Biomechanical evaluation of a new femoral stem design for total hip replacement in a canine model.

PURPOSE: To evaluate the biomechanical properties of a novel total hip replacement femoral stem. METHODS: Eight pairs of femurs from dog cadavers were used. The femurs were separated into different groups. A novel femoral stem with a convex proximal portion (Stem B) was biomechanically evaluated and compared to awell-known veterinary collared stem (Stem A). Femoral stems were inserted into the contralateral femurs from the same dog, forming 16 constructs. A flexo-compression load was applied on the axial axis of each sample. Maximum strength, deflection, stiffness, and energy absorption were analysed. RESULTS: Group B constructs showed significantly higher values (p ? 0.05) for the variables, except stiffness. The mean maximum strength was 1,347 ± 357 N for Group A and 1,805 ± 123 N for Group B (p ? 0.0069). The mean deflection was5.54 ± 2.63 mm for Group A and 10.03 ± 3.99 mm for Group B (p ? 0.0056). For the energy variable, the force was 6,203 ± 3,488 N/mm for Group A and 12,885 ± 5,056 N/mm for Group B (p ? 0.0054). Stem B had greater maximum strength, deflection, and energy. CONCLUSIONS: The new stem was effective in neutralizing the impact of axial flexion-compression stresses during biomechanical tests in cadaveric models.

Percutaneous application of allogeneic adipose-derived mesenchymal stem cell in dogs submitted to minimally invasive plate osteosynthesis of the tibia.

PURPOSE: To evaluate clinical outcome following minimally invasive plate osteosynthesis (MIPO) associated with percutaneous transplantation of allogeneic adipose-derived mesenchymal stem cells (AD-MSC) at the tibial fracture site in dogs. METHODS: Thirty-six dogs presenting with nonarticular complete tibial fracture were included in this study. All fractures were treated by the same MIPO technique. The animals were divided in group 1 (n = 20) received a percutaneous application of 3 × 106 AD-MSC at the fracture site and group 2 (n = 16) did not receive any adjuvant treatment. Postoperative radiographic examinations were made at 15, 30, 60, 90 and 120 days. RESULTS: Fifty-eight percent of the patients were classified as skeletally immature. The median weight of the animals was 18.8 kg. The mean radiographic union time differed statistically between the AD-MSC group (28.5 days) and the control group (70.3 days). Sixty percent of dogs in group 1 and 56.25% of the group 2 were considered immature. CONCLUSIONS: The use of allogeneic AD-MSC cell therapy and MIPO is a safe, viable and effective technique for promoting bone healing in nonarticular tibial fractures in dogs.

Bone alignment after minimally invasive plate osteosynthesis of the tibia in dogs / Avaliação do alinhamento ósseo após osteossíntese minimamente invasiva com placa de tíbia em cães

ABSTRACT: This study assessed radiographically changes in tibial alignment in the frontal and sagittal planes in dogs that underwent minimally invasive plate osteosynthesis (MIPO) without the aid of image intensifiers. Radiographs of dogs with complete non-articular tibial fractures submitted to MIPO were included and evaluated, without the aid of a transoperative image intensifier and / or an association of implants. The tibial mechanical angles (mMPTA, mMDTA, mCaPTA and mCrDTA) were measured by three evaluators. The data obtained were compared with results from previously published studies. Twenty-seven animals were included in the study. The mean and standard deviation of the angular changes were as follows: mMPTA, 2.54° ± 3.10 (-1.1º to 8.7º); mMDTA, 0.03º ± 0.16 (-3.44º to 0.79º); mCaPTA, 37º ± 4.29 (-6.23º to 14.87º); and mCrDTA, 8.25° ± 5.53 (-0.2º to 17.28º). There was a negative correlation between "mCaPTA" and "mCrDTA". MIPO of the tibia without using image intensifiers and implant association can potentially cause angular changes, which can lead to clinically relevant deformities after bone healing.

RESUMO: Este estudo teve como objetivo avaliar radiograficamente as alterações no alinhamento da tíbia nos planos frontal e sagital em cães submetidos à osteossíntese minimamente invasiva com placa (MIPO) sem o auxílio de intensificadores de imagem. Foram incluídas e avaliadas radiografias de cães com fraturas completas da tíbia não articulares submetidos a MIPO, sem o auxílio de intensificador de imagem transoperatório e/ou associação de implantes. Os ângulos mecânicos tibiais (mMPTA, mMDTA, mCaPTA e mCrDTA) foram mensurados por três avaliadores. Os dados obtidos pela média de todas as avaliações foram comparados com resultados de estudos previamente publicados. Vinte e sete animais foram incluídos no estudo. A média e desvio padrão das alterações angulares foram os seguintes: mMPTA= 2,54° ± 3,10 (-1,1º a 8,7º); mMDTA= 0,03º ± 0,16 (-3,44º a 0,79º); mCaPTA= 37º ± 4,29 (-6,23º a 14,87º); e mCrDTA= 8,25 ° ± 5,53 (-0,2º a 17,28º). Houve uma correlação negativa entre "mCaPTA" e "mCrDTA". A realização de MIPO em tíbia sem o uso de intensificadores de imagem e associação de implantes pode causar alterações angulares, o que pode levar a deformidades clinicamente relevantes após a cicatrização óssea.

Canal flare index evaluation for different dog breeds / Avaliação do canal flare index femoral de diferentes raças de cães

ABSTRACT: This study determined the canal flare index (CFI) of four dog breeds using two distinct femoral regions as a reference. Thirty-five radiographs of the hip joints of Golden Retrievers (GRG), German Shepherds (GSG), Labrador Retrievers (LRG), and Rottweilers (RG) of both sexes were used. Seventy experimental units were submitted to CFI calculation. Objective (CFIob) and subjective (CFIsub) values of the CFI of each experimental unit were determined according to the anatomical reference used for the calculation. A significant difference in the CFIob between the Golden Retriever and German Shepherd breeds (1.68 ± 0.16 and 1.49 ± 0.08), and in the CFIsub between Golden Retriever, German Shepherd, and Rottweiler breeds (2.09 ± 0.31, 1.86 ± 0.11, and 1.84 ± 0.18) was reported. The subjective form of measurement showed higher values than the objective form (GRG: 2.09 ± 0.31; GSG: 1.86 ± 0.11; LRG: 2.07 ± 0.12; RG: 1.84 ± 0.18). The CFI values of each breed were similar, suggesting a certain racial pattern. A significant difference in the interobserver assessment for both CFIsub and CFIob, in all races was observed. The CFI analysis identified morphological patterns of the proximal femur in the different races. Results indicated the need for standardization of the anatomical references used to calculate the CFI because there were statistical differences among the measurements among the observers.

RESUMO: Objetivou-se determinar o canal flare index (CFI) de quatro raças específicas de cães, utilizando-se duas regiões femorais distintas como referência. Foram analisadas 35 radiografias de articulações coxofemorais de cães das raças Golden Retriever (GGR), Pastor Alemão (GPA), Labrador Retriever (GLR) e Rottweiler (GR), de ambos os sexos, configurando 70 unidades experimentais submetidas ao cálculo do CFI. Determinaram-se os valores objetivo (CFIob) e subjetivo (CFIsub) do CFI de cada unidade experimental de acordo com a referência anatômica utilizada para o cálculo. Houve diferença significativa do CFIob entre as raças Golden Retriever e Pastor Alemão (1,68 ± 0,16 e 1,49 ± 0,08), e do CFIsub entre as raças Golden Retriever, Pastor Alemão e Rottweiler (2,09 ± 0,31, 1,86 ± 0,11 e 1,84 ± 0,18). A forma subjetiva de mensuração apresentou valores maiores que a forma objetiva (GGR: 2,09 ± 0,31; GPA: 1,86 ± 0,11; GLR: 2,07 ± 0,12; GR: 1,84 ± 0,18). Os valores de CFI de cada raça se apresentaram similares, sugerindo haver determinado padrão racial. Houve diferença significativa na avaliação interobservadores, tanto do CFIsub quanto CFIob, em todas as raças. A análise do CFI identificou padrões morfológicos do fêmur proximal nas diferentes raças. Os resultados indicaram a necessidade de padronização dos referenciais anatômicos utilizados para o cálculo do CFI, uma vez que houve relevância estatística entre as diferentes mensurações entre os observadores.