Evaluation of trochlear dysplasia in dogs with medial patellar luxation: comparative studies

Medial patellar luxation (MPL) is one of the commonest orthopaedic diseases in small dog breeds. Although the bone deformities associated with canine medial patellar luxation are described in numerous studies, the pathogenesis of the condition is still disputable. What is more, there is no categorical evidence that luxation of the patella is associated to a shallow trochlear groove as no objective method for determination of trochlear depth and shape has been proposed. The aim of the present study was to evaluate the depth and shape of femoral trochlear groove on radiographs obtained from healthy dogs and dogs affected with grade II and grade III MPL. A total of 45 dogs (33 with MPL and 12 healthy) from 4 small breeds (Mini-Pinscher, Pomeranian, Chihuahua and Yorkshire terrier) were included in the study. After deep sedation, stifle radiographs were obtained in tangential projection (skyline view). The dogs were positioned in ventral recumbency, the examined stifle bent as much as possible, and the central beam focused on the patella between femoral condyles. Six morphometric parameters associated with the onset of trochlear dysplasia similar to those used in human medicine were measured: trochlear sulcus angle (SA), lateral and medial trochlear inclination angles (LTI; MTI), trochlear groove depth (TD), patellar thickness (PaT) and the ratio between trochlear depth and patellar thickness (PaT/TD). The non-parametric Mann-Whitney test was used for evaluation of differences between healthy joints and those affected with grade II and III MPL. The association between measured variables was evaluated via the Spearman's rank-order correlation. TD was greater in healthy joints as compared to those affected with MPL grade II and III (P < 0.001). In healthy stifles, PaT value exceeded significantly (P < 0.01) that in joints with grade III MPL. The TD/PaT ratio was significantly greater in healthy joints vs both those with grade II (P < 0.01) and grade III MPL (P < 0.001). In healthy joints, there was a significant negative relationship (rho­0.508; P = 0.0113) between SA and TD: smaller sulcus angles corresponded to deeper trochleas. This correlation was even stronger in joints with patellar luxation (rho ­0.723; P < 0.0001). The LTI and MTI showed a very strong positive correlation in healthy joints (rho 0.854; P < 0.0001) and at the same time, lack of significant association in joints affected with MPL (rho -0.163; P = 0.327 for grade II MPL and rho 0.175; P = 0.448 for grade III MPL) was demonstrated. The altered trochlear shape and depth were more pronounced in joints with grade III MPL. As MPL grade increased, the SA became statistically significantly greater. In grade III MPL it was accompanied with considerably reduced trochlear depth, medial trochlear inclination angle and trochlear depth/patellar thickness ratio. Five of the measured morphometric parameters for radiographic detection of trochlear dysplasia in dogs were found to be important in the evaluation of trochlear morphology in dogs. The obtained results indicated the presence of trochlear dysplasia in dogs with MPL. A 3-stage classification system for assessment of abnormal trochlear development in small dog breeds: mild; moderate and severe trochlear dysplasia, was proposed. The occurrence of shallow trochlear groove and medial femoral condyle's hypoplasia could be accepted as signs of mild and moderate trochlear dysplasia. The pre-operative measurements of these parameters could improve surgical planning and decisions-making.

Dimensões da patela relacionadas à massa corporal do cão para emprego na confecção de prótese: estudo em cadáver / Patellar dimensions related to canine body mass for use in the manufacture of prosthesis: cadaver study

O objetivo deste trabalho foi mensurar as dimensões da patela de cadáveres caninos e avaliar sua relação com a massa corporal. Para a realização das medidas patelares, foram utilizados 70 cadáveres de cães adultos, com massa corpórea de 1 a 50kg, sem evidência clínica de afecção na articulação femorotibiopatelar. Com auxílio de um paquímetro, foram mensurados os comprimentos externo e interno, a largura externa no terço médio, a largura e a espessura internas nos terços proximal, médio e distal das patelas. Também foram mensuradas a largura nos terços proximal, médio e distal, a profundidade nos terços proximal, médio e distal do sulco troclear; essas medidas foram exclusivamente internas. Observou-se, de forma geral, forte correlação entre as medidas patelares e a massa corporal de cadáveres de cães. Nas condições deste estudo, pode-se concluir que o tamanho da patela varia segundo a massa corporal do cão e que essas medidas devem ser consideradas ao se planejar uma substituição protética.(AU)

The aim of this study was to measure the canine cadaver patellar dimensions and evaluate its relationship with body mass. 70 cadavers of adult dogs were used, with a body mass between 1 and 50kg, without clinical evidence of affection in the stifle joint. The external and internal lengths, external width in the middle third, width and thickness of the proximal, middle and distal thirds were measured using a pachymeter. The width was also measured in the proximal third, middle third and distal third, depth in the proximal third, middle third and distal third of the trochlear groove; these measurements were exclusively internal. A strong correlation was observed between the patellar dimension and body mass of canine cadavers. Under this study conditions, it is possible to conclude that the patellar size varies according to the canine body mass and these measures should be considered when planning a prosthetic replacement.(AU)

Técnica quirúrgica de reconstrucción de ligamento patelofemoral medial / Surgical technique of medial patellofemoral ligament reconstruction

El ligamento patelofemoral medial (LPFM) es el principal limitador de la lateralización rotuliana. En un episodio de luxación patelar externa se produce una rotura de éste ligamento, el cual tiene una baja capacidad de cicatrización, por lo que una vez dañado, en la mayoría de los casos al no cicatrizar, genera un incremento en la laxitud de las estructuras mediales y síntomas relacionados con inestabilidad. Es relevante describir en forma detallada la técnica quirúrgica, debido que ante un segundo episodio de luxación, en un joven activo (grupo que más afecta), en el cual el primero fue tratado en forma adecuada, consideramos conveniente realizar la reconstrucción de LPFM. Teniendo en cuenta que si bien es una patología que tiene baja incidencia, limita mucho el desarrollo normal del individuo y que la cirugía es un procedimiento efectivo por el bajo índice de re luxación y el alivio de la sintomatología. En la cirugía se debe intentar realizar una reconstrucción anatómica y tener en cuenta si se debe adicionar otros procedimientos como la liberación del retináculo lateral y la osteotomía de la tuberosidad anterior de la tibia (TAT).

The patellofemoral ligament is the main limiting component of the patellar lateral instability. The ligament has poor cicatrization properties, reason why, at the time of injury it does not have a good cicatrization. That situation increases the medial tissue laxity and lateral instability symptoms It is important to describe the surgical technique due to the fact that when a second episode occurs in a active young patient (the most frequent group) and when the first one had been treated correctly, we recommend the ligament reconstruction surgery. Although, this pathology has a low incidence, and it compromise the normal development of young patients. The surgery is an effective procedure, because of its low index of reluxation episodes and relief the symptoms. During the surgery we must try an anatomic reconstruction and the surgeon has to take into account the necessity to add others procedures like anterior tuberosity osteotomy or the lateral retinaculum cut.

Luxação de patela em cães: estudo retrospectivo / Patellar luxation in dogs: a retrospective study

A five-year retrospective study of dogs with patellar luxation was performed. A total of 75 dogs (n=122limbs) were studied: 82.7% (n=62) had medial luxation, 14.6% (n=11) had lateral luxation, and 2.7%(n=2) had both luxations in same stifle joint. Considering the dogs with medial patellar luxation, 6.7%(n=5) were mixed-breed and 76% (n=57) were purebred, with high prevalence in Poodles (n=27; 35.6%),Pinschers (n=13; 17.3%), and Yorkshires (n=4; 5.3%). Of the dogs with lateral patellar luxation, one(1.3%) was mixed-breed and 13.3% were purebred, with high prevalence in Poodles (n=6; 8%) andPinschers (n=2; 2.7%). Regarding the 62 dogs with medial patellar luxation, 20 were unilateral and 42bilateral. Of the 11 dogs with lateral patellar luxation, five were unilateral and six bilateral. Statistically,females were more affected than males by both medial and lateral patellar luxations. The grade II (25;33.3%) of patellar luxation was the most often in medial luxation followed by grades III (20; 26.7%), IV(11; 14.7%), and I (16; 7.9%). The grade II (5; 6.7%) was the most often in lateral luxation followed bygrade I (4; 5.3%), and simultaneously grades III (1.3%) and IV (1.3%). The surgical treatment wasperformed in 64 dogs and the others were submitted a conservative management. It was possible toconclude that among the dogs with patellar luxation evaluated in this study, the most affected were toyand miniature breeds and female dogs with medial patellar luxation.