AIP Conference Proceedings 2193, 050025 (2019); https://doi.org/10.1063/1.5139398 2193, 050025
© 2019 Author(s).
Evaluating internal forces of new design modular MegaProsthesis distal femur
Cite as: AIP Conference Proceedings 2193, 050025 (2019); https://doi.org/10.1063/1.5139398 Published Online: 10 December 2019
Sugeng Supriadi, Mohamad Fadhil Ardianov, Ahmad Jabir Rahyussalim, et al.
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Evaluating Internal Forces of New Design Modular MegaProsthesis Distal Femur
Sugeng Supriadi
1,2,a), Mohamad Fadhil Ardianov
1,2,b), Ahmad Jabir
Rahyussalim
3,4,c), Yudan Whulanza
1,2,d), Yogi Prabowo
3,4,e), Agung Shamsuddin Saragih
1,2,f)1Department of Mechanical Engineering, Faculty of Engineering, Universitas Indonesia, Kampus UI Depok 16424, Indonesia.
2Research Center for Biomedical Engineering, Universitas Indonesia, Kampus UI Depok 16424, Indonesia
3Department of Orthopedic and Traumatology, Faculty of Medicine, Universitas Indonesia - Cipto Mangunkusumo Hospital, Jl Salemba Raya No 6 Jakarta 10430, Indonesia
4Stem Cell and Tissue Engineering Research Cluster-IMERI, Universitas Indonesia, Jl Salemba Raya No 6 Jakarta 10430, Indonesia
Corresponding author: a)[email protected], b)[email protected], c)[email protected]
d)[email protected], e)[email protected], f)[email protected]
Abstract. The use of Modular prosthesis become one of the best solutions to treat bone cancer despite amputation. This study developed a new modular MegaProsthesis Distal femur by giving some modifications to the geometry and also some features. Therefore, this new model was designed and simulated by analyzing stress analysis. The simulation using internal loads calculation concept to represent the forces that happened in the model during walking, there were three types of internal loads direction; Distal-Proximal, Frontal-Dorsal, and Lateral-Medial. The result showed that the highest von Mises stress calculated far below the yield stress of the material, so this study was successfully designed and safe to use.
Keywords: internal load, modular MegaProsthesis distal femur, osteosarcoma, stress analysis.
INTRODUCTION
Osteosarcoma is one kind of many cancer types. While rare, osteosarcoma is the most common primary bone cancer [1]. Long bones such as the femur, proximal tibia, the humerus are the most affected bones by osteosarcoma [2-4]. One of the best solutions to treat osteosarcoma is to do a limb salvage procedure. But in some case, especially in developing countries, limb salvage procedures have so many difficulties, because the osteosarcoma sufferers would like to check for cancer when cancer has already very severe. So, it makes the reconstruction of the leg become difficult [5,6].
However, there is a solution for some osteosarcoma sufferers who have objection doing a limb salvage procedure.
The modular prosthesis can be preferred option following resection of the tumor, only some parts of bones which have cancer, not the whole bone. The Modular Prosthesis has better results for distal femur tumors and easy to assemble [7,8]. However, using this modular prosthesis still has some issues. Some cases that happened on pasca limb salvage surgery has some failure caused by mechanical failure which is loosening, fracture, malalignment, and instability [9].
So, the current study, we made a new design of modular prosthesis to avoid another potential failure cases that caused by mechanical joining or another reason that might disturb the patient pasca limb salvage surgery. This study also provides the proper simulation to calculate the potential mechanical movement of the implant when it used in the patient body so that it can prevent future disturbance and uncomfortable feeling pasca the surgery.
MODEL AND DESIGN
This Modular MegaProsthesis distal femur was derived from the previous model of the Kotz modular femur and tibia resection system (KMFTR) design. This design has some upgrade on femoral size, which is similar to the real femoral size. Femoral pictures scanned by MRI and printed to be DICOM file and edited with a software called #d slicer. The results of the edited femoral picture save as a CAD format, so we can measure and edited as much as we want. Therefore, the new design has more similar geometry with the real femoral, and hopefully, the patient becomes more comfortable after limb-salvage surgery.
Another development is on the joining of femoral, segment, and stem parts. The joining of one and another parts has some upgrade; there is a locking component that can lock the modular prosthesis and make them safer and more rigid. The Joining lock has a circular key geometry on one edge or segment and stem parts; the other edge has a circular key slot geometry. Circular key locking principle was chosen because it has minimum space but strong enough to hold some forces that happen on the femur during walking.
The design of the femoral, segment, and stem parts showed in Figure 1. Circular key locking (are pointed with red arrows) was designed to lock the femoral with segment or segment with the stem. Not all the parts have both circular key locking and circular key slot, only segment. But femoral part has only circular key slot and stem has a circular key lock at their tip. The total length of the new modular MegaProsthesis distal femur model is 304.2 mm that was divided into femoral, segment, and stem for about 118 mm, 63.5 mm, 139.5 mm, meanwhile this new model has 6°
slope adapted from human femur, so this model can perfectly fit to the bone and human anatomy without reducing patient comfort.
FIGURE 1. A new model of the Modular MegaProsthesis Distal Femur (Joining Lock component are pointed with red arrow)
This design simulated with titanium alloys which are considered to be the most attractive metallic for biomedical applications and has long been used by biomedical applications, especially for implant material [10,11]. There are now four grades of pure titanium and 5th grade of titanium alloys which is Ti-6Al-4V developed to fulfill the structural of implant materials needs [11]. Mechanical Properties of each grade detailed in Table 1 [11,12].
TABLE 1. Mechanical Properties of Titanium alloys for biomedical applications Alloy Tensile Strength
(UTS) (MPa)
Yield Strength
(𝝈𝒚) Elongation
(%) Modulus
(GPa)
Pure Ti grade 1 240 170 24 102.7
Pure Ti grade 2 345 275 20 102.7
Pure Ti grade 3 450 380 18 103.4
Pure Ti grade 4 550 485 15 104.1
Ti-6Al-4V ELI (mill
Annealed) 860-965 795-875 10-15 101-110
Ti-6Al-4V (Annealed) 895-930 825-869 6-10 110-114
a) b) c)
By looking to the Table 1 and choosing the availability of the material in the material library from software SolidWorks 2018, Ti-6Al-4V (Solution treated and aged) is the closest mechanical properties which have 1050 MPa UTS, 827.4 MPa (𝜎𝑦) , 104.8 (GPa). After deriving the best materials, the physical properties of the new model showed the mass, surface area, and volume values of 1873.8 grams, 130125.7 mm2, and 931133.4 mm3.
METHODS
The next step was to simulate the new model using a SolidWorks 2018 software. The parameter values that must be simulate adapted from the internal force that occurs on the femur during walking. Internal forces demonstrated that muscle works in balancing the loads within the femur. Internal forces calculated by analyzing free body diagram from all of the structures of the leg which contributed to the equilibrium state. The Equilibrium forces and moments calculated based on the equation shown below: [13,14]
∑ 𝐹𝑚𝑖
𝑖
+ (∑ 𝐹𝐼𝑗
𝑗
) + 𝐹𝑐ℎ𝑖𝑝+ 𝐺𝑘+ 𝐹𝑐𝑘𝑛𝑒𝑒+ 𝐹𝑐𝑝𝑎𝑡𝑒𝑙𝑙𝑎= 0
(1) Equation 1 showed that 𝐹𝑚𝑖 where the combination of 24 muscle force, 𝐹𝐼𝑗 are forces on a ligament, 𝐺𝑘 are the incremental weight of the thigh, 𝐹𝑐𝑘𝑛𝑒𝑒, 𝐹𝑐ℎ𝑖𝑝, 𝐹𝑐𝑝𝑎𝑡𝑒𝑙𝑙𝑎 represent contact forces on hip, knee, patella. After deriving all the forces that occur in the femur, those could be grouped to be axial load (Distal to proximal) with maximum shear forces (shown by Z-Axis), Lateral-medial (X-axis) and Frontal-Dorsal (Y-axis) movements that happened to cause the femur to restrain bending moments shown in Figure 2 [14].
FIGURE 2. Internal loads on the femur
In this analysis, the author would like to simulate the new design of modular MegaProsthesis distal femur using the illustration shown in Figure 2 as parameter and direction of forces. Figure 3 explained the loads (purple arrow) were set on the position and direction adapted from an illustration in Figure 2, assuming the femoral has no movement the fix geometry position set on the femoral pinhole.
FIGURE 3. Simulation Loads and constraints on the implant model: a) distal to proximal load direction, b) Frontal to dorsal load direction, c) Lateral to Medial load direction
Each simulation perspective has a different magnitude of loads because each simulation represents different muscle attraction against the femur. During walking, bodyweight becomes a variable of loads, and then by calculating along at the straight axis of the femur and along a gait cycle, it would determine how safe the new model is. Simulation perspective shown in Figure 1a), b), c) must be simulate with range of loads between 0.5BW-1.12BW; 0.09 BW-0.12 BW; 0.09BW-0.29BW [14,15]. The author uses his body weight that was 800N should be variable and multiple with determined range loads for each simulation perspective.
The type of stress analysis that was used in this analysis was static stress analysis, to predict the structural loading conditions and deriving magnitude of von Mises stress, displacement, and strain towards the model after restraining against the loads. The simulation test using the finite element method (FEM) as the numerical method for better results.
The steps of doing FEM there are: meshing the new model of the modular MegaProsthesis distal femur and setting the types of constraint, were arranged with the parameter values as shown in Table 2 and illustrated in Figure 4, respectively
TABLE 2. Mechanical Properties of Titanium alloys for biomedical applications Mesh Setting Distal-Proximal Frontal-Dorsal Lateral-Medial
Max Element Size 6.5 19.5 19.5
Min Element Size 2.2 3,9 3.9
Maximum Aspect Ratio 83.9 90.9 91
FIGURE 4. Simulation meshing view: a) distal to proximal load direction, b) Frontal to dorsal load direction, c) Lateral to Medial load direction
RESULTS AND DISCUSSION
Here, the analysis defines as the von Mises of the stress, the displacement of the model. The model has been given different loads according to the criteria of each perspective, as seen in Table 3. Along with the increase in the load received by the object, followed by increasing the value of all simulation aspects and each mechanical properties. In this study, the author gave the additional magnitude of loads which is the median of the load's range. The result of multiplication between the percentage of criteria and bodyweight determine the loads that should be given to the model. The values of von Mises stress, displacement, and strain, as shown in Table 3 below.
TABLE 3. Simulation Result
Simulation Perspective F/BW F (N) Σ (MPa) Δ l (mm) Distal to Proximal
0.5 400 7.002 0.0025
0.75 600 11.33 0.0041
1.125 900 15.74 0.0057
Lateral to Medial
0.09 72 3.25 0.0076
0.19 152 5.63 0.016
0.29 232 9.51 0.024
Frontal to Dorsal 0.09 72 3.05 0.014
0.105 84 3.56 0.016
0.12 96 4.07 0.019
a) b) c)
There are three calculations to determine the parameter before the model could be simulated. The first parameter is forced; this calculation determined from the force-bodyweight ratio that referred to the procedures of internal forces simulation. So, the value of force could be calculated by multiply bodyweight(800N) with the ratio. Stress is another parameter that could be determined by dividing the force and surface area. But in this calculation, we used software simulation, so it depends on another parameter such as meshing setting. Displacement is the last parameter that should be calculated to know how far the model would be run into deformation. It was determined by subtracting the initial and the final geometrical length before the forces are given to the model. Table 3 shown us that all the parameter has been calculated in accordance with the regulation of calculating internal forces happens in the femur during walking.
FIGURE 5. Von Mises acting on the new model of MegaProsthesis Distal Femur: a) 400N distal to proximal load direction, b) 152 N Lateral to Medial load direction, c) 96 N Frontal to dorsal load direction.
In Figure 5 shows us three types of load directions and positions. There is a y-axis load which has directions from distal to proximal, x-axis load has lateral to medial direction, and z-axis load has frontal to the dorsal direction. Each load directions placed on different positions. Figure 5a, the loads placed on the stem part of the modular prosthesis which has the most suitable area for y-axis load directions, 5b (x-axis loads) placed on the right side of the lower segment parts of modular prosthesis, its chosen because it was the nearest positions of the center of gravity of this overall model. Meanwhile, figure 5c has the widest loads area. It is placed in front of the center of gravity of the design along the segment part. Those positions contribute to making the meshing process faster and easily simulated.
The result of the simulation showed that von Mises distribution had various magnitude along with the increasing of loads. Figure 5 showed that the von Mises stress concentrated nearby the joining of the femoral part and segment part. But the highest magnitudes of all the perspectives still far below from the magnitude of yield strength of Ti-6Al- 4V which has 827.4 Mpa.
FIGURE 6. Displacement acting on the new model of MegaProsthesis Distal Femur: a) 400N distal to proximal load direction, b) 152 N Lateral to Medial load direction, c) 96 N Frontal to dorsal load direction.
a) b) c)
a) b) c)
Unlike von Mises stress, the furthest displacement magnitude occurs at the edge of the model, as seen in Figure 6.
The displacement showed that the variation of simulation perspective led to dimensional changes correspond to its directions of the loads. Distal to proximal perspective has the smallest displacement of all three because of its load's direction towards Y-axis; therefore, there was no significant movement when the model simulated.
FIGURE 7. Calculation of Von Mises Stress and displacement based on simulation perspective : a) Lateral-Medial Load direction, b) Frontal-dorsal Load direction, c) Distal-Proximal Load direction.
According to Figure 7, the Calculation result of this analysis showed that the different simulation perspective made the magnitude of Von Mises stress and displacement different from each other. The differences between them could be affected because of the position of the loads and also the directions of them. The Biggest Von mises happened when the new model of MegaProsthesis Distal Femur affected by Distal to Proximal loads direction which has 15.74 Mpa, and the furthest displacement of them all was Lateral-Medial loads direction which has 0.024 mm at the tip of the model.
CONCLUSION
A new model of the modular MegaProsthesis distal femur was successfully designed. The simulation-based on internal loads happened during walking has been evaluated to this new model. All the mechanical properties necessary tests have been done and proven safe by the simulation results showed that the magnitude of the highest von Mises stresses 15.74 Mpa far below the yield strength of the material itself which has 827.4 MPa. This current design that has been made also needs some geometry or density modification to reduce overall mass to achieve lightness but without surpassing the yield strength of its material.
ACKNOWLEDGMENT
This research work is supported by Universitas Indonesia with a program of Hibah Publikasi Internasional Terindeks 9 (PIT 9) Fiscal Year 2019 Number: NKB-0078/UN2.R3.1/HKP.05.00/2019.
0 0.001 0.002 0.003 0.004 0.005 0.006
400 600 900
0 2 4 6 8 10 12 14 16 18
Displacement (mm)
Loads (N)
Yield Strength (MPa)
0 0.005 0.01 0.015 0.02 0.025 0.03
0 2 4 6 8 10
72 152 232
Displacement (mm)
Yield Strength (MPa)
Loads (N)
0 0.005 0.01 0.015 0.02
0 0.5 1 1.52 2.5 3 3.54 4.5
72 84 96
Displacement (mm)
Yield Strength (MPa)
Loads (N)
REFERENCES
1. R.N. Stitzlein, et al., "The Team Approach to Osteosarcoma of the Distal Femur in an Adolescent." JBJS reviews 5.12, e5 (2017)
2. D.C. Dahlin and B.C. Mark "Osteogenic sarcoma: a study of six hundred cases." JBJS 49.1, 101-110 (1967).
3. AJ Chou and F Malek. Orthopaedic Knowledge Update: Musculoskeletal Tumors. 3rd. (Rosemont, Illinois:
American Academy of Orthopaedic Surgeons; 2014).
4. M. D. Murphey, et al., "The many faces of osteosarcoma." Radiographics 17.5, 1205-1231 (1997).
5. I. Ilyas, et al., "Limb salvage for proximal tibial tumours using a modular prosthesis." International orthopaedics 24.4, 208-211 (2000).
6. B.K.S. Sanjay and P.G. Moreau. "Limb salvage surgery in bone tumour with modular endoprosthesis." International orthopaedics 23.1, 41-46 (1999).
7. I. Ilyas, et al., "Modular megaprosthesis for distal femoral tumors." International orthopaedics 25.6, 375-377 (2001).
8. R. Capanna, et al., "Modular uncemented prosthetic reconstruction after resection of tumours of the distal femur." The Journal of bone and joint surgery. British volume 76.2, 178-186 (1994).
9. S.B. Haas, N.I. John and R.E. Windsor. "Revision total knee arthroplasty with use of modular components with stems inserted without cement." The Journal of bone and joint surgery. American volume 77, 1700-1707 (1995).
10. C.N. Elias, et al., "Biomedical applications of titanium and its alloys." Jom 60.3 , 46-49 (2008).
11. M. Niinomi, "Mechanical properties of biomedical titanium alloys." Materials Science and Engineering: A 243, 231-236 (1998).
12. N. Qosim, et al., Surface treatments of ti-alloy based bone implant manufactured by electrical discharge machining. Ingeniería y Universidad, 22, (2018).
13. Annual Book of ASTM Standards, Medical Devices; (Emergency Medical Services, vol. 13.01, ASTM, Philadelphia, PA, 1994).
14. R.A. Brand, et al., "A model of lower extremity muscular anatomy." Journal of biomechanical engineering 104.4, 304-310 (1982).
15. G.N. Duda, E. Schneider, and E.Y.S. Chao. "Internal forces and moments in the femur during walking." Journal of biomechanics 30.9, 933-941 (1997).
16. E. Schneider, et al., "Loads acting on an intramedullary femoral nail." Implantable telemetry in orthopaedics, 221-227 (1990).
