A femoral head osteotomy (FHO) in a five-year-old cat with a hip fracture.Photo courtesy Phil Zeltzman Femoral head osteotomy (FHO) is a common surgery of the hip. When should it be recommended? When should it be avoided? Hip dysplasia The most common indication of FHO is likely hip dysplasia. The diagnosis can be presumed based on the patient’s age and breed, as well as pain on hip extension and a history of “bunny hopping.” We can’t work based on assumptions, so the suspicion should be confirmed with radiographs. Proper positioning, especially in a painful patient, requires relaxation and, therefore, sedation. A thorough workup should include X-rays of the hips and the stifles since many “hip dysplasia” patients are, in fact, suffering from a torn ACL. Michelle Powers, a board-certified surgeon in New Hampshire, showed that one-third of dogs referred to a surgeon for hip dysplasia, in fact, had a torn ACL.1 Almost half of the dogs in the study consisted of Labrador retrievers, German shepherds, and golden retrievers. Radiographs indeed showed (chronic) hip dysplasia in 94 percent of these dogs, but the dogs’ (acute) pain was actually in the stifle in one-third of patients. With hind leg lameness, it’s critical to perform a thorough orthopedic exam of all joints, and image both the hips and the knees. Remember, as the saying goes, “we don’t treat X-rays, we treat dogs.” From experience, it’s pretty safe to assume a dog with hind limb lameness has a stifle issue until proven otherwise. Other rule outs for hind limb lameness should include lumbo-sacral disease (“cauda equina” syndrome), degenerative myelopathy, prostatic disease, and panosteitis. Hip luxation A traumatically luxated hip can be repaired if the acetabulum is healthy. However, if the hip is dysplastic, repairing the luxation may not lead to good results. In that case, an FHO should be considered. Hip fracture “Hip fractures” include acetabular, as well as femoral head and neck fractures. Because of a variety of reasons (clinical, financial, practical), not all hip fractures can be repaired. In some well-selected patients, an FHO may be a reasonable compromise. Spontaneous femoral capital physeal fractures are an important sub-type of hip fractures. Young adult cats (older than one year of age, with an average age of almost two years) can have a specific type of spontaneous hip fracture. Importantly, it occurs with no trauma. It is bilateral in one-third of cats. It most often happens in heavy males that were neutered before the age of six months. After the fracture, the femoral neck is subject to lysis, leading to a typical “apple core” lesion. The severity of femoral neck osteolysis increases with the duration of the injury. It’s theorized this occurs because the growth plates are not fully closed at the time of sterilization. Early neutering might cause delayed physeal closure, which often leads to tall, heavy cats. When there are no degenerative joint changes, acute slipped femoral capital physis can be treated with pins placed at diverging angles, or via an FHO. The main risk with using pins is migration, especially in soft bone. This would require a second surgery to remove the pins. Some surgeons choose an FHO to avoid this risk altogether. Legg-Perthes disease Legg-Calve-Perthes disease, or avascular/aseptic necrosis of the femoral head, is a poorly understood condition in which the head of the femur lacks vascular supply and degenerates. It is most commonly found in immature small and toy breeds (four to 12 months old). It can occasionally be found in larger breeds, such as cocker spaniels and shelties. Again, the diagnosis relies on pain on hip extension and sedated radiographs. It is important to remember an FHO, like a total hip replacement, is a salvage procedure. This means it can be done at any age. Reasons to perform an FHO include clinical factors, limited finances, and practical reasons (know-how of the referring veterinarian, equipment factors, availability of a board-certified surgeon nearby, etc.). The main limiting factor of an FHO is the outcome is more difficult to predict as the patient’s weight increases. Every surgeon has a different weight limit in mind (30, 60, 90 lbs), above which a total hip replacement (THR) is strongly recommended. (See “Other hip surgery options,” on previous page.) When a client cannot afford a THR in a heavy patient, a serious discussion about expectations is critically important to avoid surprises. The key to a successful FHO, besides patient selection and proper surgical technique, is the postop physical therapy (PT). Inactivity, or inability of the owner to perform proper PT, predictably leads to decreased range of motion and poor functional results. When pet owners are not able to perform PT, they should be referred to a certified rehabilitation therapist to improve the outcome. Ultimately, an FHO is a great option in the right hands and for the right patient. OTHER HIP SURGERY OPTIONS There are three other options for hip surgery, depending on the patient’s needs. Triple pelvic osteotomy. A triple pelvic osteotomy (TPO) is typically performed in young dogs with poor coverage of the femoral head. Surgery entails freeing up the acetabulum by making a cut in the pubis, the ischium and the ilium, hence the word “triple.” The acetabulum is rotated ventro-laterally to better cover the femoral head. The ilial cut is then stabilized with a bone plate and screws. Limitations of a TPO include severe subluxation of the hip and degenerative joint disease (DJD). Juvenile pubic symphysiodesis. The juvenile pubic symphysiodesis (JPS) involves destroying the growth plate of the pubis with electrocautery in order to stop the growth of the ventral aspect of the pelvis. As the dorsal portion of the pelvis continues to grow, both acetabuli progressively rotate ventro-laterally and slowly improve the coverage of both femoral heads. The end result is more stable hips that have less risk of DJD. In essence, the JPS has the same effect as bilateral TPOs, except it only requires one procedure. In addition, it is much less invasive and costly. The best timing for JPS is when patients are around four months old. Studies show waiting just one month beyond that age significantly decreases the effectiveness of JPS. Therefore, the main challenge is early screening of puppies at risk for hip dysplasia (German shepherds, Labradors, golden retrievers, etc.). Total hip replacement. During a total hip replacement (THR), the acetabulum is replaced with a plastic cup, and the femoral head is replaced by a metal ball attached to a metal femoral stem. THR is often considered the “Cadillac” treatment, as it provides a pristine hip to a previously arthritic, painful dog. For decades, the gold standard has been “cemented” systems. More and more surgeons progressively switched to a “noncemented” system, which relies on bone ingrowth into the implants. The various systems available can accommodate patients of almost any size, as there are now implants made for small dogs. The limiting factor of a THR is financial, which is justified by the cost of training, personnel, equipment, and implants. Phil Zeltzman, DVM, DACVS, CVJ, Fear Free Certified, is a board-certified veterinary surgeon and serial entrepreneur whose traveling surgery practice takes him all over Eastern Pennsylvania and Western New Jersey. He also is cofounder of Veterinary Financial Summit, an online community and conference dedicated to personal and practice finance (www.VetFinancialSummit.com). A.J. Debiasse, a technician in Blairstown, N.J., contributed to this article. Reference 1 M. Powers et al. “Prevalence of cranial cruciate ligament rupture in a population of dogs with lameness previously attributed to hip dysplasia: 369 cases (1994–2003).” JAVMA 2005; Oct., Vol. 227, No. 7, pp 1109-1111.
