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Srivastav A, Behera P, Dwivedi RK, Santoshi JA. Finite Element Analysis of Postoperative Stability of Transverse Scaphoid Waist Fracture. Indian J Orthop 2024; 58:785-793. [PMID: 38812856 PMCID: PMC11130101 DOI: 10.1007/s43465-024-01156-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/14/2023] [Accepted: 04/12/2024] [Indexed: 05/31/2024]
Abstract
Background and Purpose Scaphoid waist fractures are often stabilised with compression screws, Kirschner wires (K-wires), or a combination of both. While clinical and bio-mechanical studies evaluating their utility are available, the ideal configuration of implant that would provide adequate stability to permit early use of the hand is debatable. We examined configurations of a single screw, one screw along with a K-wire, and two K-wires used for a transverse scaphoid waist fracture fixation aiming to assess the stability provided by each in the immediate postoperative period. Methods Computer-aided design (CAD) models of the scaphoid, K-wire, and headless compression screw were created. A transverse fracture was created at the scaphoid waist, and the CAD models of the screw and K-wire were used to fix the fracture in different configurations in a distal to proximal direction. Finite Element Analysis (FEA) was used to examine the strength of configurations when they were subjected to compression and distraction forces. The total maximum deformation (TDef) and factor of safety (FoS) for each configuration were calculated and used as indirect indicators of postoperative stability. Results When a single screw was used, the configurations with the screw directed posteriorly from either centre or anterior had the best combined TDef and FoS values. For one screw and one K-wire, the configuration with screw and K-wire parallel to each other with the screw located along the long axis in the AP projection and anterior to the K-wire in the lateral projection had the best combined TDef and FoS values. When using two K-wires, configurations with the two wires diverging proximally on the lateral projection had the best combined TDef and FoS values. Conclusions When fixing a transverse scaphoid waist fracture with a single screw, the screw directed posteriorly from either the centre or anterior aspect of the distal pole has the best stability, a parallel configuration has the best stability when fixing it using a screw and a K-wire, and divergent configuration has the best stability when fixing it with two K-wires only.
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Affiliation(s)
- Ayush Srivastav
- Department of Mechanical Engineering, Maulana Azad National Institute of Technology, Bhopal, India
| | - Prateek Behera
- Department of Orthopaedics, All India Institute of Medical Sciences, Bhopal, India
| | - Ravi Kumar Dwivedi
- Department of Mechanical Engineering, Maulana Azad National Institute of Technology, Bhopal, India
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2
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Miller EA, Huang JI. Traditional Bone Grafting in Scaphoid Nonunion. Hand Clin 2024; 40:105-116. [PMID: 37979982 DOI: 10.1016/j.hcl.2023.08.001] [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] [Indexed: 11/20/2023]
Abstract
Management of scaphoid nonunion remains challenging despite modern fixation techniques. Nonvascularized bone graft may be used to achieve union in waist and proximal pole fractures with good success rates. Technical aspects, such as adequate debridement and restoration of scaphoid length, and stable fixation are critical in achieving union and functional wrist usage. Rigid fixation can be achieved with compression screws, K-wires, and plate constructs. The surgeon has a choice of various bone graft options including corticocancellous, cancellous, and strut grafts to promote healing and correct the humpback deformity.
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Affiliation(s)
- Erin A Miller
- Department of Surgery, Division of Plastic Surgery, University of Washington Medical Center, 325 9th Avenue, Seattle, WA 98013, USA.
| | - Jerry I Huang
- Department of Orthopaedics and Sports Medicine, University of Washington Medical Center, 4245 Roosevelt Way Northeast, Seattle, WA 98105, USA
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Berthe S, Bahlouli N, Bilasse M, Liverneaux P. Pull-out resistance of connected K-wires for osteosynthesis: development of a numerical model. Comput Methods Biomech Biomed Engin 2024:1-9. [PMID: 38293739 DOI: 10.1080/10255842.2024.2310729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Accepted: 01/19/2024] [Indexed: 02/01/2024]
Abstract
A predictive finite element model was developed to investigate the best configuration of a fixation pins system consisting of two K-wires inserted in a synthetic model (Sawbones®) at different angles and secured to a connecting rod. Two key parameters were considered to determine the best configuration delivering the higher pull-out strength and lower pull-out length: the diameter and insertion angle. Results show that as the diameter and insertion angle increased, the pull-out force increased, while the pull-out length decreased. Results are successfully compared with available experimental data in literature. This model can be used as an alternative to experimental study.
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Affiliation(s)
- Samuel Berthe
- ICube CNRS UMR7357, Strasbourg University, Strasbourg, France
- ICAM, Schiltigheim, France
| | - Nadia Bahlouli
- ICube CNRS UMR7357, Strasbourg University, Strasbourg, France
| | - Massamaesso Bilasse
- ICube CNRS UMR7357, Strasbourg University, Strasbourg, France
- ICAM, Schiltigheim, France
| | - Philippe Liverneaux
- ICube CNRS UMR7357, Strasbourg University, Strasbourg, France
- Department of Hand Surgery, Strasbourg University Hospitals, FMTS, Strasbourg, France
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Rothenfluh E, Jain S, Guggenberger R, Taylor WR, Hosseini Nasab SH. The influence of partial union on the mechanical strength of scaphoid fractures: a finite element study. J Hand Surg Eur Vol 2023; 48:435-444. [PMID: 36814409 PMCID: PMC10150260 DOI: 10.1177/17531934231157565] [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] [Indexed: 02/24/2023]
Abstract
Assessment of scaphoid fracture union on computed tomography scans is not currently standardized. We investigated the extent of scaphoid waist fracture union required to withstand physiological loads in a finite element model, based on a high-resolution CT scan of a cadaveric forearm. For simulations, the scaphoid waist was partially fused at the radial and ulnar sides. A physiological load of 100 N was transmitted to the scaphoid and the minimal amount of union to maintain biomechanical stability was recorded. The orientation of the fracture plane was varied to analyse the effect on biomechanical stability. The results indicate that the scaphoid is more prone to re-fracture when healing occurs on the ulnar side, where at least 60% union is required. Union occurring from the radial side can withstand loads with as little as 25% union. In fractures more parallel to the radial axis, the scaphoid seems less resistant on the radial side, as at least 50% union is required. A quantitative CT scan analysis with the proposed cut-off values and a consistently applied clinical examination will guide the clinician as to whether mid-waist scaphoid fractures can be considered as truly united.
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Affiliation(s)
- Esin Rothenfluh
- Department of Plastic and Hand
Surgery, University Hospital Zurich, Zurich, Switzerland
- Esin Rothenfluh, Department of Plastic and
Hand Surgery, University Hospital of Bern (Inselspital), Freiburgstrasse 18,
3010 Bern, Switzerland.
| | - Sambhav Jain
- Department of Plastic and Hand
Surgery, University Hospital Zurich, Zurich, Switzerland
- Laboratory for Movement
Biomechanics, Swiss Federal Institute of Technology (ETH) Zurich, Zurich,
Switzerland
| | - Roman Guggenberger
- Institute of Diagnostic and
Interventional Radiology, University Hospital Zurich, Zurich, Switzerland
| | - William R. Taylor
- Laboratory for Movement
Biomechanics, Swiss Federal Institute of Technology (ETH) Zurich, Zurich,
Switzerland
| | - Seyyed Hamed Hosseini Nasab
- Laboratory for Movement
Biomechanics, Swiss Federal Institute of Technology (ETH) Zurich, Zurich,
Switzerland
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Lynch D, Mickley JP, Gordon A, Roebke AJ, Goyal KS. The Effect of Derotational Kirschner Wires on Fracture Gap Reduction With Variable-Pitch Headless Screws. J Hand Surg Am 2023; 48:86.e1-86.e7. [PMID: 34802813 DOI: 10.1016/j.jhsa.2021.09.023] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2020] [Revised: 07/06/2021] [Accepted: 09/09/2021] [Indexed: 02/02/2023]
Abstract
PURPOSE We evaluated the impact of angled derotational Kirschner wires (K-wires) on fracture gap reduction with variable-pitch headless screws. METHODS Fully threaded variable-pitch headless screws (20 and 28 mm) were inserted into "normal" bone models of polyurethane blocks. In separate trials, derotational K-wires were inserted at predetermined angles of 0°, 15°, 30°, and 40° and compared with each other, with no K-wire as a control. Fluoroscopic images taken after each screw turn were analyzed. The optimal fracture gap closure, initial screw push-off, and screw back-out gap creation were determined and compared at various derotational K-wire angles. RESULTS Initial screw push-off due to screw insertion and screw back-out gap creation were not significantly affected by the angle of the derotational K-wire. With a 20-mm screw, only a 40° derotational K-wire led to significantly less gap closure compared with control and with 0°, 15°, and 30° derotational K-wires. It led to an approximately 60% decrease in gap closure compared with no K-wire. With the 28-mm screw, compared with no K-wire, 15° and 30° derotational K-wires led to statistically significant decreases in gap closure (approximately 25%), whereas a 40° derotational K-wire led to an approximately 60% decrease. With the 28-mm screw, the 40° derotational K-wire also led to a statistically significant smaller gap closure when compared with 0°, 15°, and 30° derotational K-wires. CONCLUSIONS A derotational K-wire placed in parallel to the planned trajectory of a headless compression screw does not affect fracture gap closure. With greater angulation of the derotational K-wire, the fracture gap is still closed, but less tightly. CLINICAL RELEVANCE Derotational K-wires can help prevent fracture fragment rotation during headless compression screw insertion. At small deviations from parallel (≤30°), fracture gap closure achieved by the screw is minimally affected. At greater angles (ie, 40°), fracture gap closure may be substantially reduced, preventing fracture compression.
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Affiliation(s)
- Daniel Lynch
- Ohio State University College of Medicine, Columbus, OH
| | | | - Adam Gordon
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Austin J Roebke
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, OH
| | - Kanu S Goyal
- Department of Orthopaedics, The Ohio State University Wexner Medical Center, Columbus, OH.
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Surke C, Huntington LS, Zhang X, Ek ETH, Ackland D, Tham SK. Double-Screw Osteosynthesis in an Unstable Scaphoid Fracture Model: A Biomechanical Comparison of Two Screw Configurations. J Hand Surg Am 2022; 47:1118.e1-1118.e8. [PMID: 34690014 DOI: 10.1016/j.jhsa.2021.08.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 06/28/2021] [Accepted: 08/25/2021] [Indexed: 02/02/2023]
Abstract
PURPOSE Although there is evidence that a single headless compression screw is sufficient for fixation of most scaphoid fractures, double-screw osteosynthesis has been shown to result in higher failure strength and stiffness than a single screw. However, the biomechanical effect of different screw configurations has not been determined. METHODS A standardized unstable fracture model was produced in 28 cadaveric scaphoids. Specimens were randomly allocated to 1 of 2 fixation groups using 2 internal compression screws positioned in either the sagittal or coronal plane. A specimen-specific 3-dimensionally-printed customized screw placement and osteotomy device was developed using computer-aided design-generated models derived from computed tomography scan data of each individual scaphoid. Load to failure and stiffness of the repair constructs were evaluated using a mechanical testing system. RESULTS There were no significant differences in size, weight, and density between the scaphoid specimens. The average distance between screws was significantly greater in the sagittal group than in the coronal group. There were no significant differences between the coronal and sagittal aligned double screws in load to 2 mm displacement (mean coronal 180.9 ± 109.7 N; mean sagittal 156.0 ± 85.8 N), load to failure (mean coronal 275.9 ± 150.6 N; mean sagittal 248.0 ± 109.5 N), stiffness (mean coronal 111.7 ± 67.3 N/mm; mean sagittal 101.2 ± 45.1 N/mm), and energy absorption (mean coronal 472.6 ± 261.4 mJ; mean sagittal 443.5 ± 272.7 mJ). CONCLUSIONS There are no significant biomechanical differences between the sagittal or coronal aligned double headless compression screws in a scaphoid fracture model with bone loss. CLINICAL RELEVANCE In cases where double-screw fixation of the scaphoid is being considered, the placement of double screws can be at the discretion of the surgeon, and can be dictated by ease of access, surgical preference, and fracture orientation.
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Affiliation(s)
- Carsten Surke
- Department of Plastic and Hand Surgery, Inselspital, University Hospital Bern, University of Bern, Switzerland; Hand and Wrist Biomechanics Laboratory, O'Brien Institute, Fitzroy, Victoria, Australia
| | - Lachlan S Huntington
- Hand and Wrist Biomechanics Laboratory, O'Brien Institute, Fitzroy, Victoria, Australia; Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Xin Zhang
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Eugene T H Ek
- Hand and Wrist Biomechanics Laboratory, O'Brien Institute, Fitzroy, Victoria, Australia; Division of Hand Surgery, Department of Orthopaedic Surgery, Monash University, Dandenong Hospital, Dandenong, Australia
| | - David Ackland
- Department of Biomedical Engineering, University of Melbourne, Parkville, Victoria, Australia
| | - Stephen K Tham
- Hand and Wrist Biomechanics Laboratory, O'Brien Institute, Fitzroy, Victoria, Australia; Division of Hand Surgery, Department of Orthopaedic Surgery, Monash University, Dandenong Hospital, Dandenong, Australia; Department of Plastic and Hand Surgery, St Vincent's Hospital, Fitzroy, Victoria, Australia.
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7
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Tilton M, Armstrong AD, Wee H, Hast MW, Manogharan G, Lewis GS. Finite Element-Predicted Effects of Screw Configuration in Proximal Humerus Fracture Fixation. J Biomech Eng 2020; 142:081005. [PMID: 31913444 DOI: 10.1115/1.4045907] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2019] [Indexed: 11/08/2022]
Abstract
Internal fixation with the use of locking plates is the standard surgical treatment for proximal humerus fractures, one of the most common fractures in the elderly. Screw cut-out through weak cancellous bone of the humeral head, which ultimately results in collapse of the fixed fracture, is the leading cause of failure and revision surgery. In an attempt to address this problem, surgeons often attach the plate with as many locking screws as possible into the proximal fragment. It is not thoroughly understood which screws and screw combinations play the most critical roles in fixation stability. This study conducted a detailed finite element analysis to evaluate critical parameters associated with screw cut-out failure. Several clinically relevant screw configurations and fracture gap sizes were modeled. Findings demonstrate that in perfectly reduced fracture cases, variation of the screw configurations had minor influence on mechanical stability of the fixation. The effects of screw configurations became substantial with the existence of a fracture gap. Interestingly, the use of a single anterior calcar screw was as effective as utilizing two screws to support the calcar. On the other hand, the variation in calcar screw configuration had minor influence on the fixation stability when all the proximal screws (A-D level) were filled. This study evaluates different screw configurations to further understand the influence of combined screw configurations and the individual screws on the fixation stability. Findings from this study may help decrease the risk for screw cut-out with proximal humerus varus collapse and the associated economic costs.
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Affiliation(s)
- Maryam Tilton
- Department of Mechanical Engineering, Pennsylvania State University, 230 Innovation Blvd., University Park, PA 16803
| | - April D Armstrong
- Department of Orthopaedics and Rehabilitation, Pennsylvania State University, 500 University Dr., Hershey, PA 17033
| | - Hwabok Wee
- Department of Orthopaedics and Rehabilitation, Pennsylvania State University, 500 University Dr., Hershey, PA 17033
| | - Michael W Hast
- Biedermann Lab for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pennsylvania, 3737 Market Street, 10th Floor, Suite 1050, Philadelphia, PA 19104
| | - Guha Manogharan
- Department of Mechanical Engineering, Pennsylvania State University, 230 Innovation Blvd., University Park, PA 16803
| | - Gregory S Lewis
- Department of Orthopaedics & Rehabilitation, Center for Orthopaedic Research and Translational Science, Pennsylvania State University, 500 University Dr., Hershey, PA 17033; Department of Mechanical Engineering Center for Orthopaedic Research and Translational Science, Pennsylvania State University, 500 University Dr., Hershey, PA 17033
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8
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Guo Y, Tian G, Zlotolow DA, Tian W, Zhong W, Sun L. A Cadaveric Study on the Accuracy of an Individualized Guiding Template to Assist Scaphoid Fixation Using Computed Tomography and 3-Dimensional Printing. J Hand Surg Am 2019; 44:251.e1-251.e6. [PMID: 30057220 DOI: 10.1016/j.jhsa.2018.06.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Revised: 04/28/2018] [Accepted: 06/15/2018] [Indexed: 02/02/2023]
Abstract
PURPOSE The aim of this study was to evaluate the feasibility and accuracy of scaphoid screw guidewire placement using a computer-assisted-designed, and 3-dimensional-printed, surgical guiding template in cadaver wrists. METHODS Computed tomography (CT) scans of 12 fresh-frozen cadaver wrists were performed and the data imported into a surgical planning system. A 3-dimensional skin surface template block with a guiding hole was generated from the CT data to allow a screw guidewire to be placed in the central third of the scaphoid. This 3-dimensional model was printed and then put back onto the wrist. A screw guidewire was inserted through the palmar guide hole into the intact scaphoid and then a postprocedure CT scan was obtained. These postprocedure data were introduced into the surgical planning system. Angular and linear deviation between the preprocedural simulation and the image of the guidewire was measured in the system to assess accuracy. RESULTS Mean angular deviation was 3.85° ± 1.32° (range, 1.56°-5.35°) and linear deviations of the 12 specimens were less than 1.1 mm. No specimen required a repeat drilling to the scaphoid. All the screw guidewires were considered to be centrally placed in the scaphoid based on our criterion of central placement of the scaphoid screw. CONCLUSIONS The use of a computer-assisted 3-dimensional-printed surgical guide template to assist screw guidewire placement into an intact scaphoid, mimicking a nondisplaced scaphoid fracture, showed acceptable accuracy in cadaver wrists. CLINICAL RELEVANCE Our technique may provide a simple and effective method for the guidance of screw guidewire insertion in a nondisplaced scaphoid fracture surgery.
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Affiliation(s)
- Yang Guo
- Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing, China
| | - Guanglei Tian
- Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing, China.
| | - Dan A Zlotolow
- Temple University School of Medicine, Shriners Hospital for Children of Philadelphia, Philadelphia, PA
| | - Wen Tian
- Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing, China
| | - Wenyao Zhong
- Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing, China
| | - Liying Sun
- Department of Hand Surgery, Beijing Jishuitan Hospital, Beijing, China
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Mamede J, Castro Adeodato S, Aquino Leal R. Four-Corner Arthrodesis: Description of Surgical Technique Using Headless Retrograde Crossed Screws. Hand (N Y) 2018; 13:156-163. [PMID: 28381124 PMCID: PMC5950972 DOI: 10.1177/1558944717702468] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND Four-corner fusion has been shown to be a reliable option of treatment of wrist arthritis, but there is no consensus about which implant and surgical procedure should be used in the arthrodesis. The present study aimed to describe a surgical technique using 2 crossed screws as implants, inserted in a retrograde manner, and to demonstrate preliminary results of the use of the technique. METHODS A retrospective study was conducted using medical records and imaging tests (radiographs and computed tomography) of all 15 patients who underwent a standardized 4-corner fusion technique, between December 2011 and July 2015, in the Department of Hand Surgery of Instituto Nacional de Traumatologia e Ortopedia (INTO), Rio de Janeiro, Brazil. We collected data on the following variables: fusion rate, time to fusion, and percentage of patients who had any complications or needed another surgical procedure on the same wrist. RESULTS All but one patient achieved fusion of arthrodesis. The average time to union was 5.54 months (SD = 3.84). Only the patient who developed nonunion of the 4-corner fusion required another surgery on the same wrist. CONCLUSIONS The procedure described in this study demonstrated a low complication rate and high fusion rate, and can therefore be considered a reliable surgical technique for 4-corner fusion.
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Affiliation(s)
- João Mamede
- Instituto Nacional de Traumatologia e Ortopedia, Rio de Janeiro, Brazil,João Mamede, Department of Hand Surgery, Instituto Nacional de Traumatologia e Ortopedia, Av. Brasil 500, Rio de Janeiro 20940-070, Brazil.
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10
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Schreck MJ, Kelly M, Canham CD, Elfar JC. Techniques of Force and Pressure Measurement in the Small Joints of the Wrist. Hand (N Y) 2018; 13:23-32. [PMID: 28718314 PMCID: PMC5755860 DOI: 10.1177/1558944716688529] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
BACKGROUND The alteration of forces across joints can result in instability and subsequent disability. Previous methods of force measurements such as pressure-sensitive films, load cells, and pressure-sensing transducers have been utilized to estimate biomechanical forces across joints and more recent studies have utilized a nondestructive method that allows for assessment of joint forces under ligamentous restraints. METHODS A comprehensive review of the literature was performed to explore the numerous biomechanical methods utilized to estimate intra-articular forces. RESULTS Methods of biomechanical force measurements in joints are reviewed. CONCLUSIONS Methods such as pressure-sensitive films, load cells, and pressure-sensing transducers require significant intra-articular disruption and thus may result in inaccurate measurements, especially in small joints such as those within the wrist and hand. Non-destructive methods of joint force measurements either utilizing distraction-based joint reaction force methods or finite element analysis may offer a more accurate assessment; however, given their recent inception, further studies are needed to improve and validate their use.
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Affiliation(s)
| | | | | | - John C. Elfar
- University of Rochester, NY, USA,John C. Elfar, Associate Professor, Department of Orthopaedic Surgery, University of Rochester, 601 Elmwood Avenue, Box 665, Rochester, NY 14642, USA.
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11
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Finite element analysis of the wrist in stroke patients: the effects of hand grip. Med Biol Eng Comput 2017; 56:1161-1171. [DOI: 10.1007/s11517-017-1762-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 11/25/2017] [Indexed: 11/26/2022]
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12
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Fatigue failure of plated osteoporotic proximal humerus fractures is predicted by the strain around the proximal screws. J Mech Behav Biomed Mater 2017; 75:68-74. [DOI: 10.1016/j.jmbbm.2017.07.004] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2017] [Revised: 06/19/2017] [Accepted: 07/03/2017] [Indexed: 01/20/2023]
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13
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Chamoret D, Bodo M, Roth S. A first step in finite-element simulation of a grasping task. Comput Assist Surg (Abingdon) 2016. [DOI: 10.1080/24699322.2016.1240294] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Dominique Chamoret
- UBFC, Université de technologie Belfort-Montbéliard, Belfort Cedex, France
| | - Michèle Bodo
- UBFC, Université de technologie Belfort-Montbéliard, Belfort Cedex, France
| | - Sébastien Roth
- UBFC, Université de technologie Belfort-Montbéliard, Belfort Cedex, France
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14
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Wang Y, Song M, Xu Y, He X, Zhu Y. Absorbable scaphoid screw development: a comparative study on biomechanics. Ther Clin Risk Manag 2016; 12:643-50. [PMID: 27217756 PMCID: PMC4853148 DOI: 10.2147/tcrm.s99024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND The scaphoid is critical for maintaining the stability and movement of the wrist joints. This study aimed to develop a new internal fixator absorbable scaphoid screw (ASS) for fixation of the scaphoid waist after fracture and to test the biomechanical characteristics of ASS. MATERIALS AND METHODS An ASS was prepared using polylactic acids and designed based on scaphoid measurements and anatomic features. Twenty fractured scaphoid waist specimens were randomly divided into experimental and control groups (n=10/group). Reduction and internal fixation of the scaphoid were achieved with either Kirschner wires (K-wires) or ASS. A moving target simulator was used to test palmar flexion and dorsal extension, with the range of testing (waist movement) set from 5° of palmar flexion to 25° of dorsal extension. Flexion and extension were repeated 2,000 times for each specimen. Fracture gap displacements were measured with a computerized tomography scanning. Scaphoid tensile and bending strengths were measured by using a hydraulic pressure biomechanical system. RESULTS Prior to biomechanical fatigue testing, fracture gap displacements were 0.16±0.02 mm and 0.22±0.02 mm in the ASS and K-wire groups, respectively. After fatigue testing, fracture gap displacements in the ASS and the K-wire groups were 0.21±0.03 mm and 1.52±0.07 mm, respectively. The tensile strengths for the ASS and K-wire groups were 0.95±0.02 MPa and 0.63±0.02 MPa, respectively. CONCLUSION Fixation using an ASS provided sufficient mechanical support for the scaphoid after fracture.
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Affiliation(s)
- Yi Wang
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Muguo Song
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Yongqing Xu
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - Xiaoqing He
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
| | - YueLiang Zhu
- Department of Orthopedic Surgery, Kunming General Hospital, Chengdu Military Command, People's Liberation Army, Kunming, Yunnan, People's Republic of China
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Márquez-Florez K, Vergara-Amador E, Gavilán-Alfonso M, Garzón-Alvarado D. Load distribution on the radio-carpal joint for carpal arthrodesis. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2016; 127:204-215. [PMID: 26787512 DOI: 10.1016/j.cmpb.2015.12.023] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2015] [Revised: 12/18/2015] [Accepted: 12/18/2015] [Indexed: 06/05/2023]
Abstract
BACKGROUND AND OBJECTIVE Carpal fusions are useful for treating specific carpal disorders, maximizing postoperative wrist motion, hand strength, reducing pain and instability of the joint. The surgeon selects the appropriate treatment by considering the degree of stability, the chronicity of the injury, functional demands of the patient and former patient's outcomes as well. However there are not many studies regarding the load distribution provided by the treatment. So, the purpose of this study is to analyze the load distribution through the wrist joint with an arthrodesis treatment and compare the results with a normal wrist. METHOD To this end the rigid body spring model (RBSM) method was used on a three-dimensional model of the wrist joint. The cartilage and ligaments were simulated as springs acting under compression and tension, respectively, while the bones were considered as rigid bodies. To simulate the arthrodesis, the fused bones were considered as a single rigid body. RESULTS The changes on the load distribution for each arthrodesis agree with the treatment objective, reducing load transmission through a specific articular surface. For example, for SLAC/SNAC II most of the treatments reduced the load transmitted through the radioscaphoid fossae, almost by 8%. However, the capitolunate (CL) arthrodesis was the treatment that managed to keep the load transmitted through the radiolunate joint closer to normal conditions. Also, in treatments where the scaphoid was excised (3-corner, 4-corner and capitolunate arthrodesis), the joint surface between the lunate surface compensates by doubling the transmitted force to the radius. CONCLUSIONS The common arthrodesis for treating SLAC/SNAC II-III, reduces, in fact, the load on the radioscaphoid joint. Alternative treatments that reduce load distribution on the radiocarpal joint should be three corner and capitolunate arthrodesis for treating SLAC/SNAC-II; and for SLAC/SNAC-III four corners with scaphoid excision. On Kienbock's disease. Scaphocapitate (SC) arthrodesis is more effective on reducing the load transmission through the radiolunate and ulnolunate joints. All arthrodesis treatment should consider changes on the load transmission, and also bones' fusion rates and pain reduction on patient's outcomes.
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Affiliation(s)
- Kalenia Márquez-Florez
- Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia; Biological Reactives Group: Mechanobiology of Organs and Tissues, Instituto de Biotecnología, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Enrique Vergara-Amador
- Department of Orthopaedic Surgery, School of Medicine, Universidad Nacional de Colombia, Bogotá, Colombia
| | - Maria Gavilán-Alfonso
- Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia
| | - Diego Garzón-Alvarado
- Department of Mechanical and Mechatronics Engineering, Numerical Methods and Modeling Group Research (GNUM), Universidad Nacional de Colombia, Bogotá, Colombia; Biological Reactives Group: Mechanobiology of Organs and Tissues, Instituto de Biotecnología, Universidad Nacional de Colombia, Bogotá, Colombia.
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Mahmoud M, Hegazy M, Khaled SA, Abdelatif NMN, Osman W, Elfar JC. Radiographic Parameters to Predict Union After Volar Percutaneous Fixation of Herbert Type B1 and B2 Scaphoid Fractures. J Hand Surg Am 2016; 41:203-7. [PMID: 26815328 PMCID: PMC4733887 DOI: 10.1016/j.jhsa.2015.11.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Revised: 11/06/2015] [Accepted: 11/06/2015] [Indexed: 02/02/2023]
Abstract
PURPOSE To study the angle of screw placement in relation to the scaphoid fracture plane and its effect on union after percutaneous fixation of scaphoid waist fractures. METHODS Twenty-four consecutive scaphoid waist fractures were retrospectively evaluated for the orientation of screws in relation to the fracture plane using a method in which the sum-of-smaller angles (SSA) in 3 different radiographs were used to correlate with time to fracture union. RESULTS All but one patient achieved union after percutaneous fixation of the scaphoid. Another patient required revision surgery within the study period for inadequate fixation. A shortened time to union was significantly correlated to larger SSA. CONCLUSIONS SSA may be a reasonable predictor of union after percutaneous fixation of scaphoid waist fracture. It can be reliably calculated using plain radiographs. An SSA of 190° or more correlated with union by 8 weeks postoperatively.
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Affiliation(s)
- Mostafa Mahmoud
- Kasr Al Ainy Hospital, Faculty of Medicine, Cairo University, Cairo, Egypt
| | - Mohamed Hegazy
- Kasr Al Ainy Hospital, Faculty of Medicine, Cairo University, Cairo, Egypt
| | | | | | - Walid Osman
- Department of Orthopaedics, Helwan University Hospital, Cairo, Egypt
| | - John C Elfar
- Department of Orthopaedics, University of Rochester, Rochester, NY.
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Varga P, Zysset PK, Schefzig P, Unger E, Mayr W, Erhart J. A finite element analysis of two novel screw designs for scaphoid waist fractures. Med Eng Phys 2015; 38:131-9. [PMID: 26654577 DOI: 10.1016/j.medengphy.2015.11.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 10/10/2015] [Accepted: 11/08/2015] [Indexed: 12/20/2022]
Abstract
The scaphoid is the most often fractured carpal bone. Scaphoid fracture repair with a headless compression screw allows for early functional recovery. The rotational stability of a single screw may be limited, having a potential negative impact on the healing process. Two novel screws have been designed to provide improved rotational stability compared to the existing ones. Using a computational finite element model of a scaphoid osteotomy, we compared the efficacy of one simple screw and the two new screws in restricting inter-fragmentary motion (IFM) in three functional positions of the wrist and as a function of inter-fragmentary compression force. The in-plane IFM was primary rotational and was better restricted by the new screws compared to the conventional one when the inter-fragmentary compression force was below 15-20 N, but provided no clear benefit in total flexion independently of the compression force. To better understand the differences in the non-compressed case, we analyzed the acting moments and investigated the effects of the bending and torsional screw stiffness on IFM. By efficiently restricting the inter-fragmentary shear, the new screws may be clinically advantageous when the inter-fragmentary compression force is partially or completely lost and may provide further benefits toward earlier and better healing of transverse waist fractures of the scaphoid.
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Affiliation(s)
- Peter Varga
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland; Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gußhausstraße 27-29, A-1040 Vienna, Austria.
| | - Philippe K Zysset
- Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Gußhausstraße 27-29, A-1040 Vienna, Austria; Institute for Surgical Technology & Biomechanics, Universität Bern, Stauffacherstrasse 78, CH-3014 Bern, Switzerland
| | - Philip Schefzig
- Department of Trauma Surgery, Medical University of Vienna, Austria
| | - Ewald Unger
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Winfried Mayr
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Währinger Gürtel 18-20, A-1090 Vienna, Austria
| | - Jochen Erhart
- Department of Trauma Surgery, Medical University of Vienna, Austria
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18
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Theoretical distribution of load in the radius and ulna carpal joint. Comput Biol Med 2015; 60:100-6. [DOI: 10.1016/j.compbiomed.2015.02.016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Revised: 02/21/2015] [Accepted: 02/25/2015] [Indexed: 11/17/2022]
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Ramlee MH, Kadir MRA, Murali MR, Kamarul T. Finite element analysis of three commonly used external fixation devices for treating Type III pilon fractures. Med Eng Phys 2014; 36:1322-30. [PMID: 25127377 DOI: 10.1016/j.medengphy.2014.05.015] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2013] [Revised: 05/19/2014] [Accepted: 05/24/2014] [Indexed: 11/15/2022]
Abstract
Pilon fractures are commonly caused by high energy trauma and can result in long-term immobilization of patients. The use of an external fixator i.e. the (1) Delta, (2) Mitkovic or (3) Unilateral frame for treating type III pilon fractures is generally recommended by many experts owing to the stability provided by these constructs. This allows this type of fracture to heal quickly whilst permitting early mobilization. However, the stability of one fixator over the other has not been previously demonstrated. This study was conducted to determine the biomechanical stability of these external fixators in type III pilon fractures using finite element modelling. Three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones were reconstructed from previously obtained CT datasets. Bones were assigned with isotropic material properties, while the cartilage was assigned as hyperelastic springs with Mooney-Rivlin properties. Axial loads of 350 N and 70 N were applied at the tibia to simulate the stance and the swing phase of a gait cycle. To prevent rigid body motion, the calcaneus and metatarsals were fixed distally in all degrees of freedom. The results indicate that the model with the Delta frame produced the lowest relative micromovement (0.03 mm) compared to the Mitkovic (0.05 mm) and Unilateral (0.42 mm) fixators during the stance phase. The highest stress concentrations were found at the pin of the Unilateral external fixator (509.2 MPa) compared to the Mitkovic (286.0 MPa) and the Delta (266.7 MPa) frames. In conclusion, the Delta external fixator was found to be the most stable external fixator for treating type III pilon fractures.
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Affiliation(s)
- Muhammad Hanif Ramlee
- Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia.
| | - Mohammed Rafiq Abdul Kadir
- Medical Devices and Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor, Malaysia.
| | - Malliga Raman Murali
- Tissue Engineering Group (TEG), National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Department of Orthopaedic Surgery, Faculty ofMedicine, University of Malaya, 50603 Lembah Pantai, Kuala Lumpur, Malaysia.
| | - Tunku Kamarul
- Tissue Engineering Group (TEG), National Orthopaedic Centre of Excellence in Research and Learning (NOCERAL), Department of Orthopaedic Surgery, Faculty ofMedicine, University of Malaya, 50603 Lembah Pantai, Kuala Lumpur, Malaysia.
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20
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Biomechanical evaluation of two commonly used external fixators in the treatment of open subtalar dislocation--a finite element analysis. Med Eng Phys 2014; 36:1358-66. [PMID: 25092623 DOI: 10.1016/j.medengphy.2014.07.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 06/02/2014] [Accepted: 07/02/2014] [Indexed: 01/12/2023]
Abstract
Subtalar dislocation is a rare injury caused by high-energy trauma. Current treatment strategies include leg casts, internal fixation and external fixation. Among these, external fixators are the most commonly used as this method is believed to provide better stabilization. However, the biomechanical stability provided by these fixators has not been demonstrated. This biomechanical study compares two commonly used external fixators, i.e. Mitkovic and Delta. CT imaging data were used to reconstruct three-dimensional models of the tibia, fibula, talus, calcaneus, navicular, cuboid, three cuneiforms and five metatarsal bones. The 3D models of the bones and cartilages were then converted into four-noded linear tetrahedral elements, whilst the ligaments were modelled with linear spring elements. Bones and cartilage were idealized as homogeneous, isotropic and linear. To simulate loading during walking, axial loading (70 N during the swing and 350 N during the stance phase) was applied at the end of diaphyseal tibia. The results demonstrate that the Mitkovic fixator produced greater displacement (peak 3.0mm and 15.6mm) compared to the Delta fixator (peak 0.8mm and 3.9 mm), in both the swing and stance phase, respectively. This study demonstrates that the Delta external fixator provides superior stability over the Mitkovic fixator. The Delta fixator may be more effective in treating subtalar dislocation.
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21
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Radiographic clues for determining carpal instability and treatment protocol for scaphoid fractures. J Orthop Sci 2014; 19:379-83. [PMID: 24535049 DOI: 10.1007/s00776-014-0546-y] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2013] [Accepted: 01/29/2014] [Indexed: 10/25/2022]
Abstract
The magnitude of carpal instability following scaphoid fracture is closely related to the fracture location. Middle-third fractures of the scaphoid are classified into B1 (distal oblique fractures) and B2 (complete waist fractures). Deciding preoperatively whether a fracture is B1 or B2 is clinically important, because several studies have revealed that B1 is more stable than B2. Dorsal intercalated segment instability deformity often develops in B2, creating a large, wedge-shaped bone defect, while minimal humpback deformity develops in B1, and the bone defect is much smaller, even after long-standing nonunions. However, determination of the fracture types using X-rays may be less accurate than using three dimensional computed tomography. This article suggests two radiographic clues for estimation of post-fracture carpal instability along with a treatment protocol for each fracture type.
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Faucher GK, Golden ML, Sweeney KR, Hutton WC, Jarrett CD. Comparison of screw trajectory on stability of oblique scaphoid fractures: a mechanical study. J Hand Surg Am 2014; 39:430-5. [PMID: 24559623 DOI: 10.1016/j.jhsa.2013.12.015] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2013] [Revised: 12/08/2013] [Accepted: 12/11/2013] [Indexed: 02/02/2023]
Abstract
PURPOSE To determine whether a screw placed perpendicular to the fracture line in an oblique scaphoid fracture will provide fixation strength that is comparable with that of a centrally placed screw. METHODS Oblique osteotomies were made along the dorsal sulcus of 8 matched pairs of cadaveric scaphoids. One scaphoid from each pair was randomized to receive a screw placed centrally down the long axis. In the other scaphoid, a screw was placed perpendicular to the osteotomy. Each scaphoid underwent cyclic loading from 80 N to 120 N at 1 Hz. Cyclic loading was carried out until 2 mm of fracture displacement occurred or 4,000 cycles was reached. The specimens that reached the 4,000-cycle limit were then loaded to failure. Screw length, number of cycles, and load to failure were compared between the groups. RESULTS We found no difference in number of cycles or load to failure between the 2 groups. Screws placed perpendicular to the fracture line were significantly shorter than screws placed down the central axis. CONCLUSIONS A perpendicularly placed screw provides equivalent strength to one placed along the central axis. CLINICAL RELEVANCE Compared with a screw placed centrally in an oblique scaphoid fracture, a screw placed perpendicular to the fracture line allows the use of a shorter screw without sacrificing strength of fixation.
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Affiliation(s)
- Gregory K Faucher
- Hand and Upper Extremity Surgery, The Emory Orthopaedic Center, Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA
| | - M Leslie Golden
- Hand and Upper Extremity Surgery, The Emory Orthopaedic Center, Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA
| | - Kyle R Sweeney
- Hand and Upper Extremity Surgery, The Emory Orthopaedic Center, Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA
| | - William C Hutton
- Hand and Upper Extremity Surgery, The Emory Orthopaedic Center, Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA
| | - Claudius D Jarrett
- Hand and Upper Extremity Surgery, The Emory Orthopaedic Center, Department of Orthopaedic Surgery, Emory University School of Medicine, Atlanta, GA.
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23
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Guo Y, Tian GL, Chen S, Tapia C. Establishing a central zone in scaphoid surgery: a computational approach. INTERNATIONAL ORTHOPAEDICS 2013; 38:95-9. [PMID: 24018579 DOI: 10.1007/s00264-013-2089-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Accepted: 08/15/2013] [Indexed: 10/26/2022]
Abstract
PURPOSE Scaphoid fractures are commonly fixed with headless cannulated screws positioned centrally in the scaphoid. Judgement of central placement of the screw may be difficult. We generated a central zone using computer analysis of 3D reconstructions of computed tomography (CT) images. As long as the screw axis is completely contained within this central zone, the screw would be considered as centrally placed. METHODS Thirty cases of 3D CT reconstructions of normal scaphoids in a computerised operation planning and simulation system (Vxwork software) were obtained. The central zone was established after some distance shrinkage of the original scaphoid surface reconstruction model using the function "erode" in the software. The shape of the central zone was evaluated, and the width of the central zone in the proximal pole, waist portion and distal pole was measured. We also established the long axis of the scaphoid to see whether it stays in the central zone. RESULTS All central zones could be divided into distal, waist and proximal portions according to the corresponding irregular shape of the scaphoid. As the geometry of the central zone was so irregular and its width very narrow, it was possible to completely contain the screw axis either in the proximal portion alone, waist alone or distal central zone alone. CONCLUSIONS Establishing the central zone of scaphoid 3D CT images provided a baseline for discussion of central placement of a scaphoid screw. The geometry of the scaphoid central zone determined that the screw could hardly be inserted through entire scaphoid central area during surgery.
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Affiliation(s)
- Yang Guo
- Jishuitan Hospital, Beijing, China,
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Alizadeh M, Kadir MRA, Fadhli MM, Fallahiarezoodar A, Azmi B, Murali MR, Kamarul T. The use of X-shaped cross-link in posterior spinal constructs improves stability in thoracolumbar burst fracture: a finite element analysis. J Orthop Res 2013; 31:1447-54. [PMID: 23640802 DOI: 10.1002/jor.22376] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2012] [Accepted: 04/01/2013] [Indexed: 02/04/2023]
Abstract
Posterior instrumentation is a common fixation method used to treat thoracolumbar burst fractures. However, the role of different cross-link configurations in improving fixation stability in these fractures has not been established. A 3D finite element model of T11-L3 was used to investigate the biomechanical behavior of short (2 level) and long (4 level) segmental spine pedicle screw fixation with various cross-links to treat a hypothetical L1 vertebra burst fracture. Three types of cross-link configurations with an applied moment of 7.5 Nm and 200 N axial force were evaluated. The long construct was stiffer than the short construct irrespective of whether the cross-links were used (p < 0.05). The short constructs showed no significant differences between the cross-link configurations. The XL cross-link provided the highest stiffness and was 14.9% stiffer than the one without a cross-link. The long construct resulted in reduced stress to the adjacent vertebral bodies and screw necks, with 66.7% reduction in bending stress on L2 when the XL cross-link was used. Thus, the stability for L1 burst fracture fixation was best achieved by using long segmental posterior instrumentation constructs and an XL cross-link configuration. Cross-links did not improved stability when a short structure was used.
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Affiliation(s)
- Mina Alizadeh
- Medical Implant Technology Group (MEDITEG), Faculty of Biosciences and Medical Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor, Malaysia
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Thorkildsen R, Theodorsson J, Mellgren M, Røkkum M. COMPARISON OF TWO UNCEMENTED TRAPEZIO-METACARPAL CUPS: A FINITE ELEMENT STUDY. ACTA ACUST UNITED AC 2013; 18:221-8. [DOI: 10.1142/s0218810413500275] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Trapezium components from two uncemented total joint replacements were compared in a three-dimensional finite element model. A 100 N axial and angular load was applied in a normal and an osteoporotic bone model. The axial deformation and maximum periprosthetic stress are greater for the ElektraTM than the Motec CMC® cup. The Motec CMC® design is less sensitive to changing bone quality. The ElektraTM cup transmits more stress to the cortical bone rim in all load conditions, but under angular loading the proportionate increase in stress is lower. The Motec CMC® design distributes the stress and contact pressure more evenly, whereas the ElektraTM transfers most of the load to the cortical bone rim and the screw hole base. The design features that are believed to be of greatest significance for the differences are the raised centre of rotation of the Motec CMC® cup and the collar acting as a lever arm.
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Affiliation(s)
- R. Thorkildsen
- Hand and Microsurgical Unit, Orthopaedic Department, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372 Oslo, Norway
| | | | | | - M. Røkkum
- Hand and Microsurgical Unit, Orthopaedic Department, Oslo University Hospital, Rikshospitalet, Sognsvannsveien 20, 0372 Oslo, Norway
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Prygoski MP, Sanchez Caballero S, Schmid SR, Lozier AJ, Selles MA. High speed fracture fixation: assessing resulting fixation stability and fastener withdrawal strength. J Biomech Eng 2013; 135:91008. [PMID: 23722627 DOI: 10.1115/1.4024641] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 05/18/2013] [Indexed: 11/08/2022]
Abstract
A new method of bone fracture fixation has been developed in which fixation darts (small diameter nails/pins) are driven across a fracture site at high velocity with a pneumatically powered gun. When fixation darts are inserted oblique to one another, kinematic constraints prevent fragment motion and allow bone healing to progress. The primary aim of this study is to determine if fixation darts can provide reasonable fixation stability compared to bone screws, which were used as a benchmark since they represent a simple, yet well-established, surgical technique. The first objective was to evaluate macro-level stability using different numbers of darts inserted parallel and oblique to each other; experimental comparisons were undertaken in a bone analog model. Experimental results showed fixation darts could not be substituted for screws on a one-to-one basis, but that a plurality of fixation darts provided comparable fixation to two bone screws while allowing for faster insertion and damaging less bone. A second objective was to evaluate micro-level stability; a finite element model was created in order to provide a detailed look at the stress state surrounding the fixation darts and the evolution of the fracture gap. Even with relatively weak fixation dart configurations, the fracture gap was maintained below physiological thresholds for bone healing. Most failures of the fixed fractures were attributed to fixation dart pullout from the cancellous structure. The final objective of the study was to characterize this mode of failure with separate fixation dart and screw pullout tests conducted in Sawbones® cancellous foam and fresh porcine cancellous bone. The results showed that the cancellous foam was an acceptable substitute for real bone and provided a conservative estimate of the fixation darts' performance relative to bone screws. A final comparison between experimental and numerically predicted pullout strengths provided confirmation that the model and experiments were consistent.
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Affiliation(s)
- Matthew Philip Prygoski
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, 150 Multidisciplinary Research Building, Notre Dame, IN 46637, USA.
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Finite element based estimation of contact areas and pressures of the human scaphoid in various functional positions of the hand. J Biomech 2013; 46:984-90. [DOI: 10.1016/j.jbiomech.2012.11.053] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2011] [Revised: 11/26/2012] [Accepted: 11/30/2012] [Indexed: 11/22/2022]
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Bajuri M, Kadir MRA, Raman MM, Kamarul T. Mechanical and functional assessment of the wrist affected by rheumatoid arthritis: A finite element analysis. Med Eng Phys 2012; 34:1294-302. [DOI: 10.1016/j.medengphy.2011.12.020] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2011] [Revised: 11/09/2011] [Accepted: 12/21/2011] [Indexed: 11/30/2022]
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Luria S, Lenart L, Lenart B, Peleg E, Kastelec M. Optimal fixation of oblique scaphoid fractures: a cadaver model. J Hand Surg Am 2012; 37:1400-4. [PMID: 22633229 DOI: 10.1016/j.jhsa.2012.04.021] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Revised: 04/12/2012] [Accepted: 04/15/2012] [Indexed: 02/02/2023]
Abstract
PURPOSE Acute scaphoid fractures are commonly fixed with headless cannulated screws positioned in the center of the proximal fragment. Central placement of the screw may be difficult and may violate the scaphotrapezial joint. We hypothesize that placement of the screw through the scaphoid tuberosity will achieve perpendicular fixation of an oblique waist fracture and result in more stable fixation than a screw in the center of the proximal fragment. METHODS We designed oblique osteotomies for 8 matched pairs of cadaver scaphoids and fixed each specimen with a headless cannulated screw. In 1 specimen, we positioned the screw at the center of the proximal fragment; we placed its matched pair perpendicular to the fracture. The perpendicular screw was directed through the scaphoid tuberosity. We placed the specimen under the increasing load of a pneumatically driven plunger. We compared stiffness, load, distance at failure, and mechanism of failure between the central and perpendicular screw groups. RESULTS We found no difference between groups. Stiffness was identical in both groups (131 N/mm) and load to failure was similar (central screw, 137 N vs perpendicular screw, 148 N). CONCLUSIONS In this biomechanical model of an unstable scaphoid fracture, we found that similar stability of fixation had been achieved with a screw perpendicular to the fracture plane with entry through the tuberosity, compared with a screw in a central position in the proximal fragment. This study suggests that placing the screw through the tuberosity, perpendicular to a short oblique fracture, will not impair fixation stability. CLINICAL RELEVANCE Percutaneous fixation of scaphoid fractures has become popular although it is technically challenging. An easier distal approach through the tuberosity, without violating the scaphotrapezial joint, may not impair the fixation stability of an oblique fracture.
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Affiliation(s)
- Shai Luria
- Department of Orthopaedic Surgery, Hadassah-Hebrew University Medical Center, Kiryat Hadassah, POB 12000, Jerusalem 91120, Israel.
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Johnson JE, McIff TE, Lee P, Toby EB, Fischer KJ. Validation of radiocarpal joint contact models based on images from a clinical MRI scanner. Comput Methods Biomech Biomed Engin 2012; 17:378-87. [PMID: 22631873 DOI: 10.1080/10255842.2012.684446] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
This study was undertaken to assess magnetic resonance imaging (MRI)-based radiocarpal surface contact models of functional loading in a clinical MRI scanner for future in vivo studies, by comparison with experimental measures from three cadaver forearm specimens. Experimental data were acquired using a Tekscan sensor during simulated light grasp. Magnetic resonance (MR) images were used to obtain model geometry and kinematics (image registration). Peak contact pressures (PPs) and average contact pressures (APs), contact forces and contact areas were determined in the radiolunate and radioscaphoid joints. Contact area was also measured directly from MR images acquired with load and compared with model data. Based on the validation criteria (within 25% of experimental data), out of the six articulations (three specimens with two articulations each), two met the criterion for AP (0%, 14%); one for peak pressure (20%); one for contact force (5%); four for contact area with respect to experiment (8%, 13%, 19% and 23%), and three contact areas met the criterion with respect to direct measurements (14%, 21% and 21%). Absolute differences between model and experimental PPs were reasonably low (within 2.5 MPa). Overall, the results indicate that MRI-based models generated from 3T clinical MR scanner appear sufficient to obtain clinically relevant data.
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Affiliation(s)
- Joshua E Johnson
- a Department of Mechanical Engineering , University of Kansas , 1530 W. 15th Street, 3138 Learned Hall, Lawrence , KS 66045 , USA
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Bajuri MN, Abdul Kadir MR, Amin IM, Öchsner A. Biomechanical analysis of rheumatoid arthritis of the wrist joint. Proc Inst Mech Eng H 2012; 226:510-20. [DOI: 10.1177/0954411912445846] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The wrist is the most complex joint for virtual three-dimensional simulations, and the complexity is even more pronounced when dealing with skeletal disorders of the joint such, as rheumatoid arthritis (RA). In order to analyse the biomechanical difference between healthy and diseased joints, three-dimensional models of these two wrist conditions were developed from computed tomography images. These images consist of eight carpal bones, five metacarpal bones, the distal radius and ulna. The cartilages were developed based on the shape of the available articulations and ligaments were simulated via mechanical links. The RA model was developed accurately by simulating all ten common criteria of the disease related to the wrist. Results from the finite element (FE) analyses showed that the RA model produced three times higher contact pressure at the articulations compared to the healthy model. Normal physiological load transfer also changed from predominantly through the radial side to an increased load transfer approximately 5% towards the ulnar. Based on an extensive literature search, this is the first ever reported work that simulates the pathological conditions of the rheumatoid arthritis of the wrist joint.
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Affiliation(s)
- MN Bajuri
- Medical Implant Technology Group, Faculty of Health Science and Biomedical Engineering, Universiti Teknologi Malaysia, Malaysia
| | - Mohammed Rafiq Abdul Kadir
- Medical Implant Technology Group, Faculty of Health Science and Biomedical Engineering, Universiti Teknologi Malaysia, Malaysia
| | - Iskandar M Amin
- Orthopaedic Department, Hospital Universiti Sains Malaysia, Malaysia
| | - Andreas Öchsner
- Department of Applied Mechanics, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, Malaysia
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Prygoski MP, Pasang T, Schmid SR, Lozier AJ. High speed insertion of bone fracture fixation pins: a finite element penetration model with experimental comparisons. JOURNAL OF MATERIALS SCIENCE. MATERIALS IN MEDICINE 2011; 22:2823-2832. [PMID: 22042459 DOI: 10.1007/s10856-011-4461-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2011] [Accepted: 10/11/2011] [Indexed: 05/31/2023]
Abstract
A new method of bone fracture fixation is considered in which small pins/darts are dynamically inserted into bone to prevent translation and rotation at the fracture site. An ABAQUS model was developed to analyze dart penetration in cortical and cancellous bone for varying dart diameter, material, and velocity, and cortical thickness. The method is advocated for bioresorbable darts, so polylactide (PLA) and magnesium are the materials examined in this study. Numerical results showed that magnesium darts can achieve full penetration in bone while suffering little damage. The PLA darts penetrated thin bone well, but substantial deformation was seen as the cortical thickness increased, especially for small diameter darts. As partial validation, prototype PLA fixation darts were fired into cadaveric bone with a custom nailer. As in the model, the PLA darts could penetrate thin cortices but saw gross deformation when impacted against thicker bone.
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Affiliation(s)
- Matthew P Prygoski
- Department of Aerospace and Mechanical Engineering, University of Notre Dame, Notre Dame, IN 46637, USA
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Optimal fixation of acute scaphoid fractures: finite element analysis. J Hand Surg Am 2010; 35:1246-50. [PMID: 20684923 DOI: 10.1016/j.jhsa.2010.05.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Revised: 04/03/2010] [Accepted: 05/13/2010] [Indexed: 02/02/2023]
Abstract
PURPOSE The hypothesis of this study was that more stable fixation of acute scaphoid fractures may be achieved by a screw placed perpendicular to the fracture plane than along the long axis of the scaphoid, as previously suggested. We examined this assumption on different fracture patterns using a finite element analysis model. METHODS A computed tomography scan of an intact scaphoid of a young man provided the data set for all fracture models. We used semiautomatic segmentation to create 3-dimensional computer models of the 3 simple fracture configurations: oblique, transverse waist, and proximal fractures, according to the Herbert classification. Each fracture type was analyzed, using finite elements, for its biomechanical response to 2 types of virtual fixation: a screw placed either perpendicular to the fracture plane or centrally along the long axis of the scaphoid. We measured motion at the fracture plane (in millimeters) and strain in the screw threads (in millipascals). RESULTS Considerably less motion was measured at the fracture plane with the perpendicular screw compared with the long axis screw, especially in the oblique-type fractures: (1) Herbert-type B1 oblique fracture mean motion of 0.05 mm (+/-0.03) for the perpendicular screw versus 0.28 mm (+/-0.05) for the long axis screw; (2) B2 transverse waist fracture mean motion of 0.06 mm (+/-0.03) for the perpendicular screw versus 0.18 mm (+/-0.06) for the long axis screw; and (3) B3 proximal fracture mean motion of 0.07 mm (+/-0.01) for the perpendicular screw versus 0.28 mm (+/-0.011) for the long axis screw. Higher strains were measured on the screw placed perpendicular to the fracture. CONCLUSIONS According to this model, higher fixation stability is achieved when the scaphoid is fixated perpendicular to the fracture. In transverse waist fractures, a centrally placed screw will also be perpendicular to the fracture, which explains the results of previous models.
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Soubeyrand M, Biau D, Mansour C, Mahjoub S, Molina V, Gagey O. Comparison of percutaneous dorsal versus volar fixation of scaphoid waist fractures using a computer model in cadavers. J Hand Surg Am 2009; 34:1838-44. [PMID: 19969191 DOI: 10.1016/j.jhsa.2009.07.012] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2008] [Revised: 07/20/2009] [Accepted: 07/22/2009] [Indexed: 02/02/2023]
Abstract
PURPOSE Percutaneous screw fixation (PSF) is widely used to treat acute nondisplaced scaphoid waist fractures. PSF can be performed through a volar or dorsal approach. The aim of our study was to compare a dorsal versus volar surgical approach for PSF according to the sagittal orientation of the waist fracture (B1 or B2 in Herbert and Fisher's classification scheme, in which B1 and B2 designate, respectively, oblique and transverse nondisplaced scaphoid waist fractures) on computer modeling of cadaver wrists. METHODS We used 12 upper limbs, and for each wrist we performed 3 computed tomography scans in maximal flexion, neutral position, and maximal extension. For each position, a parasagittal slice corresponding to the plane of ideal screw placement was obtained by numerical reconstruction. On each slice, we modeled B1- and B2-type fractures and the placement of the corresponding screws (S1 and S2) inserted through a volar or dorsal approach. Optimal screw orientation was perpendicular to the fracture. For each configuration, we measured the angle between the S1 screw and B1 fracture, which we designated V1 when modeling volar PSF and D1 when modeling dorsal PSF. Similarly, we measured angles V2 and D2. RESULTS For B2 fractures, virtual screw placement perpendicular to the fracture was achieved equally well with the 2 approaches. For B1 fractures, the virtual screw could not be placed perpendicular to the fracture with either approach, but the dorsal approach with maximal wrist flexion allowed the best screw placement. CONCLUSIONS For B2 fractures, the dorsal and volar approaches allow optimal virtual screw placement, and the choice of the approach depends on the surgeon's preference. For B1 fractures, we recommend the dorsal approach.
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Affiliation(s)
- Marc Soubeyrand
- Department of Orthopaedic Surgery, Hôpital Universitaire de Bicetre, Le Kremlin-Bicetre, France
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