Locking configuration on the biomechanical performance of an angle-stable intramedullary interlocking nail in a synthetic bone modelABSTRACT:
This study evaluated the biomechanical effect of a locking configuration on resistance to axial compressive loading in a novel angle-stable intramedullary interlocking nail (AS-ILN), using synthetic bone models designed to simulate complex diaphyseal fractures. Specimens were 3D-printed in polylactic acid and incorporated integrated end supports to facilitate secure gripping during mechanical testing. The ILN design included six internally threaded holes (three proximal and three distal). A custom template stand ensured consistent nail placement across all specimens. Twenty-eight samples were allocated into four groups (n = 7), differing only in locking configuration): G1 (holes 1 and 6), G2 (holes 1 and 2, and distal holes 5 and 6), G3 (proximal holes 2 and 3, and distal holes 4 and 5) and G4 (all six holes). Axial compression was applied at a rate of 5 mm/min using a universal testing machine. Data from four groups (G1- G4; n = 7 per group) were analyzed, with normality confirmed by the Shapiro-Wilk test (P = 0.070). Mean failure load was highest in G4 (9420.34N ± 4081.37N), followed by G3 (9180.20N ± 1751.38N), G2 (8101.31N ± 2372.58N), and G1 (5933.59N) ± 1300.79N). However, no statistically significant differences were detected (one-way ANOVA, P = 0.074). These findings indicated that, under axial compressive loading, construct resistance is not significantly affected by the number of bolts per fragment and their spatial distribution relative to the fracture gap. Future studies incorporating flexural and torsional loading conditions are warranted to further characterize the construct performance.
Key words:
biomechanics; bolts; angle-stable interlocking nail; 3D printing
RESUMO:
O presente estudo teve como objetivo avaliar biomecanicamente, por meio de teste de compressão axial, os diferentes posicionamentos e quantidade de bolts em haste intramedular bloqueada de ângulo estável (HIB-AE), em simulação de fratura diafisária irredutível em corpos de prova (CP). Para realizar o objetivo, os CPs, produzidos a partir do ácido polilático por impressora 3D, foram projetados e manufaturados com bloco de apoio na extremidade para a preensão na máquina de ensaios. A haste utilizada no experimento apresentava 6 orifícios (denominados de 1 a 6, de proximal para distal), com roscas internas, sendo 3 em cada extremidade (proximal e distal). Além disso, um aparato específico (bancada gabarito) foi desenvolvido para total padronização e precisa inserção da haste intramedular e bloqueios nos corpos de prova, sendo usadas 28 amostras divididas em 4 Grupos: Grupo 1) a haste foi bloqueada nos orifícios 1 e 6; Grupo 2) o bloqueio aconteceu nos orifícios proximais 1 e 2, e nos orifícios distais 5 e 6; Grupo 3) foram fixados os orifícios 2 e 3 (segmento proximal) e 4 e 5 (segmento distal); já no Grupo 4) todos os 6 orifícios foram bloqueados. Os referidos orifícios foram bloqueados utilizando-se bolts especialmente desenvolvidos para esse modelo de HIB-AE. Os testes de compressão axial foram realizados por máquina de ensaios universal a uma velocidade e 5 mm/minuto. Os resultados das avalições mostram que os dados avaliados entre os quatro Grupos (G1, G2, G3 e G4), resultaram em sete repetições a cada combinação. O teste de Shapiro-Wilk foi aplicado e concluiu-se que os dados apresentavam distribuição normal (P = 0,070). Dentre as cargas médias o maior valor foi registrado no G4 (9420,34N ± 4081,37N) seguido pelos grupos G3 (9180,20N ± 1751,38N), G2 (8101,31N ± 2372,58N) e G1 (5933,59N ± 1300,79N). Ademais, apesar das diferenças observadas entre os valores numéricos médios, nenhuma delas se mostrou estatisticamente significativa na análise de variância (ANOVA) (P = 0,074). Portanto, é possível concluir que no suporte de carga axial compressiva não há diferença significativa quanto ao número de bolts por fragmento ou em relação à distância da falha crítica que esses são posicionados. Entretanto, esses resultados devem ser associados a testes biomecânicos que avaliem cargas flexivas e torcionais, além da correlação com trabalhos clínicos.
Palavra-chave:
biomecânica; bolts; bloqueio de ângulo estável; impressão 3D
INTRODUCTION
The interlocking nail (ILN) is widely regarded as the gold standard implant for long bone fracture treatment in human medicine, owing to its well-established biological and mechanical advantages over other fixation methods (KARAARSLAN et al., 2017; YU et al., 2016; MUKERJEE et al., 2017). Biologically, ILNs are relatively straightforward to implant and support the principles of biological osteosynthesis by preserving the fracture hematoma, maintaining functional alignment, and providing sufficient stabilization to facilitate secondary bone healing (HORSTMAN et al., 2004; DERJARDIN et al., 2012; MUKERJEE et al., 2017; DEJARDIN et al., 2020).
From a mechanical perspective, ILNs offer several advantages. Their circular cross-section maximizes the area moment of inertia (AMI), allowing uniform resistance to bending regardless of load direction (MUIR et al., 1995; PATIL et al., 2008; PETTITT, 2016). Their intramedullary positioning along the mechanical neutral axis also minimizes bending stress compared to eccentrically placed implants (LANSDOWNE et al., 2007; MAZZOCCA et al., 2008). In addition, resistance to axial and torsional forces is achieved through interlocking screws or bolts (MAZZOCCA et al., 2008; PATIL et al., 2008; PETTITT, 2016). Under axial compressive loading, these components are primarily subjected to bending stresses due to their perpendicular orientation relative to the applied load (APER et al., 2003; KARAARSLAN et al., 2017). Therefore, both the AMI and material properties of the locking components are critical determinants of construct strength (CHAO et al., 2003; KARAARSLAN et al., 2015).
Early veterinary adaptations of ILNs were associated with high failure rates, largely due to excessive slack between the nail and locking components. This issue stemmed from the use of cortical screws (DÉJARDIN et al., 2009; DÉJARDIN et al., 2006; TING et al., 2009; VON PFEIL et al., 2005), whose deep thread profiles reduced core diameter and AMI, increasing susceptibility to fatigue failure (DUELAND et al., 1999; DUHAUTOIS, 2003; WHEELER et al., 2004). Consequently, screw breakage was frequently reported in these early models, which limited their clinical applicability and hindered broader adoption, including in Brazil.
Subsequent designs replaced cortical screw with threadless bolts, improving AMI and reducing - but not eliminating - slack. Complete elimination of slack was only achieved with the development of angle-stable interlocking nail systems (AS-ILNs), which are now used in human and veterinary orthopedics (KASPAR et al., 2005; DÉJARDIN et al., 2012; DÉJARDIN et al., 2020; TING et al., 2009).
Earlier ILN designs required multiple locking implants per fragment due to mechanical limitations (DUELAND et al., 1999; DUHAUTOIS, 2003, REEMS et al., 2006). However, advances in implant design have enabled more flexible locking configurations and the use of fewer bolts per fragment while maintaining stability (DÉJARDIN et al., 2012; BRÜCKNER et al., 2016; DÉJARDIN et al., 2020; KARAARSLAN et al., 2016). Despite these advances, no biomechanical studies were found in the literature comparing different locking configurations in AS-ILNs, and no consensus exists regarding the optimal locking configuration per fragment. Therefore, this study evaluated four locking configurations in a newly developed Brazilian AS-ILN, using prototyped specimens simulating irreducible diaphyseal fractures and subjected to destructive axial compressive loading.
MATERIALS AND METHODS
Prototyped test specimens
The specimens were designed using CAD (computer-aided design) software with a cortical thickness of 5 mm, outer diameter of 19 mm, canal diameter of 9 mm, and overall length of 105 mm. For each construct, two specimens were produced to simulate proximal and distal bone fragments. Each specimen included a square base (25 mm × 25 mm × 23 mm) to allow fixation in the testing machine. The proximal fragment was fully perforated along its longitudinal axis to simulate normograde nail insertion (Figure 1A). Models were exported in STL (Standard Tessellation Language) format and fabricated using fused filament 3D printing with polylactic acid (PLA) (VetCraft® Impressões 3D, Jataí, GO, Brazil).
Computer-generated schematic drawings of the implants and test specimens. A - Complete assembly following nail implantation and locking within the test specimens. The specimen dimensions and the 20 mm interfragmentary gap used to simulate a comminuted fracture are shown. The proximal specimen was fully drilled along its longitudinal axis to allow normograde nail insertion (red arrow), whereas in the distal specimen only the medullary canal was drilled, and the support block remained solid. B - Dimensions of the angle-stable intramedullary interlocking nail (AS-ILN) used in the study. C - Bolt designed specifically for this AS-ILN model. The top view of the bolt (black arrow) shows the hexagonal key interface. All dimensions are expressed in millimeters (mm).
Orthopedic implants and instrumentation
The AS-ILN consisted of a solid 316L stainless steel cylinder (180 mm × 8 mm) with six longitudinally aligned threaded holes (three proximal and 3 distal). The spacing between the first and second proximal holes was 11 mm, and 14 mm between all remaining holes. Threaded interfaces enabled angle-stable fixation of the bolts (Figure 1B). Custom-designed bolts (40 mm, 316L stainless steel) were developed based on finite element analysis and consisted of three regions: an unthreaded proximal segment contacting the cis (near) cortex (16mm × 4 mm), a threaded central segment responsible for angular stability (8 mm in length, 3.9 mm outer diameter, 3.5 mm inner diameter), and an unthreaded distal segment contacting the trans (far) cortex (16 mm × 3.5 mm) (Figure 1C).
The AS-ILN implants were inserted using a custom alignment system (“template bench”) consisting of a fixed base, adjustable vertical supports, and four adjustable positioning vises.
Initially, two horizontally mounted vises secured the specimens to the base, and a 20 mm interfragmentary gap was created to simulate a comminuted bone fracture. The interlocking nail was mounted on a dedicated applicator and inserted into the axial channel of the proximal specimen. Care was taken to align the entire length of the nail exclusively with the cylindrical segment of the specimens. Following complete insertion, the applicator was removed and an external drilling guide was attached to the proximal end of the nail. To ensure precise alignment during drilling, the template bench was adjusted so that the two movable vertical walls were positioned close to the external drilling guide. These walls, secured by additional vises, firmly stabilized the guide on both sides. Consequently, all four vises immobilized the specimens and the external drilling guide, enabling consistent bolt placement according to the predefined locking configurations of each experimental group.
Sequential drilling and locking were performed by first drilling the near cortex with a 4 mm drill bit. A modified thread-coupled drill guide was then secured to the nail to stabilize the assembly within the medullary canal and enable collinear drilling of the far cortex using a 3.5 mm drill bit. This procedure was repeated for each nail hole, following a proximal-to-distal sequence, with proximal holes locked first and distal holes; subsequently, in ascending order.
Locking configuration
Holes were numbered from 1 to 6 (proximal: 1-3; distal: 4-6). Four locking configurations were evaluated: Group 1 (G1) - holes 1 and 6 (Figure 2A-A’); G2 - proximal holes 1 and 2, and distal holes 5 and 6 (two bolts per fragment positioned further from the 20 mm fracture gap; Figure 2B-B’); G3 - proximal holes 2 and 3, and distal holes 4 and 5 (two bolts per fragment positioned closer to the 20 mm fracture gap; Figure 2C-C’); G4 - all six holes were locked (Figure 2D-D’). Seven AS-ILN constructs were tested per group, totaling 28 samples.
Computer-generated drawings and corresponding photographs illustrating the locking configurations used in the four experimental groups. A and A’ - G1 configuration, with one bolt per fragment. B and B’ - G2 configuration, with two bolts per fragment positioned farther from the 20 mm interfragmentary gap. C and C’ - G3 configuration, with two bolts per fragment positioned closer to the 20 mm interfragmentary gap. D and D’ - G4 configuration, with all six holes of the angle-stable intramedullary interlocking nail (AS-ILN) locked.
Biomechanical testing
Axial compression testing was performed at the Mechanics Laboratory of the Universidade Federal de Uberlândia (Uberlândia, MG, Brazil), using an Instron universal testing machine (model 5982) at a displacement rate of 5 mm/min, as described by OTTO et al. (2009). Specimens were loaded vertically to simulate axial loading conditions of a comminuted long bone fracture. Destructive single-cycle loading was applied until catastrophic failure of either the specimen or implant occurred, at which point the maximum load was recorded.
Statistical analysis
Data were analyzed using SigmaPlot version 12.0 (Systat Software, San Jose, CA, USA). Normality was assessed using the Shapiro-Wilk test. Subsequently, one-way analysis of variance (ANOVA) was performed, followed by Tukey’s post hoc test for pairwise comparisons. Statistical significance was set at P < 0.05.
RESULTS
The results for the seven replicates per group, including means and standard deviations, are summarized in table 1.
Maximum load values (N), including mean and standard deviation, recorded for seven replicates in each of the four experimental groups (specimens identified as S).
G1 exhibited the lowest load-bearing capacity and the greatest implant deformation, characterized primarily by bolt flexion (Figure 3A). In G2, two samples (28.6%) showed slight plastic deformation of the outermost bolts (holes 1 and 6). In G3, slight deformation of the outermost bolts (holes 2 and 5) was detected in five samples (71.4%). No macroscopic plastic deformation of the bolts was observed in G4. In all groups, specimen failure preceded implant failure and occurred either as abrupt fracture of the specimen (Figures 3B and 3C), which halted testing, or as progressive plastic deformation of the specimen holes (Figure 3C).
Representative images illustrating the mechanical behavior and most common failure modes observed during axial compression testing. A - Plastic deformation of the bolts observed during one of the tests in G1 (red lines). B - Failure of the test specimen at the level of the first two proximal holes in one of the G2 samples (red arrows). C - Progressive plastic deformation of the specimen holes during testing of a G3 sample (black arrows). D - Fracture of the test specimen at the level of the first proximal bolt in a G4 sample (white arrow).
The mechanical behavior of G2 and G3 was comparable. However, G2 exhibited early specimen failure in 3 of 7 replicates (42.8%) (Figure 3B), whereas in G3 this occurred in only two samples (28.6%). In the remaining replicates (71.4%) in G3, testing proceeded without premature fracture (Figure 3C). The highest loads were recorded in G4; however, substantial variability was observed due to abrupt specimen failure at the level of the first two proximal bolts in 57.1% of cases (4 of 7 replicates; Figure 3D). Notably, no behavior indicative of slack or instability between the bolts and the nail holes was detected in any test.
Normality testing using the Shapiro-Wilk test indicated that the data did not deviate from a normal distribution (P = 0.07). Accordingly, a one-way ANOVA test was performed, and no statistically significant differences were detected among groups (P = 0.074).
DISCUSSION
The bolt design used in this study incorporated short threads confined to the central region to promote angle-stable fixation within the nail. However, the presence of threads is directly associated with reduced bending strength, since thread geometry decreases the internal diameter of the bolt and consequently lowers the AMI of the locking implant (CHAO et al., 2007; KARAARSLAN et al., 2015). Because the bolts are oriented perpendicular to the applied compressive load, they are subjected primarily to bending during testing, a condition that also occurs in clinical applications of AS-ILNs for long bone fracture stabilization (HOU et al., 2002; APER et al., 2003; CHAO et al., 2007; KARAARSLAN et al., 2017). Accordingly, AMI, together with the elastic modulus of the implant material, is a key determinant of bending strength (MUIR et al., 1995; MAZZOCCA et al., 2008; GAUTIER, 2016)
KARAARSLAN et al. (2015) demonstrated that increasing thread depth in ILN bolts reduces fixation strength (KARAARSLAN et al., 2015) and further reported that titanium bolts exhibit lower bending strength than steel bolts. This difference is attributed to the lower modulus of elasticity (ME) of titanium (110 GPa) compared to steel (200 GPa) (MAZZOCCA et al., 2008; GAUTIER, 2016). In the present study, the locking implants were therefore manufactured from 316L stainless steel, providing high resistance to axial loading, even in G1 where only one bolt per fragment was used. Although, this configuration showed the greatest macroscopic deformation, the applied loads were substantially higher than those found in vivo.
According to Von Pfeil et al. (2005) a dog suitable for fixation with an 8 mm rod applies approximately 176 N to a single pelvic limb (VON PFEIL et al., 2005). By contrast, the lowest maximum mean recorded in this study was 5933.59 N (G1). These values also exceed typical human physiological loads since a 70 kg individual bearing full weight on one leg generates an axial load of approximately 700 N on the femur (HEINEY et al., 2009). These findings indicated that all locking configurations evaluated in this study are capable of withstanding physiologically relevant axial loads encountered in long bone fracture scenarios. The observed plastic deformation patterns, characterized primarily by bending, are consistent with previous studies identifying bending as the predominant mode of plastic deformation in ILN bolts under axial loading (HOU et al., 2002; APER et al., 2003; CHAO et al., 2007; KARAARSLAN et al., 2017). However, it is important to emphasize that this study was not to evaluate bolt strength per se, but rather to compare different locking configurations. Direct evaluation of bolt strength would require specimens with mechanical properties equal to or exceeding those of the implant (APER et al., 2003; KARAARSLAN et al., 2017).
The use of PLA-printed specimens proved appropriate for the research objectives and is supported by previous reports indicating that the mechanical variability of synthetic materials is 20 to 200 times lower than that of cadaveric bone, resulting in more consistent experimental outcomes (CRISTOFOLINI et al., 1996; PRUITT & CHAKRAVARTULA, 2011). Althoughpremature failures occurred in some specimens during mechanical testing, the use of cadaveric bone would likely have increased variability and limited the ability to compare all four experimental groups. Despite variability in load values, the data followed a normal distribution. By contrast, cadaveric models would likely yield non-normal distributions owing to greater heterogeneity. An additional advantage of synthetic models, also confirmed in this study, is the ease of obtaining and storing samples (REEMS et al., 2006).
The choice of polylactic acid (PLA) as the specimen material was based on previous studies recommending that synthetic models exhibit mechanical strength similar to or greater than that of cortical bone (ZANETTI & BIGNARDI, 2009; PRUITT & CHAKRAVARTULA, 2011). Although PLA mechanical properties vary with processing temperature, its elastic modulus is similar to that of human cortical bone (ROSA et al., 2017). The plastic behavior described for PLA in the literature (ZANETTI & BIGNARDI, 2009; PRUITT & CHAKRAVARTULA, 2011; ROSA et al., 2017) was also observed in the present study, particularly in G3, in which deformation at the level of the bolt holes was the predominant failure mode.
Incorrect insertion of locking implants is a well-recognized complication in interlocking nail systems, particularly in distal holes (DURRAL & DIAZ, 1996; DUELAND et al., 1999; DUHAUTOIS, 2003; WHEELER et al., 2004; JOHNSTON et al., 2017). This issue is even more critical in AS-ILNs, where non-linear bolt insertion prevents proper engagement between the nail and the locking implant. To address this, the present study used a custom stabilization device (template bench) to ensure alignment of the specimens, implant, and instrumentation, in line with the approach described by LUCENA et al. (2019). This system enabled accurate locking in all cases, with no insertion errors observed. Furthermore, locking was performed from proximal to distal holes, as recommended by DÉJARDIN et al. (2012), reducing guide oscillation and improving procedural stability (DÉJARDIN et al., 2012).
Failure in G4 occurred predominantly at the level of the first proximal bolt, likely due to stress concentration in this region. Constructs stabilized with three bolts per fragment may exhibit increased rigidity, promoting localized stress accumulation and predisposing the structure to early failure (HOU et al., 2002; CHAO et al., 2007; OH et al., 2010). This effect may have been further exacerbated by the proximity of the first bolt to the geometric transition between the square base and cylindrical shaft, a region known to concentrate stress (CHAO et al., 2007).
This likely explains why G2 behaved differently from G3, despite similar locking configurations (two bolts per fragment in both groups). In configurations with more than one bolt per fragment in which hole 1 was engaged, stress concentration may have been higher due to its proximity to the geometric transition zone. This hypothesis could be further investigated through finite element analysis under axial loading conditions, enabling visualization of stress distribution and identification of peak Von Mises stress regions (N/mm 2 [MPa]).
Under axial loading, forces are transmitted primarily to the most peripheral locking implants - the first proximal and last distal bolts - which bear the highest loads (HOU et al., 2002; CHAO et al., 2007; GRIFFIN et al., 2009; MAZZOCCA et al., 2008). This explains the observed deformation patterns, which were localized to the outermost bolts. In G2 and G3 (more than one bolt per fragment), deformation was limited to these peripheral bolts, indicating that intermediate bolts contributed less to load bearing. This load distribution may also explain the absence of statistically significant differences between groups, as all locking implants are aligned along the longitudinal axis of the nail, resulting in greater load bearing by the most distal bolts, whereas those closer to the fracture site contribute less. In the present study, specimen failure occurred before bolts closer to the fracture site were fully engaged.
The absence of slack observed in all configurations corroborates previous reports and can be attributed to two factors. First, AS-ILN systems are designed to eliminate slack. Second, slack is not effectively assessed using destructive single-cycle axial loading tests and is better evaluated under torsional or bending conditions (KASPAR et al., 2005, DÉJARDIN et al., 2006; DÉJARDIN et al., 2009; TING et al., 2009).
CONCLUSION
Based on the methodology used in this study, the absence of statistically significant differences between the experimental groups indicates that locking configuration, including both the number of bolts and their spatial position relative to the fracture site, does not significantly affect axial compressive load-bearing capacity. However, even the configuration using a single bolt per fragment withstood higher loads than those typically encountered in vivo.
ACKNOWLEDGMENTS
The authors would like to thank the Fundação de Amparo e Pesquisa do Estado de São Paulo (FAPESP) for funding this study (Grant No. 2018/03382-5).
REFERENCES
-
APER, R. L. et al. Effect of bone diameter and eccentric loading on fatigue life of cortical screws used with interlocking nails. American Journal of Vetenary Research, v.64, n.5, p.569-573, 2003. Available from: <Available from: https://doi.org/10.2460/ajvr.2003.64.569 >. Accessed: Jan. 15, 2019. doi: 10.2460/ajvr.2003.64.569.
» https://doi.org/10.2460/ajvr.2003.64.569.» https://doi.org/10.2460/ajvr.2003.64.569 -
BRÜCKNER, M. et al. Early clinical experience with a newly designed interlocking nail system - Targon® Vet. Vetenary Surgery, v.45, n.6, p.754-763, 2016. Available from: <Available from: https://doi.org/10.1111/vsu.12511 >. Accessed: Feb. 16, 2018. doi: 10.1111/vsu.12511.
» https://doi.org/10.1111/vsu.12511.» https://doi.org/10.1111/vsu.12511 -
CHAO, C. K. et al. Increasing bending strength of tibial locking screws: Mechanical tests and finite element analyses. Clinical Biomechanics, v.22, n.1, p.59-66, 2007. Available from: <Available from: https://doi.org/10.1016/j.clinbiomech.2006.07.007 >. Accessed: Oct. 10, 2019. doi: 10.1016/j.clinbiomech.2006.07.007.
» https://doi.org/10.1016/j.clinbiomech.2006.07.007.» https://doi.org/10.1016/j.clinbiomech.2006.07.007 -
CRISTOFOLINI, L. A. et al, Mechanical validation of whole bone composite femur models. Journal of Biomechanics, v.29, n.4, p.525-435, 1996. Available from: <Available from: https://doi.org/10.1016/0021-9290(95)00084-4 >. Accessed: Oct. 20, 2018. doi: 10.1016/0021-9290(95)00084-4.
» https://doi.org/10.1016/0021-9290(95)00084-4.» https://doi.org/10.1016/0021-9290(95)00084-4 -
DÉJARDIN, L. M. et al. Effect of bending direction on the mechanical behaviour of interlocking nail systems. Veterinary and Comparative Orthopeadics and Traumatology, v.22, n.4, p.264-269, 2009. Available from: <Available from: https://doi.org/10.3415/VCOT-08-08-0075 >. Accessed: Dec. 21, 2018. doi: 10.3415/VCOT-08-08-0075.
» https://doi.org/10.3415/VCOT-08-08-0075.» https://doi.org/10.3415/VCOT-08-08-0075 -
DÉJARDIN, L. M. et al. Interlocking nails and minimally invasive osteosynthesis. Veterinary Clinics of North America: Small Animal Practice, v.42, n.5, p.935-962. 2012. Available from: <Available from: https://doi.org/10.1016/j.cvsm.2012.07.004 >. Accessed: Feb. 14, 2018. doi: 10.1016/j.cvsm.2012.07.004.
» https://doi.org/10.1016/j.cvsm.2012.07.004.» https://doi.org/10.1016/j.cvsm.2012.07.004 -
DÉJARDIN, L. M. et al. In vitro mechanical evaluation of torsional loading in simulated canine tibiae for a novel hourglass-shaped interlocking nail with a self-tapping tapered locking design. American Journal of Vetenary Research, v.67, n.4, p.678-685, 2006. Available from: <Available from: https://doi.org/10.2460/ajvr.67.4.678 >. Accessed: Feb. 06, 2018. doi: 10.2460/ajvr.67.4.678.
» https://doi.org/10.2460/ajvr.67.4.678.» https://doi.org/10.2460/ajvr.67.4.678 -
DÉJARDIN, L. M. et al. Interlocking nails and minimally invasive osteosynthesis. Vetenary Clinics of North America: Small Animal Practice, v.50, n.1, p.67-100, 2020. Available from: <Available from: https://doi.org/10.1016/j.cvsm.2019.09.003 >. Accessed: Jan. 10, 2020. doi: 10.1016/j.cvsm.2019.09.003.
» https://doi.org/10.1016/j.cvsm.2019.09.003.» https://doi.org/10.1016/j.cvsm.2019.09.003 -
DUELAND, R. T. et al. Interlocking nail treatment of diaphyseal long-bone fractures in dogs. Journal of the American Veterinary Medical Association, v.214 n.1, p.59-66, 1999. Available from: <Available from: https://doi.org/10.2460/javma.1999.214.01.59 >. Accessed: Dec. 12, 2018. doi: 10.2460/javma.1999.214.01.59.
» https://doi.org/10.2460/javma.1999.214.01.59.» https://doi.org/10.2460/javma.1999.214.01.59 -
DUHAUTOIS, B. Use of veterinary interlocking nails for diaphyseal fractures in dogs and cats: 121 cases. Veterinary Surgery, v.32, n.1, p.8-20, 2003. Available from: <Available from: https://doi.org/10.1053/jvet.2003.50008 >. Accessed: Feb. 13, 2018. doi: 10.1053/jvet.2003.50008.
» https://doi.org/10.1053/jvet.2003.50008.» https://doi.org/10.1053/jvet.2003.50008 -
DURRAL, I.; DIAZ, M. C. Early experience with the use of an interlocking nail for the repair of canine femoral shaft fractures. Veterinary Surgery, v.25, n.5, p.397-406, 1996. Available from: <Available from: https://doi.org/10.1111/j.1532-950X.1996.tb01434.x >. Accessed: Feb. 05, 2018. doi: 10.1111/j.1532-950x.1996.tb01434.x.
» https://doi.org/10.1111/j.1532-950x.1996.tb01434.x.» https://doi.org/10.1111/j.1532-950X.1996.tb01434.x - GAUTIER, E. Biomechanics of osteosynthesis by screwed plates. In.: POITOUT, D. G. (2 ed.) Biomechanics and Biomaterials in Orthopedics. London: Springer, pp.341-372, 2016.
-
GRIFFIN, L. V. et al. Fatigue strength of common tibial intramedullary nail distal locking screws. Journal of Orthopeadics Surgery and Research, v.4, n.11, p.1-7, 2009. Available from: <Available from: https://doi.org/10.1186/1749-799X-4-11 >. Accessed: Oct. 10, 2019. doi: 10.1186/1749-799X-4-11.
» https://doi.org/10.1186/1749-799X-4-11.» https://doi.org/10.1186/1749-799X-4-11 -
HEINEY, J. P. et al. Distal femoral fixation: a biomechanical comparison of trigen retrograde intramedullary (i.m.) nail, dynamic condylar screw (DCS), and locking compression plate (LCP) condylar plate. The Journal of Trauma, v.66, n.2, p.443-449, 2009. Available from: <Available from: https://doi.org/10.1097/TA.0b013e31815edeb8 >. Accessed: Mai. 22, 2018. doi: 10.1097/TA.0b013e31815edeb8.
» https://doi.org/10.1097/TA.0b013e31815edeb8.» https://doi.org/10.1097/TA.0b013e31815edeb8 -
HORSTMAN, C. L. et al. Biological osteosynthesis versus traditional anatomic reconstruction of 20 long-bone fractures using an interlocking nail: 1994-2001. Veterinary Surgery, v.33, n.3, p.232-237, 2004. Available from: <Available from: https://doi.org/10.1111/j.1532-950X.2004.04034.x >. Accessed: Jul. 20, 2016. doi: 10.1111/j.1532-950X.2004.04034.x.
» https://doi.org/10.1111/j.1532-950X.2004.04034.x.» https://doi.org/10.1111/j.1532-950X.2004.04034.x -
HOU, S. M. et al. Mechanical strength, fatigue life, and failure analysis of two prototypes and five conventional tibial locking screws. Journal of Orthopaedic Trauma, v.16, n.10, p.701-708, 2002. Available from: <Available from: https://doi.org/10.1097/00005131-200211000-00004 >. Accessed: Oct. 15, 2019. doi: 10.1097/00005131-200211000-00004.
» https://doi.org/10.1097/00005131-200211000-00004.» https://doi.org/10.1097/00005131-200211000-00004 - JOHNSTON, S. A. et al. Internal fracture fixation. In.: TOBIAS, K. M.; JOHNSTON, S. A. (2nd ed.) Veterinary Surgery: Small Animal. Saint Louis: Elsevier. pp.1892-1983, 2017.
-
KARAARSLAN, A. A. et al. The best location for proximal locking screw for femur interlocking nailing: a biomechanical study. Indian Journal of Orthopaedics, v.50, n.1, p.94-98, 2017. Available from: <Available from: https://doi.org/10.4103/0019-5413.173508 >. Accessed: Oct. 01, 2019. doi: 10.4103/0019-5413.173508.
» https://doi.org/10.4103/0019-5413.173508.» https://doi.org/10.4103/0019-5413.173508 -
KARAARSLAN, A. A. et al. Biomechanical comparison of three-point bending resistance of titanium and stainless steel locking screws in intramedullary nails. Joint Diseases and Related Surgery, v.26, n.3, p.145-150, 2015. Available from: <Available from: https://doi.org/ 10.5606/ehc.2015.30 >. Accessed: Oct. 01, 2019. doi: 10.5606/ehc.2015.30.
» https://doi.org/10.5606/ehc.2015.30.» https://doi.org/ 10.5606/ehc.2015.30 -
KARAARSLAN, A. A. et al. The functional results of tibial shaft fractures treated with intramedullary nail compressed by proximal tube. Strategies in Trauma and Limb Reconstruction, v.11, n.1, p.25-19, 2016. Available from: <Available from: https://doi.org/10.1007/s11751-016-0242-x >. Accessed: Oct. 01, 2019. doi: 10.1007/s11751-016-0242-x.
» https://doi.org/10.1007/s11751-016-0242-x.» https://doi.org/10.1007/s11751-016-0242-x -
KASPAR, K. et al. Angle stable locking reduces interfragmentary movements and promotes healing after unreamed nailing. Study of a displaced osteotomy model in sheep tibiae. The Journal of Bone and Joint Surgery, v.87, n.9, p.2028- 2037, 2005. Available from: <Available from: https://www.ovid.com/jnls/jbjsjournal/abstract/10.2106/jbjs.d.02268~angle-stable-locking-reduces-interfragmentary-movements-and?redirectionsource=fulltextview >. Accessed: Jan. 15, 2019. doi: 10.2106/JBJS.D.02268.
» https://doi.org/10.2106/JBJS.D.02268.» https://www.ovid.com/jnls/jbjsjournal/abstract/10.2106/jbjs.d.02268~angle-stable-locking-reduces-interfragmentary-movements-and?redirectionsource=fulltextview -
LANSDOWNE, J. L. et al. In vitro mechanical comparison of screwed, bolted, and novel interlocking nail systems to buttress plate fixation in torsion and mediolateral bending. Veterinary Surgery, v.36, n.4, p.368-377, 2007. Available from: <Available from: https://doi.org/10.1111/j.1532-950X.2007.00277.x >. Accessed: Feb. 13, 2018. doi: 10.1111/j.1532-950X.2007.00277.x.
» https://doi.org/10.1111/j.1532-950X.2007.00277.x.» https://doi.org/10.1111/j.1532-950X.2007.00277.x - LUCENA, D. F. V. et al. Description of a novel veterinary biplanar interlocking nail system. Presented at: 46th Annual Veterinary Orthopedic Society Conference. Breckenridge: USA. 2017.
- MAZZOCCA, A. D. et al. Skeletal Trauma: Basic Science, Management, and Reconstruction. Filadélfia: Saunders, pp.83-141, 2008.
-
MUIR, P. et al. Area moment of inertia for comparison of implant cross-sectional geometry and bending stiffness. Veterinary and Comparative Orthopeadics and Traumatology, v.8, n.3, p.146-152, 1995. Available from: <Available from: https://doi.org/10.1055/s-0038-1632446 >. Accessed: Dec. 27, 2018. doi: 10.1055/s-0038-1632446.
» https://doi.org/10.1055/s-0038-1632446.» https://doi.org/10.1055/s-0038-1632446 -
MUKERJEE, S. M. et al. Interlocking nailing versus plating in tibial shaft fractures in adults: a comparative study. Journal of Clinical and Diagnostic Research, v.11, n.4, p.8-13, 2017. Available from: <Available from: https://pubmed.ncbi.nlm.nih.gov/28571220/ >. Accessed: Jan. 15, 2019. doi: 10.7860/JCDR/2017/25577.9746.
» https://doi.org/10.7860/JCDR/2017/25577.9746.» https://pubmed.ncbi.nlm.nih.gov/28571220/ -
OH, J. K. et al. Effect of fracture gap on stability of compression plate fixation: a finite element study. Journal of Orthopaedic Research, v.28, n.4, p.462-467, 2010. Available from: <Available from: https://doi.org/10.1002/jor.20990 >. Accessed: Jan. 15, 2019. doi: 10.1002/jor.20990.
» https://doi.org/10.1002/jor.20990.» https://doi.org/10.1002/jor.20990 -
OTTO, R. J. et al. Biomechanical comparison of polyaxial-type locking plates and a fixed-angle locking plate for internal fixation of distal femur fractures. Journal of Orthopaedic Trauma, v.23, n.9, p.645-652, 2009. Available from: <Available from: https://doi.org/10.1097/BOT.0b013e3181a567c8 > Accessed: Jan. 20, 2019. doi: 10.1097/BOT.0b013e3181a567c8.
» https://doi.org/10.1097/BOT.0b013e3181a567c8.» https://doi.org/10.1097/BOT.0b013e3181a567c8 -
PATIL, D. B. D. et al. Veterinary interlocking nailing and its augmentation for fracture repair. Polish Journal of Veterinary Sciences, v.11, n.2, p.187-191, 2008. Available from: <Available from: https://www.researchgate.net/profile/Deepak-Patil-6/publication/23152510_Veterinary_interlocking_nailing_and_its_augmentation_for_fracture_repair/links/5822d38308ae61258e37f00f/Veterinary-interlocking-nailing-and-its-augmentation-for-fracture-repair.pdf >. Accessed: Jan. 20, 2019.
» https://www.researchgate.net/profile/Deepak-Patil-6/publication/23152510_Veterinary_interlocking_nailing_and_its_augmentation_for_fracture_repair/links/5822d38308ae61258e37f00f/Veterinary-interlocking-nailing-and-its-augmentation-for-fracture-repair.pdf - PETTITT, R. Principles of fracture fixation. In.: GEMMILL, T. J.; CLEMENTS, D. N. BSAVA Manual of Canine and Feline Fracture Repair and Management. Gloucester: British Small Animal Veterinary Association, pp.55-64. 2016.
- PRUITT, L. A.; CHAKRAVARTULA, A. M. Mechanics of Biomaterials: Fundamental Principles for Implant Design. New York: Cambridge University Press, pp.463-470. 2011.
-
REEMS, M. R. et al. Ex vivo comparison of one versus two distal screws in 8 mm model 11 interlocking nails used to stabilize canine distal femoral fractures. Veterinary Surgery, v.35, n.2, p.161-167, 2006. Available from: <Available from: https://doi.org/10.1111/j.1532-950X.2006.00127.x >. Accessed: Feb. 14, 2018. doi: 10.1111/j.1532-950X.2006.00127.x.
» https://doi.org/10.1111/j.1532-950X.2006.00127.x.» https://doi.org/10.1111/j.1532-950X.2006.00127.x -
ROSA, N. et al. Recent developments on intramedullary nailing: a biomechanical perspective. Annals of the New York Academy of Sciences, v.1408, n.1, p.20-31, 2017. Available from: <Available from: https://doi.org/10.1111/nyas.13524 >. Accessed: Oct. 10, 2019. doi: 10.1111/nyas.13524.
» https://doi.org/10.1111/nyas.13524.» https://doi.org/10.1111/nyas.13524 -
TING, D. et al. In vitro evaluation of the effect of fracture configuration on the mechanical properties of standard and novel interlocking nail systems in bending. Veterinary Surgery, v.38, n.7, p.881-887, 2009. Available from: <Available from: https://onlinelibrary.wiley.com/doi/10.1111/j.1532-950X.2009.00584.x >. Accessed: Jan. 20, 2019. doi: 10.1111/j.1532-950X.2009.00584.x.
» https://doi.org/10.1111/j.1532-950X.2009.00584.x.» https://onlinelibrary.wiley.com/doi/10.1111/j.1532-950X.2009.00584.x -
VON PFEIL, D. J. et al. In vitro biomechanical comparison of a plate-rod combination-construct and an interlocking nail-construct for experimentally induced gap fractures in canine tibiae. American Journal of Veterinary Research, v.66, n.9, p.1536-1543, 2005. Available from: <Available from: https://avmajournals.avma.org/view/journals/ajvr/66/9/ajvr.2005.66.1536.xml >. Accessed: Jan. 20, 2019. doi: 10.2460/ajvr.2005.66.1536.
» https://doi.org/10.2460/ajvr.2005.66.1536.» https://avmajournals.avma.org/view/journals/ajvr/66/9/ajvr.2005.66.1536.xml -
WHEELER, J. L. et al. Intramedullary interlocking nail fixation in dogs and cats: clinical applications. Compendium, v.26, p.531-544, 2004. Available from: <Available from: https://www.researchgate.net/profile/Deepak-Patil-6/publication/23152510_Veterinary_interlocking_nailing_and_its_augmentation_for_fracture_repair/links/5822d38308ae61258e37f00f/Veterinary-interlocking-nailing-and-its-augmentation-for-fracture-repair.pdf >. Accessed: Jan. 20, 2019.
» https://www.researchgate.net/profile/Deepak-Patil-6/publication/23152510_Veterinary_interlocking_nailing_and_its_augmentation_for_fracture_repair/links/5822d38308ae61258e37f00f/Veterinary-interlocking-nailing-and-its-augmentation-for-fracture-repair.pdf -
YU, B. F. et al. Comparison of minimally invasive plate osteosynthesis and conventional plate osteosynthesis for humeral shaft fracture. Medicine Baltimore, v.95, n.39, p.1-5, 2016. Available from: <Available from: https://www.ovid.com/jnls/md-journal/fulltext/10.1097/md.0000000000004955~comparison-of-minimally-invasive-plate-osteosynthesis-and >. Accessed: Jan. 20, 2019. doi: 10.1097/MD.0000000000004955.
» https://doi.org/10.1097/MD.0000000000004955.» https://www.ovid.com/jnls/md-journal/fulltext/10.1097/md.0000000000004955~comparison-of-minimally-invasive-plate-osteosynthesis-and - ZANETTI, E. M.; BIGNARDI, C. Structural analysis of skeletal body elements: numerical and experimental methods. In: LEONDES, C. T. Biomechanical Systems Technology: Muscular Skeletal Systems. London: World Scientific Publishing, pp.185-225, 2009.
