Effect of three shoe types on the duration of breakover in sound trotting horses

In a controlled experimental study, eight sound horses were shod with a plain steel shoe on one forelimb (control limb) and with four different shoe types on the other forelimb (treated limb). The four shoe types used on the treated limb were a plain steel shoe, a rocker-toe shoe, a rolled-toe shoe, and a square-toe shoe. The selection of the treatment limb (left or right) was randomized between the horses and a replicated Latin square design was used to determine the order of application of the shoes to the treatment limb. High speed cinematography (200 frames/s) was used to film the horses trotting in hand on a concrete surface. Eight strides were analyzed for each shoeing treatment. The breakover times of both forelimbs were measured, and the breakover ratio was computed as the ratio between the breakover time of the treated limb to the breakover time of the control limb. The results of an analysis of variance, using a probability of 0.05 alpha, showed that the breakover ratio did not differ significantly between the four types of shoes (p=0.10). It is concluded that, in sound horses trotting at a slow speed on a hard surface, the application of a rocker-toe shoe, a rolled-toe shoe or a square- toe shoe did not shorten forelimb breakover duration significantly compared with a plain steel shoe.     

Wedge and Eggbar Shoes Change the Pressure Distribution Under the Hoof of the Forelimb in the Square Standing Horse

The shoe types most commonly applied to horses with navicular disease or other forms of palmar heel pain are shoes with heel wedges and eggbar shoes, although their efficacy has been a matter of debate among veterinarians and farriers for centuries. To quantify the effect of these different types of “navicular” shoeing on static hoof pressure distribution, 6 warmblood horses were shod with 6° wedge, eggbar, and plain shoes. While standing square with weight evenly distributed across both forelimbs, the center of pressure and pressures at selected areas of interest (AOI: toe, medial and lateral toe, medial and lateral heel) were measured using a Footscan (RsScan International, Belgium) pressure plate in a Latin square design using the plain shoe as a reference.Wedge shoes did not provide a significant shift in the center of pressure. The application of eggbar shoes did not alter the relative position of the center of pressure under the hoof. However, the absolute distance from the toe to the center of pressure was significantly larger with eggbar shoes (77 + 12 mm) compared with plain and wedged shoes (70 ± 8 mm, P < .05) resulting in an absolute, caudal shift of the center of pressure. When pressure (N/cm²) values at the five AOIs were averaged for each shoe type, the wedge and eggbar shoe recordings showed a significantly lower mean pressure than plain shoes (P < .05).In conclusion, mean AOI pressures decreased with wedge and eggbar shoes, and eggbar shoes provided a caudal shift in the center of pressure. These effects are believed to decrease the moment of the coffin joint and reduce the pressure on the navicular bone. Thus, the findings of this study might contribute to the scientific evidence of efficacy of the use of wedge and eggbar shoes in “navicular” lame horses.     

Modifying the Surface of Horseshoes: Effects of Eggbar,Heartbar, Open Toe,and Wide Toe Shoes on the Phalangeal Alignment,Pressure Distribution,and the Footing Pattern

This study assesses the biomechanical effects on the phalangeal alignment, the pressure force distribution, and the footing pattern on different grounds created by different horseshoes modified in the dorsopalmar surface. Twenty-five warmblood horses were divided into five groups (n = 5). In each group, radiographic and kinetic examinations were carried out for each barefoot hoof, standard, and modified horseshoe. For radiographic measurements, a modified podoblock, simulating firm and penetrable ground, was used. For kinetic examinations, hoof and horseshoe were simultaneously equipped with sensor foils and horses were walked on different grounds (concrete, rubber, firm, and deep sand). None of the horseshoes showed an effect on the bone alignment on firm ground. On penetrable ground, the bar shoes caused a steeper palmar angle (P3), whereas with a wide toe shoe, a flatter orientation of the distal phalanx was observable. The influence on the alignment of the middle and proximal phalanx showed no constant data. On penetrable ground, pressure peaks occurred at the heels after the application of bar shoes. Moreover, pressure peaks were observable beneath the ends of the branches of the open toe shoe, and the toe and thin branches of the wide toe shoe. The footing pattern was only affected by the open toe shoe. In conclusion, the biomechanical effects of the examined modified horseshoes are mainly influenced by different ground conditions. Moreover, unintended side effects such as unexpected pressure peaks or an enhanced mediolateral sink in of the hoof occur in addition to the required impacts during a therapeutical treatment.     

Measurement of vertical forces and temporal components of the strides of horses using instrumented shoes

Instrumented shoes were used to measure the vertical forces exerted by horses moving at a variety of gaits. Two types of shoes were used; one contained a single transducer positioned over the center of the frog and the second contained transducers located at the toe and both sides of the heel. Horses were shod with these instrumented shoes and walked and trotted over a force plate. Forces were simultaneously recorded from the transducers in the shoes and from the force plate. Comparisons were made between the amount and duration of the forces exerted on the transducers and the vertical and horizontal forces recorded from the force plate. Forces recorded from the single transducer shoes showed strong correlations with the forces recorded from the force plate for horses moving at the walk; however, at the trot only moderate correlations occurred between these forces. At both the walk and trot, forces recorded from each side of the heel and the total forces occurring on all three transducers from the front hooves of horses shod with three transducer shoes showed strong correlations to the vertical forces recorded from the force plate.Vertical forces were also recorded from the instrumented shoes as horses walked, trotted and galloped on a track straightaway. Forces recorded from normal horses shod with single transducer shoes on all four feet were greater on the forelimbs than the rear limbs at the walk and trot. At the gallop, forces were highest on the lead front followed by the nonlead front, lead rear and nonlead rearlimb, respectively. Forces recorded from a three transducer shoe on the right front hoof of a horse walking, trotting and galloping in a right lead were highest on the medial side of the heel and occurred during the middle of the support period. Peak forces on the toe occurred at or near the time of heel lift.The results of these studies indicate that these instrumented shoes have advantages over the methods previously used to measure locomotor forces. These instrumented shoes can be used to simultaneously record the temporal components and the amount and distribution of vertical forces exerted during consecutive strides of horses moving at a variety of gaits.     

Shoeing sound warmblood horses with a rolled toe optimises hoof-unrollment and lowers peak loading during breakover

REASONS FOR PERFORMING STUDY: Overload injuries in sport horses commonly occur; shoeing techniques are believed to be important in prevention of these injuries, but there is a paucity of scientific information identifying the potential connection. OBJECTIVES: To test a horseshoe with a modified rolled toe designed to ease the process of breakover and decrease loading of lesion-prone structures of the distal limb. METHODS: Twenty clinically sound Warmblood horses trotted over a track containing a pressure/force measuring system and 6 infrared cameras. The horses were measured with 2 types of shoes, standard flat shoes and shoes with a rolled toe. The shoeing procedure was randomised and horses had 2 days between measurements to adapt to the shoes. RESULTS: Limb placement and timing characteristics, e.g. breakover duration, did not change significantly. There was an improvement in the ease of movement to roll over the toe in the shoes with a rolled toe, due mainly to a smoother hoof-unrollment pattern. The peak indicative moment decreased substantially at the onset of breakover in the shoe with the rolled toe. CONCLUSIONS: With a rolled toe the process of hoof-unrollment is smoother, which improves the coordination of this process, and lowers peak loading of the distal limb during breakover. POTENTIAL RELEVANCE: This study stresses the importance of proper shoeing in sound horses, showing that shoe modifications can optimise the loading characteristics of the distal limb and therefore might be a means to prevent sport horses from overload injuries.     

The effect of plain, eggbar and 6 degrees-wedge shoes on the distribution of pressure under the hoof of horses at the walk

AIM: To quantify the effect of plain, wedged and eggbar shoes on the distribution of pressure under the hoof of horses at the walk, at selected areas of interest (AOI), to find scientific evidence for the perceived efficacy of these shoes in the treatment of palmar heel pain. METHODS: Six clinically sound adult Warmblood mares weighing 551 (SD 25) kg were shod (forelegs) with either plain, eggbar or 6 degrees-wedge shoes using a latin-square experimental design. All horses were shod by the same farrier, and each balanced and aligned for its individual conformation. Data were collected on three walking strides for each foreleg using a 550 x 405-mm pressure plate to quantify the distribution of pressure under each type of shoe at five AOI. RESULTS: Landing of the hoof with all three shoes was predominantly from lateral to medial (range 7-15 msec). Irrespective of the type of shoe, the greatest pressure was found in the lateral and medial toe (lateral 39.7 (SE 0.6) N/cm2 and medial 35.0 (SE 0.5) N/cm2) and the point of the toe (33.3 (SE 0.5) N/cm2). The lowest peak pressure was in the heel (lateral 25.9 (SE 0.5) N/cm2 and medial 21.1 (SE 0.4) N/cm2; p<0.05). Eggbar and wedge shoes increased total stance time (938 (SE 8) msec and 952 (SE 6) msec, respectively) compared with plain shoes (898 (SE 14) msec) (p<0.05). The wedge shoe reduced breakover compared with the plain and eggbar shoes (13.8% vs 15.8% and 14.5%, respectively; p<0.05). The eggbar shoe had lower total shoe peak pressure (29.5 (SE 0.7) N/cm2) than plain (31.8 (SE 0.5) N/cm2) and wedge (30.9 (SE 0.6) N/cm2) shoes. CONCLUSIONS AND CLINICAL RELEVANCE: Both the eggbar and 6 degrees-wedge shoe offer advantages for palmar heel pain. In comparison to the plain shoe, the eggbar shoe had less peak pressure at the heel AOI, and across the entire shoe, due to the greater bearing surface and the effect of the longer heel. The 6 degrees-wedge shoe had greater loading on the lateral heel AOI, but promoted earlier breakover at the toe. Both shoes offer advantages for the horse with palmar heel pain, though choice of shoe will depend on clear identification of the causative factors, to provide therapeutic shoeing that maximises the individual horse's response.     

Modifying the Height of Horseshoes: Effects of Wedge Shoes,Studs, and Rocker Shoes on the Phalangeal Alignment,Pressure Distribution,and Hoof-Ground Contact During Motion

This study was designed as a comparative study with the intention to accumulate fundamental data on a wide variety of farriery methods. Twenty-five warmblood/crossbred horses, allocated into five groups (n = 5), underwent radiological and kinetic examination of the barefoot hoof, the shod hoof with a standard horseshoe, and finally a modified horseshoe. For radiographic measurements, a special podoblock with embedded reference points and changeable ground surfaces was used. Kinetic examinations were performed by placing one sensor between the shoe and the hoof and the second sensor between the shoe and the ground and then walking the horses on four different ground surfaces. When wedges were applied, the palmar angle increased by approximately 5° on all surfaces. However, this effect was only seen on firm surfaces combined with studs. Using a rocker shoe, the palmar angle increased on a firm surface (0.6 ± 0.3°) and decreased on a deformable surface (0.8 ± 0.3°). No consistent data were noted for the orientation of the proximal and middle phalanx in relation to the palmar angle. Pressure distribution showed wedges and studs to cause an increased pressure load on both the toe and the heels on a firm surface. Rocker shoes led to pressure peaks at the inner section of the toe, and high pressure was exerted on the quarters. In conclusion, all modified horseshoes showed unintended side effects and their influence on biomechanical parameters varied depending on the ground surface.     

Changes in kinematic variables observed during pressure-induced forelimb lameness in adult horses trotting on a treadmill

OBJECTIVE: To determine whether kinematic changes induced by heel pressure in horses differ from those induced by toe pressure. ANIMALS: 10 adult Quarter Horses. PROCEDURE: A shoe that applied pressure on the cuneus ungulae (frog) or on the toe was used. Kinematic analyses were performed before and after 2 levels of frog pressure and after 1 level of toe pressure. Values for stride displacement and time and joint angles were determined from horses trotting on a treadmill. RESULTS: The first level of frog pressure caused decreases in metacarpophalangeal (fetlock) joint extension during stance and increases in head vertical movement and asymmetry. The second level of frog pressure caused these changes but also caused decreases in stride duration and carpal joint extension during stance as well as increases in relative stance duration. Toe pressure caused changes in these same variables but also caused maximum extension of the fetlock joint to occur before midstance, maximum hoof height to be closer to midswing, and forelimb protraction to increase. CONCLUSION AND CLINICAL RELEVANCE: Decreased fetlock joint extension during stance and increased head vertical movement and asymmetry are sensitive indicators of forelimb lameness. Decreased stride duration, increased relative stance duration, and decreased carpal joint extension during stance are general but insensitive indicators of forelimb lameness. Increased forelimb protraction, hoof flight pattern with maximum hoof height near midswing, and maximum fetlock joint extension in cranial stance may be specific indicators of lameness in the toe region. Observation of forelimb movement may enable clinicians to differentiate lameness of the heel from lameness of the toe.     

The horse-racetrack interface: a preliminary study on the effect of shoeing on impact trauma using a novel wireless data acquisition system

REASONS FOR PERFORMING STUDY: There is a need to determine accelerations acting on the equine hoof under field conditions in order to better assess the risks for orthopaedic health associated with shoeing practices and/or surface conditions. OBJECTIVES: To measure the acceleration profiles generated in Thoroughbred racehorses exercising at high speeds over dirt racetracks and specifically to evaluate the effect of a toe grab shoe compared to a flat racing plate, using a newly developed wireless data acquisition system (WDAS). METHODS: Four Thoroughbred racehorses in training and racing were used. Based on previous trials, each horse served as its own control for speed trials, with shoe type as variable. Horses were evaluated at speeds ranging from 12.0-17.3 m/sec. Impact accelerations, acceleration on break over and take-off, and temporal stride parameters were calculated. Impact injury scores were also determined, using peak accelerations and the time over which they occurred. RESULTS: Recorded accelerations for the resultant vector (all horses all speeds) calculated from triaxial accelerometers ranged 96.3-251.1 g, depending on the phase of the impact event. An association was observed between shoe type and change in acceleration in individual horses, with 2 horses having increased g on initial impact with toe grab shoes in place. In the final impact phase, one horse had an increase of 110 g while wearing toe grab shoes. Increased accelerations were also observed on break over in 2 horses while wearing toe grab shoes. CONCLUSIONS: Shoe type may change impact accelerations significantly in an individual horse and could represent increased risk for injury. Further work is needed to determine if trends exist across a population. POTENTIAL RELEVANCE: The WDAS could be used for performance evaluation in individual horses to evaluate any component of the horse-performance surface interface, with the goal of minimising risk and optimising performance.     

Effects of Shortening Breakover at the Toe on Gait Kinematics at the Walk and Trot

Point of breakover, defined as the portion of the hoof last in contact with the ground during the terminal stance phase of a limb, can be influenced by many factors including craniocaudal placement of the shoe. Shortening the point of breakover has been suggested to decrease strain on the deep digital flexor tendon and navicular bone as well as to improve the alignment of the second and third phalanx. The current experiment involved eight sound horses fitted with aluminum plates adhered to their front hooves, which were drilled and tapped to allow additional aluminum plates of various lengths to be attached (the longest plate was placed flush with the toe, while the shortest plate was moved 3.81 cm caudal to the toe). Horses were recorded on video while at the walk and trot over a distance of 70 meters for six repetitions to determine differences in gait kinematics. Results of this study show significant changes in stride kinematics caused by shortening the point of breakover. Retraction of the forelimbs was greatest when breakover was moved 1.27 cm back from the toe (P < .05), and minimum height of the fetlock at the trot was higher on all treatments where the breakover point was moved caudally (P < .05). Some improvements in gait quality were observed when breakover was shortened, although extreme caudal placement of the shoe (negative placement in relation to P3) resulted in a decrease in gait quality as seen by decreased retraction of the forelimb (P < .05) coupled with hoof height occurring earlier in the stride (P < .05).     

The Long-Term Results of Glue-on Shoes on Dorsal Hoof Wall Distortion

Every equine hoof has a certain amount of distortion. This presents in various forms: flares, dished toes, under-run heels, and cracks. Several farrier texts anecdotally suggest a correlation between hoof capsule distortion and lameness. The goal of this study was to evaluate the effects of the Sigafoos Series I glue-on shoe on hoof capsule distortion, and specifically, the effect on dorsal wall deviation. Measurements of the hoof were made using the Metron hoof evaluating system by Eponatech. Comparisons were made of the following values: dorsal length, hoof angle, dorsal wall deviation, hairline angle, hairline deviation, heel/toe height, heel height, heel angle, and support length. The study group consisted of front feet of horses shod exclusively in the Sigafoos glue-on shoe for a period of 1 year, and the control group consisted of 133 front feet from horses using nailed on shoes for a similar period and with a musculoskeletal complaint. The results indicate a 48% reduction in dorsal wall deviation for the study group. This finding supports the use of this glue-on shoe as beneficial with the goal to reduce capsular distortion of the dorsal wall.     

The effect of frog pressure and downward vertical load on hoof wall weight-bearing and third phalanx displacement in the horse--an in vitro study

A shoe was designed to combine the advantages of a reverse shoe and an adjustable heart bar shoe in the treatment of chronic laminitis. This reverse even frog pressure (REFP) shoe applies pressure uniformly over a large area of the frog solar surface. Pressure is applied vertically upward parallel to the solar surface of the frog and can be increased or decreased as required. Five clinically healthy horses were humanely euthanased and their dismembered forelimbs used in an in vitro study. Frog pressure was measured by strain gauges applied to the ground surface of the carrying tab portion of the shoe. A linear variable distance transducer (LVDT) was inserted into a hole drilled in the dorsal hoof wall. The LVDT measured movement of the third phalanx (P3) in a dorsopalmar plane relative to the dorsal hoof wall. The vertical component of hoof wall compression was measured by means of unidirectional strain gauges attached to the toe, quarter and heel of the medial hoof wall of each specimen. The entire limb was mounted vertically in a tensile testing machine and submitted to vertical downward compressive forces of 0 to 2,500 N at a rate of 5 cm/minute. The effects of increasing frog pressure on hoof wall weight-bearing and third phalanx movement within the hoof were determined. Each specimen was tested with the shoe under the following conditions: zero frog pressure; frog pressure used to treat clinical cases of chronic laminitis (7 N-cm); frog pressure clinically painful to the horse as determined prior to euthanasia; frog pressure just alleviating this pain. The specimens were also tested after shoe removal. Total weight-bearing on the hoof wall at zero frog pressure was used as the basis for comparison. Pain-causing and pain-alleviating frog pressures decreased total weight-bearing on the hoof wall (P < 0.05). Frog pressure of 7 N-cm had no statistically significant effect on hoof wall weight-bearing although there was a trend for it to decrease as load increased. Before loading, the pain-causing and pain-alleviating frog pressures resulted in a palmar movement of P3 relative to the dorsal hoof wall compared to the position of P3 at zero frog pressure (P < 0.05). This difference remained statistically significant up to 1300 N load. At higher loads, the position of P3 did not differ significantly for the different frog pressures applied. It is concluded that increased frogpressure using the REFP shoe decreases total hoof wall weight-bearing and causes palmar movement of P3 at low weight-bearing loads. Without a shoe the toe and quarter hoof wall compression remained more constant and less in magnitude, than with a shoe.     

Use of gyroscopic sensors for objective evaluation of trimming and shoeing to alter time between heel and toe lift-off at end of the stance phase in horses walking and trotting on a treadmill

OBJECTIVE: To determine whether a shoe with an axialcontoured lateral branch would induce greater lateral roll of the forelimb hoof during the time between heel and toe lift-off at end of the stance phase (breakover). Animals-10 adult horses. PROCEDURE: A gyroscopic transducer was placed on the hoof of the right forelimb and connected to a transmitter. Data on hoof angular velocity were collected as each horse walked and trotted on a treadmill before (treatment 1, no trim-no shoe) and after 2 treatments by a farrier (treatment 2, trim-standard shoe; and treatment 3, trim-contoured shoe). Data were converted to hoof angles by mathematical integration. Breakover duration was divided into 4 segments, and hoof angles in 3 planes (pitch, roll, and yaw) were calculated at the end of each segment. Multivariable ANOVA was performed to detect differences among treatments and gaits. RESULTS: Trimming and shoeing with a shoe with contoured lateral branches induced greater mean lateral roll to the hoof of 3.2 degrees and 2.5 degrees during the first half of breakover when trotting, compared with values for no trim-no shoe and trim-standard shoe, respectively. This effect dissipated during the second half of breakover. When horses walked, lateral roll during breakover was not significantly enhanced by use of this shoe. CONCLUSIONS AND CLINICAL RELEVANCE: A shoe with an axial-contoured lateral branch induced greater lateral roll during breakover in trotting horses, but change in orientation of the hoof was small and limited to the first half of breakover.     

Use of an instrument sandwiched between the hoof and shoe to measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter in horses

OBJECTIVE: To develop an instrument that could be sandwiched between the hoof and shoe of horses and that would reliably measure vertical ground reaction forces and three-dimensional acceleration at the walk, trot, and canter. ANIMALS: 5 clinically sound Thoroughbreds. PROCEDURES: The recording instrument (weight, 350 g) consisted of 2 metal plates, 2 bolts, 4 load cells, and 3 accelerometers. It was mounted to the hoof with a glue-on shoe and devised to support as much load exerted by a limb as possible. The load cells and accelerometers were wired to a 16-channel transmitter, and transmitted signals were received and amplified with a telemetry receiver. RESULTS: The recording instrument could measure in real time the 4 components of the ground reaction force or their resultant force along with acceleration in 3 dimensions as horses walked, trotted, or cantered on a treadmill. Patterns of force-time curves recorded for consecutive strides were similar to each other and to those previously reported, using a force plate. CONCLUSIONS AND CLINICAL RELEVANCE: The recording instrument developed for use in the present study allowed us to record vertical ground reaction force and acceleration in 3 dimensions in horses at the walk, trot, and canter.     

The art of horseshoeing--between empiricism and science

To correctly shoe a horse requires the farriers to have a good working knowledge of postural anomalies and movement patterns, as well as of the different concepts of horseshoeing and to be able to apply the appropriate technique to every individual horse they shoe. The correct technique for specific problem cases is frequently a subject of debate amongst specialists and many theories would benefit from objective gait analyses. The case study presented examines the influence of different shoeing conditions on selected gait analysis parameters. The measurements were conducted on a Warmblood mare: (A) shod with long toes, (B) properly trimmed without shoes, (C) conventionally shod with rolled toes and finally (D) shod using the 4-point technique. Data on force-, time- and distance parameters were recorded using an instrumented treadmill. First contact and breakover of the hooves were documented using high-speed videography. A long toe resulted in a prolongation of the breakover time and, therefore, in a prolongation of the second half of the stance phase. Additionally, the prolonged stance duration associated with an unaltered force impulse, led to decreased force peaks. It was possible to objectively record differences between the trimmed, unshod foot, the shod long-toe and the shod rolled toe configurations. The differences between the rolled toe and the 4 point shoe however, were minimal. Gait analysis is a technique well suited for objective evaluation of different shoeing techniques under standardised conditions.     

In Vitro Assessment of the Equine Hoof Wall Strains in Flat Weight Bearing and After Heel Elevation

Horseshoeing is a common practice, but effects on the hoof wall are poorly understood. Strain gauges were used to document and compare hoof behavior in vitro during flat weight bearing and after artificial heel elevation. Ten front limbs of Thoroughbred race horses, shod with conventional flat shoes, were used. Eight strain gauges were symmetrically distributed around the toe, quarters, and heels. Each limb was mounted to a testing machine (Kratos K5002; Kratos Dynamômetros, Ltda., Cotia-SP-Brazil) and subjected to a load equivalent to 30% of the donor's body weight. Strains (μ) were acquired by means of a computerized system and the results compared using Friedman and Wilcoxon statistical tests. There was greater strain variation when the heels were elevated. Compression predominated during flat weight bearing, with a tendency to horizontal traction after heel elevation. The changes in strain caused by heel elevation were not always symmetrical. Elevation of the heels tensed the toe and the medial quarter horizontally, increased load at the posterior portion of the hoof capsule, and hindered its expansion.     

Evaluation using hoof wall strain gauges of a therapeutic shoe and a hoof cast with a heel wedge as potential supportive therapy for horses with laminitis

OBJECTIVE: To evaluate using strain gauges, a hoof cast with heel wedge, and a therapeutic shoe with unsupported toe for their effectiveness in redistribution of load from the dorsal hoof wall. STUDY DESIGN: In vitro biomechanical study. SAMPLE POPULATION: Twenty forelimb specimens. METHODS: Rosette strain gauges were placed on the dorsal and lateral hoof wall of 20 normal shaped hooves. Limbs were loaded vertically using a tensile testing machine with a 1 Hz sinusoidally cycling load up to 3000 N during 15 seconds. Mean values of principal strain and direction at 2500 N load were calculated for 3 experimental conditions (unshod, therapeutic shoe with unsupported toe, and hoof cast with heel elevation) and tested by ANOVA (P<.05). RESULTS: Vertical limb loading in an unshod hoof leads to a biaxial compression of the dorsal wall with high longitudinal compression (epsilon2 = -1515 microm/m). Principal strain at the dorsal wall (epsilon2) was decreased by 23% with the therapeutic shoe and by 59% with the hoof cast. On the lateral hoof wall principal strain was unchanged with the shoe, but increased by 34% with the cast. CONCLUSIONS: Strain measurements indicate unloading of the dorsal hoof wall by both methods with the cast being more effective than the shoe. CLINICAL RELEVANCE: The hoof cast with wedge offers substantial unloading of the dorsal wall, but increases load on the quarter. Therefore a hoof cast would likely be most helpful in acute laminitis when palmar structures can still bear load. The therapeutic shoe offers rehabilitation and regrowth of the dorsal wall without increased load on the quarter wall.     

Horizontal moment around the hoof's centre of pressure during walking in a straight line

Reasons for performing study: Joint congruity and ligaments restrain the distal limb joints from excessive motion in the transverse and frontal planes, but the magnitudes and direction of the horizontal twisting moments around the hoof's centre of pressure (CoP) that induce these motions are unknown. Objectives: To quantify the horizontal moment around the vertical axis through the hoof's CoP at walk, and to determine whether these are symmetric. Methods: Nine sound Thoroughbred horses (mean age 5.3 years; mean mass 502 kg) were led at walk in a straight line across a Kistler force platform. Five trials were collected for each fore and hindlimb. The resultant moment around the hoof's CoP was calculated from the horizontal moment arms between the calculated CoP and the 4 horizontal forces in the transverse (X) and cranio‐caudal (Y) directions. Results: The calculated moments were consistent within limbs and horses, but variable between horses. Hindlimbs demonstrated a biphasic moment pattern and the largest moments were typically in the first half of stance. Mean ± s.d. peak moments were internal under both hindlimbs (L: Int 14.1 ± 4.6 Nm; R: Int 13.3 ± 5.5 Nm). In the forelimbs, 7/9 horses demonstrated an asymmetric moment pattern, with the left forelimb exerting an internal moment (L: Int 6.9 ± 2.9 Nm) and the right forelimb an external moment (R: Ext 8.4 ± 4.4 Nm), while the remaining 2 horses exerted internal moments in both forelimbs (L: Int 11.7 ± 1.4 Nm; R: Int 6.6 ± 1.9 Nm). Conclusion: In 7/9 horses, the forelimbs exerted asymmetric horizontal moments around the hoof CoP. The hindlimbs appear to behave with mechanical symmetry during stance, exerting an internal moment during retraction. Potential relevance: Extrasagittal joint motions in the forelimb are unlikely to be symmetric and future studies should account for possible bilateral variations.     

A comparison of three horseshoeing styles on the kinetics of breakover in sound horses

A variety of horseshoe designs are believed to 'ease' breakover, or the unloading of the foot once the heels leave the ground. In this study, conventional toe-clip shoes, quarter-clip shoes, fitted to the white line at the toe, and Natural Balance horseshoes were fitted to the front feet of 9 sound Irish Draught-cross type horses. Forceplate and video motion analyses were undertaken during trot locomotion to determine the moment arm of the ground reaction force on the distal interphalangeal (DIP) joint, the peak DIP joint moment and the peak compressive force on the navicular bone. DIP joint moment arm during breakover was reduced with both Natural Balance (mean +/- s.d. 77 +/- 7 mm) and quarter-clip shoes (78 +/- 9 mm) compared to the toe-clip shoes (86 +/- 6 mm) (P<0.01). Peak DIP joint moment was not significantly different (175 +/- 37,171 +/- 38 and 175 +/- 31 Nmm/kg, in Natural Balance, quarter-clip and toe-clip shoes, respectively) and neither was peak force on the navicular bone (5.52 +/- 1.52, 5.79 +/- 1.53 and 6.14 +/- 1.47 N/kg, respectively). Breakover duration (heel off to toe off) was not significantly reduced by the Natural Balance shoes (39 +/- 6 ms) or the quarter-clip shoes (40 +/- 6 ms) compared to toe-clip shoes (42 +/- 9 ms). This study has demonstrated that the use of Natural Balance shoes reduces the moment arm of the ground reaction force (GRF) during breakover but does not reduce the peak DIP joint moment or the force on the navicular bone.     

Development of a 3D model of the equine distal forelimb and of a GRF shoe for noninvasive determination of in vivo tendon and ligament loads and strains

REASONS FOR PERFORMING STUDY: As critical locomotion events (e.g. high-speed and impacts during racing, jump landing) may contribute to tendinopathies, in vivo recording of gaits kinematic and dynamic parameters is essential for 3D reconstruction and analysis. OBJECTIVE: To propose a 3D model of the forelimb and a ground reaction force recording shoe (GRF-S) for noninvasively quantifying tendon and ligament loads and strains. METHODS: Bony segments trajectories of forelimbs placed under a power press were recorded using triads of ultrasonic kinematic markers linked to the bones. Compression cycles (from 500-6000 N) were applied for different hoof orientations. Locations of tendon and ligament insertions were recorded with regard to the triads. The GRF-S recorded GRF over the hoof wall and used four 3-axis force sensors sandwiched between a support shoe and the shoe to be tested. RESULTS: Validation of the model by comparing calculated and measured superficial digital flexor tendon strains, and evaluation of the role of proximal interphalangeal joint in straight sesamoidean ligament and oblique sesamoidean ligament strains, were successfully achieved. Objective comparisons of the 3 components of GRF over the hoof for soft and hard grounds could be recorded, where the s.d. of GRF norm was more important on hard ground at walk and trot. CONCLUSIONS: Soft grounds (sand and rubber) dissipate energy by lowering GRF amplitude and diminish bounces and vibrations at impact. At comparable speed, stance phase was longer on soft sand ground. POTENTIAL RELEVANCE: The conjugate use of the GRF-S and the numerical model would help to quantify and analyse ground/shoe combination on comfort, propulsion efficiency or lameness recovery.