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The greater trochanter is a bony prominence at the top of the femur (thigh bone), making up part of the hip joint. It provides a place of attachment for the strong muscles group of the buttock area, and correct orientation is important for pain free movement of the hip.
In humans, there is a developmental condition of the hip affecting young people, whereby the greater trochanter is malpositioned. This leads to pain, especially when the leg is abducted (moved in a plane away from the body.) However, this is not a well-recognized condition in cats, which means surgical correction is rarely indicated.
Diagnosis and correctly identifying the need for greater trochanter translocation is challenging, and most likely will be made after referral to a veterinary orthopedic specialist.
The cat is given a general anesthetic and the fur clipped from the rear quarter of the affected hip. Working under strict aseptic conditions, the surgeon dissects down onto the hip joint in order to expose the greater trochanter. Depending on how muscular the cat is, this may involve sectioning tendons in order to deflect a muscle group to increase visibility.
Using detailed analysis of preoperative radiographs, the surgeon carefully plans the angles of the cuts required to remove a wedge of bone from the greater trochanter. Once removed, the greater trochanter lies at a different angle relative to the femur and femoral head. Once the surgeon is happy with the positioning, a pin and wires are used to fix it in the new position.
Transected tendons are repaired, and the skin incision closed with sutures.
The success of the outcome depends on careful pre-op planning to create the correct angulation of the greater trochanter. In people, the biggest reason for a poor result was ongoing arthritis within the hip joint, which negated the improved mobility of moving the greater trochanter.
Initially, the strength of the newly positioned greater trochanter relies on metal implants. Thus the cat must not exert itself until a bony union has formed as demonstrable on follow-up radiographs. This union may take from 4 to 12 weeks to occur, depending on the cat's age and health.
As with any surgery, there is a risk of infection, wound breakdown, or loosening of an implant.
This is a rarely performed procedure. Correctly diagnosing the problem is likely to be done by a specialist. Specialist consultations are upwards of $200. Sophisticated imaging such as a CT scan is advisable for preoperative planning, which can cost $800 to $1,500. The surgery itself at the hands of a specialist may cost $2,000 to $3,000.
Cases of greater trochanter translocation in the cat are few and far between. In part, this is due to the rarity of the underlying condition, the difficulty reaching a diagnosis, and the anatomy of the cat, which makes abduction of the limb an unusual movement.
Hereditary diseases of the feline hip are not as common as in the dog and mostly affect the femoral head rather than the greater trochanter. However, if hereditary hip disease is identified then it is best not to breed from that cat.
In addition, care should be taken that excessive force or trauma occurs to kittens and young cat, especially whilst their bones are still growing. Damage to the blood supply to the femoral head could result in problematic malformations.
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