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 : research communication

Abstract

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 dismem-bered 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 2500 Nat 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 Nload. At higher loads, the position of P3 did not differ significantly for the different frog pressures applied. It is concluded that increased frog pressure 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.

Hoof ground interaction: when biomechanical stimuli challenge the tissues of the distal limb

“…Considerable information on the anatomical and force constraints of the distal limb has been generated through in vitro and in vivo studies on various aspects of the hoof complex, which is both rigid and flexible to support and accommodate the interaction of the hoof with the surface (Back 2001;Hinterhofer et al 2001;Roepstorff et al 2001;Olivier et al 2001;Thomason et al 2001Thomason et al , 2005. Movement of the hoof capsule during movement has been quantified by the use of strain gauges, motion analysis systems and potentiometers (Dejardin et al 1999(Dejardin et al , 2001Roepstorff et al 2001;Thomason et al 2002).…”

“…The hoof deforms continually throughout loading during the stance phase. During the initial loading phase the distal phalanx pulls the dorsal hoof wall backwards and downwards, pushes the quarters outward, causing the bulbs of the heels to expand (Olivier et al 2001;Roepstorff et al 2001;Thomason et al 2002). Shoeing limits this deformation and decreases bulb expansion (Hinterhofer et al 2001;Roepstorff et al 2001).…”

“…Heel expansion ceases at the time of midstance, which is most likely due to the forward progression of the CoP van Heel et al 2004). The high loading at midstance causes the distal third of the hoof wall to expand or flare and the sole of the hoof to move distally (Olivier et al 2001). Flaring is potentiated by the application of a wedge, because of the relocation of the force or pressure towards the wedge.…”

Effects of industrial polystyrene foam insulation pads on the center of pressure and load distribution in the forefeet of clinically normal horses

“…This is supported by the myriad of homemade and commercially available products with varying degrees of evidence that weight bearing is altered. 5,[8][9][10][11][12][13] Foam supports have been advocated by many practicing veterinarians and farriers, but scientific evidence for their use has previously been unavailable. 3,4,14,15 The present study revealed that total contact surface area was significantly increased up to 48 hours after placement of foam sole supports.…”

Musculoskeletal Disease in Aged Horses and Its Management

“…The palmar/plantar part of the feet is filled using a filler paste with a higher shore value to support the not painful and still well perfused frog. 86…”