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Slocum® Hip Examination By Barclay Slocum, DVM and Theresa Devine Slocum, MS One of the most important visits to the veterinarian’s office for a dog is for a hip exam. This determines the predisposition of the hip for normal function or degenerative arthritis, and often the difference between a dog that is enthusiastic in its training, an animated winner, and one that is labeled lazy. Since the development of the hip is a dynamic process until the age of 6 months, many options are available for dogs with a borderline predisposition for abnormal hips. For this reason we recommend a hip exam for all dogs four months of age and older. While the Orthopedic Foundation for Animals provided a means to categorize dogs with hip dysplasia at two years of age, the accuracy of this program relies on pathologic changes to the joint, easily recognizable, having already occurred by this age. For the success of any preventative or reparative work, recognition of the signs of abnormal hips is desired much earlier, when the dog’s cartilage has minimal damage, and the ability to restore normal function and activity is at its optimum. For working dogs, knowledge of the status of the hips is imperative before time and energy is placed into training.
The first stage of the hip exam involves gathering information from the owner, for owners have become quite educated about the movement of their dog, and recognizing the initial signals of difference. The next stage of hip examination is to perform a gait analysis. The dog is analyzed at a walk, trot and run. Specific attention is paid to weight bearing, compensation by any other muscle groups, gait width, stride length, foot flight patterning, crossing over, and rigidity of motion. Jumping up, sitting, and climbing stairs all contribute valuable information. The performance in movement reveals how the muscle groups work together. They accentuate areas of strength and weakness, and neurologic status. Stage III of the hip examination is the physical examination. The dog is examined from the tip of its nose to the tip of its tail. All aspects of the physical condition of the dog contribute to the overall health of the dog and its function and ability to be active. Since any other injured limb can contribute stress on hips, a thorough examination involves orthopedic testing of the entire dog. In the dog the hip is a six-degree of freedom joint, which means it allows movement about three axes and movement parallel to the same three axes. The range of motion in each of these directions is measured. With the dog standing, the hind leg is slowly moved forward and back, as if the dog were running. Any hesitancy or tenseness is noted. Hip problems often show a restricted extension. The leg is internally and externally rotated, again noting the flexibility of the joint. The leg is then abducted (as when a male dog is urinating) and externally rotated. Any apprehension or a pain response is indicative of pinching of inflamed tissue. Inability to abduct the leg indicates a contracted pectineus muscle. Since back problems often mimic hip dysplasia, a lordosis test which tests the flexibility of the back is preformed. Perhaps the most important aspects of the hip examination is palpation of the hip under anesthesia. The information obtained from palpation surpasses any available with the animal awake. To the veterinary orthopedist, palpation reveals the details of the viability of the cartilage of the femoral head and the acetabulum. Identification and position of eburnated bone can be evaluated. Information is obtained that determines if the joint capsule is torn, or just stretched, and whether the labrum is fractured. The amount and position of smooth cartilage determines if surgery, and which technique, is applicable. Of the many tests performed under anesthesia, the angle of subluxation and the angle of reduction are among the most valuable. The dog is placed on its back. With the femur perpendicular to the table, the leg is abducted from vertical, until a point occurs when the hip returns to its socket. The angle measured from vertical is the angle of reduction. From this position, the leg is adducted, so the femur retraces its path to vertical. The angle from vertical when the hip subluxates is called the angle of subluxation. These measurements provide information regarding the amount and quality of surface contact the femur has with the acetabulum. If the labrum is fractured, a precipitous drop is recorded. If the pectineus is contracted, it becomes quite obvious with this test. A trochanter compression test is performed with the dog on its side. A medially directed force is placed on the greater trochanter. With subluxation, the hip is forced into the socket. When the force is released, the hip returns to its subluxated position. Ventral luxation can also be detected with this test. There are three radiographic views that are taken with a hip examination. The most informative is the dorsal acetabular rim (DAR) radiographic view. The dog is placed in sternal position with its legs in a sit position. The radiographic beam is angled through the ilium so that the weight-bearing portion of the acetabulum is outlined. In normal dogs, the dorsal acetabulum is straight and pointed. With mild forms of hip dysplasia, sclerosis of the bone is evident, with some rounding of the rim of the dorsal acetabulum. More severe cases of dysplasia show beveled and blunted rims, with arthritic signs along the edge of the dorsal rim. Dorsal osteophytes are isolated easily. When the acetabular cup becomes filled with osteophytes, the femur is improperly positioned in the hip socket. The importance of this view is that it depicts the weight-bearing portion of the hip joint. If the hip is incongruent, or unstable, it is readily identified. If the cup is too shallow or full of arthritis, the prognosis for treatment lessens immensely. The most common radiograph used for diagnosis in hips is the ventrodorsal position. The dog is placed on its back, and the legs are aligned parallel with the table. This view provides information that the hips are seated normally in the socket and if the acetabulum and the femur are congruent. Perhaps most important from this position is the determination if the femur has any torsion, or femoral head anteversion. In these cases, the socket or acetabulum may be deep enough to accept the femoral head, but muscular forces do not direct the femur into the acetabulum. If the femoral neck has any disease or is thickened, it will contact the acetabulum which restricts movement and causes impingement of tissue. The amount of acetabular margin overlap of the femoral head can be measured from this view. If the acetabulum is filled with osteophytes, or if there is sufficient arthritis around the dorsal rim of the acetabulum, this shows up on this radiograph. With the dog on its side in lateral recumbency, a lateral radiograph is taken. This view shows the congruency and stability of the hip by means of the concentricity and density of the femoral head and the adjacent acetabular subchondral bone. Abnormalities of the spine and sacrum can be detected with this view. A thorough examination of the hips is good insurance that your dog can perform to the best of its ability. Some signals to recognize of possible damage to the hips are: a puppy tires easy or refuses to play with its littermates; soreness in the morning after activity; reluctance to jump, or climb stairs; difficulty in rising; sitting crooked (may also be knees). Avoid excessive weight and over exercise in puppies. Rapid growth during the four to six month age can change the status of the hips due to muscle forces and femoral growth. Good hips are a joy to the dog, to the owner and to us. We are as delighted as the owners are when we can say, "Your dog has excellent hips!"
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