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Keywords:

  • horse;
  • hoof mechanism;
  • shoeing;
  • heel movement;
  • glued shoe

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

Reasons for performing study: It has been suggested that the heel of the horse's hoof expands in the stance phase and this reduces the concussion at impact and helps pump blood into the hoof. Therefore, farriers usually leave a gap in the heel region when using the traditional nailed shoe. Recently glued shoes which are attached firmly to the heel have been developed and these could restrict heel movement.

Objective: To compare the degree of mediolateral heel movement between glued and nailed shoes.

Methods: Seven Thoroughbreds were used. Either their fore- or hind hooves were shod with plain aluminium shoes, attached first with glue and later with nails. Measurements were collected continuously with a displacement sensor fixed between the medial and lateral hoof walls at the heel. The horses ran on a treadmill at a walk (1.8 m/s), trot (3.5 m/s), canter (8 m/s) and gallop (12 m/s). The mediolateral heel movement in a nonweightbearing position was set at zero for each hoof and thus positive and negative numbers represented expansion and contraction, respectively. Average values of 10 consecutive strides at each speed were compared between the 2 shoeing methods by paired t test.

Results: At all running speeds, the heels expanded in the first 70–80% of the stance phase and contracted at breakover. The total heel movement calculated as the sum of the maximum expansion and contraction value was less with glued shoeing than with nailed shoeing for walking (all limbs), trotting (all limbs), cantering (leading forelimb and both hindlimbs) and galloping (both hindlimbs).

Conclusions: Glueing restricted heel movement, suggesting possible interference with shock absorption and blood pumping in the hoof. Further study is needed to evaluate the influence of glued shoeing on hoof mechanics.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

The deformation of the hoof with locomotion, called the hoof mechanism, has been described since the 19th century. It has been suggested that the wall of the heel expands during weightbearing, absorbing shocks and pumping blood. Therefore, to allow for the lateral movement of the hoof at the heel, farriers tend to fit the shoe slightly wider than the outside border of the hoof in the heel region and do not nail the shoe posterior to the quarter of the hoof wall (Stashak et al. 2002; O'Grady and Poupard 2003).

The hoof mechanism has been measured by strain gauge, photoelastic material (Davies 1997; Dejardin et al. 2001) and potentiometer (Roepstorff et al. 2001). Since the heel area of the hoof is more elastic than the toe or quarter area, the heels expand and sink caudally and the toe retracts when the hoof is loading (Douglas et al. 1998; Back 2001). Additionally, the mechanical loading is greater in the caudal area than in the cranial area in the early stance phase, so the heels seem to take a prominent part in dampening concussion and supporting bodyweight (Barrey 1990). According to the previous studies of surface strain on the hoof, there was no difference in the magnitudes of the vertical compressive strain (Thomason 1998) and heel expansion (Colles 1989) between nailed shoeing and the unshod foot. However, shoeing reduced the mediolateral heel movement (Roepstorff et al. 2001).

Nailing directly into a hoof wall is the most common way to attach a horseshoe to sound hoof wall. Meanwhile, attaching a shoe to a compromised hoof wall without nailing is a challenge to the veterinarian and the farrier. Glueing on a shoe provides a nontraumatic way of attaching a shoe to the horse's foot. Since the 1980s, methods of glueing shoes have been developed in conjunction with adhesive technology. Hoof adhesive materials can be divided into 4 classes of compounds: polymethyl methacrylate acrylics (PMMA), polyurethanes, cyanoacrylates and epoxies. Depending on the adhesive materials, the shoe is either glued to the ground surface and heel quarter perimeter of the hoof or to complete outer surface of the hoof wall using tabs or cuffs of the shoe (Cheramie and O'Grady 2003).

These methods are used in concert with medical or surgical treatment of severe hoof disease such as laminitis, hoof wall avulsions, white line disease, quarter cracks and third phalanx fractures. Glue-on shoes can also be used to a sound horse with a thin or poor hoof wall to which a shoe cannot be nailed securely. Thus, glued shoeing has come to be widely used in many kinds of horse, such as racehorses, 3-day eventers or showjumpers (Curtis 2006). Although the glued shoeing has some beneficial effect on the hoof, some authors suggested that normal heel expansion would seem to be inhibited by glueing (O'Grady and Poupard 2003; Curtis 2006). However, the long-term effects of the glued shoe are not fully understood.

There are 4 methods of attaching shoes with glue in recent years: 1) attaching a shoe with PMMA; 2) attaching a shoe with polyurethanes; 3) attaching a shoe with thermoplastic cuff and 4) attaching a shoe with fibreglass/Kevlar cuff. For racing Thoroughbreds, glueing an aluminium shoe with PMMA is the most common method in Japan. However, as this method attaches the shoe firmly to the heel, we hypothesised that glueing would interfere with the hoof mechanism by restricting the mediolateral heel movement. So the aim of this study was to compare the degree of mediolateral heel movement between glued and nailed shoes.

Materials and methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

Horses

Seven clinically normal without lameness, well trained Thoroughbreds (4–9 years, 488–576 kg) were used. Each horse had normal limb conformation and their hooves were corrected routinely by experienced farriers. Mean hoof angle of fore- and hindlimbs were 50.3 ± 3.5° and 54.7 ± 1.4° respectively, and each heel was somewhat sloping.

Data collection

A displacement sensor and a target wire (WP20-30)1 were attached with urethane adhesive (Super Fast)2 on the lateral and medial sides of the heel, respectively. The target wire was inserted into the displacement sensor, and both were placed parallel to the solar surface of the hoof just below the level of the bulb to measure the mediolateral heel movement (Fig 1). To reveal the stance phase, a strain gauge (N22-FA-10-120-11-VS3)3 was bonded with alpha-cyanoacrylate adhesive (Aron Alpha)4 to the middle of the dorsal hoof wall. The lead wires from the displacement sensor and the strain gauge were connected to each amplifier (CV051 and DPM-612B5, respectively). The data were recorded at 1000 Hz on a personal computer with a data acquisition system (DI-720)6.

image

Figure 1. Location of the displacement sensor bonded to the palmar hoof wall of the right forelimb in (a) lateral view and (b) palmar view. The axis of measurement was parallel to the solar surface of the hoof.

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Protocol

Both fore- and both hindlimbs were tested separately. Each hoof was trimmed 6–24 h before the experiment and a plain aluminium shoe attached to the ground surface of the hoof with methylmethacrylate/cyano-methylmethacrylate adhesive (Equilox)7. The procedure for attaching shoes was similar to the standard technique (Curtis 2006), apart from using a different adhesive material and a shock absorbing material (McKinlay Shoe Liners)8, which was run around the inner half of the web of the shoe to protect the sole from compression by an adhesive material. The heel movements were measured with glued shoe first, and then the shoes removed. Immediately, the same shoe was nailed to the hoof without refixing the sensors, and the heel movements measured again. Each horse walked (1.8 m/s), trotted (3.5 m/s), cantered (8 m/s) and galloped (12 m/s) in random order on a treadmill with a rubber belt (Mustang 2200)9.

Data processing

The mediolateral heel distance during the swing phase was set at zero for each hoof, and thus positive and negative values represented heel expansion and heel contraction, respectively. The maximum heel expansion and contraction were measured, and the total heel movement calculated as the sum of the absolute values.

Statistical analysis

Means of 10 consecutive strides were analysed for each horse. Significant differences between the 2 shoeing methods were compared by paired t test (R vs. 2.7.2)10 at P<0.05.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

Data were obtained from 9 forelimbs of 6 (except one limb at canter) and 9 hindlimbs of 5 horses. Displacement time curves of one horse during the stance phase at each running speed are shown in Figure 2 (forelimbs) and Figure 3 (hindlimbs). The shapes of the curves were similar at any speed, that is, the heels expanded during the first 70–80% of stance phase and contracted at breakover. The degree of maximum heel expansion increased with increasing running speed. However, the degrees of maximum heel contraction were almost constant at all running speeds.

image

Figure 2. Sample displacement time curves of a forelimb with glued (grey line) or nailed (black line) shoeing at walk (a), trot (b), canter (c, d) and gallop (e, f). The displacement curves are plotted against time as a percentage of the stance phase.

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image

Figure 3. Sample displacement time curves of a hindlimb with glued (grey line) or nailed (black line) shoeing at walk (a), trot (b), canter (c, d) and gallop (e, f). The displacement curves are plotted against time as a percentage of the stance phase.

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The shapes of the curves were similar between the 2 shoeing methods, but the degrees of expansion and contraction were different. The results of each variable are shown in Table 1 (walk and trot), Table 2 (canter) and Table 3 (gallop). In the forelimbs, degrees of the maximum heel contraction with glued shoeing was significantly smaller than with nailed shoeing at walk, trot and gallop. At canter, this tended to be smaller with glued shoeing than nailed shoeing. However, the degree of maximum heel expansion of the forelimbs did not differ significantly between shoeing methods at any speed. In the hindlimbs, glued shoeing restricted both maximum heel expansion and contraction at any speed, apart from expansion of trailing hindlimbs at canter (P = 0.052) and leading hindlimbs at gallop (no significance).

Table 1. Mean ± s.d. of heel movement during walking (1.8 m/s) and trotting (3.5 m/s) on a treadmill
 WalkTrot
Forelimb (n = 9)Hindlimb (n = 9)Forelimb (n = 9)Hindlimb (n = 9)
GlueNailGlueNailGlueNailGlueNail
  1. n = number of measurements. * Significant differences between glued and nailed shoeing (P<0.05).

Maximum heel expansion (mm)1.89 ± 0.511.99 ± 0.561.80*± 0.512.43 ± 0.723.78 ± 1.123.93 ± 1.013.69*± 1.384.67 ± 1.70
Maximum heel contraction (mm)−1.20*± 0.44−2.08 ± 0.81−1.97*± 0.42−2.45 ± 0.37−0.90*± 0.50−1.60 ± 0.79−1.59*± 0.32−2.23 ± 0.43
Total heel movement (mm)3.09*± 0.884.07 ± 1.083.77*± 0.774.88 ± 0.914.68*± 1.465.53 ± 1.605.28*± 1.446.90 ± 1.60
Table 2. Mean ± s.d. of heel movement during cantering (8 m/s) on a treadmill
 Leading forelimb (n = 4)Trailing forelimb (n = 4)Leading hindlimb (n = 5)Trailing hindlimb (n = 4)
GlueNailGlueNailGlueNailGlueNail
  1. n = number of measurements. * Significant differences between glued and nailed shoeing (P<0.05).

Maximum heel expansion (mm)9.11 ± 1.369.10 ± 1.196.42 ± 1.036.96 ± 1.888.05*± 1.4810.03 ± 1.627.31 ± 1.598.83 ± 1.90
Maximum heel contraction (mm)−1.54 ± 0.68−2.53 ± 0.64−0.79 ± 0.20−1.65 ± 0.49−1.90*± 0.47−2.56 ± 0.52−2.44*± 0.22−3.13 ± 0.30
Total heel movement (mm)10.64 ± 2.0111.63 ± 1.637.21 ± 0.958.61 ± 2.319.95*± 1.7312.59 ± 2.069.75*± 1.6311.95 ± 2.07
Table 3. Mean ± s.d. of heel movement during galloping (12 m/s) on a treadmill
 Leading forelimb (n = 5)Trailing forelimb (n = 4)Leading hindlimb (n = 5)Trailing hindlimb (n = 4)
GlueNailGlueNailGlueNailGlueNail
  1. n = number of measurements. * Significant differences between glued and nailed shoeing (P<0.05).

Maximum heel expansion (mm)11.47 ± 1.6811.27 ± 0.669.60 ± 1.639.40 ± 1.8910.72 ± 1.3112.15 ± 1.5510.38*± 0.7512.30 ± 1.13
Maximum heel contraction (mm)−1.76*± 0.73−2.78 ± 0.81−0.84*± 0.33−1.70 ± 0.37−2.62*± 0.91−3.30 ± 0.62−2.84*± 0.53−3.51 ± 0.42
Total heel movement (mm)13.22 ± 2.2814.05 ± 1.3010.44 ± 1.4411.10 ± 2.1513.34 ± 2.0315.44 ± 2.1513.22*± 0.8515.81 ± 1.43

Therefore, the total heel movement of all 4 limbs was smaller with glued shoeing than with nailed shoeing at walk and trot. At canter, glued shoeing significantly restricted the total heel movement of both hindlimbs and tended to restrict that of leading forelimb (P = 0.086). At gallop, glued shoeing significantly restricted the total heel movement of trailing hindlimb and tended to restrict that of the leading hindlimb (P = 0.050).

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

The effects of the nailed horseshoeing on the hoof mechanism was investigated by Roepstorff et al. (2001). The results of measuring the net mediolateral heel movement indicated that the nailed shoeing restricted the heel expansion (Roepstorff et al. 2001). The popularity of glued shoeing has increased with the evolution of this method in recent years. In the most popular method of glued shoeing, traditional rigidity metallic shoes are firmly attached to the heel, so there is a possibility of further restriction of the heel movement than in the nailed shoeing. We compared the displacement of the heels in the glued shoeing and nailed shoeing condition. A strain gauge is usually used to evaluate hoof deformation, and is able to be placed anywhere on the hoof wall; however, it cannot measure the net hoof deformation. We used a displacement sensor to compare the heel movement between nailed and glued shoeing as this can measure the net mediolateral movement of the heels.

The time displacement curves were similar to those of a previous study using a potentiometer (Roepstorff et al. 2001): the heels expanded during the first 70–80% of the stance phase and then contracted at breakover. Although the patterns were similar at all running speeds, the degree of the maximum heel expansion increased as running speed increased. The heels may be expanded by the vertical ground reaction force in the caudal region of the hoof, which account for a major part of the total ground reaction force from impact to midstance (Kai et al. 2000). Because the vertical ground reaction force at midstance increases with running speed (Niki et al. 1982, 1984; Merkens et al. 1985, 1993a,b), it is likely that the maximum heel expansion increased similarly with running speed in the present study. On the other hand, the vertical ground reaction force is distributed exclusively in the toe region of the hoof at breakover (Kai et al. 2000). It is likely that the increase of the vertical force of the toe region induces the contraction of the heels (Roepstorff et al. 2001). The vertical ground reaction force at breakover remains almost constant regardless of running speed (Niki et al. 1982, 1984; Merkens et al. 1985, 1993a,b; Kai et al. 2000). These facts explain the constant heel contraction at all running speeds obtained in this study.

There was no difference in the maximum heel expansion in the forelimb between nailed and glued shoes, but in the hindlimb, the maximum heel expansion in glued shoes was smaller that in nailed shoes. One reason for the smaller heel expansion is the smaller vertical ground reaction force in the hind- than the forelimb (Niki et al. 1982, 1984; Merkens et al. 1985, 1993a,b), which makes it easier for the glued shoe to restrict the heel expansion. Another reason is the hoof angle: the distribution of the vertical ground reaction force on the caudal region reduces when the hoof angle increases (Barrey 1990). In this study, the hoof angle of the hindlimb is larger than that of the forelimb. This larger angle would further reduce the ground reaction force on the caudal region in the hindlimb, and might contribute to the restriction of the heel expansion with the glued shoe in the hindlimb.

The maximum heel contractions of the glued hoof were smaller than those of the nailed hoof in both fore- and hindlimbs at all speeds. The vertical ground reaction force causing heel contraction at breakover is smaller than the force at midstance regardless of running speed (Niki et al. 1982, 1984; Merkens et al. 1985, 1993a,b; Kai et al. 2000). Therefore, the restriction of heel contraction by glued shoes was greater than that imposed on heel expansion. The total heel movements of both fore- and hindlimbs were restricted by the glued shoes at low speed because the ratio of the maximum heel contraction to the total heel movement was larger at low speed than at high speed. The glued shoes did not restrict the total heel movement of the forelimb at high speed. However, there may be negative long-term effects of the glued shoe because horses spend more time walking than cantering and galloping.

The hoof mechanics seem to have the effects of absorbing shocks and pumping blood. The digital venous pressure increases during the early stance phase and breakover during walking and trotting (Ratzlaff et al. 1985). The increasing of digital venous pressure may be induced by the compression of the venous plexuses in the foot. The venous plexuses may be compressed by ground reaction force and the outward movements of the lateral cartilages (Bowker et al. 1998). Because the temporary increase of the venous pressure and the beginning of the heel expansion occurred simultaneously at the early stance phase, the heel expansion could be related to the change of the venous pressure induced by the movements of the lateral cartilages. In addition, the heel contraction might also be related to the second temporary peak of the venous pressure at breakover. However, this peak was smaller than the first peak related to the heel expansion. Additionally, heel expansion also decreases the pressure in the digital cushion, indicating shock absorption at impact (Dyhre-Poulsen et al. 1994). Consequently, heel expansion is more likely to affect the hoof mechanism than heel contraction. Because heel expansion was more restricted in the hindlimb than in the forelimb, glued shoeing could interfere with the hoof mechanism more strongly in the hindlimb.

In this study, we glued a rigid metallic shoe to the ground surface and heel quarter perimeter of the foot. Although this method is the most popular of glueing a shoe, it was suggested in this study that it restricted heel movement more than conventional nailing. It is likely that the restriction of the heel movement exerts a force to the adhesive material of the heel region. This force may reduce the lifetime of the glued shoeing. Additionally, it is possible that the glued shoeing induces the contracted heels by interfering with the hoof mechanics. To cover the shortcomings of this method, a purpose-built shoe was developed, which has flexibility in the heel region and is attached to the outer surface of the hoof wall using a fabric cuff. On the other hand, it is possible to use the glueing method of this study for therapeutic shoeing of third phalanx fractures and quarter cracks, where restricting movement of the caudal part of the hoof is required. Further studies are needed to evaluate the influence of other methods of glued shoeing on hoof mechanics and to measure hoof movement of other parts.

Manufacturers' addresses

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References

1 Levex Co., Kyoto, Japan.

2 Vettec, Inc., Oxnard, California, USA.

3 NEC San-ei Instruments, Ltd, Tokyo, Japan.

4 Toagosei Co. Ltd, Tokyo, Japan.

5 Kyowa Electronic Instruments, Tokyo, Japan.

6 DATAQ Instruments, Inc., Akron, Ohio, USA.

7 Equilox International, Inc., Pine Island, Minnesota, USA.

8 Thoro'Bred, Inc., Anaheim, California, USA.

9 Kagra, Fahrwangen, Swizerland.

10 R Development Core Team (2008). http://www.R-project.org

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Discussion
  7. Manufacturers' addresses
  8. Conflicts of interest
  9. References
  • Back, W. (2001) The role of the hoof and shoeing. In: Equine Locomotion, Eds: W.Back and H.M.Clayton, W.B. Saunders, London. pp 135-166.
  • Barrey, E. (1990) Investigation of the vertical hoof force distribution in the equine forelimb with an instrumented horseboot. Equine vet. J., Suppl. 9, 35-38.
  • Bowker, R.M., Van Wulfen, K.K., Springer, S.E. and Linder, K.E. (1998) Functional anatomy of the cartilage of the distal phalanx and digital cushion in the equine foot and a hemodynamic flow hypothesis of energy dissipation. Am. J. vet. Res. 59, 961-968.
  • Cheramie, H.S. and O'Grady, S.E. (2003) Hoof repair and glue-on shoe adhesive technology. Vet. Clin. N. Am.: Equine Pract. 19, 519-530.
  • Colles, C.M. (1989) A technique for assessing hoof function in the horse. Equine vet. J. 21, 17-22.
  • Curtis, S. (2006) Nail-less horseshoeing. In: Corrective Farriery 2, Ed: S.Curtis, Newmarket Farrier Consultancy, Suffolk. pp 495-514.
  • Davies, H.M. (1997) Noninvasive photoelastic method to show distribution of strain in the hoof wall of a living horse. Equine vet. J., Suppl. 23, 13-15.
  • Dejardin, L.M., Arnoczky, S.P., Cloud, G.L. and Stick, J.A. (2001) Photoelastic stress analysis of strain patterns in equine hooves after four-point trimming. Am. J. vet. Res. 62, 467-473.
  • Douglas, J.E., Biddick, T.L., Thomason, J.J. and Jofriet, J.C. (1998) Stress/strain behaviour of the equine laminar junction. J. expt. Biol. 201, 2287-2297.
  • Dyhre-Poulsen, P., Smedegaard, H.H., Roed, J. and Korsgaard, E. (1994) Equine hoof function investigated by pressure transducers inside the hoof and accelerometers mounted on the first phalanx. Equine vet. J. 26, 362-366.
  • Kai, M., Aoki, O., Hiraga, A., Oki, H. and Tokuriki, M. (2000) 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. Am. J. vet. Res. 61, 979-985.
  • Merkens, H.W., Schamhardt, H.C., Hartman, W. and Kersjes, A.W. (1985) Ground reaction force patterns of Dutch Warmblood horses at normal walk. Equine vet. J. 18, 207-214.
  • Merkens, H.W., Schamhardt, H.C., Van Osch, G.J. and Hartman, W. (1993a) Ground reaction force patterns of Dutch Warmbloods at the canter. Am. J. vet. Res. 54, 670-674.
  • Merkens, H.W., Schamhardt, H.C., Van Osch, G.J. and Bogert, A.J. (1993b) Ground reaction force patterns of Dutch warmblood horses at normal trot. Equine vet. J. 25, 134-137.
  • Niki, Y., Ueda, Y. and Masumitsu, H. (1984) A force plate study in equine biomechanics 3. The vertical and fore-aft components of floor reaction forces and motion of equine limbs at canter. Bull. equine Res. Inst. 21, 8-18.
  • Niki, Y., Ueda, Y., Yoshida, K. and Masumitsu, H. (1982) A force plate study in equine biomechanics 2. The vertical and fore-aft components of floor reaction forces and motion of equine limbs at walk and trot. Bull. equine Res. Inst. 19, 1-17.
  • O'Grady, S.E. and Poupard, D.A. (2003) Proper physiologic horseshoeing. Vet. Clin. N. Am.: Equine Pract. 19, 333-351.
  • Ratzlaff, M.H., Shindell, R.M. and DeBowes, R.M. (1985) Changes in digital venous pressures of horses moving at the walk and trot. Am. J. vet. Res. 46, 1545-1549.
  • Roepstorff, L., Johnston, C. and Drevemo, S. (2001) In vivo and in vitro heel expansion in relation to shoeing and frog pressure. Equine vet. J., Suppl. 33, 54-57.
  • Stashak, T.S., Hill, C., Klimesh, R. and Ovnicek, G. (2002) Trimming and shoeing for balance and soundness. In: Adams' Lameness in Horses, 5th edn., Ed: T.S.Stashak, Lippincott Williams & Wilkins, Baltimore. pp 1081-1144.
  • Thomason, J.J. (1998) Variation in surface strain on the equine hoof wall at the midstep with shoeing, gait, substrate, direction of travel, and hoof shape. Equine vet. J., Suppl. 26, 86-95.