Introduction

In 1909, Waldenström firstly described aseptic necrosis of the femoral head or Legg-Calvé-Perthes Disease (LCPD); however, he attributed its cause to tuberculosis. In 1910, Arthur Legg in the United States, Jacques Calvé in France and George Perthes in Germany independently acknowledged such necrosis as a unique entity of unknown etiology (Soni et al. 2004). Various theories have been proposed to explain the cause leading to the transitory obstruction of the femoral head circulation, including hormonal interference, hereditary factors, anatomic conformation, intracapsular pressure and femoral head infarction (Fossum et al. 2007). Incidence varies according to location, ranging from 1:1200 to 1:12500 (Kealey et al. 2000). Synovitis or prolonged abnormal position of the limb may increase intra-joint pressure, leading to the collapse of more fragile veins and inhibition of blood flow. After cell death, a restorative process begins. Bone content is mechanically weakened during the revascularization period, and normal physiological weight-bearing forces may cause the collapse and fragmentation of the femoral epiphysis. When this occurs, the incongruence between the femoral epiphysis and the acetabulum results in aseptic necrosis. The fragmentation (fractures) of the femoral epiphysis and osteoarthritis cause pain and, consequently, lameness (Fossum et al. 2007). Clinical conditions are manifested by pain, lameness and limitation of movement amplitude, and these signs vary in intensity for each patient. Pain can be described in the hips; however, it is usually reported in the medial region of the thigh or knee. Abduction, flexion and hip internal rotation are decreased (Tsao et al. 1997). In general, affected animals show lameness which begins slowly and gradually worsens. Crepitation may be present in more advanced stages. Other clinical signs may include irritability, appetite reduction and the action of biting the skin on the affected limb (Fossum et al. 2007). The diagnosis is based on clinical conditions and confirmed by radiographic examination and/or complementary tests (Tachdjian 2001, Santili 2003). Initial bone alterations in canine idiopathic aseptic necrosis are not radiographically shown. They are also limited to a subtle increase in the bone density of the proximal femoral epiphysis affected. Trabecular thickening and subchondral compact bone formation continue until a slight increase in the density of the femoral head becomes evident (Kealy & McAlliester 2000, Sturion & Sturion 2000). The excision of the femoral head and neck is the treatment of choice since the diagnosis is rarely achieved before the collapse of the femoral head, and the limitation of weight bearing on the limb during the revascularization period is enough to prevent the collapse of the femoral head. The prognosis in relation to the normal use of the limb is favorable after surgery due to the weight of affected dogs. Nevertheless, animal owners must be informed that mild and intermittent lameness may still occur in wet climates or after heavy exercise and inactivity periods. Unsatisfactory results are occasionally obtained, and they are related to the absence of weight bearing prior to surgery, serious pre-operative muscular atrophy and inappropriate surgical techniques (Fossum et al. 2007). Knowledge about the disease becomes important due to its genetic component. Hence, owners are advised with regard to neutering affected animals.

Materials and Methods

Forty-six cases of Legg-Perthes assisted by the surgical clinic service of Governador Laudo Natel Veterinary Hospital of the School of Agrarian and Veterinary Sciences at Jaboticabal--UNESP from January 01, 1996 to November 30, 2008 were studied. During the animals' chart assessment, the data concerning the patients' initial characteristics were evaluated, namely: age, breed, age, sex, body weight, pain, lameness, crepitation during physical examination, muscular atrophy, trauma history and radiographic examination.

Results

The affected breeds were mostly small-sized as shown in Figure 1. The weight of affected dogs varied from 1.3 kg to 17.3 kg, with 97.82% of the animals (n = 45) weighing from 1.3 kg to 7.1 kg. The age at which clinical manifestation occurred was from 2 to 24 months, and 67.39% (n = 31) were between 2 and 10 months old. A frequency of 25 females and 21 males was observed, that is, 54.34% of females and 45.65% of males.

Concerning clinical conditions, pain was reported in 22 (47.82%) patients, and 46 (100%) showed lameness. In our study, 34.78% (n = 16) of the patients showed muscular atrophy, 19.56% (n = 9) presented crepitation in the musculature adjacent to the femoral head, and 19.56% (n = 9) had suffered some type of trauma.

Radiographic assessment showed lesions in the right femoral head in 14 (30.43%) animals and on the left side in 22 (47.82%). Bilateral lesions were found in 9 (19.56%) animals. In 100% of the cases, the treatment of choice was femoral head excision.

Figure 1. Percentage of breeds affected by the Legg-Perthes Disease at the Veterinarian Hospital of UNESP - Jaboticabal. UB: undefined breed.

Discussion and Conclusions

It has been observed that the disease affects mostly toy breeds of dogs, according to Denny & Butterworth (2000). However, the occurrence of Legg-Perthes among the subjects in this study, namely in a Rottweiler, in a Brazilian Fila and in a dog of undefined breed (UB) weighing 17.3 kg, the anamneses of which did not show reports of any trauma type, is noteworthy. The Poodle breed showed a higher incidence of Legg-Perthes (36.95%/n = 17) when compared to the others involved in this study due to the large number of animals of that breed in the region, thus corroborating the reports by Sturion et al. (2006), who verified the predominance of the Poodle breed (43.75%) in his studies. The affected animals were young, at a mean age of 10.63 months, as also described by Denny & Buttermorth em 2000.

The lesion is usually unilateral and, differently from men, no sexual predominance exists (Robinson 1992). In the present study, an approximate percentage of 50% was obtained for males and females, and 78.26% showed unilateral lesion.

The major complaint by the owners in relation to their animals was lameness of the pelvic limb, and some animals also showed muscular atrophy and/or crepitation, which are signs that have been described in the literature (Fossum et al. 2007).

During clinical assessment, in addition to lameness, the animals showed pain and functional powerlessness, which were recorded on their charts. When animals are affected by the disease, pronounced lameness of the pelvic limbs due to pain caused by tissue lysis of the femoral head is evident. Such lameness leads to muscular atrophy resulting from disuse of the limb (Sturion et al. 2006). Sensitivity to palpation, appetite reduction and irritability result from pain.

As regards radiographic findings, femoral head deformity, femoral neck shortening and/or lysis and points showing bone opacity reduction on the femoral epiphysis were observed, similarly to the reports by Fossum et al. (2007).

Conservative treatment with anti-inflammatory drugs and collar-limited exercises or exercises without weight bearing, such as swimming, can provide pain relief for a small percentage of dogs, but most of them require surgical interventions (Fossum et al. 2007).

From the comparative analysis of the results obtained in the present study, it is concluded that:

 The dogs affected by Legg-Perthes are mostly represented by toy-breed animals at an approximate age of 10 months without a gender influence;

 Surgery is the treatment of choice due to femoral head degeneration;

 One of the first signs is lameness;

 When assisting animals affected by congenital disease, veterinarians, who are knowledgeable on the subject, must advise owners with regard to their animals' neutering.

References

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