Legg-Calve Perthes

Legg Calve Perthes is the common name givien to avascular necrosis of the head of the femur. It also may be called toxa plana, osteochronditis deformans juvenilis or aseptic necrosis of the femoral head. The acetabulum (hip socket) does not ossify at all prior to birth but begins that process when the pup is about 3 weeks into post-natal life. Two very small arteries branching off the extracapsular arterial ring are the only blood supply to the bone-growth center at the head of the femur. The best evidence suggests that the arterial circulation to the femoral head is lost or compromised in this disease condition leading to necrosis (tissue death).

SYMPTOMS

The symptoms of Legg-Perthes are most frequently mild. The puppy will limp but will rarely cry-out or evidence severe pain. Owners will usually suspect a mild strain or sprain at first and may or may not confine the puppy to a crate. At any sign of a limp, a puppy should be confined to a crate for several days and if limping persists, orthopedic examination should be sought. Abduction (movement of the limb away from the body) of the limb will cause discomfort or frank pain. While bilateral disease is known, most pups will have the disease in only one hip so the signs will be unilateral. Depending on the elapsed time since onset as determined by limping, the muscle bulk of the affected limb may be decreased (atrophy) and the leg may be shorter than the normal limb. Without treatment the puppy may cease to use the painful limb, causing a three-legged gait. Radiography is the only means to confirm a diagnosis. The hip joint (particularly the femoral head) will be asymmetrical compared with the normal side. The head may be flattened or more severely deformed. The joint space will be wider and the head will show areas of different density on the film (moth-eaten appearance). The Veterinarian also will make note of any changes in the joint socket (acetabulum) which may include spurs and osteoarthritic changes that add to joint pain. The latter problems, however, occur late in disease process.

TREATMENT

To emphasize a critical point, any puppy with a limp should be confined to a crate immediately. The size of the crate should permit comfort but not allow walking or jumping. The puppy should be carried outside several times a day only for elimination activities and should eat and sleep in the crate. An exercise pen is NOT satisfactory for such confinement. Crating the animal, while usually an effective way to treat sprains and the like, is highly unlikely to be effective in limiting or stopping the progression of Legg-Perthes disease. Naturally the owner cannot know what he is dealing with until the Vet makes a diagnosis - so immediate crating remains the initial treatment of choice. Once the diagnosis of L-P is confirmed, the treatment of choice in Veterinary medicine is surgical excision of the head of the femur. While this may sound extreme, it is effective; it is a cure. Most persons will be unable to detect a limp in the dog after recovery from the procedure if the disease has been detected early. The surgeon will have several choices of operative approach, but correctly done, the result will be the same - a pain-free animal. The femur will gradually form a new joint (pseudarthrosis) with the pelvis; the extremity will be stable and, most importantly, usable. More expensive procedures, such as a total hip replacement are available, and these may be more functional, but in no case can or should the dog be used for show or breeding.

SUMMARY

Legg-Perthes disease is the result of multiple factors. A genetic predisposition, however weak, is combined with other determinants among which may be mild trauma, to set off the chain of events that lead to the clinical destruction of the capital femoral epiphysis. The several processes involved include mechanical collapse, asymmetric growth and disturbed endochondral ossification of the growth plate. A correctly treated puppy makes a marvelous pet but never a show or breeding animal.

adapted from "Legg-Calve Perthes" By Helen M. Hislop, PHD