in the sagittal plane, Spin Echo T1 in the dorsal plane and 3D SST1 and XBONE T1 in the transverse plane, and to determine which sequences have the highest diagnostic value in imagining the canine elbow. High Resolution Gradient Echo, XBONE T2 and Spin Echo T1 sequences in the sagittal plane proved to be very useful in evaluations of osseous structures such as the medial coronoid process, the anconeal process of the ulna and joint surfaces. The above sequences facilitate evaluations of radial extensor muscle of the wrist, biceps brachii muscle, triceps brachii muscle and the flexor carpi ulnaris muscle. 3D SST1 and XBONE T1 sequences in the transverse plane produce high-quality images of the medial humeral condyle and surfaces of the elbow joint. Those sequences are also useful for evaluating the surrounding muscles: extensor digitorum communis muscle, extensor carpi radialis muscle, deltoid muscle, biceps brachii muscle, pronator teres muscle and flexor carpi ulnaris muscle. The Spin Echo T1 sequence in the dorsal plane facilitates assessments of joint surfaces, medial humeral condyle, superficial digital flexor muscle, deep digital flexor muscle, triceps brachii muscle and extensor digitorum lateralis muscle. The Spin Echo T1 sequence in the sagittal plane has a short scan time, but it produces images of lower quality than High Resolution Gradient Echo and XBONE T2 sequences in the sagittal plane.

Identification of surgically-induced longitudinal lesions of the equine deep digital flexor tendon in the digital flexor tendon sheath using contrast-enhanced ultrasonography: an ex-vivo pilot study.

BackgroundLongitudinal tears in the lateral aspect of the deep digital flexor tendon are the most common causes of pain localised to the equine digital flexor tendon sheath. However conventional ultrasonographic techniques provide limited information about acute lesions. Ultrasonographic contrast agents are newly developed materials that have contributed to advancement in human diagnostic imaging. They are currently approved for intravenous use in human and animal models. In this study we described intrathecal use in the horse. This study was undertaken to evaluate the reliability of standard and angle contrast-enhanced ultrasonography to detect and characterize surgically-induced longitudinal lesions in the deep digital flexor tendons.In this pilot study surgically-induced lesions were created in the lateral aspect of the deep digital flexor tendon within the digital flexor tendon sheath in 10 isolated equine limbs to generate a replicable model for naturally occurring lesions. Another 10 specimens were sham operated. All the limbs were examined ultrasonographically before and shortly after the intrasynovial injection of an ultrasound contrast agent containing stabilised microbubbles. The images were blindly evaluated to detect the ability to identify surgically-created lesions. The deep digital flexor tendons were dissected and a series of slices were obtained. The depth of longitudinal defects identified with contrast-enhanced ultrasound scans was compared to the real extent of the lesions measured in the corresponding gross tendon sections.ResultsContrast-enhanced ultrasonography with both angle and standard approach provided a significant higher proportion of correct diagnoses compared to standard and angle contrast ultrasonography (p < 0.01). Contrast-enhanced ultrasonography reliably estimated the depth of surgically-induced longitudinal lesions in the deep digital flexor tendons.ConclusionContrast-enhanced ultrasound of the digital flexor tendon sheath could be an effective tool to detect intrasynovial longitudinal tears of the deep digital flexor tendon, although an in vivo study is required to confirm these results for naturally occurring lesions.

Deep digital flexor tendon rupture in two horses: A potential complication of comminuted second phalangeal fractures

SummaryThis case report describes the history, clinical findings, treatment and outcome of 2 horses with damage and eventual rupture of the deep digital flexor tendon as a result of a comminuted second phalangeal fracture. The rupture of the deep digital flexor tendon complicated the treatment and in one horse contributed to its eventual euthanasia. The athletic outcome was limited in the second case and the lack of palmar soft tissue support likely had a significant effect on the stability and biomechanics of the repair.

Determination of equine deep digital flexor muscle volume based on distances between anatomical landmarks

In equine medicine the use of Botox® is experimental. Dosages are determined from human treatment-protocols and limited numbers of equine studies. Determination of target-muscle volume can be helpful to extrapolate human dosages. The aim of the study was to calculate a formula enabling the estimation of the deep digital flexor muscle (DDFM) volume based on distances between anatomical landmarks.Nineteen cadaveric limbs were collected and distance A (top of olecranon to Os carpi accessorium) and B (circumference of limb) were measured. Converting mathematical formulas, C was calculated: π × (((0.5B)/π)2) × A. DDFM volume was determined by water displacement. Linear Regression Analysis was used to analyse data.The line best fitting the observed points was: Ln(volume[ml]) = −1.89 + 0.98 × Ln(value C[cm3]). Correlation was highest when natural logarithm was applied to both variables and was 0.97.The calculated formula enables estimating DDFM volume of a living horse. This estimated volume can be useful to apply human Botox® treatment-protocols.

Interobserver Agreement of Standing Magnetic Resonance Imaging for Assessment of Deep Digital Flexor Tendon Pathology

Reasons for performing studyStanding magnetic resonance imaging (sMRI) is commonly used to evaluate the distal aspect of the deep digital flexor tendon (DDFT) of lame horses. There is paucity of information comparing interobserver agreement of this imaging modality.ObjectivesTo determine the interobserver agreement for assessment of the DDFT on sMRI using a newly developed grading system. It was hypothesised that different lesion types would be more frequently observed at different anatomical locations of the DDFT, and that interobserver agreement would be better for the presence of a lesion compared to lesion grading.Study designA retrospective study assessing interobserver agreement.MethodssMRI studies of 40 equine front feet were retrospectively graded by 2 observer teams using a newly developed grading system based on previous studies. Individual DDFT parameters and an overall DDFT grade were scored. A Pearson's Chi‐square test quantified the association between anatomical location and lesion type and interobserver agreement was quantified by calculating weighted‐kappa statistic.ResultsObserver team B found a statistically significant association between anatomical location and lesion type but observer team A did not. Interobserver agreement was fair to moderate for the majority of individual DDFT parameters. For most parameters, better interobserver agreement was found for presence of a lesion than for lesion grading. Interobserver agreement was fair for the overall DDFT grade.ConclusionsInterobserver agreement was acceptable for overall DDFT grade and was better for the presence of an overall grade. Interobserver agreement was also acceptable for most DDFT parameters and was better for assessing whether a lesion was present compared to the grading of lesions. This study highlights the value of a standardised grading system for assessing the DDFT on sMRI, and provides a method to improve the repeatibilty and reliability of future studies using sMRI.Ethical animal research: This project was granted ethical approval by the RVC Ethics and Welfare Committee as part of James Whitmore's final year research project. Explicit owner informed consent for participation in this study was not stated. Sources of funding: None. Competing interests: None.

Concurrent Proximal Suspensory Desmopathy And Injury of the Proximal Aspect of the Accessory Ligament of the Deep Digital Flexor Tendon in Forelimbs and Hindlimbs

Reasons for performing studyThere are no reports of proximal suspensory desmopathy (PSD) and concurrent injuries of the proximal aspect of the accessory ligament of the deep digital flexor tendon (ALDDFT).ObjectivesTo describe clinical features, response to local analgesia and ultrasonographic features.Study designRetrospective study.MethodsReview of case records, January 2009–2014.ResultsThere were 8 horses with forelimb lameness, 4 unilateral and 4 bilateral (2 with bilateral injuries of the suspensory ligament [SL] and ALDDFT and 2 with PSD and injury of the ALDDFT in one limb and injury of the ALDDFT alone in the other). One horse had pain on palpation of the proximal aspect of the ALDDFT. Lameness was abolished by palmar metacarpal (subcarpal) nerve blocks in 10/12 limbs; in 2 limbs an ulnar nerve block was required to abolish lameness. There were 5 horses with bilateral hindlimb lameness; concurrent desmopathy of the ALDDFT and PSD was identified in one horse. In the other 4 horses there was a history of bilateral PSD which had undergone treatment. Recurrent lameness was associated with unilateral (n = 3) or bilateral (n = 1) PSD and desmopathy of the ALDDFT. In 2 horses there was soft tissue swelling in the proximomedial aspect of the metatarsus in the region of the ALDDFT. Lameness was abolished by local infiltration of mepivacaine in the proximoplantar aspect of the metatarsus in 3 limbs; in one limb a tibial nerve block was required to eliminate lameness. In all horses lesions were characterised ultrasonographically by enlargement of both the ALDDFT and the proximal aspect of the SL and a diffuse decrease in echogenicity. There was echogenic material between the SL and ALDDFT in 5 limbs.ConclusionsAll soft tissue structures in the proximal aspect of the metacarpus/metatarsus should be evaluated ultrasonographically if pain is localised to this area.Ethical animal research: The study was approved by the Ethical Review Committee of the Animal Health Trust and there was informed owner consent. Sources of funding: None. Competing interests: None.

The use of magnetic resonance imaging in diagnosing equine deep digital flexor tendinopathies--own experience.

Deep digital flexor tendinopathy is a common problem in horses of different athletic disciplines. Nowadays, the use of magnetic resonance imaging is considered to be a noninvasive and superior choice for recognizing bone and soft tissue pathologies especially related to difficult to access structures within the hoof capsule.

Ultra‐High Field MRI Clinical Anatomy of the Equine Fetlock to Aid Clinical Image Interpretation

Reasons for performing studyInterpretation of clinical diagnostic imaging of the equine musculoskeletal system requires accurate reference anatomical materials. In the case of MRI, this includes images acquired from low and high field systems. Using ultra‐high field MRI, higher resolution images with small slice thickness and gap suitable for reconstruction in any anatomical plane can be produced.ObjectivesTo describe the normal equine metacarpophalangeal joint using ultra‐high field MRI and compare ultra‐high and high field MR images.Study designLimbs (n = 14) from horses (n = 5) with no history of orthopaedic disease were frozen at ‐20°C until imaging. Fetlock joints were scanned using an ultra‐high field (7T) MRI unit. T1 (280 slices, thickness = 0.356 mm) and T2 (140 slices, thickness = 0.713 mm) weighted sequences were acquired. Limbs were scanned using a 1.5T MRI unit in transverse, sagittal, and dorsal planes using T1 (60 slices, thickness 2.2–3.5 mm) and T2 (60 slices, thickness 2.2–3.5 mm) sequences. Images were analysed using OsiriX software.ResultsUltra‐high field MR images visualised the fine detail of trabecular and subchondral bone, the articular cartilage surface of P1 and McIII, the short, oblique, straight and oblique sesamoidean ligaments including origins and insertions, the fasicular structure of superficial digital flexor tendon, deep digital flexor tendon and ligaments and the regional neurovascular structures. Whilst T1 high field images visualised the majority of tissues, structural detail was reduced compared to ultra‐high field imaging, margins were less well defined in some instances, e.g. articular cartilage, and a number of smaller structures were indistinct, e.g. short and cruciate sesamoidean ligaments.Conclusions7T MRI produced images of the fetlock with excellent anatomical detail. Future publication of open‐source ultra‐high field MRI files could aid the interpretation of 0.3T and 1.5T field MR images, especially with the capacity to reconstruct image slices orientated exactly to match those of interest.Ethical animal research: The study was approved by the Ethics Committee of the School of Veterinary and Life Sciences, University of Glasgow. Explicit owner informed consent for participation in this study was not stated but permission was given for post mortem examination and the use of materials in research. Sources of funding: The Royal Saudi Arabia Cultural Bureau. Competing interests: None.

Different regions of bovine deep digital flexor tendon exhibit distinct elastic, but not viscous, mechanical properties under both compression and shear loading

Tendons in different locations function in unique, and at times complex, invivo loading environments. Specifically, some tendons are subjected to compression, shear and/or torsion in addition to tensile loading, which play an important role in regulating tendon properties. To date, there have been few studies evaluating tendon mechanics when loaded in compression and shear, which are particularly relevant for understanding tendon regions that experience such non-tensile loading during normal physiologic function. The objective of this study was to evaluate mechanical responses of different regions of bovine deep digital flexor tendons (DDFT) under compressive and shear loading, and correlate structural characteristics to functional mechanical properties. Distal and proximal regions of DDFT were evaluated in a custom-made loading system via three-step incremental stress-relaxation tests. A two-relaxation-time solid linear model was used to describe the viscoelastic response. Results showed large differences in the elastic behavior between regions: distal region stresses were 4–5 times larger than proximal region stresses during compression and 2–3 times larger during shear. Surprisingly, the viscous (i.e., relaxation) behavior was not different between regions for either compression or shear. Histological analysis showed that collagen and proteoglycan in the distal region distributed differently from the proximal region. Results demonstrate mechanical differences between two regions of DDFT under compression and shear loading, which are attributed to variations of composition and microstructural organization. These findings deepen our understanding of structure–function relationships of tendon, particularly for tissues adapted to supporting combinations of tension, compression, and shear in physiological loading environments.

Early stage fatigue damage occurs in bovine tendon fascicles in the absence of changes in mechanics at either the gross or micro-structural level

Many tendon injuries are believed to result from repetitive motion or overuse, leading to the accumulation of micro-damage over time. In vitro fatigue loading can be used to characterise damage during repeated use and investigate how this may relate to the aetiology of tendinopathy.This study considered the effect of fatigue loading on fascicles from two functionally distinct bovine tendons: the digital extensor and deep digital flexor. Micro-scale extension mechanisms were investigated in fascicles before or after a period of cyclic creep loading, comparing two different measurement techniques – the displacement of a photo-bleached grid and the use of nuclei as fiducial markers.Whilst visual damage was clearly identified after only 300 cycles of creep loading, these visual changes did not affect either gross fascicle mechanics or fascicle microstructural extension mechanisms over the 900 fatigue cycles investigated. However, significantly greater fibre sliding was measured when observing grid deformation rather than the analysis of nuclei movement. Measurement of microstructural extension with both techniques was localised and this may explain the absence of change in microstructural deformation in response to fatigue loading. Alternatively, the data may demonstrate that fascicles can withstand a degree of matrix disruption with no impact on mechanics. Whilst use of a photo-bleached grid to directly measure the collagen is the best indicator of matrix deformation, nuclei tracking may provide a better measure of the strain perceived directly by the cells.

Fatigue in the Superficial and Deep Digital Flexor Muscles During Exercise in Thoroughbred Horses

IntroductionOne of the causes of injury to the superficial digital flexor tendon (SDFT) is assumed to be repeated high intensity loading of the tendon. Earlier fatigue of the deep digital flexor muscle (DDFM) in comparison to the time of fatigue of the superficial digital flexor muscle (SDFM) is also assumed to increase load on the SDFT during long distance running. This study evaluated the fatigue of SDFM and DDFM with maximal exercise.MethodsTwo wire electrodes were inserted into the SDFM and DDFM of 6 Thoroughbred horses (461–557 kg). Electromyogram (EMG) and hoof strain gauge signals were recorded at 2,500 Hz with horses on an inclined treadmill (6%), and filter processing was applied (high‐pass 10 Hz for EMG and low‐pass 200 Hz for strain gauge). Integrated EMG (iEMG), the median frequency (MF) of EMG, and the stride frequency (SF) were compared using paired t‐test during 100–105% heart rate max exercise and trotting before and after maximal exercise.ResultsThe SF significantly decreased and iEMG of SDFM tended to decrease during maximal exercise (P = 0.055), while MF of EMG in SDFM and DDFM did not change. The iEMG of SDFM and DDFM significantly decreased and MF of EMG in DDFM tended to decrease at a trot after maximal exercise (P = 0.063).ConclusionsThe DDFM may fatigue earlier than SDFM during long distance running. Further study is needed to evaluate the relationship between the decrease in iEMG of SDFM and DDFM during maximal exercise and the injury to SDFT.Ethical Animal ResearchThe study was approved by the Animal Welfare and Ethics Committee of the Japan Racing Association Equine Research Institute. Sources of funding: Japan Racing Association. Competing interests: none.

Kinetics of the Forelimb in Horses Trotting an Uphill and Downhill Slope

IntroductionEquine training often includes running on tracks with different uphill (UP) or downhill (DOWN) slopes and examination of lame horses on a slope can be used to investigate the origin of lameness. However little is known about the kinetics of horses in such circumstances. The aim of this study was to quantify and compare ground reaction force, acceleration and sliding of the hoof in the forelimb of horses trotting an uphill and downhill slope.MethodsThe right front hoof of 5 horses was equipped with a dynamometric horseshoe and an accelerometer allowing the measurement of 3D ground reaction force and hoof acceleration and displacement. The horses were trotted in hand (3.5 m/s) on a 7% inclined asphalt area successively uphill and downhill. Data were analysed using an ANOVA, accounting for correlated repeated measurements within each horse (P&lt;0.01).ResultsSpeed was not significantly different between UP and DOWN. The maximal longitudinal breaking force of the hoof, maximal vertical force, vertical impulse and longitudinal sliding of the hoof at impact were significantly increased on DOWN compared to UP (respectively +97.7%, +8.4%, +16.6% and +450%). Stride frequency and longitudinal propulsive force were significantly decreased on DOWN compared to UP (respectively −5.1% and −48.7%).ConclusionsThe results of this study (increased longitudinal breaking force and maximal vertical force on a downward slope) are consistent with previous measurements of superficial digital flexor tendon loading on the same area [1]. Conversely increased propulsive force on an uphill slope needs to be taken into account during rehabilitation of horses with deep digital flexor tendon injuries.Ethical Animal ResearchThe local Animal Care and Ethics Committee advised that no formal approval was required for this study. Sources of funding: Conseil Régional de Basse‐Normandie, the Fonds Unique Interministériel, the French Ministry of Agriculture, the FEDER and the Institut Français du Cheval et de l'Equitation (IFCE). Competing interests: none.

Internal Foot Kinematics Using High‐Speed Fluoroscopy

IntroductionThe navicular bone (NB) and the deep digital flexor tendon (DDFT) are common sites of lameness. Greater knowledge of foot mechanics will aid in understanding of the aetiopathogenesis and may provide new opportunities for treatment and prevention. It was hypothesised that changes in the distal interphalangeal joint (DIPj) and movement of the NB and DDFT during the stance phase will lead to changes in the moment arm of the DDFT around the DIPj.MethodsInternal hoof kinematics were determined using a high‐speed fluoroscopy system. Six horses were walked and trotted over a raised platform consisting of four force plates, through the field of view of the fluoroscopy system. The angles of the DIPj and the DDFT around the navicular bone and the moment arm of the DDFT were measured. Changes in these parameters during stance and differences between strides, gaits and horses were assessed using an ANOVA or paired T‐test as appropriate (P&lt;0.05).ResultsThe range of motion (ROM, mean ± SD) during stance of the DIPJ was 28.6 ± 4.6° (walk) and 26.5 ± 6.3 (trot) with significant differences between gaits, strides and horses (P&lt;0.001). The angle change of the DDFT around the NB was 21.9 ± 6.0° in walk and 26.6 ± 6.5 in trot. The change in moment arm of the DDFT around the DIPj was 3.7 ± 1.3 mm in walk and 4.1 ± 2.2 mm in trot. There were no significant differences between the different time points during stance or between gaits.ConclusionsHigh‐speed fluoroscopy is a novel method that allows assessment of internal foot kinematics. The observed changes between gaits during stance may result in altered stress distribution in the DDFT. Further studies will evaluate the effect of farriery intervention on internal foot kinematics.Ethical Animal Researchthis study was approved by the authors′ institution's ethics and welfare committee. Sources of funding: Royal Veterinary College. Competing interests: none.

Outcome of palmar/plantar digital neurectomy in horses with foot pain evaluated with magnetic resonance imaging: 50 cases (2005–2011)

There is limited knowledge of the foot lesions that influence the outcome of palmar/plantar digital neurectomy (PDN). 1) To report the short- and long-term outcomes of horses that underwent PDN to alleviate chronic foot pain due to lesions diagnosed by magnetic resonance imaging (MRI) and 2) factors that may influence the outcome of PDN. Multicentre retrospective study. Medical records of 50 horses subjected to PDN due to chronic foot pain were reviewed. Age, breed, sex, athletic activity, duration of lameness, affected limb(s), response to anaesthesia of the palmar/plantar digital nerves, MRI findings and surgical technique were analysed together with follow-up data to identify factors that influenced the long-term outcomes. Forty-six of 50 horses (92%) responded positively to surgery; 40 (80%) were able to return to their previous athletic use for a median time of 20 months (range: 12-72 months). Eighteen (36%) horses developed post operative complications including residual lameness, painful neuromas, or early recurrence of lameness. Horses with pre-existing core or linear lesions of the deep digital flexor tendon (DDFT) had significantly shorter periods of lameness resolution after surgery than horses with dorsal border lesions of the DDFT or other foot lesions. Palmar/plantar digital neurectomy can improve or resolve lameness in horses with foot pain unresponsive to medical therapy without serious post operative complications. However, horses with core or linear lesions of the DDFT should not be subjected to PDN as these horses experience residual lameness or early recurrent lameness after surgery. Magnetic resonance imaging can be used to identify these horses.