Plate-screw and screw-washer stability in a Schatzker type-I lateral tibial plateau fracture: a comparative biomechanical study / Comportamento biomecânico de dois tipos de fixação usados como suporte na fratura do platô tibial lateral do tipo I de Schatzker

ABSTRACT The aim of this study was to evaluate the biomechanical role of both a non-locking two-hole small fragment dynamic compression plate with 3.5-mm screws and a 4.5-mm cortical screw with a washer applied to a Schatzker type-I tibial plateau fracture. Sixteen right synthetic tibiae were used to create an anterolateral shear tibial plateau fracture (Schatzker type-I fracture). Eight models were fixed with a small fragment non-locked straight dynamic compression plate with one 3.5-mm bicortical screw (plate-screw construction) and eight models were fixed with a 4.5-mm cortical screw and a washer (screw-washer construction), both inserted at 1.0 mm distal to the apex of the fracture. Specimens were tested up to the onset of yielding at a constant strain rate of 5.0-mm/min. Stiffness ranged from 311.83 N/mm to 199.54 N/mm, with a mean + SD of 260.32 + 33.8 N/mm in the plate-screw construction, and from 290.34 N/mm to 99.16 N/mm, with a mean + SD of 220.46 + 63.12 N/mm in screw-washer construction. There was no significant difference (p=0.172). Use of a two-hole small-fragment non-locked plate with one 3.5-mm cortical screw or a 4.5-mm cortical screw with a washer applied at 1.0 mm distal to the apex of the fracture as buttressing present similar stiffness in terms of preventing axial displacement in synthetic tibiae models tested up to the onset of yielding.

RESUMO O objetivo do estudo foi avaliar o comportamento biomecânico de dois tipos de fixação: placa de compressão dinâmica de pequenos fragmentos, não bloqueada com parafuso de 3,5mm e parafuso cortical de 4,5mm com arruela, ambos posicionados no vértice de fratura do platô tibial do tipo I de Schatzker. Dezesseis tíbias sintéticas foram utilizadas para criar uma fratura por cisalhamento na face ântero-lateral do platô tibial (tipo I de Schatzker). Oito modelos foram fixados com placa de compressão dinâmica de pequenos fragmentos não bloqueada com parafuso de 3,5mm, inserido 1,0mm distal ao vértice da fratura (construção placa-parafuso), e oito modelos foram fixados com parafuso cortical de 4,5mm com arruela, inserido 1,0mm distal ao vértice da fratura (construção parafuso-arruela). Os modelos foram testados em compressão axial até o início da falha mecânica na interface construção-osso, com taxa de deformação constante de 5,0mm/min. A rigidez variou de 311,83 N/mm a 199,54 N/mm, com média + DP de 260,32 + 33,8 N/mm nos modelos da construção placa-parafuso, e de 290,34 N/mm a 99,16 N/mm, com média + DP de 220,46 + 63,12 N/mm nos modelos da construção parafuso-arruela. Não houve diferença estatisticamente significativa (p=0,172). A utilização de placa de compressão dinâmica de pequenos fragmentos não bloqueada com parafuso de 3,5mm ou de parafuso cortical de 4,5mm com arruela, posicionados no vértice da fratura do platô tibial do tipo I de Schatzker, apresenta rigidez similar na prevenção do desvio axial da fratura.

Mechanical study in vitro of the resistance of axial forces of 3.5 mm cannulated and conventional screws in head and femoral neck fractures / Estudo mecânico in vitro da resistência a forças axiais dos parafusos canulado e convencional de 3, 5 mm de diâmetro em fraturas de cabeça e colo femoral

Background: Proximal femoral fractures account for 25% of all femoral fractures in dogs and are more common in younganimals. Osteosynthesis of femoral head and neck fractures is a complex procedure that can be performed using conventionalscrews or wires. However, proper fracture reduction and fi xation are diffi cult to achieve and, despite many advancements,such fractures remain challenging to solve. Cannulated screws have good compressive capacity and can be employed tosimplify the surgical procedure while optimizing outcomes. This study was designed to compare the resistance of conventional and cannulated screws to axial loading following experimental femoral neck fracture in dogs.Materials, Methods & Results: Fourteen cadaveric canine femurs were used in this study. Femurs were collected from dogsover 20 pounds in body weight with no gross or radiographic signs of orthopedic disease. Cadaveric femurs were submitted to experimental femoral neck fracture using a Gigli saw and allocated to osteosynthesis using either conventional orcannulated screws (seven bones each). All screws were inserted below the greater trochanter of the femur from the lateralaspect of the bone and screw topography confi rmed radiographically. Test specimens were then potted in polymethylmethacrylate, coupled to a hinged device and submitted to axial loading. Data on maximum load, maximum displacement, loadwithin the proportional limit, offset within the proportional limit and load required to produce a 3 mm displacement werecollected. Mean values were calculated and compared using the Student’s t test (P < 0.05). Mean values varied greatlywithin groups. Maximum load and displacement correspond to the critical point from which biomechanical testing becomesdestructive. Data were missing from one test specimen (conventional screw group) due to abrupt diaphyseal fracture atthe start of the axial loading trial...

Mechanical study in vitro of the resistance of axial forces of 3.5 mm cannulated and conventional screws in head and femoral neck fractures / Estudo mecânico in vitro da resistência a forças axiais dos parafusos canulado e convencional de 3, 5 mm de diâmetro em fraturas de cabeça e colo femoral

Background: Proximal femoral fractures account for 25% of all femoral fractures in dogs and are more common in younganimals. Osteosynthesis of femoral head and neck fractures is a complex procedure that can be performed using conventionalscrews or wires. However, proper fracture reduction and fi xation are diffi cult to achieve and, despite many advancements,such fractures remain challenging to solve. Cannulated screws have good compressive capacity and can be employed tosimplify the surgical procedure while optimizing outcomes. This study was designed to compare the resistance of conventional and cannulated screws to axial loading following experimental femoral neck fracture in dogs.Materials, Methods & Results: Fourteen cadaveric canine femurs were used in this study. Femurs were collected from dogsover 20 pounds in body weight with no gross or radiographic signs of orthopedic disease. Cadaveric femurs were submitted to experimental femoral neck fracture using a Gigli saw and allocated to osteosynthesis using either conventional orcannulated screws (seven bones each). All screws were inserted below the greater trochanter of the femur from the lateralaspect of the bone and screw topography confi rmed radiographically. Test specimens were then potted in polymethylmethacrylate, coupled to a hinged device and submitted to axial loading. Data on maximum load, maximum displacement, loadwithin the proportional limit, offset within the proportional limit and load required to produce a 3 mm displacement werecollected. Mean values were calculated and compared using the Students t test (P < 0.05). Mean values varied greatlywithin groups. Maximum load and displacement correspond to the critical point from which biomechanical testing becomesdestructive. Data were missing from one test specimen (conventional screw group) due to abrupt diaphyseal fracture atthe start of the axial loading trial...(AU)

Biomechanical study: resistance comparison of posterior antiglide plate and lateral plate on synthetic bone models simulating Danis-Weber B malleolar fractures / Comparação da resistência mecânica pela osteossíntese com placas fixadas nas posições lateral e posterior em fraturas Danis-Weber B: estudo experimental

OBJECTIVE: The purpose of this study was to compare different positions of plates in lateral malleolar Danis-Weber B fractures on synthetic bone: a lateral plate and a posterior antiglide plate. METHODS : Short oblique fractures of distal fibula at the level of the syndesmosys were simulated with a fibular osteotomy in sixteen synthetic fibula bones (Synbone®). Eight fractures were fixed with lateral plating associated with an independent lag screw, and the other eight were fixed with posterior antiglide plating with a lag screw through the plate. A strain gage was installed at the center of each plate at the osteotomy site. Supination and external rotation forces were applied to each of the two groups at the bend. RESULTS : The lateral position plate group suffered more deformity in response to supination forces compared to the group with the posterior antiglide plate, but this result was not statistically significant. In the tests with external rotation forces, the posterior antiglide plating group had significantly higher resistance (p < 0.05). CONCLUSION : When subjected to external rotation forces, osteosynthesis with posterior antiglide plate models simulating type B fractures of the lateral malleolus of the ankle is more resistant than that of the neutralization plate. .

OBJETIVO: Comparar a resistência mecânica da fixação do maléolo lateral do tornozelo com placa em posição lateral ou posterior com o maléolo em modelos de fíbula sintética, com simulação de fraturas tipo B de Danis-Weber. MÉTODO: A simulação da fratura em 16 fíbulas sintéticas (Synbone®) foi feita por corte oblíquo com serra oscilatória de 1 mm. Em oito modelos, a falha foi fixada por placa de neutralização (posição lateral); as demais por placa anticisalhante (posição posterior). Em seguida instalamos um extensômetro no centro de cada placa, visando a mensurar a deformação determinada pelas forças em supinação produzidas durante experimento na bancada nos dois grupos. Outro ensaio foi produzido com força de rotação externa sobre o implante. RESULTADOS : O grupo com osteossíntese de neutralização sofreu deformação maior aos esforços em supinação quando comparado com o grupo com placa anticisalhante, porém sem significância estatística. Nos ensaios com força em rotação externa houve significância estatística em favor da eficiência das placas posteriores (p < 0,05). CONCLUSÃO : A osteossíntese com placa anticisalhante em modelos que simulam fraturas tipo B do maléolo lateral do tornozelo é mais resistente do que a placa de neutralização quando submetidas às forças em rotação externa. .

Estudo biomecânico do comportamento de diferentes espessuras de capa de cimento ósseo em novo modelo de prótese modular diafisária femoral em cão submetidas a ensaio de torção / Biomechanical Analysis in the Use of Different Cement Layers in a New Model of Modular Diaphyseal Femoral Implant Relative to Torsion Forces

Background: The feasibility of modular cemented prosthesis in the femoral diaphysis was demonstrated in dogs, but several authors report loosening of bone-cement-implant interface as a major complication and have yet to reach a consensus on the ideal cement layer thickness for reducing postoperative morbidity. The objective of this study was to evaluate the stabilization of the prosthesis using different thicknesses of cement layer, subjected to torsion forces. Materials, Methods & Results: For this study 48 femurs from 24 dogs weighing over 15 kg were used. The animals used did not have any prior diagnosis of bone or nutritional diseases, which was an exclusion criteria for this study. All biological materials were obtained immediately after death or euthanasia of the animal, and then subjected to conventional storage in a freezer at a temperature of - 24°C. The prosthesis was composed of a cylindrical part with rods for attachment to the intramedullary canal, made of alloy steel 316L. After thawing the femurs and subsequent stabilization at room temperature we performed osteotomies of the femoral diaphysis with an oscillating saw and the installation of the prosthesis. As preparatory measures for prosthesis fixation with cement, the intramedullary canals were cleaned, washed with saline and aspirated. They were separated in four groups, the first group with eight femurs used a cement mantle of 1.0 to 1.5 mm, the second group, with eight femurs, used a cement mantle of 2.0 to 2.5 mm and the third group, with eight femurs, used a cement layer of 3.0 to 3.5 mm. The femurs were submitted to destructive torsion tests using a universal testing machine with a load cell of 981 N (100 kg) and an essay speed of 22 mm / min. They were evaluated due to the values of torsional rigidity and maximum torque shown by the implant, bone and bone cement interface. The fourth group consisted of the remaining intact femurs, they were evaluated using the same torsion test used on the other groups. The results were analyzed using the Statistical Analysis System (SAS, 2001) and the normality of residuals was previously verified by the Shapiro-Wilk test. It was established to conduct the testing using an external rotation protocol in order to standardize, assuming a situation where the dog was in movement during a uniform curvilinear motion, trying to mimic a situation where the rotational forces were acting more significantly on the femur. Discussion: In our study the importance of cleaning up the intramedullary canal for proper bone cement penetration, a good reaming of the intramedullary canal and drying the area before the cement implantation was made clear. Statistical analysis showed that the thicknesses of the cement layer ranging from 1 mm to 2.5 mm, although bringing a gradual increase in maximum torque and torsional rigidity, are not sufficient to be statistically significant and may be considered equal in their biomechanical behavior assessed by this study. A similar result was found when we compared the 2 mm to 3.5 mm layers. The comparison that was statistically significant and can be considered in relation to the different biomechanical behavior of the cement layer was seen between the group I of 1 mm to 1.5 mm, and group III of 3 mm to 3.5 mm. Although some results were not statistically significant we must remember that, in absolute values, the torsional rigidity and maximum torque increased linearly with the increasing of the cement layer. From these results we can infer about the real advantage of using a thicker cement layer over an increment in the diameter of the intramedullary component, giving greater resistance to the prosthesis.

Biomechanical analysis in the use of different cement layers in a new model of modular diaphyseal femoral implant relative to torsion forces / Estudo biomecânico do comportamento de diferentes espessuras de capa de cimento ósseo em novo modelo de prótese modular diafisária femoral em cão submetidas a ensaio de torção

Background: The feasibility of modular cemented prosthesis in the femoral diaphysis was demonstrated in dogs, but several authors report loosening of bone-cement-implant interface as a major complication and have yet to reach a consensus on the ideal cement layer thickness for reducing postoperative morbidity. The objective of this study was to evaluate the stabilization of the prosthesis using different thicknesses of cement layer, subjected to torsion forces. Materials, Methods & Results: For this study 48 femurs from 24 dogs weighing over 15 kg were used. The animals used did not have any prior diagnosis of bone or nutritional diseases, which was an exclusion criteria for this study. All biological materials were obtained immediately after death or euthanasia of the animal, and then subjected to conventional storage in a freezer at a temperature of - 24C. The prosthesis was composed of a cylindrical part with rods for attachment to the intramedullary canal, made of alloy steel 316L. After thawing the femurs and subsequent stabilization at room temperature we performed osteotomies of the femoral diaphysis with an oscillating saw and the installation of the prosthesis. As preparatory measures for prosthesis fixation with cement, the intramedullary canals were cleaned, washed with saline and aspirated. They were separated in four groups, the first group with eight femurs u

O fêmur canino é submetido a uma grande carga excêntrica durante a sustentação de peso e deambulação, sendo que suas propriedades biomecânicas afetam diretamente a forma como se comportam em relação às forças a que são submetidos no animal vivo. [...]

Biomechanical analysis in the use of different cement layers in a new model of modular diaphyseal femoral implant relative to torsion forces / Estudo biomecânico do comportamento de diferentes espessuras de capa de cimento ósseo em novo modelo de prótese modular diafisária femoral em cão submetidas a ensaio de torção

Background: The feasibility of modular cemented prosthesis in the femoral diaphysis was demonstrated in dogs, but several authors report loosening of bone-cement-implant interface as a major complication and have yet to reach a consensus on the ideal cement layer thickness for reducing postoperative morbidity. The objective of this study was to evaluate the stabilization of the prosthesis using different thicknesses of cement layer, subjected to torsion forces. Materials, Methods & Results: For this study 48 femurs from 24 dogs weighing over 15 kg were used. The animals used did not have any prior diagnosis of bone or nutritional diseases, which was an exclusion criteria for this study. All biological materials were obtained immediately after death or euthanasia of the animal, and then subjected to conventional storage in a freezer at a temperature of - 24C. The prosthesis was composed of a cylindrical part with rods for attachment to the intramedullary canal, made of alloy steel 316L. After thawing the femurs and subsequent stabilization at room temperature we performed osteotomies of the femoral diaphysis with an oscillating saw and the installation of the prosthesis. As preparatory measures for prosthesis fixation with cement, the intramedullary canals were cleaned, washed with saline and aspirated. They were separated in four groups, the first group with eight femurs u

O fêmur canino é submetido a uma grande carga excêntrica durante a sustentação de peso e deambulação, sendo que suas propriedades biomecânicas afetam diretamente a forma como se comportam em relação às forças a que são submetidos no animal vivo. [...]