Femoral neck osteosynthesis using interfragmentary compression or position screw in synthetic bones. What are the mechanical differences?

PURPOSE: We aim to compare interfragmentary compression with the position osteosynthesis in the fixation of different femoral neck fractures (FN) in synthetic bones subjected to vertical load. METHODS: Forty-two synthetic femurs were subjected to neck fractures and separated into 3 groups according to the Pauwels classification: Pauwels I had 6 units (PI); Pauwels II, 24 units, with and without comminution (PII); and Pauwels III, 12 units, with and without comminution (PIII). After, they were fixed with 2 different ways: three 7, 0 mm cannulated lag screws (CSs) versus three 6, 5 mm solid fully threaded screws (SSs). Screws positioning was oriented by the Pauwels classification: inverted triangle or crossed screws. All specimens were submitted to vertical loading until failure. RESULTS: The average force was 79.4 ± 22.6 Kgf. The greatest one was recorded in model 1 (135.6 Kgf), and the lowest in model 41 (39.6 Kgf). CSs and SSs had similar resistance until failure (p = 0.2). PI showed heightened resistance and PIII showed a worse response (p < 0,01). CSs had better performance in PIII (p = 0.048). Comminution and screws orientation caused no difference on peak force (p = 0.918 and p = 0.340, respectively). CONCLUSIONS: In synthetic bones, the resistance of a femoral neck fracture osteosynthesis using a 7, 0 mm cannulated lag screw or 6, 5 mm solid fully threaded screw are similar. There was no loss of efficiency with comminution in the femoral neck. Osteosynthesis resistance decreased with the verticalization of the fracture line and, in the more vertical ones, interfragmentary compression with CSs was more resistant than positional osteosynthesis with SSs.

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. .

Biomechanical Study: Resistance Comparison of Posterior Antiglide Plate and Lateral Plate on Synthetic Bone Models Simulating Danis-Weber B Malleolar Fractures.

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.

ANALYSIS ON THE VARIATION OF MEDIAL ROTATION VALUES ACCORDING TO THE POSITION OF THE HUMERAL DIAPHYSIS.

OBJECTIVE: To analyze the validity of measurements of medial rotation (MR) of the shoulder, using vertebral levels, according to the variation in the position of the humeral diaphysis, and to test the bi-goniometer as a new measuring instrument. METHODS: 140 shoulders (70 patients) were prospectively evaluated in cases presenting unilateral shoulder MR limitation. The vertebral level was evaluated by means of a visual scale and was correlated with the angle obtained according to the position of the humeral diaphysis, using the bi-goniometer developed with the Department of Mechanical Engineering of Mackenzie University. RESULTS: The maximum vertebral level reached through MR on the unaffected side ranged from T3 to T12, and on the affected side, from T6 to the trochanter. Repositioning of the affected limb in MR according to the angular values on the normal side showed that 57.13% of the patients reached lower levels, between the sacrum, gluteus and trochanter. From analysis on the maximum vertebral level attained and the variation between the affected angle x (frontal plane: abduction and MR of the shoulder) and the unaffected angle x in MR, we observed that the greater the angle of the diaphyseal axis was, the lower the variation in the vertebral level attained was. From evaluating the linear correlation between the variables of difference in maximum vertebral level reached and variation in the affected angle y (extension and abduction of the shoulder) and the unaffected angle y in MR, we observed that there was no well-established linear relationship between these variables. CONCLUSION: Measurement of MR using vertebral levels does not correspond to the real values, since it varies according to the positioning of the humeral diaphysis.

Análise da variação dos valores da rotação medial conforme a posição da diáfise do úmero / Analysis on the variation of medial rotation values according to the position of the humeral diaphysis

OBJETIVO: Analisar a validade da medida de rotação medial (RM) do ombro pelos níveis vertebrais conforme a variação da posição da diáfise do úmero, testando o bigoniômetro como novo instrumental de aferição. MÉTODOS: Foram avaliados, prospectivamente, 140 ombros (70 pacientes) que tinham limitação da RM do ombro unilateral. Avaliou-se, por meio da escala visual, o nível vertebral e correlacionou-se com o ângulo obtido conforme a posição da diáfise do úmero utilizando o bigoniômetro desenvolvido com a Engenharia Mecânica do Mackenzie. RESULTADOS: O nível vertebral máximo alcançado na RM do lado não acometido variou de T3 a T12, e para o lado acometido variou de T6 a trocânter. Já quando o membro acometido foi reposicionado em RM de acordo com os valores angulares do lado normal, 57,13% dos pacientes alcançaram níveis mais baixos entre sacro, glúteo e trocânter. Analisando o nível vertebral máximo alcançado e a variação entre o ângulo x (plano frontal: abdução e RM do ombro) acometido e o ângulo x não acometido em RM, verificamos que quanto maior a angulação do eixo da diáfise menor a variação do nível vertebral alcançado. Avaliando a correlação linear entre as variáveis diferença do nível vertebral máximo alcançado e a variação do ângulo y (extensão e adução do ombro) acometido e ângulo y não acometido em RM, verificamos que não há uma relação linear bem estabelecida entre estas variáveis. CONCLUSÃO: A medida da RM pelos níveis vertebrais não corresponde aos valores reais, pois varia conforme o posicionamento da diáfise do úmero.

OBJECTIVE: To analyze the validity of measurements of shoulder medial rotation (MR) of the shoulder, using vertebral levels, according to the variation in the position of the humeral diaphysis, and to test the bi-goniometer as a new measuring instrument. METHODS: 140 shoulders (70 patients) were prospectively evaluated in cases presenting unilateral shoulder MR limitation. The vertebral level was evaluated by means of a visual scale and was correlated with the angle obtained according to the position of the humeral diaphysis, using the bi-goniometer developed with the Department of Mechanical Engineering of Mackenzie University. RESULTS: The maximum vertebral level reached through MR on the unaffected side ranged from T3 to T12, and on the affected side, from T6 to the trochanter. Repositioning of the affected limb in MR according to the angular values on the normal side showed that 57.13% of the patients reached lower levels, between the sacrum, gluteus and trochanter. From analysis on the maximum vertebral level attained and the variation between the affected angle x (frontal plane: abduction and MR of the shoulder) and the unaffected angle x in MR, we observed that the greater the angle of the diaphyseal axis was, the lower the variation in the vertebral level attained was. From evaluating the linear correlation between the variables of difference in maximum vertebral level reached and variation in the affected angle y (extension and abduction of the shoulder) and the unaffected angle y in MR, we observed that there was no well-established linear relationship between these variables. CONCLUSION: Measurement of MR using vertebral levels does not correspond to the real values, since it varies according to the positioning of the humeral diaphysis.