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Islam S, Dembowski M, Schemitsch EH, Bougherara H, Bagheri ZS, Zdero R. Biomechanical design of a new proximal humerus fracture plate using alternative materials. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2024:e3868. [PMID: 39243184 DOI: 10.1002/cnm.3868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Revised: 08/17/2024] [Accepted: 08/23/2024] [Indexed: 09/09/2024]
Abstract
Comminuted proximal humerus fractures are often repaired by metal plates, but potentially still experience bone refracture, bone "stress shielding," screw perforation, delayed healing, and so forth. This "proof of principle" investigation is the initial step towards the design of a new plate using alternative materials to address some of these problems. Finite element modeling was used to create design graphs for bone stress, plate stress, screw stress, and interfragmentary motion via three different fixations (no, 1, or 2 "kickstand" [KS] screws across the fracture) using a wide range of plate elastic moduli (EP = 5-200 GPa). Well-known design optimization criteria were used that could minimize bone, plate, and screw failure (i.e., peak stress < ultimate tensile strength), reduce bone "stress shielding" (i.e., bone stress under the new plate ≥ bone stress for an intact humerus, titanium plate, and/or steel plate "control"), and encourage callus growth leading to early healing (i.e., 0.2 mm ≤ axial interfragmentary motion ≤ 1 mm; shear/axial interfragmentary motion ratio <1.6). The findings suggest that a potentially optimal configuration involves the new plate being manufactured from a material with an EP of 5-41.5 GPa with 1 KS screw; but, using no KS screws would cause immediate bone fracture and 2 KS screws would almost certainly lead to delayed healing. A prototype plate might be fabricated using alternative materials suggested for orthopedics and other industries, like fiber-metal laminates, fiber-reinforced polymers, metal foams, pure polymers, shape memory alloys, or 3D-printed porous metals.
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Affiliation(s)
- Sabrina Islam
- Department of Mechanical Engineering, George Mason University, Fairfax, Virginia, USA
| | - Mitchell Dembowski
- Department of Mechanical Engineering, Toronto Metropolitan University, Toronto, Ontario, Canada
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, Ontario, Canada
- Division of Orthopaedic Surgery, Western University, London, Ontario, Canada
| | - Habiba Bougherara
- Department of Mechanical Engineering, Toronto Metropolitan University, Toronto, Ontario, Canada
| | - Z Shaghayegh Bagheri
- Department of Mechanical Engineering, George Mason University, Fairfax, Virginia, USA
- Kite Research Institute, Toronto Rehabilitation Institute, University Health Network, Toronto, Ontario, Canada
| | - Radovan Zdero
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, Ontario, Canada
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Tanaka A, Matsushita T, Nakatsuji T, Katsui Y, Nagai K, Nishida K, Mukai T, Kuroda R. Setting hinge position distal to the proximal margin of the distal lateral femur reduces the maximum principal strains of the hinge area and risk of hinge fractures. J Exp Orthop 2024; 11:e12015. [PMID: 38590755 PMCID: PMC11000132 DOI: 10.1002/jeo2.12015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2024] [Accepted: 03/06/2024] [Indexed: 04/10/2024] Open
Abstract
Purpose The optimal hinge position to prevent hinge fractures in medial closing wedge distal femoral osteotomy (MCWDFO) based on the biomechanical background has not yet been well examined. This study aimed to examine the appropriate hinge position in MCWDFO using finite element (FE) analysis to prevent hinge fractures. Methods Computer-aided design (CAD) models were created using composite replicate femurs. FE models of the MCWDFO with a 5° wedge were created with three different hinge positions: (A) 5 mm proximal to the proximal margin of the lateral epicondylar region, (B) proximal margin level and (C) 5 mm distal to the proximal margin level. The maximum and minimum principal strains in the cortical bone were calculated for each model. To validate the FE analysis, biomechanical tests were performed using composite replicate femurs with the same hinge position models as those in the FE analysis. Results In the FE analysis, the maximum principal strains were in the order of Models A > B > C. The highest value of maximum principal strain was observed in the area proximal to the hinge. In the biomechanical test, hinge fractures occurred in the area proximal to the hinge in Models A and B, whereas the gap closed completely without hinge fractures in Model C. Fractures occurred in an area similar to where the highest maximal principal strain was observed in the FE analysis. Conclusion Distal to the proximal margin of the lateral epicondylar region is an appropriate hinge position in MCWDFO to prevent hinge fractures. Level of Evidence Level V.
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Affiliation(s)
- Atsuki Tanaka
- Department of Orthopaedic SurgeryKobe University Graduate School of MedicineKobeHyogoJapan
| | - Takehiko Matsushita
- Department of Orthopaedic SurgeryKobe University Graduate School of MedicineKobeHyogoJapan
| | - Tatsuya Nakatsuji
- Department of Mechanical EngineeringKobe University Graduate School of EngineeringKobeHyogoJapan
| | - Yosuke Katsui
- Department of Mechanical EngineeringKobe University Graduate School of EngineeringKobeHyogoJapan
| | - Kanto Nagai
- Department of Orthopaedic SurgeryKobe University Graduate School of MedicineKobeHyogoJapan
| | - Kyohei Nishida
- Department of Orthopaedic SurgeryKobe University Graduate School of MedicineKobeHyogoJapan
| | - Toshiji Mukai
- Department of Mechanical EngineeringKobe University Graduate School of EngineeringKobeHyogoJapan
| | - Ryosuke Kuroda
- Department of Orthopaedic SurgeryKobe University Graduate School of MedicineKobeHyogoJapan
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Freitas A, Lobo MDO, Alves GHD, Barbosa RFC, Blanco LGR, Shimano AC. In vitro mechanical analysis of X-shaped femoroplasty with polymethyl methacrylate boundary a fall on the greater trochanter . Injury 2023; 54 Suppl 6:110747. [PMID: 38143120 DOI: 10.1016/j.injury.2023.04.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 04/10/2023] [Accepted: 04/14/2023] [Indexed: 12/26/2023]
Abstract
To evaluate with mechanical testing (MT) using synthetic femurs, an X-shaped femoroplasty technique with polymethyl methacrylate (PMMA), analyzing the results applied to the prophylaxis of proximal femur (PF) fractures caused by low-energy trauma. MT was performed simulating a fall on the greater trochanter, using fifteen Sawbones™ models. They were divided into three experimental groups (n = 5): control (DP) group, drilled without augmentation (DWA) group, and X-shaped augmentation (DX) group. Maximum load, stiffness, absorbed energy and displacement were analyzed primarily in all groups; and secondarily then, morphology and fracture type were verified in all groups while PMMA volume, temperature and time polymerization were analyzed only in the DX group. The MT results obtained for synthetic models respectively in the DP, DWA, and DX groups were: mean maximum load (5562.0 ± 464.8) N, (4798.0 ± 121.2) N, and (7132.0 ± 206.9) N; mean stiffness values (673 ± 64.34) N/mm, (636 ± 8.7) N/mm, and (738 ± 17.13) N/mm, and mean absorbed energy values (36,203 ± 3819) N.mm, (27,617 ± 3011) N.mm, (44,762 ± 3219) N.mm; mean displacement values (13.6 ± 1.45) N, (11.1 ± 0.5) N, and (13.2 ± 0.69) N. The mean volume, temperature reached during filling in the DX group were 9.8 mL, 42.54ºC with 1' 56" of polymerization. The fracture types were similar between the DP and DWA groups, affecting the trochanteric region, as distinctly to those in the DX group, which were restricted to the femoral neck. The values obtained in MT showed statistical significance when analyzed by one-way ANOVA (5%) for maximum load, stiffness, and absorbed energy between groups. In conclusion, X-shaped PMMA augmentation presents a protective biomechanical characteristic against PF fractures generated in synthetic models by boundary a fall on the greater trochanter.
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Affiliation(s)
- Anderson Freitas
- Hospital Ortopédico e Medicina Especializada (HOME), Orthopedic Trauma Service, Hospital Regional do Gama, Brasília, DF, Brazil.
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Abbassi K, Janghorban M, Javanmardi F, Mobasseri S. Feasibility study of femur bone with continuum model. J Med Eng Technol 2023; 47:355-366. [PMID: 38625882 DOI: 10.1080/03091902.2024.2336512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 03/23/2024] [Indexed: 04/18/2024]
Abstract
It is known that the geometric structures of bones are very complex. This has made researchers unable to model them with the continuum approach and suffice to model them with simulation or experimental tests. Undoubtedly, provide a simple and accurate continuum model for studying bones is always desirable. In this article, as the first serious endeavour, a suggested beam model is investigated to see whether it is suitable for modelling femur bones or not. If this model gives an acceptable answer, it can be a link to the continuum theories for beams. In other words, the approximated beam model can be formulated with continuum approach to study femur bone. For feasibility study of the approximated model for femur bones, both static and dynamic analysis of them are investigated and compared. It is found that in most cases for vibration analysis, the suggested model has acceptable results but in static analysis, the mean difference between the results is about 16%. This research is hoped to be the first serious step in this category.
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Affiliation(s)
- Kianoosh Abbassi
- Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran
| | - Maziar Janghorban
- Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran
| | | | - Saleh Mobasseri
- Department of Mechanical Engineering, Marvdasht Branch, Islamic Azad University, Marvdasht, Iran
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Zdero R, Brzozowski P, Schemitsch EH. Biomechanical properties of artificial bones made by Sawbones: A review. Med Eng Phys 2023; 118:104017. [PMID: 37536838 DOI: 10.1016/j.medengphy.2023.104017] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2023] [Revised: 06/23/2023] [Accepted: 06/27/2023] [Indexed: 08/05/2023]
Abstract
Biomedical engineers and physicists frequently use human or animal bone for orthopaedic biomechanics research because they are excellent approximations of living bone. But, there are drawbacks to biological bone, like degradation over time, ethical concerns, high financial costs, inter-specimen variability, storage requirements, supplier sourcing, transportation rules, etc. Consequently, since the late 1980s, the Sawbones® company has been one of the world's largest suppliers of artificial bones for biomechanical testing that counteract many disadvantages of biological bone. There have been many published reports using these bone analogs for research on joint replacement, bone fracture fixation, spine surgery, etc. But, there exists no prior review paper on these artificial bones that gives a comprehensive and in-depth look at the numerical data of interest to biomedical engineers and physicists. Thus, this paper critically reviews 25 years of English-language studies on the biomechanical properties of these artificial bones that (a) characterized unknown or unreported values, (b) validated them against biological bone, and/or (c) optimized different design parameters. This survey of data, advantages, disadvantages, and knowledge gaps will hopefully be useful to biomedical engineers and physicists in developing mechanical testing protocols and computational finite element models.
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Affiliation(s)
- Radovan Zdero
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
| | - Pawel Brzozowski
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada.
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada; Division of Orthopaedic Surgery, Western University, London, ON, Canada
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Zdero R, Gide K, Brzozowski P, Schemitsch EH, Bagheri ZS. Biomechanical design optimization of distal femur locked plates: A review. Proc Inst Mech Eng H 2023; 237:791-805. [PMID: 37366552 DOI: 10.1177/09544119231181487] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Clinical findings, manufacturer instructions, and surgeon's preferences often dictate the implantation of distal femur locked plates (DFLPs), but healing problems and implant failures still persist. Also, most biomechanical researchers compare a particular DFLP configuration to implants like plates and nails. However, this begs the question: Is this specific DFLP configuration biomechanically optimal to encourage early callus formation, reduce bone and implant failure, and minimize bone "stress shielding"? Consequently, it is crucial to optimize, or characterize, the biomechanical performance (stiffness, strength, fracture micro-motion, bone stress, plate stress) of DFLPs influenced by plate variables (geometry, position, material) and screw variables (distribution, size, number, angle, material). Thus, this article reviews 20 years of biomechanical design optimization studies on DFLPs. As such, Google Scholar and PubMed websites were searched for articles in English published since 2000 using the terms "distal femur plates" or "supracondylar femur plates" plus "biomechanics/biomechanical" and "locked/locking," followed by searching article reference lists. Key numerical outcomes and common trends were identified, such as: (a) plate cross-sectional area moment of inertia can be enlarged to lower plate stress at the fracture; (b) plate material has a larger influence on plate stress than plate thickness, buttress screws, and inserts for empty plate holes; (c) screw distribution has a major influence on fracture micro-motion, etc. Recommendations for future work and clinical implications are then provided, such as: (a) simultaneously optimizing fracture micro-motion for early healing, reducing bone and implant stresses to prevent re-injury, lowering "stress shielding" to avoid bone resorption, and ensuring adequate fatigue life; (b) examining alternate non-metallic materials for plates and screws; (c) assessing the influence of condylar screw number, distribution, and angulation, etc. This information can benefit biomedical engineers in designing or evaluating DFLPs, as well as orthopedic surgeons in choosing the best DFLPs for their patients.
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Affiliation(s)
- Radovan Zdero
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
| | - Kunal Gide
- Department of Mechanical Engineering, George Mason University, Fairfax, VA, USA
| | - Pawel Brzozowski
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
- Division of Orthopaedic Surgery, Western University, London, ON, Canada
| | - Z Shaghayegh Bagheri
- Department of Mechanical Engineering, George Mason University, Fairfax, VA, USA
- Kite Research Institute, Toronto Rehab Institute, University Health Network, Toronto, ON, Canada
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Nägl K, Reisinger A, Pahr DH. The biomechanical behavior of 3D printed human femoral bones based on generic and patient-specific geometries. 3D Print Med 2022; 8:35. [PMID: 36418789 PMCID: PMC9685985 DOI: 10.1186/s41205-022-00162-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Accepted: 10/18/2022] [Indexed: 11/25/2022] Open
Abstract
BACKGROUND Bone is a highly complex composite material which makes it hard to find appropriate artificial surrogates for patient-specific biomechanical testing. Despite various options of commercially available bones with generic geometries, these are either biomechanically not very realistic or rather expensive. METHODS In this work, additive manufacturing was used for the fabrication of artificial femoral bones. These were based on CT images of four different commercially available femoral bone surrogates and three human bones with varying bone density. The models were 3D printed using a low-budget fused deposition modeling (FDM) 3D printer and PLA filament. The infill density was mechanically calibrated and varying cortical thickness was used. Compression tests of proximal femora simulating stance were performed and the biomechanical behavior concerning ultimate force, spring stiffness, and fracture pattern were evaluated as well as compared to the results of commercial and cadaveric bones. RESULTS Regarding the ultimate forces and spring stiffness, the 3D printed analogs showed mechanical behavior closer to their real counterparts than the commercially available polyurethan-based surrogates. Furthermore, the increase in ultimate force with increasing bone density observed in human femoral bones could be reproduced well. Also, the fracture patterns observed match well with fracture patterns observed in human hip injuries. CONCLUSION Consequently, the methods presented here show to be a promising alternative for artificial generic surrogates concerning femoral strength testing. The manufacturing is straightforward, cheap, and patient-specific geometries are possible.
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Affiliation(s)
- Katharina Nägl
- Division Biomechanics, Karl Landsteiner University of Health Science, Dr.-Karl-Dorrek-Straße 30, 3500, Krems an der Donau, Austria
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060, Wien, Austria
| | - Andreas Reisinger
- Division Biomechanics, Karl Landsteiner University of Health Science, Dr.-Karl-Dorrek-Straße 30, 3500, Krems an der Donau, Austria
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060, Wien, Austria
| | - Dieter H Pahr
- Division Biomechanics, Karl Landsteiner University of Health Science, Dr.-Karl-Dorrek-Straße 30, 3500, Krems an der Donau, Austria.
- Institute for Lightweight Design and Structural Biomechanics, TU Wien, Getreidemarkt 9, 1060, Wien, Austria.
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Djuricic A, Gee A, Schemitsch EH, Quenneville CE, Zdero R. Biomechanical design of a new percutaneous locked plate for comminuted proximal tibia fractures. Med Eng Phys 2022; 104:103801. [DOI: 10.1016/j.medengphy.2022.103801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2021] [Revised: 03/14/2022] [Accepted: 04/12/2022] [Indexed: 11/25/2022]
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Fan J, Xu X, Zhou F. The lateral femoral wall thickness on the risk of post-operative lateral wall fracture in intertrochanteric fracture after DHS fixation: A finite element analysis. Injury 2022; 53:346-352. [PMID: 34789386 DOI: 10.1016/j.injury.2021.11.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 11/04/2021] [Accepted: 11/08/2021] [Indexed: 02/02/2023]
Abstract
BACKGROUND Patients with a lateral femoral wall (LFW) fracture were reported to have high rates of re-operation and complication. Although the LFW thickness was a reliable predictor of post-operative or intra-operative LFW fracture, there was a paucity of literature evaluating the critical stress distributions on the femur and screws of intertrochanteric fractures treated with dynamic hip screw (DHS). This study aimed to investigate the biomechanical performance of intertrochanteric fractures with different LFW thickness treated with DHS device. METHODS A three-dimensional model of the proximal femur was established by computed tomography images. The intertrochanteric fracture model with three different LFW thickness (10 mm, 20.5 mm and 30 mm, respectively) was created, which was fixed by DHS. The von Mises stress on the proximal femur, lateral femoral wall, DHS and the total displacement of the device components were evaluated and compared for three different LFW thickness model. RESULTS The maximum von Mises stress in the proximal fragment of the 10 and 20.5 mm model increased by 80.56% and 57.97% when compared with the 30 mm model. The peek von Mises stress around the blade entry point of the 10 mm and 20.5 mm model increased by 89.26% and 66.39% when compared with the 30 mm model. The peek von Mises in the DHS located near the junction of the barrel and side plate of each model and the 30 mm model had the smallest von Mises stress compared with the other two models. Furthermore, the maximum displacement in the 30 mm model was much smaller than that in the10mm model and 20 mm model. CONCLUSIONS The intertrochanteric fracture with a thinner LFW tended to have a higher risk of LFW fracture stabilized by a DHS device. Thus, the intertrochanteric fractures with a thinner LFW should not be treated by DHS alone and the intramedullary nail or an addition of trochanteric stabilization plate(TSP) was recommended.
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Affiliation(s)
- Jixing Fan
- Department of Orthopedics, Peking University Third Hospital, No. 49, North Garden Rd., Haidian District, Beijing 100191, China; Engineering Research Center of Bone and Joint Precision Medicine, Ministry of Education, Beijing, China, 10091
| | - Xiangyu Xu
- Department of Orthopedics, Peking University Third Hospital, No. 49, North Garden Rd., Haidian District, Beijing 100191, China; Engineering Research Center of Bone and Joint Precision Medicine, Ministry of Education, Beijing, China, 10091
| | - Fang Zhou
- Department of Orthopedics, Peking University Third Hospital, No. 49, North Garden Rd., Haidian District, Beijing 100191, China; Engineering Research Center of Bone and Joint Precision Medicine, Ministry of Education, Beijing, China, 10091.
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Varshney A, Upadhaya GK, Sinha S, Arya RK, Jain VK. Association between lateral femoral wall thickness and BMD with the occurrence of lateral wall fracture in DHS fixation. J Orthop 2022; 29:71-74. [PMID: 35241880 PMCID: PMC8858758 DOI: 10.1016/j.jor.2022.01.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Nearly 50% of all hip fractures are intertrochanteric fractures (ITF) and are linked to osteopenia and advancing age. For secure ITF repair, the dynamic hip screw (DHS) fixation is regarded gold standard surgery. However, controversy exists regarding the use of DHS in the treatment of unstable ITF especially in patients with pre-operative lateral femoral wall fracture (LWF). The purpose of this study is to find if there's a link between lateral femoral wall thickness, bone mineral density and the risk of LWF in DHS fixation. PATIENT AND METHODS A prospective, observational cohort analysis of 70 consecutive patients with ITF was undertaken in a tertiary care government hospital. All patients were treated with a 135° DHS fixation under regional anaesthesia and fluoroscopic guidance. Lateral femoral wall thickness was assessed pre-operatively on radiographs and during surgery. Mean T score as a measure of bone mineral density was recorded in all patients. RESULT Postoperative LWFs occurred in 11 individuals. In 11 patients who had a postoperative LWF, the mean lateral femoral wall thickness was 19.545 mm, while the remaining 54 patients had a mean lateral femoral wall thickness of 29.285 mm (P < 0.001) With 81.5% sensitivity, the lateral femoral wall thickness threshold that could predict LWF was determined to be less than 25 mm. The mean T score of the contralateral hip in LWF patients was -2.255 standard deviation, whereas it was -2.428 standard deviation in patients without LWF, the difference of which was statistically not significant. CONCLUSION DHS fixation alone should be avoided in ITF patients with lateral femoral wall thickness <25 mm and other implant choices should be explored for management of these patients.
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Affiliation(s)
- Anurag Varshney
- Department of Orthopaedics, Atal Bihari Vajpayee Institute of Medical Sciences & Dr. Ram Manohar Lohia Hospital, New Delhi, 110001, India
| | | | - Skand Sinha
- Sports Injury Centre, Safderjung Hospital, New Delhi, India
| | | | - Vijay Kumar Jain
- Department of Orthopaedics, Atal Bihari Vajpayee Institute of Medical Sciences & Dr. Ram Manohar Lohia Hospital, New Delhi, 110001, India
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Güngörürler M, Gürsan O, Havıtçıoğlu H. Computational analysis of the effects of interprosthetic distance on normal and reduced cortical thickness femur models. Proc Inst Mech Eng H 2021; 236:169-178. [PMID: 34425723 DOI: 10.1177/09544119211040998] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Distal femoral fractures associated with the femoral stem in a well-fixed hip arthroplasty pose a risk of an interprosthetic fracture, the treatment of which is known as difficult. To effectively prevent and treat IP fractures, biomechanical effects must be demonstrated. We defined eight variations of the interprosthetic distance ranging from 48 mm overlap to 128 mm gap. Femoral geometries with normal and reduced cortical thickness were modeled to evaluate the effects of cortical thickness. In addition to the intact model, a total of 16 finite element models were analyzed under physiological boundary conditions. Maximum and minimum principal strains on the lateral and medial cortex surfaces were always found to be greater in models with reduced cortical thickness than in normal femurs. The model with 48 mm overlapping interprosthetic distance produced the least peak strain and the model with 16 mm interprosthetic gap produced the greatest strain with both normal and reduced cortical thickness. The screw holes produced local strain concentrations and increased the peak strains on the cortex surfaces, especially close to the stem tip. Statistically, a significant correlation (R2 = 0.9483) was found between strain shielding and interprosthetic distance. Axial stiffness, interfragmentary shear motion, and maximum von-Mises stress on the distal plate showed a high correlation with the interprosthetic distance. It was concluded that the overlapping structures are superior to other fixations we analyzed in that they offer better mechanical stability and eliminates the local strain concentrations.
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Affiliation(s)
- Musa Güngörürler
- Department of Biomechanics, School of Medicine Health Science Institute, Dokuz Eylul University, Izmir, Turkey
| | - Onur Gürsan
- Department of Orthopaedics and Traumatology, Dokuz Eylul University, Izmir, Turkey
| | - Hasan Havıtçıoğlu
- Department of Orthopaedics and Traumatology, Dokuz Eylul University, Izmir, Turkey
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Lee WC, Chou SM, Tan CW, Chng LS, Yam GJM, Chua THI. Intertrochanteric fracture with distal extension: When is the short proximal femoral nail antirotation too short? Injury 2021; 52:926-932. [PMID: 33082031 DOI: 10.1016/j.injury.2020.10.059] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 09/25/2020] [Accepted: 10/13/2020] [Indexed: 02/02/2023]
Abstract
INTRODUCTION The lesser trochanter (LT) fragment in the multifragmentary intertrochanteric femur fracture (AO 31A2.2) may extend distally. If the fragment extends too distally, fixation with a short proximal femoral nail antirotation (PFNA-II) device may not be sufficient. The exact length of distal extension that can be tolerated by the short PFNA-II is not known, therefore it is our objective to determine it. MATERIALS AND METHODS A finite element analysis was performed on AO 31A2.2 fracture fixed with a 200mm length size 10 PFNA-II. The construct was loaded vertically to clinical failure of 10mm displacement. This was repeated with the size of the LT fragment increasing distally at intervals, up to 120mm from the base of the LT. The process was also repeated with the bone properties substituted with osteoporotic properties. The stiffness, maximum vertical reaction force, and the plastic deformation area were investigated. RESULTS In both non-osteoporotic and osteoporotic model, the stiffness and the maximum vertical reaction force of the construct dropped significantly when the LT fragment is larger than 40mm. Beyond 40mm of LT fragment size, there was a rapid increase in the area of plastic deformation of the cortical bone distal to the intertrochanteric fracture, signifying structural failure of the construct. CONCLUSION A long PFNA-II should be considered when fixing a multifragmentary intertrochanteric fracture if the LT fragment extends 40mm distal to the distal base of the LT as the construct fails rapidly upon uniaxial load to failure. Clinically, this threshold may be smaller to account for the multi-axial and dynamic stresses.
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Affiliation(s)
- Wu Chean Lee
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore.
| | - Siaw Meng Chou
- School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Chee Wei Tan
- Advanced Analysis, Advisian, Alexandra Technopark, 438B Alexandra Road #04-09, Singapore 119968, Singapore
| | - Li Sing Chng
- School of Mechanical & Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore
| | - Gui Jie Michael Yam
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore
| | - Tjun Huat Ivan Chua
- Department of Orthopaedic Surgery, Annex 1 Level 2, Tan Tock Seng Hospital, 11 Jalan Tan Tock Seng, Singapore 308433, Singapore
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Sarwar A, Gee A, Bougherara H, Kuzyk PRT, Schemitsch EH, Zdero R. Biomechanical optimization of the far cortical locking technique for early healing of distal femur fractures. Med Eng Phys 2021; 89:63-72. [PMID: 33608126 DOI: 10.1016/j.medengphy.2021.02.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 10/22/2022]
Abstract
This finite element study optimized far cortical locking (FCL) technology for early callus formation in distal femur fracture fixation with a 9-hole plate using FCL screws proximal to, and standard locking screws distal to, the fracture. Analyses were done for 120 possible FCL screw configurations by varying FCL screw distribution and number. A hip joint force of 700 N (i.e. 100% x body weight) was used, which corresponds to a typical 140 N "toe-touch" foot-to-ground force (i.e. 20% x body weight) suggested to patients immediately after surgery. Increased FCL screw distribution (i.e. shorter plate working length) caused a decrease at the medial side and an increase at the lateral side of the axial interfragmentary motion (AIM), mildly affected shaft and condylar cortex Von Mises max stress (σMAX), increased plate σMAX, and decreased shaft FCL screw and condylar locking screw σMAX. Increased FCL screw number decreased AIM and σMAX on the shaft cortex, condylar cortex, plate, and FCL screws, but not condylar screws. The optimal FCL screw configuration had 3 FCL screws in plate holes #1, 5, and 6 (proximal to distal) for optimal AIM of 0.2 - 1 mm and reduce shear fracture motion, thereby encouraging early callus formation.
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Affiliation(s)
- Ahmed Sarwar
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Aaron Gee
- Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Paul R T Kuzyk
- Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada
| | - Radovan Zdero
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada; Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada; Department of Mechanical and Materials Engineering, Western University, London, ON, Canada.
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Gee A, Bougherara H, Schemitsch EH, Zdero R. Biomechanical design using in-vitro finite element modeling of distal femur fracture plates made from semi-rigid materials versus traditional metals for post-operative toe-touch weight-bearing. Med Eng Phys 2020; 87:95-103. [PMID: 33461680 DOI: 10.1016/j.medengphy.2020.11.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 11/23/2020] [Accepted: 11/29/2020] [Indexed: 01/19/2023]
Abstract
This proof-of-concept study designs distal femur fracture plates from semi-rigid materials vs. traditional metals for toe-touch weight-bearing recommended to patients immediately after surgery. The two-fold goal was to (a) reduce stress shielding (SS) by increasing cortical bone stress thereby reducing the risk of bone absorption and plate loosening, and (b) reduce delayed healing (DH) via early callus formation by optimizing axial interfragmentary motion (AIM). Finite element analysis was used to design semi-rigid plates whose elastic moduli E ensured plates permitted AIM of 0.2 - 1 mm for early callus formation. A low hip joint force of 700 N (i.e. 100% x body weight) was applied, which corresponds to a typical 140 N toe-touch foot-to-ground force (i.e. 20% x body weight) recommended to patients after surgery. Analysis was done using 2 screw materials (steel or titanium) and types (locked or non-locked). Steel and titanium plates were also analyzed. Semi-rigid plates (vs. metal plates) had lower overall femur/plate construct stiffnesses of 508 - 1482 N/mm, higher cortical bone stresses under the plate by 2.02x - 3.27x thereby reducing SS, and lower E values of 414 - 2302 MPa to permit AIM of 0.2 - 1 mm thereby reducing DH.
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Affiliation(s)
- Aaron Gee
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada.
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada.
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada; Department of Surgery (Division of Orthopaedic Surgery), Western University, London, Canada.
| | - Radovan Zdero
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada; Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada; Department of Surgery (Division of Orthopaedic Surgery), Western University, London, Canada; Department of Mechanical and Materials Engineering, Western University, London, Canada.
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15
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Three-Dimensional Visualisation of Skeletal Cavities. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1171:73-83. [PMID: 31823241 DOI: 10.1007/978-3-030-24281-7_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Bones contain spaces within them. The extraction and the analysis of those cavities are crucial in the study of bone tissue function and can inform about pathologies or past traumatic events. The use of medical imaging techniques allows a non-invasive visualisation of skeletal cavities opening a new frontier in medical inspection and diagnosis. Here, we report the application of a new mesh-based approach for the isolation of skeletal cavities of different size and geometrical structure. We apply a mesh-based approach to extract (i) the main virtual cavities inside the human skull, (ii) a complete human endocast, (iii) the inner vasculature of the malleus bone and (iv) the medullary of a human femur. The detailed description of the mesh-based isolation method and its pioneristic application to four different case-studies show the potential of this approach in medical visualisation.
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PENG MATTHEWJIANQIAO, XU HONGWEN, CHEN HAIYAN, JU XIANGYANG, HU YONG, AYOUB ASHRAF, KHAMBAY BALVINDER, GUO YUEMING, BAI BO. COMPARATIVE ANALYSIS FOR THREE FIXTURES OF PAUWELLS-II BY THE BIOMECHANICAL FINITE ELEMENT METHOD. J MECH MED BIOL 2019. [DOI: 10.1142/s0219519419500799] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Little is known about why and how biomechanics govern the hypothesis that three-Lag-Screw (3LS) fixation is a preferred therapeutic technique. A series models of surgical internal-fixation for femoral neck fractures of Pauwells-II will be constructed by an innovative approach of finite element so as to determine the most stable fixation by comparison of their biomechanical performance. Seventeen sets of CT scanned femora were imported onto Mimics extracting 3D models; these specimens were transferred to Geomagic Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; three sorts of internal fixators were expressed virtually by Pro-Engineer. Processed by Hypermesh, all compartments were assembled onto three systems actually as “Dynamic hip screw (DHS), 3LS and DHS+LS”. Eventually, numerical models of Finite Elemental Analysis (FEA) were exported to AnSys for solution. Three models for fixtures of Pauwells-II were established, validated and analyzed with the following findings: Femoral-shaft stress for [Formula: see text](3LS) is the least; Internal-fixator stress (MPa) for [Formula: see text]; Integral stress (MPa) for [Formula: see text]; displacement of femoral head (mm) for a[Formula: see text](DHS+LS) = 0.735; displacement of femoral shaft (mm) for [Formula: see text]; and displacement of fixators for [Formula: see text]. Mechanical comparisons for other femoral parks are insignificantly different, and these data can be abstracted as follows: the stress of 3LS-system was checked to be the least, and an interfragmentary displacement of DHS+LS assemblages was assessed to be the least”. A 3LS-system should be recommended to clinically optimize a Pauwells-II facture; if treated by this therapeutic fixation, breakage of fixators or secondary fracture is supposed to occur rarely. The strength of this study is that it was performed by a computer-aided simulation, allowing for design of a preoperative strategy that could provide acute correction and decrease procedure time, without harming to humans or animals.
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Affiliation(s)
- MATTHEW JIAN-QIAO PENG
- Department of Orthopedics, First Affiliated Hospital, GuangZhou Medical University, P. R. China
| | - HONGWEN XU
- Department of Pediatric Orthopaedics, GuangZhou Women and Children’s Medical Center, P. R. China
| | - HAI-YAN CHEN
- Department of Orthopedics, HuiDong People’s Hospital, HuiDong, P. R. China
| | - XIANGYANG JU
- Department of Clinical Physics and Bioengineering, University of Glasgow, U.K
| | - YONG HU
- Neural Electrophysiology Lab, University of Hong Kong, Hong Kong
| | - ASHRAF AYOUB
- Department of Clinical Physics and Bioengineering, University of Glasgow, U.K
| | - BALVINDER KHAMBAY
- Department of Clinical Physics and Bioengineering, University of Glasgow, U.K
| | - YUEMING GUO
- Department of Pediatric Orthopaedics, FoShan Hospital of Traditional Chinese Medicine, FoShan, P. R. China
| | - BO BAI
- Department of Orthopedics, First Affiliated Hospital, GuangZhou Medical University, P. R. China
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Ketata H, Affes F, Kharrat M, Dammak M. A comparative study of tapped and untapped pilot holes for bicortical orthopedic screws – 3D finite element analysis with an experimental test. ACTA ACUST UNITED AC 2019; 64:563-570. [DOI: 10.1515/bmt-2018-0049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2018] [Accepted: 12/10/2018] [Indexed: 11/15/2022]
Abstract
Abstract
The aim of this study was to compare the screw-to-bone fixation strength of two insertion techniques: self-tapping screw (STS) and non-self-tapping screw (NSTS). Finite element analysis (FEA) was used for the comparison by featuring three tests (insertion, pull-out and shear) in a human tibia bone model. A non-linear material behavior with ductile damage properties was chosen for the modeling. To validate the numerical models, experimental insertion and pull-out tests were carried out using a synthetic bone. The experimental and numerical results of pull-out tests correlated well. Thread forming was successfully simulated during the insertion process of STS and NSTS. It is demonstrated that the STS generates higher insertion torque, induces a higher amount of stress after the insertion process and relatively more strength under the pull-out and shear tests than the NSTS. However, the NSTS induces more stiffness under the two tests (pull-out and shear) and less damage to the screw-bone interface compared to the STS. It is concluded that the use of STS ensures tighter bony contact and enables higher pull-out strength; however, the use of NSTS improves the stiffness of the fixation and induces less damage to the cortical bone-screw fixation and thus minimum risk is obtained in terms of bone necrosis.
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18
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Samiezadeh S, Bougherara H, Abolghasemian M, D'Lima D, Backstein D. Rotating hinge knee causes lower bone-implant interface stress compared to constrained condylar knee replacement. Knee Surg Sports Traumatol Arthrosc 2019; 27:1224-1231. [PMID: 30039293 DOI: 10.1007/s00167-018-5054-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2017] [Accepted: 07/06/2018] [Indexed: 11/24/2022]
Abstract
PURPOSE To compare the stresses at bone-arthroplasty interface of constrained and semi-constrained knee prostheses, using the finite element (FE) method as a predictor of the survivorship of the implants. METHODS Three-dimensional FE models of the knee implanted with rotating hinge (RHK) and legacy constrained condylar (LCCK) prostheses were generated to study the loads and stresses for two situations: medial- and lateral collateral ligament deficiencies in full extension. RESULTS On average, the shear stress developed at bone-implant interface dropped from 16.9 to 13.7 MPa (18.9%), and the interface von Mises stress lowered from 37.6 to 30.2 MPa (19.6%) in RHK compared to those in LCCK prostheses. RHK design also resulted in a more uniform stress distribution at the interfaces in both femur and tibia. The average polyethylene liner stress dropped from 9.6 to 2.6 MPa (a 72.7% decrease) in RHK design when compared to that in LCCK design. CONCLUSION The more uniform interface stress suggests fewer density changes at the periprosthetic regions due to bone remodelling. Moreover, the lower polyethylene stresses are likely to reduce wear and damage. These findings reveal that the RHK design may have more favorable mechanical features compared to LCCK design in full extension boundary conditions, implying a potentially better survivorship. However, the findings should be interpreted cautiously as other configurations were not investigated.
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Affiliation(s)
- Saeid Samiezadeh
- Orthopaedic Biomechanics Laboratory, Sunnybrook Research Institute, 2075 Bayview Avenue, Toronto, ON, M4N 3M5, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, 350 Victoria Street, Toronto, ON, M5B 2K3, Canada
| | - Mansour Abolghasemian
- Bone and Joint Reconstruction Research Center, Shafa Hospital, Iran University of Medical Sciences, Jaleh Street, Baharestan Square, Tehran, Iran.
| | - Darryl D'Lima
- Orthopaedic Research Laboratories, Shiley Center for Orthopaedic Research and Education at Scripps Clinic, 11025 N Torrey Pines Rd, La Jolla, CA, 92037, USA
| | - David Backstein
- Head of Gluskin Granovsky, Division of Orthopedic Surgery, Mount Sinai Hospital, University of Toronto, 600 University Avenue, Toronto, ON, M5G 1X5, Canada
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19
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Jian-Qiao Peng M, Chen HY, Ju X, Hu Y, Ayoub A, Khambay B, Liu Z, Bai B. Comparative analysis for five fixations of Pauwels-I by the biomechanical finite-element method. J INVEST SURG 2018; 33:428-437. [PMID: 30516078 DOI: 10.1080/08941939.2018.1533054] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Background: Little is known about how biomechanics govern the five fixtures such as DHS, MLS, DHS + LS, LP, and HA are accepted as common therapeutic techniques. Aims and objectives: A series of numerical models for a femoral neck fracture of Pauwels-I will be constructed by innovative approach of finite element in order to determine the most optimized option in comparison with biomechanical performance. Method: Twenty sets of computer tomography scanned femora were imported onto Mimics to extract 3 D models; these specimens were transferred to Geomagic-Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; 5 sorts of fixture were then expressed by Pro-Engineer virtually. After processing with HyperMesh, all compartments (fracture model + internal implant) were assembled onto 5 systems: "Dynamic Hip Screw (DHS), Multiple Lag screw (MLS), DHS + LS, femoral Locking Plate (LP) and HemiArthroplasty (HA)." Eventually, numerical models of the finite-elemental analysis were exported to AnSys to determine the solution. Result: Four models of fixation and a simulation of HA for Pauwels-I were established, validated, and analyzed with the following findings: In term of displacement, these 5 fixtures ranged between 0.3801 and 0.7536 mm have no significant difference; in term of stress, the averages of peaks for integral assemblage are b(MLS) = 43.5766 ≈< d(LP) = 43.6657 ≈< e(Ha) = 43.6657 < c(DHS + LS) = 66.5494 < a(DHS) = 105.617 in MPa indicate that MLS, LP and HA are not significantly different, but less than DHS + LS or DHS in each. Conclusion: A fixture of MLS or LP with optional HA should be recommended to clinically optimize a Pauwels-I facture.
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Affiliation(s)
- Matthew Jian-Qiao Peng
- Orthopedics Dept. of 1st Affiliated Hospital, GuangZhou Medical University, GuangDong, China
| | - Hai-Yan Chen
- Orthopedics Dept. of HuiDong People's Hospital, HuiZhou, GuangDong, China
| | - XiangYang Ju
- Dept. of Clinical Physics and Bioengineering, University of Glasgow, Glasgow, U.K
| | - Yong Hu
- Neural Electrophysiology Lab, University of Hongkong, Hongkong
| | - Ashraf Ayoub
- Dept. of Clinical Physics and Bioengineering, University of Glasgow, Glasgow, U.K
| | - Balvinder Khambay
- Dept. of Clinical Physics and Bioengineering, University of Glasgow, Glasgow, U.K
| | - ZiQing Liu
- Traumatic Orthopedics Dept. of SanShui People's Hospital, FoShan, GuangDong, China
| | - Bo Bai
- Orthopedics Dept. of 1st Affiliated Hospital, GuangZhou Medical University, GuangDong, China
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20
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Chavoshnejad P, Ayati M, Abbasspour A, Karimpur M, George D, Rémond Y, Heidary Rouchi A, Baniassadi M. Optimization of Taylor spatial frame half-pins diameter for bone deformity correction: Application to femur. Proc Inst Mech Eng H 2018; 232:673-681. [PMID: 29962324 DOI: 10.1177/0954411918783782] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Using external fixtures for bone deformity correction takes advantages of less soft tissue injury, better bone alignment and enhances strain development for bone formation on cutting section, which cause shorter healing time. Among these fixtures, Taylor spatial frame is widely used and includes two rings and six adjustable struts developing 6 degrees of freedom, making them very flexible for this type of application. The current study describes a method to optimize Taylor spatial frame pin-sizes currently chosen from the surgeon's experiences. A three-dimensional model of femur was created from computed tomography images; segmentation of the medical images was made based on the Hounsfield unit (gray scale) in order to allocate adequate mechanical properties into cortical and trabecular bone sections. Both the cortical and trabecular sections were assumed to be isotropic and homogeneous. The diameter optimization of Taylor spatial frame's half-pins was carried out by coupling genetic algorithm and finite element analysis. The finite element analysis was based on a static mechanical load corresponding to a standing person's body weight. Finite element analysis results were validated with experimentally measured strains obtained from bone compression tests. A cost function, based on the developed bone stresses, was defined close to the Taylor spatial frame's half-pins. The calculated cost function showed a decrease of over 33% from the initial half-pin selection by the surgeon and the genetic algorithm optimization. Consequently, the maximum stresses experienced by the bone in the connected location of the half-pins decreased from 121.4 MPa in the surgeon's selection to 73.07 MPa as a result of the optimization process.
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Affiliation(s)
- Pooria Chavoshnejad
- 1 School of Mechanical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran
| | - Moosa Ayati
- 1 School of Mechanical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran
| | - Aziz Abbasspour
- 2 Department of Orthopedics, Institute of Health Biosciences, The University of Tokushima Graduate School, Tokushima, Japan
| | - Morad Karimpur
- 1 School of Mechanical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran
| | - Daniel George
- 3 ICube Laboratory, CNRS, University of Strasbourg, Strasbourg, France
| | - Yves Rémond
- 3 ICube Laboratory, CNRS, University of Strasbourg, Strasbourg, France
| | - Alireza Heidary Rouchi
- 4 Iranian Tissue Bank & Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Majid Baniassadi
- 1 School of Mechanical Engineering, Faculty of Engineering, University of Tehran, Tehran, Iran.,3 ICube Laboratory, CNRS, University of Strasbourg, Strasbourg, France
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21
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Comparative Analysis for Internal Fixations of Pauwels II by Biomechanical Finite Element Method. Int Surg 2018. [DOI: 10.9738/intsurg-d-16-00236.1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Purpose:
A series models of surgical internal fixation for femoral neck fracture of Pauwels II will be constructed by an innovative approach of finite element so as to determine the most stable fixation by comparison of their biomechanical performance.
Method:
Seventeen specimens of proximal femurs scanned by computed tomography in Digital Imaging and Communications in Medicine (DICOM) format were input onto Mimics rebuilding 3D models; their stereolithography (STL) format dataset were imported into Geomagic Studio (3D Systems, Rock Hill, South Carolina) for simulative osteotomy and non-uniform rational basis spline kartograph; the generated IGS dataset were interacted by UG to fit simulative 3D-solid models; 3 sorts of internal fixators were expressed in 3D model by ProE (PTC, Boston, Connecticut) program virtually. Processed by HyperMesh (Altair, Troy, Michigan), all compartments (fracture model + internal immobilization) were assembled onto 3 systems actually as: Dynamic hip screw (DHS) / Lag screw (LS) / DHS+LS. Eventually, a numerical model of finite elemental analysis was exported to ANSYS for solution.
Result:
Three models of internal fixations for femoral neck fracture of Pauwels II were established and validated effectively, the stress and displacement of each internal pin were analyzed, the advantages of each surgical therapy for femoral neck fracture of Pauwels II were compared and demonstrated synthetically as: “The contact stress of 3-LS-system was checked to be the least; the interfragmentary displacement of DHS+1-LS assemblages was assessed to be the least.”
Conclusion:
3-LS-system is recommended to be a clinical optimization for Pauwels II femoral neck facture, by this therapeutic fixation mechanically, breakage of fixators, or secondary fracture rarely occurs.
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Conlisk N, Howie CR, Pankaj P. An efficient method to capture the impact of total knee replacement on a variety of simulated patient types: A finite element study. Med Eng Phys 2016; 38:959-68. [PMID: 27387906 DOI: 10.1016/j.medengphy.2016.06.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2016] [Revised: 04/08/2016] [Accepted: 06/08/2016] [Indexed: 11/17/2022]
Abstract
Osteoporosis resulting in a reduction in bone stiffness and thinning of the cortex is almost universal in older patients. In this study a novel method to generate computational models of the distal femur which incorporate the effects of ageing and endosteal trabecularisation are presented. Application of this method to pre- and post-knee arthroplasty scenarios is then considered. These computational methods are found to provide a simple yet effective tool for assessing the post-arthroplasty mechanical environment in the knee for different patient types and can help evaluate vulnerability to supracondylar periprosthetic fracture following implantation. Our results show that the stresses in the periprosthetic region increase dramatically with ageing; this is particularly true for higher flexion angles. Stresses in the anterior region of the femoral cortex were also found to increase significantly post-implantation. The most dramatic increases in stresses and strains at these locations were observed in old osteoporotic patients, explaining why this patient group in particular is at greater risk of periprosthetic fractures.
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Affiliation(s)
- Noel Conlisk
- School of Clinical Sciences, The University of Edinburgh, Edinburgh, UK; School of Engineering, The University of Edinburgh, Edinburgh, UK.
| | - Colin R Howie
- Department of Orthopaedics, New Royal Infirmary of Edinburgh, Old Dalkeith Road, Little France, Edinburgh, UK
| | - Pankaj Pankaj
- School of Engineering, The University of Edinburgh, Edinburgh, UK
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23
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Davis ML, Vavalle NA, Stitzel JD, Gayzik FS. A technique for developing CAD geometry of long bones using clinical CT data. Med Eng Phys 2015; 37:1116-23. [DOI: 10.1016/j.medengphy.2015.08.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 06/23/2015] [Accepted: 08/19/2015] [Indexed: 11/26/2022]
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24
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Liu CC, Xing WZ, Zhang YX, Pan ZH, Feng WL. Three-dimensional finite element analysis and comparison of a new intramedullary fixation with interlocking intramedullary nail. Cell Biochem Biophys 2014; 71:717-24. [PMID: 25280782 DOI: 10.1007/s12013-014-0254-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This study was set to introduce a new intramedullary fixation, explore its biomechanical properties, and provide guidance for further biomechanical experiments. With the help of CT scans and finite element modeling software, finite element model was established for a new intramedullary fixation and intramedullary nailing of femoral shaft fractures in a volunteer adult. By finite element analysis software ANSYS 10.0, we conducted 235-2,100 N axial load, 200-1,000 N bending loads and 2-15 Nm torsional loading, respectively, and analyzed maximum stress distribution, size, and displacement of the fracture fragments of the femur and intramedullary nail. During the loading process, the maximum stress of our new intramedullary fixation were within the normal range, and the displacement of the fracture fragments was less than 1 mm. Our new intramedullary fixation exhibited mechanical reliability and unique advantages of anti-rotation, which provides effective supports during fracture recovery.
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Affiliation(s)
- Chang-cheng Liu
- Department of Orthopedics, Third Hospital of Hebei Medical University, Shijiazhuang, 050000, Hebei, China
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25
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Samiezadeh S, Tavakkoli Avval P, Fawaz Z, Bougherara H. Biomechanical assessment of composite versus metallic intramedullary nailing system in femoral shaft fractures: A finite element study. Clin Biomech (Bristol, Avon) 2014; 29:803-10. [PMID: 24951320 DOI: 10.1016/j.clinbiomech.2014.05.010] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2014] [Revised: 05/02/2014] [Accepted: 05/07/2014] [Indexed: 02/07/2023]
Abstract
BACKGROUND Intramedullary nails are the primary choice for treating long bone fractures. However, complications following nail surgery including non-union, delayed union, and fracture of the bone or the implant still exist. Reducing nail stiffness while still maintaining sufficient stability seems to be the ideal solution to overcome the abovementioned complications. METHODS In this study, a new hybrid concept for nails made of carbon fibers/flax/epoxy was developed in order to reduce stress shielding. The mechanical performance of this new implant in terms of fracture stability and load sharing was assessed using a comprehensive non-linear FE model. This model considers several mechanical factors in nine fracture configurations at immediately post-operative, and in the healed bone stages. RESULTS Post-operative results showed that the hybrid composite nail increases the average normal force at the fracture site by 319.23N (P<0.05), and the mean stress in the vicinity of fracture by 2.11MPa (P<0.05) at 45% gait cycle, while only 0.33mm and 0.39mm (P<0.05) increases in the fracture opening and the fragments' shear movement were observed. The healed bone results revealed that implantation of the titanium nail caused 20.2% reduction in bone stiffness, while the composite nail lowered the stiffness by 11.8% as compared to an intact femur. INTERPRETATION Our results suggest that the composite nail can provide a preferred mechanical environment for healing, particularly in transverse shaft fractures. This may help bioengineers better understand the biomechanics of fracture healing, and aid in the design of effective implants.
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Affiliation(s)
- Saeid Samiezadeh
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Pouria Tavakkoli Avval
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Zouheir Fawaz
- Department of Aerospace Engineering, Ryerson University, Toronto, ON, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada.
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26
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Aziz MSR, Nicayenzi B, Crookshank MC, Bougherara H, Schemitsch EH, Zdero R. Biomechanical Measurements of Stiffness and Strength for Five Types of Whole Human and Artificial Humeri. J Biomech Eng 2014; 136:051006. [DOI: 10.1115/1.4027057] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Accepted: 04/10/2014] [Indexed: 11/08/2022]
Abstract
The human humerus is the third largest longbone and experiences 2–3% of all fractures. Yet, almost no data exist on its intact biomechanical properties, thus preventing researchers from obtaining a full understanding of humerus behavior during injury and after being repaired with fracture plates and nails. The aim of this experimental study was to compare the biomechanical stiffness and strength of “gold standard” fresh-frozen humeri to a variety of humerus models. A series of five types of intact whole humeri were obtained: human fresh-frozen (n = 19); human embalmed (n = 18); human dried (n = 15); artificial “normal” (n = 12); and artificial “osteoporotic” (n = 12). Humeri were tested under “real world” clinical loading modes for shear stiffness, torsional stiffness, cantilever bending stiffness, and cantilever bending strength. After removing geometric effects, fresh-frozen results were 585.8 ± 181.5 N/mm2 (normalized shear stiffness); 3.1 ± 1.1 N/(mm2 deg) (normalized torsional stiffness); 850.8 ± 347.9 N/mm2 (normalized cantilever stiffness); and 8.3 ± 2.7 N/mm2 (normalized cantilever strength). Compared to fresh-frozen values, statistical equivalence (p ≥ 0.05) was obtained for all four test modes (embalmed humeri), 1 of 4 test modes (dried humeri), 1 of 4 test modes (artificial “normal” humeri), and 1 of 4 test modes (artificial “osteoporotic” humeri). Age and bone mineral density versus experimental results had Pearson linear correlations ranging from R = −0.57 to 0.80. About 77% of human humeri failed via a transverse or oblique distal shaft fracture, whilst 88% of artificial humeri failed with a mixed transverse + oblique fracture. To date, this is the most comprehensive study on the biomechanics of intact human and artificial humeri and can assist researchers to choose an alternate humerus model that can substitute for fresh-frozen humeri.
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Affiliation(s)
- Mina S. R. Aziz
- Institute of Medical Science, University of Toronto, Toronto, ON M5S-1A8, Canada
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Toronto, ON M5B-1W8, Canada
| | - Bruce Nicayenzi
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Toronto, ON M5B-1W8, Canada
| | - Meghan C. Crookshank
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Toronto, ON M5B-1W8, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON M5B-2K3, Canada
| | - Emil H. Schemitsch
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Toronto, ON M5B-1W8, Canada
- Faculty of Medicine, University of Toronto, Toronto, ON M5S-1A8, Canada
| | - Radovan Zdero
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Li Ka Shing Building (West Basement, Room B116), 209 Victoria Street, Toronto, ON M5B-1W8, Canada
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON M5B-2K3, Canada e-mail:
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How accurately can we predict the fracture load of the proximal femur using finite element models? Clin Biomech (Bristol, Avon) 2014; 29:373-80. [PMID: 24485865 DOI: 10.1016/j.clinbiomech.2013.12.018] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/10/2013] [Revised: 12/30/2013] [Accepted: 12/31/2013] [Indexed: 02/07/2023]
Abstract
BACKGROUND Current clinical methods for fracture prediction rely on two-dimensional imaging methods such as dual-energy X-ray absorptiometry and have limited predictive value. Several researchers have tried to integrate three-dimensional imaging techniques with the finite element (FE) method to improve the accuracy of fracture predictions. Before FE models could be used in clinical settings, a thorough validation of their accuracy is required. In this paper, we try to evaluate the current state of accuracy of subject-specific FE models that are used for prediction of the fracture load of proximal femora. METHODS All the studies that have used FE for prediction of fracture load and have compared the predicted fracture load with experimentally measured fracture loads in vitro are identified through a systematic search of the literature. A quantitative analysis of the results of those studies has been carried out to determine the absolute prediction error, percentage error, and linear correlations between predicted and measured fracture loads. FINDINGS The reported coefficients of determination (R(2)) vary between 0.773 and 0.96 while the percentage error in prediction of fracture load varies between 5 and 46% with most studies reporting percentage errors between 10 and 20%. INTERPRETATION We conclude that FE models, which are currently used only experimentally, are in general more accurate than clinically used fracture risk assessment techniques. However, the accuracy of FE models depends on the details of their modeling methodologies. Therefore, modeling procedures need to be optimized and standardized before FE could be used in clinical settings.
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Abstract
Although the importance of lateral femoral wall integrity is increasingly being recognised in the treatment of intertrochanteric fracture, little attention has been put on the development of a secondary post-operative fracture of the lateral wall. Patients with post-operative fractures of the lateral wall were reported to have high rates of re-operation and complication. To date, no predictors of post-operative lateral wall fracture have been reported. In this study, we investigated the reliability of lateral wall thickness as a predictor of lateral wall fracture after dynamic hip screw (DHS) implantation. A total of 208 patients with AO/OTA 31-A1 and -A2 classified intertrochanteric fractures who received internal fixation with a DHS between January 2003 and May 2012 were reviewed. There were 103 men and 150 women with a mean age at operation of 78 years (33 to 94). The mean follow-up was 23 months (6 to 83). The right side was affected in 97 patients and the left side in 111. Clinical information including age, gender, side, fracture classification, tip–apex distance, follow-up time, lateral wall thickness and outcome were recorded and used in the statistical analysis. Fracture classification and lateral wall thickness significantly contributed to post-operative lateral wall fracture (both p < 0.001). The lateral wall thickness threshold value for risk of developing a secondary lateral wall fracture was found to be 20.5 mm. To our knowledge, this is the first study to investigate the risk factors of post-operative lateral wall fracture in intertrochanteric fracture. We found that lateral wall thickness was a reliable predictor of post-operative lateral wall fracture and conclude that intertrochanteric fractures with a lateral wall thickness < 20.5 mm should not be treated with DHS alone. Cite this article: Bone Joint J 2013;95-B:1134–8.
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Affiliation(s)
- C-E. Hsu
- Taichung Veterans General Hospital, Department
of Orthopedics, Taichung, Taiwan
| | - C-M. Shih
- Taichung Veterans General Hospital, Department
of Orthopedics, Taichung, Taiwan
| | - C-C. Wang
- Taichung Veterans General Hospital, Department
of Orthopedics, Taichung, Taiwan
| | - K-C. Huang
- Taichung Veterans General Hospital, Department
of Orthopedics, Taichung, Taiwan
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29
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Zdero R, Saidi K, Mason SA, Schemitsch EH, Naudie DDR. A biomechanical comparison of four different cementless press-fit stems used in revision surgery for total knee replacements. Proc Inst Mech Eng H 2013. [PMID: 23185955 DOI: 10.1177/0954411912453246] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Few biomechanical studies exist on femoral cementless press-fit stems for revision total knee replacement (TKR) surgeries. The aim of this study was to compare the mechanical quality of the femur-stem interface for a series of commercially available press-fit stems, because this interface may be a 'weak link' which could fail earlier than the femur-TKR bond itself. Also, the femur-stem interface may become particularly critical if distal femur bone degeneration, which may necessitate or follow revision TKR, ever weakens the femur-TKR bond itself. The authors implanted five synthetic femurs each with a Sigma Short Stem (SSS), Sigma Long Stem (SLS), Genesis II Short Stem (GSS), or Genesis II Long Stem (GLS). Axial stiffness, lateral stiffness, 'offset load' torsional stiffness, and 'offset load' torsional strength were measured with a mechanical testing system using displacement control. Axial (range = 1047-1461 N/mm, p = 0.106), lateral (range = 415-462 N/mm, p = 0.297), and torsional (range = 115-139 N/mm, p > 0.055) stiffnesses were not different between groups. The SSS had higher torsional strength (863 N) than the other stems (range = 167-197 N, p < 0.001). Torsional failure occurred by femoral 'spin' around the stem's long axis. There was poor linear correlation between the femur-stem interface area versus axial stiffness (R = 0.38) and torsional stiffness (R = 0.38), and there was a moderate linear correlation versus torsional strength (R = 0.55). Yet, there was a high inverse linear correlation between interfacial surface area versus lateral stiffness (R = 0.79), although this did not result in a statistical difference between stem groups (p = 0.297). These press-fit stems provide equivalent stability, except that the SSS has greater torsional strength.
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Affiliation(s)
- Radovan Zdero
- Biomechanics Lab, St. Michael's Hospital, Toronto, ON, Canada
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Stanbury SJ, Salo A, Elfar JC. Biomechanical analysis of a volar variable-angle locking plate: the effect of capturing a distal radial styloid fragment. J Hand Surg Am 2012; 37:2488-94. [PMID: 23174062 DOI: 10.1016/j.jhsa.2012.09.009] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/13/2012] [Revised: 09/10/2012] [Accepted: 09/14/2012] [Indexed: 02/02/2023]
Abstract
PURPOSE Variable-angle volar locked constructs for distal radius fractures are a recent treatment addition. This study sought to biomechanically evaluate a variable-angle volar locking plate as compared with a fixed-angle construct. METHODS We created 2 different AO-C3 osteotomies in fourth-generation synthetic composite distal radiuses and labeled them proximal and distal. The distal osteotomy consisted of a smaller radial styloid fragment. We then fixed both sets of specimens with either a fixed-angle or variable-angle volar locking construct. We tested samples in axial compression with regard to cyclical loading and load to failure. Articular stepoff, stiffness, and load to failure data were then analyzed. RESULTS Neither the proximal nor the distal osteotomy groups showed articular failure after cyclic loading, significant loss of stiffness over cycling, or superior stiffness compared with the other. After load to failure in the proximal osteotomy, 1 of 8 fixed-angle and none of 8 variable-angle constructs had articular failure, whereas in the distal osteotomy, all 8 fixed-angle and none of 8 variable-angle constructs had articular failure. CONCLUSIONS Variable-angle and fixed-angle volar locked fixation of unstable intra-articular distal radius fractures in fourth-generation composite radii provide mechanically sound constructs with high load to failure values and no loss of stiffness over testing. The variable-angle construct exhibited excellent resistance to articular stepoff at load to failure and no loss of stiffness throughout cyclic loading, and did not exhibit significantly less overall stiffness compared with fixed-angle constructs. The variable-angle fixation exhibited a distinct mechanical advantage over fixed-angle fixation in the setting of a smaller radial styloid fragment. CLINICAL RELEVANCE Variable-angle constructs could be expected to hold up to standard loads in the postoperative period as well as traditional fixed-angle devices. The additional cost associated with variable-angle constructs may be warranted when treating distal radius fractures with radial styloid fragments, owing to the fragment-specific fixation allowed by customized screw placement.
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Affiliation(s)
- Spencer J Stanbury
- Department of Orthopaedic Surgery and Sports Medicine, University of Rochester, Rochester, NY 14608, USA.
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31
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Ebrahimi H, Rabinovich M, Vuleta V, Zalcman D, Shah S, Dubov A, Roy K, Siddiqui FS, H. Schemitsch E, Bougherara H, Zdero R. Biomechanical properties of an intact, injured, repaired, and healed femur: An experimental and computational study. J Mech Behav Biomed Mater 2012. [DOI: 10.1016/j.jmbbm.2012.09.005] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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Zdero R, Gallimore CH, McConnell AJ, Patel H, Nisenbaum R, Morshed G, Koo H, McKee MD, Schemitsch EH, Bougherara H. A preliminary biomechanical study of cyclic preconditioning effects on canine cadaveric whole femurs. J Biomech Eng 2012; 134:094502. [PMID: 22938376 DOI: 10.1115/1.4007249] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Biomechanical preconditioning of biological specimens by cyclic loading is routinely done presumably to stabilize properties prior to the main phase of a study. However, no prior studies have actually measured these effects for whole bone of any kind. The aim of this study, therefore, was to quantify these effects for whole bones. Fourteen matched pairs of fresh-frozen intact cadaveric canine femurs were sinusoidally loaded in 4-point bending from 50 N to 300 N at 1 Hz for 25 cycles. All femurs were tested in both anteroposterior (AP) and mediolateral (ML) bending planes. Bending stiffness (i.e., slope of the force-vs-displacement curve) and linearity R(2) (i.e., coefficient of determination) of each loading cycle were measured and compared statistically to determine the effect of limb side, cycle number, and bending plane. Stiffnesses rose from 809.7 to 867.7 N/mm (AP, left), 847.3 to 915.6 N/mm (AP, right), 829.2 to 892.5 N/mm (AP, combined), 538.7 to 580.4 N/mm (ML, left), 568.9 to 613.8 N/mm (ML, right), and 553.8 to 597.1 N/mm (ML, combined). Linearity R(2) rose from 0.96 to 0.99 (AP, left), 0.97 to 0.99 (AP, right), 0.96 to 0.99 (AP, combined), 0.95 to 0.98 (ML, left), 0.94 to 0.98 (ML, right), and 0.95 to 0.98 (ML, combined). Stiffness and linearity R(2) versus cycle number were well-described by exponential curves whose values leveled off, respectively, starting at 12 and 5 cycles. For stiffness, there were no statistical differences for left versus right femurs (p = 0.166), but there were effects due to cycle number (p < 0.0001) and AP versus ML bending plane (p < 0.0001). Similarly, for linearity, no statistical differences were noted due to limb side (p = 0.533), but there were effects due to cycle number (p < 0.0001) and AP versus ML bending plane (p = 0.006). A minimum of 12 preconditioning cycles was needed to fully stabilize both the stiffness and linearity of the canine femurs. This is the first study to measure the effects of mechanical preconditioning on whole bones, having some practical implications on research practices.
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Affiliation(s)
- Rad Zdero
- Martin Orthopaedic Biomechanics Lab, St. Michael's Hospital, Toronto, ON, Canada, M5B-1W8.
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33
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Latifi MH, Ganthel K, Rukmanikanthan S, Mansor A, Kamarul T, Bilgen M. Prospects of implant with locking plate in fixation of subtrochanteric fracture: experimental demonstration of its potential benefits on synthetic femur model with supportive hierarchical nonlinear hyperelastic finite element analysis. Biomed Eng Online 2012; 11:23. [PMID: 22545650 PMCID: PMC3464958 DOI: 10.1186/1475-925x-11-23] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Accepted: 04/30/2012] [Indexed: 12/23/2022] Open
Abstract
Background Effective fixation of fracture requires careful selection of a suitable implant to provide stability and durability. Implant with a feature of locking plate (LP) has been used widely for treating distal fractures in femur because of its favourable clinical outcome, but its potential in fixing proximal fractures in the subtrochancteric region has yet to be explored. Therefore, this comparative study was undertaken to demonstrate the merits of the LP implant in treating the subtrochancteric fracture by comparing its performance limits against those obtained with the more traditional implants; angle blade plate (ABP) and dynamic condylar screw plate (DCSP). Materials and Methods Nine standard composite femurs were acquired, divided into three groups and fixed with LP (n = 3), ABP (n = 3) and DCSP (n = 3). The fracture was modeled by a 20 mm gap created at the subtrochanteric region to experimentally study the biomechanical response of each implant under both static and dynamic axial loading paradigms. To confirm the experimental findings and to understand the critical interactions at the boundaries, the synthetic femur/implant systems were numerically analyzed by constructing hierarchical finite element models with nonlinear hyperelastic properties. The predictions from the analyses were then compared against the experimental measurements to demonstrate the validity of each numeric model, and to characterize the internal load distribution in the femur and load bearing properties of each implant. Results The average measurements indicated that the constructs with ABP, DCPS and LP respectively had overall stiffness values of 70.9, 110.2 and 131.4 N/mm, and exhibited reversible deformations of 12.4, 4.9 and 4.1 mm when the applied dynamic load was 400 N and plastic deformations of 11.3, 2.4 and 1.4 mm when the load was 1000 N. The corresponding peak cyclic loads to failure were 1100, 1167 and 1600 N. The errors between the displacements measured experimentally or predicted by the nonlinear hierarchical hyperelastic model were less than 18 %. In the implanted femur heads, the principal stresses were spatially heterogeneous for ABP and DCSP but more homogenous for LP, meaning LP had lower stress concentrations. Conclusion When fixed with the LP implant, the synthetic femur model of the subtrochancteric fracture consistently exceeds in the key biomechanical measures of stability and durability. These capabilities suggest increased resistance to fatigue and failure, which are highly desirable features expected of functional implants and hence make the LP implant potentially a viable alternative to the conventional ABP or DCSP in the treatment of subtrochancteric femur fractures for the betterment of clinical outcome.
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Affiliation(s)
- Mohammed Hadi Latifi
- National Orthopaedic Centre of Excellence in Research and Learning, University of Malaya, 50603 Kuala Lumpur, Malaysia
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Shah S, Bougherara H, Schemitsch EH, Zdero R. Biomechanical stress maps of an artificial femur obtained using a new infrared thermography technique validated by strain gages. Med Eng Phys 2012; 34:1496-502. [PMID: 22430061 DOI: 10.1016/j.medengphy.2012.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2011] [Revised: 02/20/2012] [Accepted: 02/26/2012] [Indexed: 01/21/2023]
Abstract
Femurs are the heaviest, longest, and strongest long bones in the human body and are routinely subjected to cyclic forces. Strain gages are commonly employed to experimentally validate finite element models of the femur in order to generate 3D stresses, yet there is little information on a relatively new infrared (IR) thermography technique now available for biomechanics applications. In this study, IR thermography validated with strain gages was used to measure the principal stresses in the artificial femur model from Sawbones (Vashon, WA, USA) increasingly being used for biomechanical research. The femur was instrumented with rosette strain gages and mechanically tested using average axial cyclic forces of 1500 N, 1800 N, and 2100 N, representing 3 times body weight for a 50 kg, 60 kg, and 70 kg person. The femur was oriented at 7° of adduction to simulate the single-legged stance phase of walking. Stress maps were also obtained using an IR thermography camera. Results showed good agreement of IR thermography vs. strain gage data with a correlation of R(2)=0.99 and a slope=1.08 for the straight line of best fit. IR thermography detected the highest principal stresses on the superior-posterior side of the neck, which yielded compressive values of -91.2 MPa (at 1500 N), -96.0 MPa (at 1800 N), and -103.5 MPa (at 2100 N). There was excellent correlation between IR thermography principal stress vs. axial cyclic force at 6 locations on the femur on the lateral (R(2)=0.89-0.99), anterior (R(2)=0.87-0.99), and posterior (R(2)=0.81-0.99) sides. This study shows IR thermography's potential for future biomechanical applications.
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Affiliation(s)
- Suraj Shah
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
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Crookshank M, Coquim J, Olsen M, Schemitsch EH, Bougherara H, Zdero R. Biomechanical measurements of axial crush injury to the distal condyles of human and synthetic femurs. Proc Inst Mech Eng H 2012; 226:320-9. [DOI: 10.1177/0954411912438038] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Few studies have evaluated the ‘bulk’ mechanical properties of human longbones and even fewer have compared human tissue to the synthetic longbones increasingly being used by researchers. Distal femur fractures, for example, comprise about 6% of all femur fractures, but the mechanical properties of the distal condyles of intact human and synthetic femurs have not been well quantified in the literature. To this end, the distal portions of a series of 16 human fresh-frozen femurs and six synthetic femurs were prepared identically for mechanical testing. Using a flat metal plate, an axial ‘crush’ force was applied in-line with the long axis of the femurs. The two femur groups were statistically compared and values correlated to age, size, and bone quality. Results yielded the following: crush stiffness (human, 1545 ± 728 N/mm; synthetic, 3063 ± 1243 N/mm; p = 0.002); crush strength (human, 10.3 ± 3.1 kN; synthetic, 12.9 ± 1.7 kN; p = 0.074); crush displacement (human, 6.1 ± 1.8 mm; synthetic, 2.8 ± 0.3 mm; p = 0.000); and crush energy (human, 34.8 ± 15.9 J; synthetic, 18.1 ± 5.7 J; p = 0.023). For the human femurs, there were poor correlations between mechanical properties versus age, size, and bone quality (R2 ≤ 0.18), with the exception of crush strength versus bone mineral density (R2 = 0.33) and T-score (R2 = 0.25). Human femurs failed mostly by condyle ‘roll back’ buckling (15 of 16 cases) and/or unicondylar or bicondylar fracture (7 of 16 cases), while synthetic femurs all failed by wedging apart of the condyles resulting in either fully or partially displaced condylar fractures (6 of 6 cases). These findings have practical implications on the use of a flat plate load applicator to reproduce real-life clinical failure modes of human femurs and the appropriate use of synthetic femurs. To the authors’ knowledge, this is the first study to have done such an assessment on human and synthetic femurs.
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Affiliation(s)
- Meghan Crookshank
- Faculty of Medicine, University of Toronto, Canada
- Martin Orthopaedic Biomechanics Laboratory, St Michael’s Hospital, Canada
| | - Jason Coquim
- Department of Mechanical and Industrial Engineering, Ryerson University, Canada
| | - Michael Olsen
- Faculty of Medicine, University of Toronto, Canada
- Martin Orthopaedic Biomechanics Laboratory, St Michael’s Hospital, Canada
| | - Emil H Schemitsch
- Faculty of Medicine, University of Toronto, Canada
- Martin Orthopaedic Biomechanics Laboratory, St Michael’s Hospital, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Canada
| | - Rad Zdero
- Martin Orthopaedic Biomechanics Laboratory, St Michael’s Hospital, Canada
- Department of Mechanical and Industrial Engineering, Ryerson University, Canada
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Zhang J, Malcolm D, Hislop-Jambrich J, Thomas CDL, Nielsen P. Automatic Meshing of Femur Cortical Surfaces from Clinical CT Images. LECTURE NOTES IN COMPUTER SCIENCE 2012. [DOI: 10.1007/978-3-642-33463-4_5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Zdero R, McConnell AJ, Peskun C, Syed KA, Schemitsch EH. Biomechanical Measurements of Torsion-Tension Coupling in Human Cadaveric Femurs. J Biomech Eng 2010; 133:014501. [DOI: 10.1115/1.4002937] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The mechanical behavior of human femurs has been described in the literature with regard to torsion and tension but only as independent measurements. However, in this study, human femurs were subjected to torsion to determine if a simultaneous axial tensile load was generated. Fresh frozen human femurs (n=25) were harvested and stripped of soft tissue. Each femur was mounted rigidly in a specially designed test jig and remained at a fixed axial length during all experiments. Femurs were subjected to external and internal rotation applied at a constant angulation rate of 0.1 deg/s to a maximum torque of 12 N m. Applied torque and generated axial tension were monitored simultaneously. Outcome measurements were extracted from torsion-versus-tension graphs. There was a strong relationship between applied torsion and the resulting tension for external rotation tests (torsion/tension ratio=551.7±283.8 mm, R2=0.83±0.20, n=25), internal rotation tests (torsion/tension ratio=495.3±233.1 mm, R2=0.87±0.17, n=24), left femurs (torsion/tension ratio=542.2±262.4 mm, R2=0.88±0.13, n=24), and right femurs (torsion/tension ratio=506.7±260.0 mm, R2=0.82±0.22, n=25). No statistically significant differences were found for external versus internal rotation groups or for left versus right femurs when comparing torsion/tension ratios (p=0.85) or R2 values (p=0.54). A strongly coupled linear relationship between torsion and tension for human femurs was exhibited. This suggests an interplay between these two factors during activities of daily living and injury processes.
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Affiliation(s)
- Rad Zdero
- Martin Orthopaedic Biomechanics Laboratory, Shuter Wing (Room 5-066), St. Michael’s Hospital, 30 Bond Street, Toronto, ON, M5B 1W8, Canada; Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, M5B 2K3, Canada
| | | | - Christopher Peskun
- Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Khalid A. Syed
- Division of Orthopaedic Surgery, Toronto Western Hospital, Toronto, ON, M5T 2S8, Canada
| | - Emil H. Schemitsch
- Martin Orthopaedic Biomechanics Laboratory, St. Michael’s Hospital, Toronto, ON, M5B 1W8, Canada; Department of Surgery, Faculty of Medicine, University of Toronto, Toronto, ON, M5S 1A8, Canada
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