Limb fracture
and pinning of the broken bone
Esther van Praag Ph.D.
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Rabbits are preyed-on animals,
which must be able to flee and run rapidly. Their limbs are therefore
powerful, while their skeleton is light, and comprises only 7 to 8% of the
body weight. In comparison, the skeleton of a cat makes up about 12 to 13% of
the body weight. Spine and limbs are thus more prone to fracture in rabbits,
as compared to other animals.
Back injuries are often observed
at the lumbar level. Additional health problems, like osteoporosis and/or low
calcium diet can render the bones brittle and fracture can happen when a
rabbit panics, is improperly restrained or picked up, or dropped. The result
is often paralysis of the lower limbs, accompanied by incontinence. Fracture of the tibia is another
danger in rabbits. They are often caused by improper handling, or caging,
when a limb becomes trapped in improperly sized wire mesh. Fractures of limbs
are often comminuted (more than two broken pieces of bone). Fractures in
lower limbs (below elbow) are often open, due to the minimal presence of soft
tissue. They are often difficult to treat, and need to be mended with
patience, in order to avoid further tearing of the skin. The wound must be
sterilized, and the fractured bone pinned or splinted if the lower part of
the limb is affected. Osteomyelitis (bone infection) and/or gas gangrene can
quickly set, and should be treated appropriately with broad-spectrum
antibiotics. It is furthermore advisable to do a bacterial culture, in order
to determine which ones (aerobic - anaerobic) have possibly contaminated the
wound. Diagnosis
and first aid A rabbit that has a broken limb
does not necessitate emergency medical care, unless there is shock, bleeding,
respiratory or cardiovascular problems. Immediate pain medication is
recommended, in order to comfort the rabbit and keep him/her quiet. X-rays and a complete physical
and neurological examination must be done in order to determine the damage,
further treatment and prognosis of wound healing.
Use of
intramedullary fixation The technique of intramedullary
pinning is of common use in small animals and is relatively simple. It
requires nevertheless patience and technical expertise, associated to a good
understanding of biomechanics and healing of fractured bones. Intramedullary fixation is
optimal for use in rabbits as the implant will help give bear the weight of
the body, although healing-time may be delayed. Steinmann
pins, Kirschner wires and/or cerclage wire is commonly used in
rabbits. Smooth intramedullary pins are preferred over partially or fully
threaded pins. In dwarf or small rabbit breeds, the pin can be replaced by a
(hypodermic) needle. The pin or needle must, however, imperatively take
60 to 70% of the medullar center.
The Steinmann pin is usually
inserted by hand or by means of a Jacobs chuck. It can be inserted either at
the fracture site (retrograde insertion) or at the end of the bone
(normograde insertion) and be driven through the fracture site. The
protruding end of the pin is cut, in order to avoid damage of the skin,
bacterial infection, or interference with the joint, unless an external
skeleton fixation system is used, in which case the pin should be left
protruding.
Open fracture repair techniques
necessitate appropriate sterile working conditions, accompanied by profuse
cleaning of the surgery site. According to the location of the
fracture, padded bandages, auto-adhesive bandage or casts can be used.
Post-surgical
treatment Post-surgical care includes regular examination of
the mended fracture for bacterial infection, loosening of the pin or needle,
and fracture healing. The removal of the pin is based on X-ray pictures. It
is usually around 6 weeks post-surgery. In rare cases, where the health of
the rabbit is affected, the pin can be left in the bone.
Pain is a signal
that leads to a decreased use of the body part, in order to avoid further
damage. It is deleterious, as lack of use and spasms lead to weakness, loss
of muscle tone, and irreversible damage. Pain medication is thus very
important. A good choice of analgesics is available for orthopedic pain: • Opioids: -
Butorphanol; -
Buprenorphine. • NSAIDs: -
Flunixin; -
Meloxicam; -
Aspirin. See “Analgesics drugs for
use in rabbits” for dosages. Pain will moreover cause a loss of appetite and
decreased water intake. It is thus important to keep the rabbit well
hydrated. Acknowledgement All my
gratitude to Sandy Minshull and Akira Yamanouchi (Veterinary Exotic
Information Network, http://vein.ne.jp/), for the permission to use their
pictures. Thanks also to 11 year old Herman. Further
information Flecknell P. BSAVA Manual of Rabbit Medicine and
Surgery, UK: British Small Animal Veterinary Association; 2000. Hillyer E.V. and Quesenberry K.E. Ferrets,
Rabbits, and Rodents: Clinical Medicine and Surgery, New York: Saunders;
1997. Manning P.J., Ringler D.H., Newcomer C.E. The
Biology of the Laboratory Rabbit, New York: Academic Press; 1994. Richardson V., Rabbits: Health, Husbandry and
Disease. Blackwell
Science; 2000. |
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