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Total Hip Replacement
in the Dog
The hip joint is the only joint in the dog that can be
replaced in its entirety. The main indication for
performing a total hip replacement is hip dysplasia and
the associated secondary osteoarthritis that ensues.
However not all dogs with hip dysplasia require hip
replacement. When assessing dogs for total hip replacement
the following criteria should be met
- An obvious hind limb lameness
- Pain on the manipulation of the hip joint
- Failure to respond to conservative modes of therapy
- No other orthopaedic disease e.g. elbow
osteoarthritis
- No evidence of neurological disease
- No skin disease
- No evidence of a septic focus anywhere in the dog
- Skeletally mature (i.e. fully grown)
- Owners who are willing to accept the inherent risks
associated with hip replacement
- Owners who are willing to accept the financial
burden of this procedure and the possible
complications.
Hip dysplasia is a common condition in the large dog
population. This developmental disorder may have no
adverse effects on individual dogs. However there are two
reasons why dogs may suffer from problems with this
condition.
- Dogs are not born with hip dysplasia it occurs as
the puppy grows. Initial problems with regard to hip
development may be picked up as young as 4-5 months of
age. The initial changes that occur are in the soft
tissue attachments that hold the hip together. These
soft tissues stretch and become lax allowing the
femoral head to partially escape from the acetabulum (subluxation)
. As a consequence of this the acetabulum will become
shallower and the femoral head will change in shape,
which compounds the whole problem, thus young dogs may
suffer pain, discomfort and lameness as a result
of this pathology. However if these young dogs are
managed conservatively 75% of them will have dramatic
improvements in their hip stability at 18-24 months of
age due to thickening of the joint capsule.
These hips are not normal but functionally dogs will
be able to exercise to an acceptable "pet
level" of activity. The remaining 25% will either
require ongoing conservative/ medical therapy or may
require surgery to be performed.
- As already mentioned dogs with hip dysplasia will
develop a degree of osteoarthritis. The main reason
why dogs may become lame as a result of osteoarthritis
is because of progress loss of the cartilage surface
of the joint. This may be managed conservatively or
surgically.
There are other indications for hip replacement but
these are relatively rare e.g. treatment of fractures of
the femoral head and neck, healed fractures of the
acetabulum, hip dislocation where the original hip
conformation was poor and tumors of the femoral neck.
Currently there are several "hip systems"
available for use in the dog (Richards 2, Biomedtrix,
Biomechanique, Perot, Howmedica cement less system and the
Zurich hip system). In the UK the most commonly used hip
system is the Biomedtrix system; this is a modular system
where the implants are held in place with bone cement.
Essentially there are 3 components to this system: a
high-density polyethylene cup, a metallic femoral stem and
femoral head. This system is modular which means that the
size of the implants can be tailored to the individual
needs of the patient.
If implantation and the subsequent convalesces from the
hip replacement goes well then we can expect the
"new" hip to function to 95% of a total normal
hip. However there are several major complications that
can occur:
- Bacterial infection (acute surgically induced
infection and delayed infection as a result of a
distant focus of infection which has seeded into the
hip replacement via the blood stream)
- Hip dislocation (this can occur in the initial
recovery phase of 4-6 weeks)
- Femoral shaft fracture
- Aseptic loosening of the implants
These complications can result in revision surgery
being necessary and potentially removal of the hip
replacement. One or more of these complications will
affect 10-15% of dogs that undergo hip replacement.
Hip replacement in the dog can be a very rewarding
surgery for everyone concerned however it can also be
extremely frustrating and costly exercise.
Article kindly written by Mr. D.G. Thomson BVMS MRCVS
CertVR CertSAS. David White Veterinary Specialists.
Hertfordshire.
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Joint
Replacement
Here Mr D G Thomson BVMS, MRCVS,
CertVR, CertSAS takes us through the hip replacement procedure. |