Disabling conditions of the hip joint are commonly seen in our canine patients. A variety of conditions exist that produce or lead to severe pain and muscle mass loss of the rear limb. Hip dysplasia, coxofemoral luxation, capital physeal fracture (Salter I-V types), femoral neck fracture, pelvic and acetabular fractures, and avascular necrosis of the femoral head and neck (Legg-Calve-Perthes disease). Trauma is the most common cause of femoral head aseptic necrosis. An alteration in blood supply to the femoral head is the cause of the vascular necrosis. These conditions generally lead to severe degenerative changes in the hip joint. These conditions are all painful and lead to varying degrees of loss of normal range of motion, loss of muscle mass, and decreased quality of life.

The decision to intervene with surgery is based on the amount of pain, discomfort, and lameness exhibited by the dog. Typically the patient has been refractory to NSAID therapy or has not returned to an acceptable level of performance. Other orthopedic as well as neurologic diseases should be considered and ruled-out prior to surgery of the hip joint. Radiographs of the pelvis should confirm that the hip is affected and that there are no neoplastic changes present. The veterinarian should not wait until there is severe pain and loss of muscle mass before considering surgery.

The decision to intervene with surgery is based on the amount of pain, discomfort, and lameness exhibited by the dog. Typically the patient has been refractory to NSAID therapy or has not returned to an acceptable level of performance. Other orthopedic as well as neurologic diseases should be considered and ruled-out prior to surgery of the hip joint. Radiographs of the pelvis should confirm that the hip is affected and that there are no neoplastic changes present. The veterinarian should not wait until there is severe pain and loss of muscle mass before considering surgery.

Femoral head and neck ostectomy is a form of excision arthroplasty and is a common surgical procedure in small breed dogs. It is used as a salvage method if surgical intervention for the above mentioned maladies of the hip joint is required. By removing the articulating portion of the hip joint, pain is relieved. Postoperatively, a “pseudo-arthrosis” develops, composed of dense fibrous connective tissue, lined by a synovial membrane. Unfortunately, there is a lack of good, objective (ie based on force-plate analysis) clinical studies that evaluate the long term outcome of this surgery. Body weight has been reported to be the most important factor to affect outcome. 1 Dogs weighing less than 17 kg have good to excellent results, and larger dogs demonstrate less consistent outcomes. Dogs will typically take 6-8 months to recover and exhibit inadequate muscle mass. The limb will also lack normal range of motion, and there will be dorsal displacement and limb shortening.

A poor outcome with the femoral head and neck ostectomy (FHO) is normally attributed to “bone-to-bone” contact. For this reason a variety of muscle interpositional techniques have been developed. To date none of these techniques have been proven to improve the clinical outcome of this surgery. The outcome of this surgery in small dogs is unpredictable. It is not uncommon for these small breed dogs to be nonweightbearing for weeks after this surgery. Clinically, these dogs are reported to be doing well. However, when they are objectively evaluated for muscle mass and range of motion, months after the surgery, the results are not encouraging. Typically they have not regained normal muscle mass, have poor range of motion, and are painful with manipulation.

Until recently, total hip replacement has been limited to large breed dogs. They have been successfully performed in dogs since 1974, and have enjoyed excellent results. This surgery has shown superior results when compared to excision arthroplasty. Greater than 90% of patients receiving a total hip return to normal function following the surgery. Until recently, total hip replacement was unavailable in the small breed dog due to the lack of smaller implants. This is no longer the case, with the advent of several small implant sizes that allow total hip replacement in a dog as small as 7-8 lbs of body weight. Miami Veterinary Specialists is the first veterinary hospital in Florida to have performed a total hip replacement in a Yorkshire terrier. The results to date have been excellent. Normal weightbearing was achieved several days postoperatively, in a dog that was lame for several months prior to the surgery. Four weeks postoperatively, there was no discernable difference between the two legs. These clinical results were infinitely better than any we could have expected with excision arthroplasty. Dr. Liska, a surgeon in Texas, will be presenting his clinical experience with these cases at the ACVS conference this fall. Total hip replacement has been the gold standard in the treatment of degenerative conditions of the hip joint in large breed dogs for over 30 years. Now with the availability of smaller size implants, smaller breed dogs can enjoy the same benefits and lead a more improved quality of life.

1. D. Slatter. Textbook of Small Animal Surgery, 3rd ed.
2. Implants manufactured by Biomedtrix, Co. New Jersey.