Modified cementless total coxofemoral prosthesis: development, implantation and clinical evaluation / Prótese coxofemoral não cimentada: desenvolvimento, implantação e avaliação clínica

The aim of this study was to modify canine coxofemoral prostheses and the clinical evaluation of the implantation. Fifteen canine hips and femora of cadavers were used in order to study the surface points of modification in prostheses and develop a perforation guide. Femoral stems and acetabular components were perforated and coated with biphasic calcium phosphate layer. Twelve young adult male mongrel dogs were implanted with coxofemoral prostheses. Six were operated upon and implanted with cemented canine modular hip prostheses, establishing the control group. The remaining six were implanted with a novel design of cementless porous tricalcic phosphate-hydroxyapatite coated hip prostheses. Clinical and orthopedic performance, complications, and thigh muscular hypotrophy were assessed up to the 120th post-operatory day. After 120 days, animals with cementless prostheses had similar clinical and orthopedic performance compared to the cemented group despite the increased pain thigh hypotrophy. Animals that underwent cementless hip prosthesis evidenced more pain, compared to animals with cemented hip prosthesis that required longer recuperation time. No luxations, two fractures and two isquiatic neurapraxies were identified in the course of the study. Using both the cemented and the bioactive coated cementless model were suitable to dogs, showing clinical satisfactory results. Osseointegration and biological fixation were observed in the animals with the modified cementless hip prosthesis.

O objetivo deste estudo foi modificar a prótese coxofemoral canina cimentada e avaliar os efeitos clínicos. Foram utilizadas 15 pelves e 15 fêmures de cadáveres de cães para modificações da haste, do componente acetabular e para a confecção de guia de perfuração. As hastes e componentes acetabulares foram perfurados e revestidos com uma camada de fosfato de cálcio bifásico. Doze cães machos, adultos jovens, sem raça definida, foram submetidos à cirurgia para o implante de prótese coxofemoral total. Seis cães receberam prótese modular cimentada, grupo controle, e seis, a prótese modificada não cimentada com revestimento de fosfato de cálcio bifásico. Foram avaliados a técnica de implantação, o desempenho clínico, o grau de hipotrofia muscular da coxa e as complicações durante 120 dias. Os animais com prótese não cimentada mostraram desempenho clínico similar aos animais com a prótese cimentada, porém mostraram maior hipotrofia muscular decorrente de dor e maior tempo de recuperação. Não foram observadas luxações. No entanto, duas fraturas e dois casos de neurapraxia isquiádica foram observados. A utilização de ambas as próteses coxofemorais, cimentada e não cimentada, com recobrimento bioativo são eficientes no cão, com resultados clínicos satisfatórios, mas a osteointegração e fixação biológica ocorreram na prótese com recobrimento de fosfato de cálcio bifásico, objetivo do tratamento que previne afrouxamento futuro.

Associação entre o ângulo de Norberg, o percentual de cobertura da cabeça femoral, o índice cortical e o ângulo de inclinação em cães com displasia coxofemoral / Associations among Norberg angle, percentage of femoral head coverage, cortico-medullary index, and femoral inclination angle in dogs with hip dysplasia

Foram avaliadas 386 radiografias da articulação coxofemoral, sendo 220 de cães da raça Pastor Alemão, 112 machos e 108 fêmeas, e 166 da raça Labrador Retriever, 69 machos e 97 fêmeas. As radiografias foram classificadas segundo o grau de displasia coxofemoral (DCF), e foram mensurados o ângulo de inclinação, o ângulo de Norberg, o índice cortical e o percentual de cobertura da cabeça femoral de ambos os lados. As variáveis foram associadas mediante análise estatística multivariada de componentes principais. As variáveis índice cortical e ângulo de inclinação foram inversamente associadas. A raça Pastor Alemão apresentou valores de índice cortical e graus de DCF mais baixos em relação à raça Labrador Retriever. Maior ângulo de inclinação foi associado a menor ângulo de Norberg e menor percentual de cobertura. Animais mais velhos apresentaram menor ângulo de Norberg, menor porcentagem de cobertura e maior grau de DCF. Nas fêmeas, foram observados menor porcentagem de cobertura, menor ângulo de Norberg e maior grau de DCF. Pode-se concluir que o ângulo de inclinação e o índice cortical não demonstraram associação com a DCF.

A total of 386 radiographs of the pelvis were evaluated, being 220 of German Shepherd dogs (112 males and 108 females) and 166 of Labrador Retrievers (69 males and 97 females). The radiographs were degree classified regarding the of hip dysplasia (DHD). The Norberg and inclination angles, the cortico-medullary index, and the percentage coverage of the femoral head were measured and associated using multivariate statistical technique (principal component analysis). The cortico-medullary index and the inclination angle were inversely associated. The results indicated that German Shepherd Dogs showed lower cortico-medullary index and DHD compared with Labrador Retrievers. The higher the inclination angle, the lower the Norberg angle and percentage coverage of the femoral head. It was observed that with age, animals showed lower Norberg angles and percentage coverage of the femoral head, thus more hip dysplasia severity. Females were associated to lower femoral head coverage and Norberg angles, and more severe DHD. Femoral inclination angle and cortico-medullary index did not demonstrate a correlation to DHD.

Freqüência da displasia coxofemoral em cães da raça Pastor Alemão / Frequency of hip dysplasia in German Shepherd dogs

One hundred twenty-three radiographs of German Shepherd dogs (47 females and 76 males) from Military Police of Minas Gerais State were studied from April 2001 to july 2004, with the purpose of establishing the frequency and asymmetry of hip displasia. The radiographs were taken with the animals in the ventrodorsal position, with the limbs parallel and the pelvis symmetric. The average age of the dogs was 33.8±23.5 months-old. The study indicated that 89.4 percent of them had hip dysplasia (91.5 percent of females and 88.2 percent of males), being 6.3 percent unilateral, 17.3 percent bilateral asymmetric, and 76.4 percent bilateral symmetric. The frequency of hip displasia in the studied population was high, indicating the necessity of an efficient control program of the disease.