A comparative biomechanical study of the Distal Tibia Nail against compression plating for the osteosynthesis of supramalleolar corrective osteotomies

The Distal Tibia Nail (DTN; Mizuho, Japan) has demonstrated higher biomechanical stiffness to locking plates in previous research for A3 distal tibia fractures. It is here investigated as a fixation option for supramalleolar corrective osteotomies (SMOT). Sixteen Sawbones tibiae were implanted with either a DTN (n = 8) or Medial Distal Tibia Plate (MDTP; n = 8) and a SMOT simulated. Two surgical outcome scenarios were envisaged: “best-case” representing an intact lateral cortex, and “worst-case” representing a fractured lateral cortex. All samples were subjected to compressive (350 N, 700 N) and torsional (± 4 Nm, ± 8 Nm) testing. Samples were evaluated using calculated construct stiffness from force–displacement data, interfragmentary movement and Von Mises’ strain distribution. The DTN demonstrated a greater compressive stiffness for the best-case surgical scenario, whereas the MDTP showed higher stiffness (p < 0.05) for the worst-case surgical scenario. In torsional testing, the DTN proved more resistant to torsion in the worst-case surgical setup (p < 0.05) for both ± 4 Nm and ± 8 Nm. The equivalent stiffness of the DTN against the MDTP supports the use of this implant for SMOT fixation and should be considered as a treatment option particularly in patients presenting vascularisation problems where the MDTP is an inappropriate choice.

Motion Analysis of Torsional Testing Machine to Reduce Impact Load Using SOLIDWORK

Mechanical testing is a standard and essential part of any design and manufacturing process, for ensuring safe working of mechanical component and for ensuring a cost-effective design. Torsion Testing Machine is designed for conducting Torsion and Twist on various metal wires, tubes, sheet materials, torque measurement, in this torque can be applied to testing specimen by geared motor through gear box. But the main difficulty with analytical torsion testing machine is that after test is complete and specimen breaks the trolley on which the test specimen is clamped it can impacted heavily to the rubber stopper mounted on the guide ways of the machine which distort the machine assembly. In this study motion study is done, using SOLIDWORK software by introducing spring at the place of stopper and try to minimise this impact load of the trolley on the machine. Keywords: Torsion testing, Motion analysis, impact load, spring design, SOLIDWORK software

Biomechanical evaluation of an intramedullary clavicle screw in simple oblique and butterfly wedge fractures

This biomechanical study evaluates the performance of a solid titanium-alloy intra-medullary ( IM) clavicular screw in torsion and cantilever bending in cadaveric clavicle specimens with simulated simple oblique and butterfly wedge midshaft fractures. Thirty-two fresh-frozen male clavicles were sorted into six experimental groups: Torsion Control, Torsion Simple Oblique Fracture, Torsion Butterfly Wedge Fracture, Bending Control, Bending Simple Oblique Fracture, and Bending Butterfly Wedge Fracture. The experimental groups were controlled for density, length, diameter, and laterality. All other samples were osteotomy-induced and implanted with a single 90 mm × 3 mm clavicle screw. All groups were tested to physiologically relevant cutoff points in torsion or bending. There were no statistically significant differences in the performance of the oblique and butterfly wedge fracture models for any torsion or bend testing measures, including maximum torsional resistance ( p = 0.66), torsional stiffness ( p = 0.51), maximum bending moment ( p = 0.43), or bending stiffness ( p = 0.73). Torsional testing of samples in the direction of thread tightening tended to be stronger than samples tested in loosening, with all groups either approaching or achieving statistical significance. There were no significant differences between the simple oblique or the butterfly-wedge fracture groups for any of the tested parameters, suggesting that there is no difference in the gross biomechanical properties of the bone-implant construct when the IM clavicle screw is used in either a simple midshaft fracture pattern or a more complex butterfly wedge fracture pattern.

Influence of the Production Process on the Binding Mechanism of Clinched Aluminum Steel Mixed Compounds

The multi-material design and the adaptability of a modern process chain require joining connections with specifically adjustable mechanical, thermal, chemical or electrical properties, whereby previous considerations have focused primarily on the mechanical properties. With clinching, the multitude of possible combinations of requirements, materials and component or joint geometry makes it impossible to determine these joint properties empirically. As a result of the established and empirically based procedure, no model exists to date that considers all questions of joinability, i.e. the materials (suitability for joining), the design (joining safety) and the production (joining possibility) and allows a calculation of the achievable properties. It is therefore necessary to describe the physical properties of the joint as a function of the three bonding mechanisms force closure, form closure and material closure in relation to the application. This approach enables the illustration of the relationships along the causal chain "joint requirement - binding mechanism - joining parameters". In this way the adaptability of the mechanical joining technology can be improved. A geometric comparison is made using metallographic cross sections, of clinched joints of the combination of aluminum and steel. The torsional testing of the rotationally symmetric clinching points for detection of the mechanical stress state are qualified as examination method and technological test. By measuring the electrical resistance in the base material, in the clinch joint and during the production cycle (after clinching, before precipitation hardening and after precipitation hardening), this change in the stress state can also be detected.

Axial Micromotion Locking Plate Construct Can Promote Faster and Stronger Bone Healing in an Ovine Osteotomy Model

Fixing bone fractures with controlled axial interfragmentary micromotion improves bone healing; however, the optimal type of implant construct for this purpose is still lacking. The present study describes a novel axial micromotion locking plate (AMLP) construct that allows axial interfragmentary micromotion of 0.3 or 0.6 mm. We investigated whether the AMLP constructs enhance bone healing compared to an ordinary locking plate (LP) using an ovine osteotomy model. The stiffness of the constructs was tested under axial loading. We created a 3-mm osteotomy in the left hind leg tibia of sheep that was then stabilized with a 0.3- or 0.6-mm AMLP or LP construct (n = 6/group). Bone healing was monitored weekly by X-ray radiography starting from week 3 after surgery. At week 9, the specimens were collected and evaluated by computed tomography and torsional testing. We found that the AMLPs had a lower stiffness than the LP; in particular, the stiffness of the 0.6-mm AMLP construct was 86 and 41% lower than that of the LP construct for axial loads &lt;200 and &gt;200 N, respectively. In the in vivo experiments, tibial osteotomies treated with the 0.6-mm AMLP construct showed the earliest maximum callus formation (week 5) and the highest volume of bone callus (9.395 ± 1.561 cm3 at week 9). Specimens from this group also withstood a 27% greater torque until failure than those from the LP group (P = 0.0386), with 53% more energy required to induce failure (P = 0.0474). These results demonstrate that AMLP constructs promote faster and stronger bone healing than an overly rigid LP construct. Moreover, better bone healing was achieved with an axial micromotion of 0.6 mm as compared to 0.3 mm.

A Biomechanical Evaluation of the Tibia after Retrograde Intramedullary Reaming

Category: Hindfoot; Ankle; Ankle Arthritis; Basic Sciences/Biologics; Trauma Introduction/Purpose: Autologous bone graft is an important tool in the foot and ankle surgeon’s arsenal, and remains the gold standard despite the release of new biologics. The Reamer-Irrigator-Aspirator (RIA) system has become an option for local intramedullary bone graft harvest. Evidence supports the quality of graft and safety of RIA in the femur, and some series have demonstrated its value in tibial reaming for hindfoot fusion. However, there has been no analysis of the mechanical effects of the system on the tibia. The purpose of this study is to investigate the effect of retrograde intramedullary reaming on the mechanical properties of cadaveric tibias, with the hypothesis that this will produce no significant difference in torsional strength between groups. Methods: Intact, fresh frozen tibias were obtained for testing, totaling 11 matched pairs. One tibia was chosen for reaming from each pair with pre-test randomization. The selected tibia was reamed in a retrograde fashion over a guidewire to 12mm, which is the smallest diameter RIA device available. Each tibia was potted and mounted in a custom jig for testing on a servohydraulic test frame. Each specimen was first tested non-destructively for compressive properties using standardized loading rates. Each specimen was then loaded in torsion under constant angular velocity of 9˚/second until failure or the limit of the load cell was reached. Mechanical properties were determined from the load-displacement curve and compared between reamed and unreamed matched pairs using paired samples statistics, with statistical significance set at p=0.05. Results: Specimens were of mean age 56 (range 39-67) years, with 55% being female. The mean compressive stiffness of reamed (560.4 +- 111.7 N/mm) and unreamed (628.2 +- 117.2 N/mm) tibias were not statistically different (p = 0.167). Nine of the reamed specimens and 10 of the unreamed specimens fractured during torsional testing. Torsional testing for stiffness (178.4 Nm/rad +- 59.4 vs 168.1 +- 40.8, p=0.370), rigidity (50.4 Nm2/rad +- 19.1 vs 47.0 +- 13.7, p=0.331), and ultimate load capacity (71.2 Nm +- 24.3 vs 71.9 +- 20.5, p=0.880) showed minimal differences between reamed and unreamed specimens, respectively. Conclusion: Mechanical testing identified no statistically significant differences in torsional or compressive properties of our cadaveric tibias after intramedullary reaming. There was a trend towards decreased compressive stiffness, but this is not a common mechanism of fracture. Our findings suggest that the use of the smallest size RIA system in the tibia does not drastically alter the mechanical properties or require prophylactic fixation. The RIA can be used safely as a method of bone graft harvest or intramedullary debridement in the tibia, as long as appropriate technique is used to avoid eccentric reaming or excessive blood loss.

Performance-Related Characterization of Forming-Induced Initial Damage in 16MnCrS5 Steel under a Torsional Forward-Reverse Loading Path at LCF Regime

Forming technology and in particular cold forward rod extrusion is one of the key manufacturing technologies with regard to the production of shafts. The selection of process parameters determines the global and local material properties. This particularly implies forming-induced initial damage in representation of pores. On this background, this study aims on describing the influence of these pores in the performance of the material 16MnCrS5 (DIN 1.7139, AISI/SAE 5115) under a torsional load path in the low cycle fatigue regime, which is highly relevant for shafts under operation conditions. For this purpose, the method of cyclic forward-reverse torsional testing was applied. Additionally, intermittent testing method and the characterization of the state of crack growth using selective electron microscopy analysis of the surface were combined. A first attempt was made to describe the influence of forming-induced initial damage on the fatigue performance and the crack growth mechanisms. The correlation of fatigue performance and initial damage was contiguous in the sense that the initial damage corresponds with a decrease of material performance. It was concluded that the focus of further investigations must be on small crack growth and the related material changes to identify the role of initial damage under cyclic loads.

Platform for Mechatronics Education Using: (1) Mechatronics Technology Demonstrator, and (2) Web Based Virtual Experimentation

Increasing demands on the productivity of complex systems, such as machine tools and their steadily growing technological importance will require the application of new methods in the product development process. This paper shows that the analysis of the simulation results from the simulation based mechatronic model of a complex system followed by a procedure that allows a better understanding of the dynamic behavior and interactions of the components. This paper will highlight the results of interaction between National Institute of Technology, (NITK) Surathkal, India and University of District of Columbia (UDC) in the area of Mechatronics and virtual testing. Mechatronics is a design philosophy, which is an integrating approach to engineering design. Through a mechanism of simulating interdisciplinary ideas and techniques, mechatronics provides ideal conditions to raise the synergy, thereby providing a catalytic effect for the new solutions to technically complex situations. Many real-world systems can be modeled by the mass-spring-damper system and hence considering one such system, namely Mechatronics Technology Demonstrator (MTD) is taken as the first example. MTD is a portable low cost, technology demonstrator that can be used for teaching mechatronics system design. The paper highlights design optimization of several mechatronic products using the procedures derived by the use of mass spring damper based mechatronic system. The second example is on web based virtual experimentation, where the experiment is conducted by remote triggering of Torsion Testing Machine. Remote triggered (RT) experimentation is a method of remotely controlling the laboratory equipment by an internet based system from a webpage. RT lab is an excellent way for the students to get access to expensive state of the art labs and equipment. The present work deals with the systematic approach of realizing a remote triggered experimentation on a horizontal torsional testing machine which can be triggered from a tablet PC or a laptop through an internet connection directed to the server computer system. RT lab algorithms are built in the server computer and the information and controls will be displayed on an html webpage where the experiment can be conducted. In this experiment the machine is remotely started through a command in the webpage which will be directed to the main server computer system from a wireless handheld internet enabled device such as laptops or tablet PCs and render the suitable graph of the experiment in the device. The experiment is completely in the control of the user. The person can either on/off the main equipment with the help of the device within the given slot of time and the data from the graph can be retrieved for further analysis. The first example uses a software platform of VisSim and the second example uses a software platform LabView. Although located in two different locations and countries, this paper examines the common mechatronics philosophy and the design approach used in modeling, simulation, optimization and virtual experimentation in building robust mechatronics product and procedures.

Biomechanics of the Proximal Radius Following Drilling of the Bicipital Tuberosity to Mimic Cortical Button Distal Biceps Repair Technique

Background: A fracture through the proximal radius is a theoretical concern after cortical button distal biceps fixation in an active patient. The permanent, nonossified cortical defect and medullary tunnel is at risk during a fall eliciting rotational and compressive forces. We hypothesized that during simulated torsion and compression, in comparison with unaltered specimens, the cortical button distal biceps repair model would have decreased torsional and compressive strength and would fracture in the vicinity of the bicipital tuberosity bone tunnel. Methods: Sixteen fourth-generation composite radius Sawbones models were used in this controlled laboratory study. A bone tunnel was created through the bicipital tuberosity to mimic the exact bone tunnel, 8 mm near cortex and 3.2 mm far cortex, made for the BicepsButton distal biceps tendon repair. The radius was then prepared and mounted on either a torsional or compression testing device and compared with undrilled control specimens. Results: Compression tests resulted in average failure loads of 9015.2 N in controls versus 8253.25 N in drilled specimens ( P = .074). Torsional testing resulted in an average failure torque of 27.3 Nm in controls and 19.3 Nm in drilled specimens ( P = .024). Average fracture angle was 35.1° in controls versus 21.1° in drilled. Gross fracture patterns were similar in compression testing; however, in torsional testing all fractures occurred through the bone tunnel in the drilled group. Conclusion: There are weaknesses in the vicinity of the bone tunnel in the proximal radius during biomechanical stress testing which may not be clinically relevant in nature. Clinical Relevance: In cortical button fixation, distal biceps repairs creates a permanent, nonossified cortical defect with tendon interposed in the bone tunnel, which can alter the biomechanical properties of the proximal radius during compressive and torsional loading.

Effect of headless compression screw on construct stability for centre of rotation and angulation-based levelling osteotomy

Summary Objective: To compare the biomechanical properties of bone and implant constructs when used for the centre of rotation and angulation (CORA) based levelling osteotomy, with and without implantation of a trans-osteotomy headless compression screw tested under three-point flexural and torsional forces; thereby determining the contribution of a trans-osteotomy headless compression screw with regards to stability of the construct. Methods: Experimental biomechanical study utilizing 12 pairs of cadaveric canine tibias. Using the CORA based levelling osteotomy (CBLO) procedure, the osteotomy was stabilized with either a standard non-locking CBLO bone plate augmented with a headless compression screw (HCS) or a CBLO bone plate alone. Tibial constructs were mechanically tested in three-point craniocaudal flexural testing or in torsion. Results: In three-point flexural testing, the difference between the two constructs was not significant. In torsion, the difference in the angle of failure between constructs with a HCS (48.46°) and constructs without a HCS (81.65°) was significant (p = 0.036). Maximum torque achieved by constructs with a HCS (21.7 Nm) was greater than those without (18.7 Nm) (p = 0.056). Stiffness differences between both groups in torsion and bending were not significant. Use of a HCS did increase the stability of the CBLO construct in torsional testing, but not in flexural testing.