Deformed X
and O limbs in rabbits
Esther van Praag Ph.D.
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Rabbits
may suffer from deformations of limbs when they are seen from the front or
the side: ·
Acquired
or congenital angular deformation at the level of the limb joint; ·
Congenital
deformation and bowing of the long bones of limbs; ·
Laxity or hypermobility of
ligaments. The
etiopathology of angular limb deformation is not well documented in rabbits.
In other animals, including foals, there are several bone or muscle related
causes, while laxity (mobility) of the peri-articular structures and
ossification retardation of bones have often a congenital origin. Growth of
bones is influenced by a number of factors: genetic, hormonal
(hypothyroidism), metabolic, but also vascular or electric and the failure of
one of these can lead to an abnormal bone growth and elongation of the longer
bones of the limbs. In young growing animals, an asymmetrical mechanical
pressure (e.g. the weight of the body or slippery floor, when the doe keeps
removing all the hay and other material from the nest) on growing cartilages
of long bones of the extremities can lead to angular deformation of the
joints with inward or outward deviation of the limb. In this case, the
deformity corrects itself naturally once the rabbit kit is placed in an
environment without slippery floor. A wrong diet of the doe at the end of
gestation (nutritive deficiency, imbalanced food, intoxication) can also lead
to limb deformation in her offspring. A
hereditary origin related to a single autosomal recessive gene appears to
cause bending of the upper limbs in some rabbit breeds: Beveren rabbits,
Belgian giants, French Silver and Dutch rabbits. The curvature of the limbs
appears at the age of 2 or 3 weeks. The upper limbs start to bend inwards,
while the paws are deviated laterally. The deformity reaches a maximal stage
at the age of 2 to 3 months. Even if the cartilage problem corrects itself
naturally at the age of 2.5 months, the deformity is definitive with inward
curvature of the ulna and radius (forearm bones, between the elbow and the
front paw). Angular joint
deformation
Angular
joint deformities of the upper limbs are sometimes observed in rabbits. They
are present before or soon after birth, before the closure of the osseous
growth plate. Lateral deviations frequently observed in rabbits include: ·
Lateral,
valgus misalignment or X limb,
with lateral (outward) deviation of the limb distal to, or below the point of
deformity:
·
Medial, in varus or in O, with a lateral inward deviation of the limb distal
to, or below the point of deformity:
Osteo-articular deformities affect upper limbs more than
lower limbs in rabbits. Exceptionally, an upper may be affected by a double
deformity at the ulnar and carpal joints. It is usually present at birth or
it appears later during growth, at the age of 2 or 3 weeks. Finally, angular
deformities can be accompanied by the rotation of the limb. Faulty limb conformation
can have numerous causes
Ligament
laxity. It is usually present at the
newborn’s birth and does not cause pain, but may also appear later in the
life of a rabbit. Morphology of the affected limbs appears normal on X-rays.
This deformity disappears spontaneously in most foals. Rabbits suffering from
this problem may develop juvenile arthritis accompanied by joint pain. In older
animals, deformity of the limbs in the sagittal plane can relate to
osteoarthritis. This syndrome is irreversible and painful, and the rabbit
should be administrated analgesics. Treatment with glucosamine and chondroitin may also
help.
Cuboid
bones hypoplasia. The
cuboid bone is part of the tarsal bones. It ossifies rapidly after birth.
Thyroid dysfunction (hypothyroidism) is responsible for the lack of osseous
development in foals, and hinders a normal ossification of the bones. A
spontaneous correction is possible when cartilage is still immature. After
that period, the deformity becomes permanent. The deformed joint will ossify,
degenerate and bone hypoplasia is irreversible. This deformity increases the
risks of partial luxation or fracture of the limb. Deformation
of long bones. Growth
inequality between the medial and lateral parts of long bones leads to an
angular deformation of the limb, commonly in valgus or X. This deformity is
present at birth, but may also appear later, during the growing phase of the
young rabbit. In foals, positioning in the uterus is suspected to cause an
abnormal compression of the growing cartilage during gestation. Le caused
trauma lead to unequal growth of long bones. This type of deformity does not
cause pain. Preterm offspring and overweight. Joint deformation is also observed in animals that
are born prematurely, before calcification of bones takes place. Weight of
the newborn can lead to angular deformity of joints. A similar problem is
observed with single born rabbit kits. They have a bigger size at birth, with
a strong bone structure and a rapid growth as they are well-fed by the does.
Clinical signs
A rabbit
suffering from deformed X or O-legs have a normal appetite and are in good
health. The sole clinical signs are an abnormal or a difficult gait. Clinical examination
A rabbit
that presents articular deformities is examined from the front, from the side
and from the back, at rest and during exercise on a non-slippery surface.
Palpation of the limb helps evaluate the presence of physical deformities, of
pain, swelling, etc. The radiographic evaluation of limb bones and joints
allows identifying the origin: primary congenital cause or secondary to an
osteo-articular trauma. The front view must be perfect in order to detect
lateral joint deformities. In the case of sagittal deformation, front and
side views are necessary. Treatment
If the
problem is discovered at a young age, a splint or rigid bandaging of the affected
limb may help correct the deformation. Movement and exercised possibilities
of the young rabbit should not be limited, in order to help develop muscles
in the limbs. There is
no treatment for deformed limbs in rabbits. Amputation of the affected limbs
may be helpful when it hinders movement and exercise of the rabbits or when
it causes pain. When the curvature and deformation of the limbs is severe,
euthanasia should be considered. Indeed, secondary complications of the skin
may appear in region that supports the weight of the body. Ulceration of the
skin (very painful) and pododermatitis are often observed. Acknowledgements
Many thanks
are due to Michel Gruaz (Switzerland)
and to Stefan Röthlisberger (Switzerland) for their gracious permission
to use their pictures in this article. Literature
references
Arendar GM, Milch RA.
Splay-leg - a recessively inherited form of femoral neck anteversion, femoral
shaft torsion and subluxation of the hip in the laboratory lop rabbit: its
possible relationship to factors involved in so-called "congenital
dislocation" of the hip. Clin Orthop. 1966;44:221-9. Barichard, T. Etude rétrospective du traitement des déviations angulaires des poulains par des ondes de choc extracorporelles : 92 déviations. Thèse de médecine vétérinaire. 2012. Wilson DG. Les déformations angulaires des membres chez le poulain: prise en
charge et conséquences de l’angulation sur la performance athlétique. la
médecine vétérinaire des grands animaux. Rondes cliniques. Vol 6, 2006. |
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