Page 112 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition
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Musculoskeletal system: 1.3 The foot                              87



  VetBooks.ir  where the heel bulbs and heel buttresses are closer   the hoof may be an incidental finding in lameness
            Contracted heels are described as the condition
                                                         examinations.
          together than normal. It is invariably associated with
          a narrow frog, and frequently with high or underrun  Differential diagnosis
          heels. The condition is thought to occur secondary   Any chronic lameness originating within the foot;
          to heel pain, reduced weight bearing by the heels,   healed traumatic hoof wounds.
          and subsequent reduced expansion of the heels dur-
          ing the normal cycle of the stride.            Diagnosis
            Underrun  heels  occur  when  the  heels  are  more   Diagnosis of imbalance and poor conformation of
          acutely angled to the ground than normal, and usu-  the  hoof  and distal limb is  made  by  careful  visual
          ally occur in horses with excessive length of toe.   inspection and  measurement (Fig. 1.149).  Any
          Typically, the heels are longer than normal and   changes observed reflect movement of the coro-
          they may be curved dorsally and axially so that the   nary band, distortion of the hoof wall and change
          weight-bearing surface of the heels is displaced dor-  in the spacing of the growth rings. The distal limb
          sal to the base of the frog. The foot–pastern axis is   should be examined with the foot both on and off
          usually broken back. While the aetiology has not   the  ground.  When  observed  on the  ground,  the
          been definitively determined, it appears that some   ground surface of the foot should be approximately
          breeds, particularly Thoroughbreds, are genetically   perpendicular to the axis of the limb. When the
          predisposed. In other instances, trimming practices   foot is observed off the ground, typically with the
          that result in excessive length of heel or shoeing
          practice that causes excessive weight bearing on the
          heels encourage the heels to become underrun. An       1.149
          upright  foot with  high heels usually accompanies
          either contracted heels or a flexural deformity of
          the DIP joint. However, in the latter, in contrast to
          the former, the heels are frequently widely spaced.
          Upright heels are frequently associated with a bro-
          ken forward foot–pastern axis. When a horse has
          one upright foot with contracted heels, the contra-
          lateral foot often has low/underrun heels.
            Sheared heel is a condition in which one  heel
          bulb of the foot is displaced proximally compared
          with the other. While the condition is called
          sheared heel(s), the proximal displacement of the
          coronary band frequently begins in the quarter, so
          it might be more appropriately termed sheared heel
          and quarter. This condition is often associated with
          contracted heels. The exact cause of sheared heels is
          undetermined, although it is thought to be second-
          ary to inappropriate trimming prior to shoeing in
          many horses. Sheared heels may be associated with
          lameness  that  is  abolished  with  a  palmar  digital
          nerve block.
                                                         Fig. 1.149  View from the front of a foot with
          Clinical presentation                          chronic mediolateral imbalance. Note the sloping
          Horses with hoof imbalance frequently present with   coronary band, asymmetrical walls and obvious flaring
          lameness, although abnormal shape or movement of   of the medial wall.
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