Inferior Check Ligament Desmotomy as a
Treatment of Flexural Deformity or Chronic Unilateral Laminitis in
the Adult Horse
Inferior check ligament desmotomy is frequently performed on foals
(ages 2-8 months) for flexural deformity involving the distal
interphalangeal joint (1). There are very few reports in the
literature of this procedure being performed on adult horses (2),
but some reports indicate that poor results are achieved in adults
(3,4). Flexural deformity, when seen in the young racing
thoroughbred, can lead to chronic intermittent lameness resulting
in poor performance. This deformity may be the result of the
animal not being treated successfully as a foal and the condition
worsening due to the rigors of training. Flexural deformity may
also be acquired secondary to chronic excessive trimming of a
steeply angled hoof in an attempt to balance the feet. If the
flexural deformity is severe, it can lead to unilateral laminitis
secondary to constant trauma to the lamina of the toe area,
resulting in marked rotation of the third phalanx. Unilateral
laminitis could also be present secondary to other etiologies. In
all cases, the affected foot shows an increased hoof angle (> 60
degrees), a broken forward hoof -pastern axis, a prominent
coronary band and a long heel with a relatively short toe, i.e. a
club foot. Pain is thought to result from the increased angulation
of the third phalanx and the thin flattened sole which leads to
chronic foot bruising.
The purpose of this paper is to describe the use of inferior check
ligament desmotomy as a successful treatment of flexural
deformities (11 cases) and, coupled with additional therapy, as a
treatment for unilateral chronic laminitis (4 cases) in adult
horses. This paper also outlines the need for a close working
relationship with a farrier for a successful outcome to these
Materials and Methods:.
Fifteen horses 2 years old or older had inferior check ligament
desmotomy performed as a treatment for flexural deformity (11
horses) or chronic unilateral laminitis (4 horses). The
differential diagnosis of a flexural deformity or chronic
laminitis was determined from the history, radiographic evaluation
and the gross appearance of the solar surface of the foot.
All horses included in this study had a history of low grade
lameness and poor performance, especially when training was
intensified. When presented, all horses showed a shortness of
stride on the affected limb when trotted in a straight line and a
grade II (I-V) lameness when trotted in a tight circle with the
affected limb on the inside. The affected foot showed a steep
angle, the hoof pastern axis was broken forward, there was a
bending of the horn tubules in the anterior hoof wall ("dish") and
the sole was flat. The consistency of the hoof wall in the region
of the toe was poor. Hoof testers revealed discomfort when applied
to the solar area of the toe. Intra-articular anesthesia of the
distal interphalangeal (DIP) joint did not improve the lameness.
Posterior digital nerve block improved but did not eliminate the
lameness. Abaxial nerve block eliminated the lameness in all
cases, thereby localizing the discomfort to the dorsal portion of
the foot. Radiographs of both the normal and affected foot were
taken in all cases and were used to determine radiographic changes
in the DIP joint, the coffin bone, the amount of sole depth
present and the position of the third phalanx within the hoof
capsule. Horses that were judged to have marked rotation of the
third phalanx (>10 degree rotation) and minimal or no sole depth
were diagnosed with laminitis (5). Prior to surgery, the affected
foot was trimmed using the radiographs as a guide in order to
realign the third phalanx. The horse was then shod with an egg bar
shoe with a three quarter inch toe extension.
In the cases with chronic laminitis, the heel area of the affected
foot was also trimmed according to the radiographs. In order to
increase the sole depth, the affected foot was elevated 16 degrees
by attaching a stack of wedge pads. The horse was confined to a
stall four to six weeks until the sole depth reached 1 cm as
determined by serial radiographs (6) The wedges were then removed,
the heel was trimmed as necessary, the horse was shod as described
previously and three wedges (12 degrees total) were taped to the
shoe prior to surgery.
All horses were placed under general anesthesia in lateral
recumbency with the affected limb up. The surgery was performed as
described elsewhere(2) with a few variations. Aftercare consisted
of twenty minutes of hand walking daily for the first ten days.
Anti-inflammatory agents were used during this time. Bandage
changes were done only as necessary and bandages were maintained
for six weeks post operatively. After ten days, sutures were
removed and walking was increased to twice daily for the next two
weeks. The toe extension was then removed and the horse was turned
out in a small paddock. The horseshoes were reset at three week
intervals. Horses returned to training in 90 days.
Chronic laminitis cases were walked immediately following surgery
with the wedge pads taped to the shoe. The wedges were removed
gradually, one at a time, during the first ten days. The remainder
of the convalescent period was identical to that outlined
previously except that these horses were given an additional month
of turn-out before training was resumed.
Seventeen inferior check ligament desmotomies were performed on
fifteen horses (Table 1, below). The median age of the horses was
three years. Eleven horses were thoroughbreds and four were
Hanovarians. One horse died of colic post-operatively. All horses
were examined monthly for six months; thereafter, long-term
follow-up was through telephone communication with the trainer.
Success in this study was defined using three criteria. Firstly,
all survivors became sound and resumed training. Secondly, over
50% of the horses improved in performance (won or placed in races
or shows) and the remainder of the horses continued in training
with no subsequent lameness. Thirdly, the surgery and farrier care
allowed the third phalanx to be realigned within the hoof capsule
and the gross appearance of the affected hoof improved to within
75% of the normal foot. The cosmetic appearance of the operated
leg was acceptable with a small fibrous thickening present.
In cases of flexural deformity of the DIP joint, there is a
functional shortening of the deep digital flexor musculo-tendonous
unit. This shortening is responsible for the abnormal changes that
occur within the foot. The increased tension of the flexor tendon
causes the DIP joint to be constantly flexed, which causes a
change in angulation of the third phalanx and increased weight
bearing on the apex of the bone instead of the entire solar
surface. This abnormal weight bearing leads to chronic foot
bruising and lameness. All flexural deformities appear to have
some radiographic signs of rotation but this may be due in part to
the distortion of the hoof capsule, the bending of the horn
tubules of the anterior hoof wall and the flat thin sole resulting
from the increased pressure on the apex of the third phalanx.
Various forms of corrective trimming and shoeing have been used to
correct this deformity but in the authors' experience they have
not been as successful in the older animal. The check ligament
surgery coupled with therapeutic trimming appears to be the
treatment of choice in the older animal. Inferior check ligament
desmotomy creates a lengthening of the deep flexor tendon allowing
the hoof angle to be lowered. This brings the hoof-pastern axis
into normal alignment and allows the necessary changes to be made
within the hoof capsule.
We believe that the farrier input in this study was as important
as the surgery. The feet were trimmed and shod before surgery so
that the operated limb did not have to be handled post
operatively, the bandage was not distorted and the horse could be
hand-walked immediately. The foot was trimmed using the
radiographs for guidance. The emphasis of the trimming was placed
on lowering the heel area, beginning at the apex of the frog or
the widest section of the foot palmed to the heel. The toe was
shortened by removing the hoof wall from the dorsal surface,
trying to remove as much of the "dish" as possible. The toe area
on the ground surface of the foot was left untouched. This method
of trimming was continued on the subsequent resets. It is our
opinion that the gross normal appearance of the hoof capsule is
attained during the post operative period. A toe extension was
used on all cases to force the heel down and delay breakover,
causing the flexor tendon to stretch just before breakover. This
appears to prevent premature reattachment of the severed ends of
the check ligament. An egg bar shoe, extending beyond the heels
was used in all cases. If the flexural deformity is severe, the
angulation of the third phalanx will cause disruption of the
lamina leading to marked rotation. The rotation causes these
horses to have minimal or no sole depth. Various methods of
corrective shoeing revolving around frog support have been
employed for chronic laminitis with inconsistent results (7). One
problem often encountered with shoeing laminitic horses is the
re-establishment of a normal sole depth with a good consistency.
Elevating the heels 16 degrees prior to surgery decreases tension
on the deep flexor tendon allowing the re-establishment of a
normal sole depth. The surgery, through functional lengthening of
the musculo-tendonous unit, then allows the third phalanx to be
realigned within the hoof capsule. With the heels being elevated
prior to surgery, it was believed that there could be additional
shortening of the flexor tendon, this being the reason the foot
was again elevated prior to surgery and the wedge pads removed
gradually afterwards. It also gave a clear indication of the
ability of the musculo-tendonous unit to stretch following
Controversy surrounds the long term athletic performance of adult
horses following inferior check ligament desmotomy. The horses in
this study, although a small population, have remained sound,
their level of performance has increased and they have withstood
the rigors of training and jumping. These data therefore
demonstrate the benefit of inferior check ligament desmotomy to
treat flexural deformity and chronic laminitis in the adult horse.
It has also been shown that, through corrective trimming, the hoof
angle can be permanently changed restoring a more normal anatomic
and physiologic function. Finally, we were encouraged by the
combined therapy in the laminitic horses which gave us consistent
results in a limited number of cases.
Stephen E. O'Grady, DVM, MRCVS
Dr. Stephen E. O'Grady is an equine
practitioner and farrier practicing in the Northern Virginia area.
He operates the Northern Virginia Equine Podiatry Center near
Middleburg Virginia. He is also a member of the Farrier's Liaison
Committee of the American Association of Equine Practitioners.
||Flexure Deformity (FD)
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