Legg-Perthes disease, also known as aseptic necrosis of the femoral head, Legg-Calve-Perthes disease, Perthes disease or simply Legg's disease, is defined as the spontaneous degeneration, lysis and necrosis of the head and neck of the femur, leading to collapse of the hip (coxofemoral) joint and, ultimately, to osteoarthritis. The femur is the long thigh bone that forms part of the knee joint at one end and part of the hip joint at the other. With Legg-Perthes disease, the head (or ball) of the femur – which normally fits snugly into the pelvic socket (called the acetabulum) - suddenly starts to disintegrate, ultimately leading to painful and progressive death of the cells in that part of the femur bone (this process is called "necrosis").
Causes of Legg-Perthes Disease
Legg-Perthes disease in domestic dogs is considered to be "idiopathic" – which means that it has no known cause. It tends to occur in young, small or miniature-breed dogs of either gender and is thought to have a strong genetic component. For some reason, the normal blood supply to the upper part of the femur bone becomes disrupted, without any recognizable precipitating traumatic event. Interruption of the blood supply (called "ischemia") causes the affected bone and surrounding cartilage to degenerate, deform, fracture and die. The entire area around the affected hip joint becomes irritated, inflamed and increasingly painful. Once the cells of the upper part of the femur die, they start to be replaced by fibrous and granulation tissues that are not as strong as bone. The body tries to revascularize the area and remodel the dead and dying bone and cartilage as it is reabsorbed by the body, but these attempts are not successful. This degenerative process causes the hip joint to become disfigured, lose its structural integrity and become non-weight-bearing. Eventually, the hip collapses. Legg-Perthes disease can show up bilaterally (in both hip joints) or unilaterally (in just one).
Preventing Legg Perthes Disease
Most reputable authorities agree that dogs diagnosed with Legg Perthes disease should be spayed or neutered, to try and prevent propagation of dogs with this likely inherited disorder. Breeders should also be discouraged from repeating matings that produced affected offspring.
The outlook for dogs with Legg Perthes disease is good. Even if surgery is needed, most dogs are able to enjoy a long and active life with minimal restrictions on physical activities.
Legg-Perthes disease is a painful disorder that primarily affects young, small-breed dogs and terriers. For some unknown reason, the neck and head of the dog's femur (the long upper leg bone that joins the pelvis to form the hip joint) spontaneously degenerates and dies, causing the ball-and-socket hip joint to deteriorate and, ultimately, to collapse. Once this happens, the affected dog cannot bear weight on that hip, because the joint has completely lost its structural integrity.
Symptoms of Legg-Perthes Disease
Typically, the owner of an animal with Legg-Perthes disease notices her dog gradually developing varying degrees of lameness in one or both hind legs over the course of several months. The symptoms usually begin when the dog is less than one year of age. In particular, the owner may see one or more of the following signs in their dog:
Hind limb lameness; gradual onset; one or both rear legs
Pain upon flexion, extension and/or physical manipulation of the affected hip joints and hind legs
Reluctance to rise, run, jump or play
Wasting of the thigh muscles (atrophy)
Chewing, licking, bothering the affected hip joint
Audible clicking or snapping coming from the hip joint during movement or when rising (crepitus); unusual early in the disease; becomes more common later in untreated dogs.
When an owner notices progressive lameness in her dog, she should contact the veterinarian promptly.
Dogs At Increased Risk
Legg-Perthes disease occurs most commonly in young miniature, toy and small-breed dogs between 5 and 12 months of age. Manchester Terriers are thought to have a strong genetic predisposition to developing this disorder, and other terrier breeds seem prone to Legg-Perthes disease as well. Predisposed breeds include the Yorkshire Terrier, Manchester Terrier, Miniature Pinscher, Poodle (toy and miniature), Lakeland Terrier, West Highland White Terrier, Cairn Terrier, Australian Shepherd, Chihuahua, Dachshund, Lhasa Apso and Pug.
Legg-Perthes disease is not particularly difficult for a veterinarian to diagnose. However, the symptoms of Legg-Perthes disease can mimic those resulting from other causes of hind limb lameness, such as patellar luxation, hip dysplasia, trauma/injury/fracture of the femur or pelvis, degenerative joint disease and septic arthritis of the hip joint, among others.
How Legg-Perthes Disease is Diagnosed
Most veterinarians presented with a limping dog will get a complete history from the owner and then conduct a thorough physical examination. Of course, when a patient is lame, the veterinarian will carefully examine, palpate (feel) and manipulate the affected leg and surrounding area to assess pain, reflexes, bone integrity, inflammation, swelling, temperature/heat and the like. An initial database of blood work (complete blood count and serum biochemistry profile) and a urinalysis are routinely performed as well, to assess the overall health of the dog's primary organ systems and to look for evidence of infection. If Legg-Perthes disease is the only abnormality in the dog, the results of these tests will be normal.
If the physical examination localizes the site of pain or injury to the hip area, the next nearly universal diagnostic step is to take radiographs (x-rays) of the pelvis, both femurs (the long thigh bones) and both hips. This is important, even if only one side seems affected, so that the veterinarian can compare the radiographic images of both femurs and hips. Early in the course of the disease, radiographs may only disclose a slight widening of the space between the ball of the femur and the pelvic socket (the acetabulum), together with changes in the density of surrounding bone. As the disease progresses, these radiographic changes become more dramatic and almost always become diagnostic of Legg-Perthes disease. The changes can include severely abnormal bone density, irregular shape of the femoral neck and head, fractures, bone fragmentation and other evidence of degenerative joint disease.
Advanced radiographic imaging studies, such as magnetic resonance imaging (MRI), computed tomography (CT/CAT scan) and/or nuclear scintigraphy, typically are not required to diagnose Legg-Perthes disease in dogs. The age, size and breed of the animal, together with the history, physical examination and radiographs, should be all that is needed to make a definitive diagnosis.
As with most diseases or disorders, it is best if Legg-Perthes disease is diagnosed early in its course. Treatment and management are all that much easier before the problem has become chronic.
Legg-Perthes disease is an irreversible disorder that causes hind limb lameness, pain and disfigurement of affected hip joints. Left untreated, this condition will progress, the hip joint will continue to deteriorate and the dog's pain and other symptoms will worsen and become more obvious. Fortunately, despite the progressive nature of Legg-Perthes disease, surgical and non-surgical treatment options are available to help alleviate pain and improve the dog's quality of life. The choice of treatment will depend largely upon the size of the dog, the severity of its symptoms, the degree of tissue and bone deterioration, the preferences and skills of the attending veterinarian and the financial and other considerations of the owners. Some dogs may need no formal treatment for Legg-Perthes disease, while others may require strict confinement and physical therapy. In many cases, surgical intervention is necessary, together with appropriate follow-up supportive care.
When an owner suspects that her dog is suffering from some form of hip or hind limb lameness, it is time to get a veterinarian's assessment of the dog's health and physical status. The therapeutic goals of treating Legg-Perthes disease are to return the dog to normal (or near-normal) pain-free activity, stabilize the hip joint and restore mechanical weight-bearing hip function.
Treatment Options for Legg-Perthes Disease
In mild or very early cases of Legg-Perthes disease, non-surgical medical management may be sufficient to alleviate the dog's pain and lameness. This might involve enforced activity restriction and strict cage rest, together with intermittent or chronic administration of oral pain-relief medications (analgesics) and/or nonsteroidal anti-inflammatory drugs (NSAIDs). Physical therapy may also be very helpful. Corticosteroids, which can be quite effective at reducing inflammation, should not be administered together with NSAIDs, because the interaction between these two classes of drugs can cause several gastrointestinal discomfort, up to and including intestinal ulceration and even perforation.
Surgical treatment has a much higher rate of success than does medical management alone. In most cases, surgery ultimately will be necessary as the disease progresses, even if non-surgical approaches are tried first. The most common surgical procedure is a femoral head and neck ostectomy (FHO), also sometimes called a femoral head and neck excision (FHNE). This involves surgically removing the head and usually the neck of the long upper thigh bone (the femur) that, together with the pelvis and surrounding cartilage, forms the hip joint. The procedure basically allows a "false joint" to form from fibrous tissue, granulation tissue and other scar tissues that fill in and replace the removed ball-and-socket joint of the affected dog's hip.
A total hip replacement is another surgical option. This procedure in dogs, as in people, involves removing the entire damaged joint and replacing it with an artificial femoral head and pelvic hip joint socket. This is usually reserved for the uncommon large dog that is affected by Legg-Perthes disease. The procedure requires tremendous technical skill by the surgeon and should only be performed by a veterinarian who specializes in complicated orthopedic surgeries. The recovery time and expense of a total hip replacement are prohibitive to many owners, as well.
Use of a non-weight-bearing sling, sometimes called an Ehmer sling, reportedly allowed one dog's damaged femoral head and neck to remodel sufficiently without surgical intervention. However, this is highly controversial and is not considered to be a reliable treatment option by most veterinary orthopedic specialists.
Post-operative bandaging, cold-packing the affected site (cryotherapy) and activity restriction are all critical to a dog's recovery from hip surgery. Physical therapy is particularly important to rehabilitating the affected limb, sometimes including early limited weight-bearing exercises, depending upon the advice of the surgeon and other rehabilitation professionals. Small lead weights may be attached above the hock joint as "anklets" to encourage leg use, once exercise becomes safe and appropriate. Physical range-of-motion exercises are often part of the physical therapy protocol, as are swimming and other water exercises. Owners must manage their dogs' diet carefully to prevent obesity, which can put enormous stress on the hip joints.
Other less traditional techniques that may benefit dogs with Legg-Perthes disease, in addition to medical treatment, might include: massage therapy to help reduce pain, maintain healthy muscular tone and reduce collateral strain from compensation; possible application of acupuncture and/or acupressure techniques; use of herbal or other non-regulated supplements or homeopathic "remedies"; and other forms of supportive care that may help to ease pain, increase circulation, speed healing and otherwise promote wellness, relaxation and comfort. Some of these adjunct approaches lack controlled studies of their effectiveness and may not have established quality control methods or ways to assess their benefit to dogs with Legg-Perthes disease or other degenerative musculoskeletal disorders.
The prognosis for dogs treated surgically for Legg-Perthes disease is very good to excellent, as long as owners are diligent about post-operative physical rehabilitation and supportive care. After treatment and rehabilitation, most dogs regain pain-free function of the affected hind leg and hip and are able to enjoy normal canine activities such as running, jumping, walking and playing throughout the course of a normal life span.