Imágenes Diagnósticas, Plataforma de Servicios Veterinarios Manizales, Manizales, Colombia
Hip dysplasia is a multifactorial, clinically complex arthropathy with structural alterations of the coxofemoral joints. Although dogs are afflicted most commonly, cats also have hip dysplasia. One or both hips may be involved.1 The causes of canine hip dysplasia are numerous and possibly interactive; is an inherited disorder, environmental factors influence the phenotypic expression of hip dysplasia.2 The role of nutrition has been studied extensively, overnutrition is regarded as one of the principal non-genetic factors that influence the expression of canine hip dysplasia. Any breed of dog or cat can be affected, highest incidence is in large- and giant-breed dogs and in purebred cats.3 We must consider that this is a developmental, age-related disorder; it is not present at birth; a variable amount of time must elapse before radiographic changes are manifest. Once present, these radiographic changes usually progress as the affected animal ages.2 The clinical signs include an abnormal gait, low exercise tolerance, reluctance to rise or climb stairs, and muscle atrophy; many animals remains asymptomatic for years, but in other cases animals with severe hip dysplasia may exhibit signs at less than 1 year of age. The diagnosis of hip dysplasia is tentatively based on history, clinical signs and palpation, but is confirmed on radiographs.3
Radiological Hip Evaluation
The ventrodorsal leg extended radiographic view is the most common image obtained for the evaluation of the hips. For this view the dog is placed on its back, and the rear limbs are pulled straight back until the stifle and hocks are fully extended; the limbs are then adducted until the femurs are parallel to each other. The femurs are rotated medially until the patellas are centered dorsally, the patient must be symmetrically positioned so that there is no rotation of the pelvis. The entire pelvis and enough of the femurs to show the position of the patellas should be included on the radiograph. In terms of technique radiographic the ray beam should be centered at the level of the hip joints, exposure should be sufficient to allow visualization of the dorsal acetabular margin through the femoral head and neck; and the time should be sufficiently fast to prevent motion artifact.4 Proper positioning and image quality are essential, and if not done correctly can lead to errors in radiological interpretation of normal versus abnormal hips. Radiographically pelvic symmetry is present when: the obturator foramen are equal in size, the ilial wings have the same diameter, and a line drawn through the caudal lumbar spinous processes continues through the pelvic symphysis.5
The earliest change is the coxofemoral joint laxity we can see when femoral head is not well seated in acetabulum, and results in abnormal wearing, which leads to bone remodeling and degenerative join disease.3
The radiological findings of hip dysplasia include
Femoral head subluxation or luxation. Present when approximately 50% or more of the femoral head is not within the acetabulum or if the Norberg angle measurement is abnormal.
Remodelling of the femoral head and neck: loss of spherical shape of the head (exclude the fovea capitis).
Remodelling of the acetabulum: shallow "C" or cup-shaped acetabulum, remodeling of craniodorsal margin.
Shift in position of the femoral head in young dogs.
Irregularity of the cranial acetabular margin to flattened or double-curved line.
Periarticular osteophytes on the margins of the femoral head and acetabulum.
Osteophyte formation on the caudal aspect of the femoral neck, known as a caudolateral curvilinear osteophyte (CCO) or Morgan's line.
Osteophyte formation on the margin of the femoral head parallel to the physeal scar, which is known as femoral head rimming.
Subchondral sclerosis of the acetabular margin.4,5
In cats the reported incidence of hip dysplasia amongst breeds ranges from about 6% to 32%, the diagnosis is usually made on a VD extended hip view identical to the positioning used in dogs.5 Radiographic criteria for diagnosing feline hip dysplasia include the presence of signs of coxofemoral subluxation, enthesophyte formation on the acetabular margins, and remodeling and degenerative changes of the femoral head and neck. Unlike canine hip dysplasia, most degenerative changes in cats appear on the craniodorsal acetabular margins, with a low incidence of degenerative remodeling reported on the femoral head and neck.2
Is important to know there are various systems for assessment of normal hips versus hip dysplasia, in the following table we can find the comparison between different hip control programmes.5
Table 1. Hip control programmes
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Hip control programmes
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Details
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British Veterinary Association Kennel Club Hip Dysplasia Programme
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- The minimum age for evaluation is 1 year with no upper age limit.
- VD extended hip radiographs of dogs are voluntarily submitted by a veterinary surgeon for interpretation by two scrutineers who are appointed by the BVA. Each animal and radiograph must be properly identified and the radiograph must be of acceptable diagnostic quality.
- A score for each hip, as agreed by the two scrutineers, is assigned based on a point system using nine radiological criteria. These include the Norberg angle, femoral head subluxation, shape of the acetabulum and osteoarthrosis changes. The greater the abnormality, the higher the score for each criterion.
- The minimum (best) score for each hip is 0 and the maximum (worst) is 53. The lower score, the less the degree of evident hip dysplasia.
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Orthopedic Foundation for Animals (OFA)
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- The minimum age for an official evaluation is two years. There is no upper age limit. Preliminary evaluations can be requested for dogs between four months and two years of age.
- VD extended hip radiographs are voluntarily submitted by the dog's owner for interpretation by three veterinary radiologists selected by the OFA who are diplomates of the American College of Veterinary Radiology. Each animal and radiograph must be properly identified and the radiograph must be of acceptable diagnostic quality.
- Each dog's hips are scored subjectively into seven phenotypes: excellent normal, good normal, fair normal, borderline, mild dysplasia, moderate dysplasia, and severe dysplasia. The categories of mild, moderate and severe dysplasia are based on the subjective assessment of the degree of subluxation and osteoarthrosis present.
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PennHIP®
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- Requires three radiographic views (VD extended hip, distraction and compression views). Only certified PennHIP veterinary surgeons and technicians may take the radiographs and must submit (not voluntary) the radiographs of all dogs examined.
* Each animal and radiograph must be properly identified and all radiographs must be of acceptable diagnostic positioning and quality.
* Hip dysplasia is diagnosed when there is osteoarthrosis present on the VD extended hip view.
* Joint laxity (passive) is determined quantitatively by comparing the compression and distraction views. For the compression view, the coxofemoral joints are compressed manually so that the femoral heads are fully seated in the acetabulum for maximum congruity. For the distraction view, a specially designed distraction device is placed between the femurs and the femurs are manually compressed against the device, creating a fulcrum to force the femoral heads laterally, in order to visualize the maximum amount of hip joint laxity. When the compression and distraction views are compared, any hip laxity is quantified by a quantitaive unitless measure called the distraction index (01). The minimum amount of laxity is 0.001 (tightest hip) and a 01 of 1.0 is the loosest hip.
- PennHIP® has identified 01 thresholds for specific breeds, below which dogs are not at risk of developing osteoarthrosis. If laxity is present (greater than 0.3 01), there is a direct relationship between the amount ot-laxity and the development of osteoarthrosis. Dogs with a 01 of less than 0.3 are not at risk of developing osteoarthrosis.
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Bibliography
1. Burk R, Feeney D. Small Animal Radiology and Ultrasonography. 3rd ed. Kealy-McAllister; 2003:477–606.
2. Thrall D. Textbook of Veterinary Diagnostic Radiology. 4th ed. St Louis, MO: Saunders; 2002:190–195.
3. Muhlbauer MC, Kneller SK. Radiography of the Dog and Cat: Guide to Making and Interpreting Radiographs. Ames, IA: Wiley-Blackwell; 2013:213–219.
4. Herny G. Radiographic development of canine hip displasia. Veterinary Clinics of North America: Small Animal Practice. 1992;22(3):559–577.
5. Biery D. The hip joint and pelvis. In: Kirberger RM, Fourie SL, eds. BSAVA Manual of Canine and Feline Musculoskeletal Imaging. 2006:119–134.
Signos Radiologicos de Displasia de Cadera
Diana Carolina Villamil González, DVM
Imágenes Diagnósticas, Plataforma de Servicios Veterinarios Manizales, Manizales, Colombia
La displasia de cadera es un complejo multifactorial con alteraciones en las estructuras de las articulaciones coxofemorales. A pesar de que los perros son los que la sufren más comúnmente, los gatos también pueden sufrirla. Una o ambas caderas pueden estar afectadas.1 Las causas de displasia de cadera son numerosas y posiblemente interactúan entre ellas; es un desorden hereditario, donde los factores ambientales pueden influir en la expresión fenotípica de la displasia de cadera.2 El rol de la nutrición se ha estudiado extensivamente, la sobrealimentación es considerada como uno de los principales factores no genéticos que influyen en la expresión de la displasia de cadera canina. Cualquier raza de perro o gato puede verse afectada, la incidencia es más alta en razas grandes y gigantes de perros y gatos de raza pura.3 Debemos tener en cuenta que este es un trastorno del desarrollo, relacionado con la edad, que no está presente en el nacimiento, debe transcurrir un tiempo antes de que los cambios radiográficos se manifiesten. Una vez que están presentes, estos cambios radiográficos suelen progresar con el envejecimiento de los animales afectados.2
Los signos clínicos incluyen alteración de la marcha, baja tolerancia al ejercicio, renuencia a subir escaleras y atrofia muscular; muchos animales permanecen asintomáticos durante años, pero en otros casos animales con displasia de cadera severa pueden presentar signos con menos de 1 año de edad. El diagnóstico de displasia de cadera se basa tentativamente en la historia, los signos clínicos y la evaluación fìsica, pero se confirma con radiografías.3
La Evaluación Radiológica de la Cadera
La proyección radiográfica ventro-dorsal con piernas extendidas, es la más común para la evaluación de la cadera. Para esta vista, se ubica al perro en decúbito dorsal y las extremidades traseras se estiran hacia atrás hasta que la rodilla y la articulación del tarso se encuentren totalmente extendidas; las extremidades se deben girar hacia medial hasta que los fémures estén paralelos entre sí. Cada fémur se rota medialmente hasta que las rótulas se centren dorsalmente, el paciente debe ser posicionado de manera simétrica y que no exista rotación de la pelvis. Toda la pelvis y gran parte de los fémures deben incluirse en esta vista, para que las rotulas se puedan distinguir; en cuanto a la técnica radiográfica el haz de rayos X debe estar centrado a nivel de las articulaciones de la cadera, la exposición debe ser suficiente para permitir la visualización del margen dorsal acetabular a través de la cabeza y cuello femoral; y el tiempo debe ser lo suficientemente rápido como para evitar los artefactos de movimiento.4
La posición correcta y la calidad de imagen son esenciales, y si no se logran puede dar lugar a errores en la interpretación radiológica. La simetría radiológica de la cadera está presente cuando el agujero obturador es igual en tamaño, las alas del ilion tienen el mismo diámetro y una línea trazada a través de las apófisis espinosas lumbares caudales continúa a través de la sínfisis pélvica.5
El primer cambio es la laxitud de la articulación coxofemoral, se puede ver cuando la cabeza femoral no se encuentra bien articulada (asentada) en el acetábulo, lo que genera un uso anormal generando remodelación y enfermedad articular degenerativa.4
Los hallazgos radiológicos de displasia de cadera incluyen
Subluxación o luxación de la cabeza femoral, presente cuando aproximadamente el 50% o más de la cabeza femoral no se encuentra dentro del acetábulo o si la medida del ángulo de Norberg es anormal.
Remodelación de la cabeza o el cuello femoral: perdida de la forma esférica de la cabeza femoral (excluyendo la Capitus Fovea).
Remodelación del acetábulo: remodelación del margen craneodorsal del acetábulo en forma de "C" o en forma de copa.
Cambios en la posición de la cabeza femoral en perros jóvenes.
Irregularidad en el margen craneal acetabular por aplanamiento.
Osteofitos periarticulares en la margen de la cabeza femoral y el acetábulo.
Formación de osteofitos en el aspecto caudal del cuello femoral, conocido como un Osteofito Caudolateral Curvilineo (CCO) o línea de Morgan.
Formación de osteofitos en el margen de la cabeza femoral paralela a la cicatriz de la fisis.
Esclerosis subcondral del margen acetabular.4,5
En los gatos la incidencia de displasia de cadera entre razas varía de aproximadamente 6–32%, el diagnóstico es por lo general hecho en una proyección VD de cadera en extensión, en una posición idéntica a la utilizada en los perros.5 Los criterios radiográficos para el diagnóstico de displasia de cadera felina incluyen la presencia de signos de subluxación coxofemoral, la formación de entesiofitos en las márgenes del acetábulo, y la remodelación y cambios degenerativos de la cabeza y cuello femoral. A diferencia de la displasia de cadera canina, la mayoría de cambios degenerativos en los gatos aparecen en las márgenes del acetábulo craneodorsal, con una baja incidencia de remodelación degenerativa reportada de cabeza y cuello femoral.2
Es importante saber que hay varios sistemas para la evaluación de la cadera, en la siguiente tabla (Tabla 1) podemos encontrar la comparación entre los diferentes sistemas de control.5
Tabla 1: Programas de control de cadera
Bibliografìa
1. Burk R, Feeney D. Small Animal Radiology and Ultrasonography. 3rd ed. Kealy-McAllister; 2003:477–606.
2. Thrall D. Textbook of Veterinary Diagnostic Radiology. 4th ed. St Louis, MO: Saunders; 2002:190–195.
3. Muhlbauer MC, Kneller SK. Radiography of the Dog and Cat: Guide to Making and Interpreting Radiographs. Ames, IA: Wiley-Blackwell; 2013:213–219.
4. Herny G. Radiographic development of canine hip displasia. Veterinary Clinics of North America: Small Animal Practice. 1992; 22(3): 559–577.
5. Biery D. The hip joint and pelvis. In: Kirberger RM, Fourie SL, eds. BSAVA Manual of Canine and Feline Musculoskeletal Imaging. 2006:119–134.