How to Manage a Quarter Crack
Reprinted with permission from the American Association of Equine Practitioners.
Originally printed in the 2010 AAEP Convention proceedings
Stephen E. O'Grady, BVSc, MRCVS
Author's address: Northern Virginia Equine, PO Box 746, Marshall, Virginia 20116; e-mail: firstname.lastname@example.org. © 2010 AAEP.
Hoof-wall defects, especially quarter cracks, are a
common cause of decreased athletic performance in
competition horses and frequently lead to foot lameness.
1-3 Hoof-wall defects are generally described
by their location in the hoof, such as a toe, quarter,
or heel crack.4 A true quarter crack originates at
the coronet and extends through the full thickness of
the hoof wall into the dermis, leading to instability,
inflammation, and/or infection. These cracks can
be painful because of infection and/or more commonly,
instability caused by movement of the hoof
wall, especially the vertical movement of the heel
bulb on the affected side. The recurrent nature of
quarter cracks involving a performance horse presents
a challenging and often frustrating problem
for equine veterinarians, farriers, and horse owners,
because these horses often need to continue to
Many causes of quarter cracks have been described,
such as trauma to the coronet, pre-existing
damage to the dermis from infection, abnormal hoof
conformation, short shoes, inappropriate farrier
practices, or an abnormal landing pattern when the
foot strikes the ground. The most consistent finding
in all quarter-crack cases is a foot conformation
with sheared heels and an abnormal strike pattern
during the impact phase of the stride.a In fact, it is
extremely rare to find a quarter crack that is not
accompanied by limb conformation that leads to
sheared heels combined with an abnormal strike
pattern.1a Various materials and techniques exist
for repairing hoof cracks, but none will be successful
unless the cause of the hoof-wall defect is determined
and addressed through basic farriery.1-3
This paper will discuss the foot conformation and
proposed etiology leading to a quarter crack, appropriate
farriery, and a repair technique that has provided
|Fig. 1. Palmar view of a foot with a sheared heel. Note the disparity between lateral and medial heel length and the compression of the structures above the medial heel.
|Fig. 2. An acute quarter crack. Note the bleeding.
2. Foot Conformation
Sheared heels can be defined as a hoof-capsule distortion
resulting from displacement of one heel bulb
proximally relative to the adjacent heel bulb (Fig.
1).5-8 This disparity between the lateral and medial
heel bulb is generally 0.5 cm or more.9 When
the weight of the horse is not distributed uniformly
over the entire hoof during the landing phase of the
stride, one focal area of the foot, usually a heel and
accompanying heel quarter, receives a disproportionate
amount of the total load. This resultant
force leads to a remodeling of the affected heel bulb.
The degree of distortion in the affected heel is dependent
on the amount of the load sustained by the
individual foot. Sheared heels can occur in the
hind as well as the forefeet. This continual disproportionate
load and the increased compressive stresses placed on one side of the foot predispose the
foot to injury such a quarter crack (Fig. 2).5
3. Structural Changes to the Foot
The equine hoof capsule is a viscoelastic structure
that has the unique ability to deform when weight is
accepted uniformly.10 However, if the unequal load
is continually placed on one quarter/heel, over time,
structural changes will become apparent. The increased
load on one side of the foot causes the hoof
wall to assume a steeper angle (that is, the wall
becomes straighter). Along with the increased
hoof-wall angle, other changes, such as contracture
of the heel subjected to the greater load, will soon
follow. This decreases the ground surface of the
foot, resulting in a lack of expansion on that side of
the foot and making the solar surface in the palmar/
plantar section of the foot asymmetrical. Over
time, the hoof wall begins to roll under on the affected
side, which further decreases ground surface
under that area of the foot. The side of the foot that
first impacts the ground develops a flare because of
bending of the hoof tubules.
Over time, the stresses placed on the overloaded
side of the foot exceed the ability of the hoof wall to
deform.10 The submural tissue on the affected side will be subjected to excessive compressive forces
that result in hemorrhage along with stretching or
tearing of the lamellae. It is thought that the exudation
of fluid in the submural tissue increases pressure
and will eventually disrupt the coronary
corium, consequently leading to the formation of a
quarter crack. Furthermore, a recent study of a
group of horses with quarter cracks showed the free
margin of the ungual cartilage above the coronet
resulting from the displaced quarter/heel to be less
than 15 mm.11 This lack of free margin seems to
prevent lateral expansion of the ungual cartilage,
leading to increased pressure in the sheared heel
and trauma to the adjacent coronet.
The presence of a sheared heal indicates a disproportionate
weight distribution over a section of
the hoof that anatomically cannot resist the additional
stresses without distortion or displacement.
Horses with conformation that causes the limbs to
land and load asymmetrically across the hoof will be
subject to this type of deformation. The growth
rate around the circumference of the hoof is usually
approximately uniform, but regional disturbances in
growth rate can occur to either increase or decrease
growth. The position of the coronary band is related
to the balance between hoof wall growth at the
coronary band and the rate of migration of the hoof
wall distally. Furthermore, the rate of migration of
the hoof wall is a balance between an active process
occurring in the lamellae to cause them to move
distally and the force on the wall from the ground
reaction force. Clinical evidence suggests that hoof
wall growth is at least in part, if not predominantly,
inversely determined by the force of weight bearing
at the ground surface of the wall. If the rate of hoof
wall growth exceeds the rate of migration distally,
the coronary band displaces proximally. This appears
to be the mechanism in horses with sheared
heels/quarters. Due to the fact that the growth
rings below the coronet are usually very close together
where the hoof wall is displaced and that the
slow hoof wall growth is most likely related to increased
weight bearing (force) by the wall; this
would suggest that the wall is forced proximally.
Whether or not this is a real phenomenon as suggested
by clinical experience has not been confirmed
in a scientific manner.
|Fig. 3. DP radiograph of a foot with sheared heels. Markers placed at the coronary band of the heels show the different heel height while the distal phalanx remains parallel with the ground. Note that the distal phalanx is offset to the lateral side.
It was assumed for years that inappropriate farrier
practices may lead to sheared heels when trimming
methods such as leaving the heels long or
excessively lowering one side of the foot would result
in excessive forces/stresses being placed on a given
section of the foot. The term used to discribe this
type of hoof capsule distortion was a lateral medial
imbalance. To substantiate this theory, the author
reviewed 50 dorsopalmar 0° (DP) radiographs on
horses that had a foot with one heel bulb displaced
proximally 0.5 cm or greater. In all cases, it was
found that the solar surface of the distal phalanx was approximately horizontal (parallel) with the
ground, indicating that the disparity in heel height
was not originating from the hoof wall and sole
located beneath the distal phalanx in the heel (Fig.
3). Also, the distal phalanx occupies the dorsal section
of the hoof capsule anatomically, whereas the
majority of the space in the palmar/plantar foot is
occupied by soft tissue (Fig. 4). The displacement
of the heel occurs palmar/plantar to the body of the
distal phalanx in the section of the hoof comprised of
soft tissue. This may account for the proliferation
of soft tissue and the additional hoof-wall growth
occurring above the ground surface of the foot.
|Fig. 4. This illustration shows the ratio of bone to soft tissue in the foot. The hoof-capsule distortion noted in a sheared heel will involve the soft-tissue structures palmar to the distal phalanx. Note the dotted line. (Courtesy of Dr. Andrew Parks.)
|Fig. 5. Foot shows focal proximal displacement of coronet at the origin of crack, which coincides with the illustration in figure 4. This is the point of maximum stress.
To formulate a rational approach to management, it
is necessary to discuss the etiology of sheared heels.
Traumatic wounds to the coronary band in the palmar/
plantar region of the foot often lead to a quarter
crack. Treatment here involves appropriate wound
care and stabilization of the coronet to promote healing.
Inappropriate farrier care or lack of appropriate
farriery over time may contribute to the
formation of a quarter crack. Inappropriate farriery
may lead to hoof-capsule distortions where the forces/pressure on a given section of the foot become
excessive, leading to a hoof-wall defect. Conformational
faults in the upper limb that change the
horse's flight phase of the stride lead to a hoofcapsule
distortion termed sheared heels. The presence
of a sheared heel combined with a spontaneous
quarter crack seems to provide ample evidence that
this type of hoof-capsule distortion plays a major
role in the etiology. Sheared heels seem to result
from unequal loading of the foot as it impacts the
ground. In this instance, the altered flight pattern
causes the horse to impact the ground with one side
of the foot before full weight-bearing on other side of
the foot. This focal disproportionate weight-bearing
displaces the heel bulb proximally, creating the
unequal heel height. In the conformationally predisposed
horse, the horse will generally have a narrow
chest, and the carpus will be rotated laterally.
When viewed from the front, although the entire
limb faces outward or in some instances, medially,
the axial alignment of the limb from the carpus to
the ground surface of the foot forms a straight line,
indicating a rotational deviation of the limb. With
the knee facing outward, it changes breakover such
that it occurs in an outward or lateral direction, thus
changing the optimal straight flight path of the foot
during the stride so that the foot is unable to land
under the horse evenly on both heels. As the horse
approaches the landing phase of the stride, this
flight pattern forces the foot to contact the ground on
one side of the foot and then sustain excessive load
on the opposite side. Using a slow-motion video
camera, one can actually distinguish the point
where the foot impacts the ground on one side and
the point where the hoof loads the surface on the
other side. Quarter cracks usually occur directly
above the point of the greatest load and most force
within the hoof wall. This point can be readily
observed, because there will be a small focal displacement
in the coronet proximally above the quarter
crack (Fig. 5). Furthermore, there seems to be a
correlation between an offset distal phalanx and
sheared heels. Most commonly, the distal phalanx
is offset laterally within the hoof capsule rather than directly under the proximal and middle phalanges,
causing the medial side of the hoof capsule to
assume more load.
The evaluation of sheared heels begins with visual
assessment of the hoof and limb conformation with
the horse standing on a hard, level surface. The
gross changes noted in the foot are proportional to
the amount of continual load sustained, the extent of
structural damage, and the duration of the condition.
When sheared heels are present, the heel
bulb on the affected side is displaced proximally
when viewed from behind the horse. When viewed
from the front, the hoof wall on the affected side is
straighter and in chronic cases, will begin to roll
under the foot. There is a marked flare of the hoof
wall present on the side opposite the affected heel.
When viewed from the side, the coronary band is
displaced proximally above the damaged heel instead
of having a gradual uniform slope from the toe
to the heel. The solar surface of the foot reflects
changes elsewhere in the hoof capsule. The foot
will be less symmetrical; the sole in the quarter and
heel area will appear wider on the side with the flare
and narrower on the side with the sheared heel.
It is important to view the horse in motion, again on
a hard, level surface, from the front and rear. This
should be done at a walk and a trot. When viewed
from behind, this should determine which section of
the foot is contacting the ground initially and which
portion of the foot is receiving the impact. The
direction of breakover should be noted when viewed
from the front.
Farriery is directed to unloading the hoof wall and
decreasing the forces on the side of the foot with the
quarter crack. This is accomplished by improving
the conformation of the hoof, trimming methods,
and applying the appropriate shoe. When a horse
develops a full-thickness quarter crack, it is advisable
to take the animal out of training to allow
healing, but this is not always an option with competition
horses. There will also be constraints
placed on the farriery because of the training and
competition schedule of the horse. For example,
the author likes to remove the shoes and stand the
horse on a hard surface for 24 h before trimming and
shoeing the horse. This alone allows the affected
side of the foot to settle into a more acceptable conformation.
Furthermore, when possible, the author
will perform the farriery and wait for the
coronet to settle into a more acceptable position or
slope before a repair is considered. If the repair is
performed immediately, the defect is fixed with the
coronet in a displaced position.
When infection is present, it is characterized by
marked lameness, pain on palpation, and a swollen
discolored coronary band above the defect. Occasionally,
exudate can be expressed when digital pressure is applied to the coronet. Infection often
occurs shortly after a defect is patched with some
type of composite that generates heat. If infection
is present, the patch (if present) is removed, the
crack should be opened for drainage, and the foot is
bandaged with a suitable disinfectant agent for at
least 48 h.
|Fig. 6. This illustration shows proportions of a well-trimmed foot. A foot with a sheared heel shows increased ground surface on the affected side after trimming (blue line).
Farriery is initiated by removing the shoes and
again observing the horse walking on a hard surface,
noting the strike pattern of the foot. The foot is
trimmed appropriately using the guidelines of a parallel
hoof-pastern axis, and the center of articulation
and heels of the hoof capsule are trimmed to include
the base of the frog. To start, a line can be drawn
across the widest part of the foot with a felt-tip pen.
The frog is trimmed to where it is pliable, and the
quarters and heels of the hoof capsule from the
middle of the foot are rasped palmarly so that the
heels of the hoof capsule and the trimmed frog are on
the same plane. An attempt is made to create as
much ground surface under the affected heel as possible,
which will result in that side being marginally
lower than the other side of the foot. The toe and
quarters are reduced appropriately so when the trim
is completed, the surface area on either side of the
line drawn on the widest part of the foot will be
approximately equal (Fig. 6). Lowering the heel on
the displaced side of the foot is logical, because it is
the taller heel and it increases the ground surface of
the foot on that side. Bearing in mind that the
mechanism that accounts for this foot conformation
is not completely understood, the trim is based on
clinical impressions having successfully treated a
large number of cases. After the trim, the horse is
again walked on a hard surface, and some improvement
in the landing pattern will be noted.
Any horse with a full-thickness quarter crack
should be placed in a bar shoe, if possible. Various
configurations of bar shoes, such as a straight-bar,
heart-bar, or Z-bar shoe, can be used. All of these
shoes effectively increase the surface area of the
foot, provide palmar/plantar support, and decrease the independent vertical movement at the bulbs of
the heels. No nails are placed palmar to the defect
in the foot.
|Fig. 7. Straight-bar shoe with a leather pad.
|Fig. 8. Straight-bar shoe with heel unloaded. Note the taper from the quarter to the heel.
|Fig. 9. Hole being drilled into the ledge created in the debrided quarter crack.
The author's choice is a wide web-steel straightbar
shoeb fitted symmetrically to the trimmed foot,
and a leather pad is attached to the shoe (Fig. 7).
Before applying the shoe, the medial quarter and
heel of the affected side of the foot is further lowered
in a tapered fashion with a rasp. Impression materialc
is placed in the palmar section of the foot from
the apex of the frog palmarly, except under the medial
heel. The shoe is then attached to the foot.
Lowering the hoof wall at the quarter/heel will create
a space between the shoe and the hoof wall on
the medial side (Fig. 8). This improves the foot
conformation, the landing pattern, unloads the medial
heel, and allows the heel bulb to settle down and
assume a more acceptable position.
8. Repairing the Defect
The use of a composite (with fiberglass) alone may
not provide sufficient stability for a quarter-crack
repair. Combining an implant with the composite
in the repair increases the strength and durability of
the repair. Types of implants described previously include fiberglass and screws, screws and wires, various
suture patterns, and clamps that apply tension
across the crack.12-15 These methods have been
somewhat cumbersome; the screws present a risk,
because they often impinge on the dermis and uniform
tension is rarely achieved across or within the
When a decision is made to repair the quarter
crack, the hoof wall should be thoroughly cleaned
and dried. The defect is explored through its entire
length using a Dremel toold with a tungsten carbide
bit, being careful not to create any unnecessary
hemorrhage. All loose undermined horn should be
removed, the defect is widened, and the burr is used
to create a solid ledge on either side of the trough.
The hoof surface on either side of the defect should
be sanded with a coarse sanding block. Two sets of
paired 0.047-in holes spaced 0.25-in apart are then
drilled across from each other on either side of the
crack beginning at least 0.375-0.500 in from the
margin of the crack and ending within the ledge of
the trough (Fig. 9). Stainless steel wire formed in a
hair-pin shape 2.5-in long with a small steel tab on
each wire unit is commercially available.e One
wire unit is passed through the holes from a palmar
to dorsal direction, and another wire unit is passed
through the opposing holes in a dorsal to palmar
direction into the depth of the crack. The ends of
the wires are pulled tight and bent outwards. The
tab placed on the wire unit will now lie against the
outer hoof wall. This prevents the wires from cutting
into the hoof wall. Additional sets of these
wire units can be used according to the length of the
defect or until the desired stabilization is achieved.
The internal length of the defect usually exceeds
the external length, and therefore, it cannot be completely
eliminated, thus allowing a portal of entry
into the submural tissue. This necessitates some
form of drain or interface between the composite and
the floor of the defect. If the interior of the crack is
soft and pliable or if hemorrhage has been encountered,
a drain should be used. A drain or interface can be placed in the defect before it is covered with
the composite. A small amount of medicated puttyf
is rolled into a tubular shape the length of the
trough and placed within the debrided defect to act
as an interface. If a drain is desired, thin rubber
flexible tubing is pressed into the putty. The tubing
will exit at the coronary band and below the
crack to form the drain. The ends of all the opposing
wires are now joined together and twisted until
resistance is felt. The excess wire in front of the
twist is cut off within the defect (Fig. 10, A-C).
There should be no movement in the hoof wall on
either side of the crack when digital pressure is
|Fig. 10. (A-C). A shows the wires joined together and being twisted. B shows the wires cut just above the twist. C shows the completed implant with a drain.
The completed implant is now covered with a composite
patch. Elastic adhesive tape is placed
around the coronary band to prevent irritation from
contact with the composite. The polymethylmethacrylate
(PMMA)d composite is mixed thoroughly
with strands of fiberglass, the mixture is
placed on a section of plastic wrap, and it is applied
over the implant. The composite is molded into the
desired shape through the plastic wrap and then
covered with a cohesive bandage placed around the
hoof wall to compress the composite. On completion
of the cure cycle, which takes 2-3 min depending
on the ambient temperature, the rubber drain is
removed, and the repair is sanded to remove excess
The importance of determining the underlying cause
and implementing the appropriate farriery cannot
be overemphasized when managing a quarter crack.
The strong association of sheared heels with limb
conformation and the landing pattern of the horse
when a quarter crack is present is hard to ignore.
Assessing the limb conformation, improving the foot
conformation, and applying the appropriate shoe
seem to be as important as the repair technique used
for the defect. Inadequate attention to these factors
may account for the many failures encountered
and the recurring nature of quarter cracks. The
use of a composite (with fiberglass) alone may not
provide sufficient stability for a quarter-crack repair
to heal. Combining an implant with the composite in repairing a defect increases the strength and stability
of the repair. Types of implants described
previously include fiberglass and screws, screws and
wires, various suture patterns, and clamps that apply
tension across the crack.12-15 These methods
have been somewhat cumbersome; the screws
present a risk, because they often impinge on the
dermis and uniform tension is rarely achieved
across or within the crack.
The advantage of the repair method described in
this paper is that the procedure is exceptionally
strong and increases stability while being relatively
simple and easy to learn. Additionally, the wires
are placed from opposing sides of the defect and
joined together within the defect, creating uniform
tension within the crack. Another advantage of
this technique is that, because the implant is contained
within the hoof wall, there is very little metal
on the surface of the hoof wall to interfere with the
adhesion of the composite.
References and Footnotes
- O'Grady SE. Quarter crack repair: an overview. Equine Vet Edu 2001;3:280-282.
- Moyer W. Hoof wall cracks. In: Colahan J, Mayhew IG, Merritt AM, et al., eds. Equine medicine and surgery, 5th ed. St. Louis, MO: Mosby, 1999;P1509-P1510.
- O'Grady SE. How to repair a quarter crack, in Proceedings. 47th Annual American Association of Equine Practitioners Convention 2001;287-291.
- Moyer W. Hoof wall defects: chronic hoof wall separations and hoof wall cracks. Vet Clin North Am [Equine Pract] 2003;19:333-344.
- Moyer W, Anderson JP. Sheared heels: diagnosis and treatment. J Am Vet Med Assoc 1975;166:53-55.
- O'Grady SE. Shoeing management of sheared heels. In: Robinson NE, ed. Current therapy in equine medicine, 5th ed. Philadelphia, PA: W.B. Saunders, 2002;528-532.
- O'Grady SE. How to manage sheared heels, in Proceedings. 51st Annual American Association of Equine Practitioners Convention 2005;451-456.
- Snow VE, Birdsall DP. Specific parameters used to evaluate hoof balance and support, in Proceedings. 36th Annual American Association of Equine Practitioners Convention 1990;299-311.
- Turner TA. The use of hoof measurements for the objective assessment of hoof balance, in Proceedings. 38th Annual American Association of Equine Practitioners Convention 1992;389-395.
- Parks AH. Form and function of the equine digit. Vet Clin North Am [Equine Pract] 2003;19:285-296.
- Castelijns HH. Pathogenesis and treatment of spontaneous quarter cracks—quantifying vertical mobility of the hoof capsule at the heels. Pferdeheilkunde 2006;5:569-576.
- Moyer W. Repairing hoof cracks in the horse: a review and a report of a new technique. Compend Cont Educ Pract Vet 1983;5:495-497.
- Moyer W, Sigafoos R. Preliminary experience and uses of composite hoof wall repair, in Proceedings. 37th Annual American Association of Equine Practitioners Convention 1991;681-686.
- Butler J. The repair of hoof cracks using fiberglass and screws, in Proceedings. 22nd Annual American Association of Equine Practitioners Convention 1976;235-237.
- Norman S, Personal communication, 2010.
- Kerckhaert Shoes, FPD, Shelbyville, KY 40066.
- Equilox Pink, Equilox International, Pine Island, MN 55963.
- Dremel, Dremel Tool Co., Emerson Electric, Racine, WI 53401.
- Tenderhoof Solutions, Morpeth, Ontario NOP 1XO, Canada.
- Keratex Medicated Hoof Putty, Brookeville, MD 208333.