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Femoral Head Ostectomy (FHO)

Mischief's Story and Femoral Head Ostectomy (FHO) Surgery in Cats

“Mischief” was a lovely, petite, three-year-old Tortoiseshell cat. She was named well, as she was always getting into all sorts of mischief and scrapes. Mischief did live near a busy road, and she did tend to wander off at night. With the shorter winter days and dark nights, this meant that she was at risk of accidents and injury. Sadly, she was rushed into the surgery one evening, as she had been in road accident.  

Mischief was admitted immediately for a full examination and to stabilise her after the shock of her accident. When she was stabilised, her X-Rays revealed that she had a fractured Right hind femur bone. The fracture site was situated high up in her Right thigh bone, and after further appraisal by the orthopaedic surgeon, a surgical procedure called Femoral Head Ostectomy was advised. 

An FHO, or femoral head ostectomy, is a surgical procedure that aims to restore pain-free mobility to a diseased or damaged hip by removing the damaged head and neck of the femur, the thighbone. 

The normal hip is a ball-and-socket joint. The acetabulum, which is a part of the pelvis, composes the socket “cup” of the joint. The head of the femur, the thighbone, is the “ball” that fits within this socket. The head of the femur should fit comfortably and securely within the acetabulum, allowing the hip to move freely in all directions. 

If the hip becomes damaged or diseased, this mobility can be affected. If the acetabulum and the head of the femur do not fit together properly, this can influence the degree of movement that the joint can achieve and can lead to chronic hip pain and lameness. 

A Femoral Head Ostectomy Surgery restores mobility to the hip by removing the “head” of the femur. This removes the “ball” of the ball-and-socket joint, leaving just an empty socket. The muscles of the leg will initially hold the femur in place, and, over time, a scar tissue will form between the acetabulum of the Hip and the femur to provide cushioning that is referred to as a 'false joint'. Although this joint is anatomically very different from a normal hip joint, it provides a pain-free mobility in most patients. 

This procedure is commonly recommended for cats with Hip fractures, Hip luxation and dislocations, severe osteoarthritic Hip joint changes, or degenerative necrosis of the Hip “head”. The FHO surgery works well in cats who are at a healthy fit weight. Active, fit cats experience better results than less-active cats, as the muscle mass that has been built up through activity helps to stabilize the joint, allowing the cat to regain pain-free mobility more quickly than inactive cats. Inactive cats have less muscle mass around the joint, making the joint less stable post-operatively and leading to longer recovery times. 

The primary goal of FHO surgery is to remove any bone-on-bone contact, restoring comfort and a pain-free mobility.  

Confinement within the home, allowing a degree of mobility to encourage some gentle movement, is advised for the first few weeks after surgery.  To attain this a “Hospitalisation” area is advised at home, confining your cat to a small, quiet room during this period, and removing any potential temptations to run or jump.  

After this healing phase the focus shifts to rebuilding the hindlimbs muscle mass and strength. Keeping your cat confined safely to the house but mobile, will help keep the scar tissue within the false joint from forming too tightly, allowing your cat to remain flexible. Physiotherapy sessions aid the recovery process tremendously. Most cats will show signs of complete recovery approximately six weeks post-operatively and at this point, they can resume their regular activities.  

Healing may be more rapid in cats that had normal function up until shortly before the procedure, for example, in the case of a cat that had a sudden, traumatic injury to the hip, and will be slower in cats with longstanding, chronic issues because these chronic issues often lead to muscle wasting, which takes time to resolve. 

Most cats recover well after FHO surgery and regain essentially normal function of the affected leg. Although the leg may have a slightly decreased range of motion and shortened limb length after surgery, these impacts are typically minimal and do not impact the cat’s quality of life. 

“Mischief” was a good candidate for this surgery as she was young, fit, and active and her damaged limb was well muscled before the accident. She did have physiotherapy after her healing phase to improve her mobility, and she made a wonderful recovery after her operation and her rehabilitation period. 

Mischief's owners did keep her indoors in the dark winter’s nights now, to try to ensure that she didn’t get into any further trouble! 

Alison Laurie-Chalmers
Senior Consultant
Crown Vets

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