1
|
Glowacki J, Bartkowiak T, Paczos P, Mietlinski P, Zawadzki P, Lapaj L. Effect of screw angulation and multiple insertions on load-to-failure of polyaxial locking system. PLoS One 2023; 18:e0295526. [PMID: 38079421 PMCID: PMC10712845 DOI: 10.1371/journal.pone.0295526] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2023] [Accepted: 11/21/2023] [Indexed: 12/18/2023] Open
Abstract
PURPOSE Polyaxial locking plates rely on the alignment between the thread-to-thread connections of the screw head and the plate hole. These implants have provided substantial support for surgeons. In particular, extended screw positioning have proven to be beneficial in the fixation of challenging fractures. This study aimed to investigate the mechanical properties of ChM 5.0 ChLP polyaxial screws inserted in off-axis trajectories, including multiple insertions and to correlate these parameters with the screw head and the plate hole thread-to-thread engagement. METHODS Polyaxial locking screws were inserted into the plates at various angles (0°,10°,15°, -15° off-axis). Multiple time inserted screws were placed firstly at 15°, then 0° and finally -15° off-axis in the same plate hole. A microCT scan of the plate-hole and screw-head interface was conducted before destructive tests. Representative screws from each group were also examined by Scanning Electron Microscope. RESULTS The standard insertion at 0° sustained the greatest maximum bending strength without relocation in the screw hole. Screws inserted at 10° and 15° (one time) showed a significant reduction in load-to-failure of up to 36% and 55%, (p = 0.001) (p = 0.001) respectively. Screws inserted at -15° after a maximum of three multiple insertions with angle shift, showed a total reduction in force of up to 70% (p = 0.001). A microCT analysis of thread engagement showed significant correlations. However, the results obtained for multiple insertions were highly variable. CONCLUSIONS ChM 5.0 ChLP polyaxial locking system has valuable properties that foster fracture fixation, providing various surgical options. Nevertheless, the freedom of off-axis placement and multiple insertions of the screws comes at the price of reduced force. When possible surgeons should minimize the angles of insertions.
Collapse
Affiliation(s)
- Jakub Glowacki
- Department of General Orthopaedics, Musculoskeletal Oncology and Trauma Surgery, Poznan University of Medical Sciences, Poznań, Poland
| | - Tomasz Bartkowiak
- Institute of Mechanical Technology, Poznan University of Technology, Poznań, Poland
| | - Piotr Paczos
- Institute of Applied Mechanics, Poznan University of Technology, Poznań, Poland
| | - Patryk Mietlinski
- Institute of Mechanical Technology, Poznan University of Technology, Poznań, Poland
| | - Pawel Zawadzki
- Institute of Mechanical Technology, Poznan University of Technology, Poznań, Poland
| | - Lukasz Lapaj
- Department of General Orthopaedics, Musculoskeletal Oncology and Trauma Surgery, Poznan University of Medical Sciences, Poznań, Poland
| |
Collapse
|
2
|
Glowacki J, Bartkowiak T, Paczos P, Gapinski B, Mietlinski P, Zawadzki P, Weiss W, Lapaj L. Effect of screw angulation on the bending performance of polyaxial locking interfaces: a micro-CT evaluation. Sci Rep 2023; 13:21740. [PMID: 38066023 PMCID: PMC10709442 DOI: 10.1038/s41598-023-48791-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2023] [Accepted: 11/30/2023] [Indexed: 12/18/2023] Open
Abstract
Polyaxial locking plates rely on a specific thread-to-thread interface of the screw head and the plate hole. The objective of this study was to evaluate the mechanical performance of single screw interfaces when inserted off-axis and to establish correlations between those parameters and the engagement of the screw head and the plate hole thread. Three polyaxial locking screw systems were inserted into the corresponding plates at various angles (0°, 5°, 10°, and 15° off-axis). The screws were tested until failure. A micro-CT was performed to examine the interface between the plate hole and the screw head. The standard insertion at 0° sustained the greatest maximum bending strength without relocation in the screw hole. Screws inserted at 15° showed a significant reduction in force of up to 44%, 55% and 57%, respectively. Micro-CT analysis of the interface showed a significant loss of thread engagement for off-axis insertion. Polyaxial plates offer additional advantages for off-axis placement of screws. However, this flexibility is related to a significant decrease in both thread engagement and bending strength compared to monoaxial insertion. Regardless the insertion angle, the loss of stability is comparable when screws are placed off-axis. Surgeons are advised to consider off-axis insertion as a salvage option, providing access to better bone stock.
Collapse
Affiliation(s)
- Jakub Glowacki
- Department of General Orthopaedics, Musculoskeletal Oncology and Trauma Surgery, Poznan University of Medical Sciences, Poznan, Poland.
| | - Tomasz Bartkowiak
- Institute of Mechanical Technology, Poznan University of Technology, Poznan, Poland
| | - Piotr Paczos
- Institute of Applied Mechanics, Poznan University of Technology, Poznan, Poland
| | - Bartosz Gapinski
- Institute of Mechanical Technology, Poznan University of Technology, Poznan, Poland
| | - Patryk Mietlinski
- Institute of Mechanical Technology, Poznan University of Technology, Poznan, Poland
| | - Pawel Zawadzki
- Institute of Mechanical Technology, Poznan University of Technology, Poznan, Poland
| | - Weronika Weiss
- Institute of Mechanical Technology, Poznan University of Technology, Poznan, Poland
| | - Lukasz Lapaj
- Department of General Orthopaedics, Musculoskeletal Oncology and Trauma Surgery, Poznan University of Medical Sciences, Poznan, Poland
| |
Collapse
|
3
|
Hu Z, Ren W, Peng J, Gu Z, Wu C, Wu W, Zhang W, Xu W, Li L. Biomechanics and finite element analysis comparing posterior T-plates with LCP for fixation of posterolateral tibial plate fractures. Front Bioeng Biotechnol 2023; 11:1286993. [PMID: 38130819 PMCID: PMC10733506 DOI: 10.3389/fbioe.2023.1286993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Accepted: 11/27/2023] [Indexed: 12/23/2023] Open
Abstract
Objective: The treatment for posterolateral tibial plateau fractures (PTPF) have been subjects of controversy. We conducted a study to improve the fixation of PTPF through a lateral approach. Methods: We utilized 40 synthetic tibias and categorized the fracture models into five groups based on the locking compression plate (LCP) and T-distal radius plate (TPP) via various forms of fixation with screws through the posterolateral (PL) fracture fragments. I: Two-screw fixation using two locking screws (LPTL). Ⅱ: Two-screw fixation with both variable angle locking screws (LPTV). Ⅲ: One-screw fixation with one locking screw (LPOL). Ⅳ: One-screw fixation with one locking screw and two anteroposterior lag screws (LPOLTL). Ⅴ: a distal radius plate with three locking screws (TPP). Biomechanical tests were conducted to observe the axial compression displacement of the PL fracture fragments at force levels of 250 N, 500 N, and 750 N, as well as to determine the failure load and the axial stiffness for each respective group. Results: Under a 750 N load condition, the displacements within the five experimental groups exhibited the following trend: Ⅴ < Ⅱ < Ⅰ< Ⅳ < Ⅲ. However, there were no significant differences between Group V and Group II, Group I and Group IV (p > 0.05), and only Group Ⅲ demonstrated a displacement exceeding 3 mm. The failure load and the axial stiffness exhibited the same trend. Conversely, statistical significance was identified among the remaining group compared with Group Ⅲ (p < 0.05). Regarding the finite element analysis, the maximum displacements for the five models under the load of 750 N exhibited the following trend: Ⅴ < Ⅱ < Ⅰ< Ⅳ < Ⅲ. The following trends were observed in maximum von Mises stresses for these models under the load of 750 N: Ⅴ < Ⅱ < Ⅳ< Ⅰ < Ⅲ. Conclusion: It is crucial to address the inadequate mechanical strength associated with single screw fixation of LCP for fixing PL fractures in a clinical setting. The biomechanical strength of two-screw fixation surpasses that of single-screw fixation. Introducing variable-angle screws can further enhance the fixation range. Furthermore, the addition of two lag screws threaded from anterior to posterior can compensate the mechanical stability, when PL fracture is fixed with single screw in clinic.
Collapse
Affiliation(s)
- Zhenghui Hu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Weizhi Ren
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Jian Peng
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Zenghui Gu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Chenying Wu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Weicheng Wu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Wen Zhang
- Orthopedic Institute of Soochow University, Suzhou, China
| | - Wei Xu
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| | - Liubing Li
- Department of Orthopedics, The Second Affiliated Hospital of Soochow University, Suzhou, China
| |
Collapse
|
4
|
Adamović P, Matoc L, Knežević P, Sabalić S, Kodvanj J. Biomechanical analysis of a novel screw system with a variable locking angle in mandible angle fractures. Med Biol Eng Comput 2023; 61:2951-2961. [PMID: 37535297 DOI: 10.1007/s11517-023-02895-y] [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: 05/08/2023] [Accepted: 07/19/2023] [Indexed: 08/04/2023]
Abstract
Locking plates nowadays represent an important treatment in bone trauma and bone healing due to its strong biomechanical properties. The purpose of this study was to both computationally and experimentally validate a novel screw locking system by comparing it to another locking system from state-of-the-art and to apply it in an environment of a fractured mandible. FEA was used to test both systems prior to experimental tests. The systems were locked in the plate holes at 0°, 10°, 15°, and 20°. Cyclic bending tests and push-out tests were performed in order to determine the stiffness and push-out forces of both locking systems. Finally, newly designed locking system was implemented in mandibular angle fracture. Control locking system was biomechanically superior in push-out test, but with no greater significance. In contrast, the new locking system showed greater stiffness by 17.3% at the deflection angle of 20° in cyclic tests, with lower values for other deflection angles. Similar values were displayed in fractured mandible angle environment. Greater stiffness of the new locking system in cyclic loading tests, together with polyaxiallity of the new locking screw, could lead to easier application and improved biomechanical stability of the mandible angle fractures.
Collapse
Affiliation(s)
- Petra Adamović
- Experimental Mechanics Laboratory, Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000, Zagreb, Croatia
| | - Lovro Matoc
- Department of Maxillofacial Surgery, University Hospital Centre Zagreb, Kišpatićeva Ulica 12, 10000, Zagreb, Croatia.
| | - Predrag Knežević
- Department of Maxillofacial and Oral Surgery, Dubrava University Hospital, Avenija Gojka Šuška 6, 10000, Zagreb, Croatia
| | - Srećko Sabalić
- Department of Traumatology, Sestre Milosrdnice University Hospital Center, Draškovićeva 19, 10000, Zagreb, Croatia
- School of Medicine, University of Split, Šoltanska 2, 21000, Split, Croatia
| | - Janoš Kodvanj
- Experimental Mechanics Laboratory, Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb, Ivana Lučića 5, 10000, Zagreb, Croatia
| |
Collapse
|
5
|
Failure analysis of a locking compression plate with asymmetric holes and polyaxial screws. J Mech Behav Biomed Mater 2023; 138:105645. [PMID: 36603526 DOI: 10.1016/j.jmbbm.2022.105645] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Revised: 11/27/2022] [Accepted: 12/25/2022] [Indexed: 12/31/2022]
Abstract
Locking compression plates (LCP) with asymmetrical holes and polyaxial screws are effective for treating mid-femoral fractures, but are prone to failure in cases of bone nonunion. To understand the failure mechanism of the LCP, this study assessed the material composition, microhardness, metallography, fractography and biomechanical performance of a retrieved LCP used for treating a bone fracture of AO type 32-A1. For the biomechanical assessment, a finite element surgical model implanted with the intact fixation-plate system was constructed to understand the stresses and structural stiffness on the construct. Also, to avoid positioning screws around the bone fracture, different working lengths of the plate (the distance between the two innermost screws) and screw inclinations (±5°, ±10° and ±15°) were investigated. The fracture site of the retrieved LCP was divided into a narrow side and broad side due to the asymmetrical distribution of holes on the plate. The results indicated that the chemical composition and microhardness of the LCP complied with ASTM standards. The fatigue failure was found to originate on the narrow side of the hole, while the broad side showed overloading characteristics of crack growth. When the screws were inserted away from the region of the bone fracture by increasing the working length, the stress of the fixation-plate system decreased. Regardless of the screw insertion angle, the maximum stress on the LCP always appeared on the narrow side, and there was little change in the structural stiffness. However, angling the screws at -10° resulted in the most even stress distribution on the fixation-plate system. In conclusion, the LCP assessed in this study failed by fatigue fracture due to bone nonunion and stress concentration. The narrow side of the LCP was vulnerable to failure and needs to be strengthened. When treating an AO type 32-A1 fracture using an LCP with asymmetrical holes and polyaxial screws, inserting the screws at -10° may reduce the risk of implant failure and positing screws around the fractured area of the bone should be avoided.
Collapse
|
6
|
Gupta R, Schmidt EC, Namdari S, Stone MA, Hast MW. The addition of cerclage wiring does not improve proximal bicortical fixation of locking plates for Type C periprosthetic fractures in synthetic humeri. Clin Biomech (Bristol, Avon) 2022; 97:105709. [PMID: 35780699 PMCID: PMC10096358 DOI: 10.1016/j.clinbiomech.2022.105709] [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: 02/10/2022] [Revised: 06/05/2022] [Accepted: 06/14/2022] [Indexed: 02/07/2023]
Abstract
BACKGROUND Treatment of proximal humerus periprosthetic fractures is challenging. It remains difficult to achieve robust fixation of the proximal fragment to the locking plate using cerclage wiring and/or unicortical screws. Use of polyaxial tangentially directed bicortical locking screws increases screw purchase, but it is unclear if this option provides robust fixation. This biomechanical study compares fixation of constructs using cerclage wires, bicortical locking screws, and a hybrid method utilizing both methods. METHODS Uncemented humeral stems were implanted into synthetic humeri and Type C periprosthetic fractures were simulated with a 1 cm transverse osteotomy. Distal ends of locking plates were secured with bicortical non-locking screws. The proximal ends were supported by either isolated cerclage wires, polyaxial locking screws, or a hybrid combination of both (n = 6 for each group). A universal test frame was used for non-destructive torsion and cyclic axial compression tests. 3-D motion tracking was employed to determine stiffnesses and relative interfragmentary motions. FINDINGS Isolated screw constructs showed significantly increased resistance against torsional movement, bending, and shear, (p < 0.05) in comparison to cerclage constructs. The hybrid construct provided no significant changes in stability over the isolated screw construct. INTERPRETATION Addition of cerclage wires in this synthetic bone model of Type C periprosthetic humerus fractures did not add significant stability to proximal bicortical locking plate fixation. Considering risks of tissue stripping and nerve injury, usage of cerclage wires in a similar clinical setting should be chosen carefully, especially when bicortical fixation around the prosthetic stem can be achieved.
Collapse
Affiliation(s)
- Richa Gupta
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA.
| | - Elaine C Schmidt
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA
| | - Surena Namdari
- Rothman Orthopaedic Institute, Thomas Jefferson University, Philadelphia, PA, USA.
| | - Michael A Stone
- Rothman Orthopaedic Institute, Thomas Jefferson University, Philadelphia, PA, USA
| | - Michael W Hast
- McKay Orthopaedic Research Laboratory, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, PA, USA.
| |
Collapse
|
7
|
Schader JF, Mischler D, Dauwe J, Richards RG, Gueorguiev B, Varga P. One size may not fit all: patient-specific computational optimization of locking plates for improved proximal humerus fracture fixation. J Shoulder Elbow Surg 2022; 31:192-200. [PMID: 34298147 DOI: 10.1016/j.jse.2021.06.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Revised: 06/04/2021] [Accepted: 06/12/2021] [Indexed: 02/01/2023]
Abstract
BACKGROUND Optimal treatment options for proximal humerus fractures (PHFs) are still debated because of persisting high fixation failure rates experienced with locking plates. Optimization of the implants and development of patient-specific designs may help improve the primary fixation stability of PHFs and reduce the rate of mechanical failures. Optimizing the screw orientations in locking plates has shown promising results; however, the potential benefit of subject-specific designs has not been explored yet. The purpose of this study was to evaluate by means of finite element (FE) analyses whether subject-specific optimization of the screw orientations in a fixed-angle locking plate can reduce the predicted cutout failure risk in unstable 3-part fractures. METHODS FE models of 19 low-density proximal humeri were generated from high-resolution computed tomographic images using a previously developed and validated computational osteosynthesis framework. The specimens were virtually osteotomized to simulate unstable malreduced 3-part fractures and fixed with the PHILOS plates using 6 proximal locking screws. The average principal compressive strain in cylindrical bone regions around the screw tips-a biomechanically validated surrogate for the risk of cyclic screw cutout failure-was defined as the main outcome measure. The angles of the 6 proximal locking screws were optimized via parametric analysis for each humerus individually, resulting in subject-specific screw orientations (SSO). The average peri-implant strains of the SSO were statistically compared with the previously reported cohort-specific (CSO) and original PHILOS screw orientations (PSO) for females vs. males. RESULTS The optimized SSO significantly reduced the peri-screw bone strain vs. CSO (6.8% ± 4.0%, P = .006) and PSO (25.24% ± 7.93%, P < .001), indicating lower cutout risk for subject-specific configurations. The benefits of SSO vs. PSO were significantly higher for women than men. CONCLUSION The findings of this study suggest that subject-specific optimization of the locking screw orientations could lead to lower cutout risk and improved PHF fixation. These computer simulation results require biomechanical and clinical corroboration. Further studies are needed to evaluate whether the potential benefit in stability could justify the increased efforts related to implementation of individualized implants. Nevertheless, computational exploration of the biomechanical factors influencing the outcome of fracture fixations could help better understand the fixation failures and reduce their incidence.
Collapse
Affiliation(s)
| | | | - Jan Dauwe
- AO Research Institute Davos, Davos, Switzerland; Department of Trauma Surgery, UZ Leuven, Leuven, Belgium
| | | | | | - Peter Varga
- AO Research Institute Davos, Davos, Switzerland.
| |
Collapse
|
8
|
Cristino DM, Schmidt EC, Metikala S, Mahmoud K, Hast MW, Farber DC. A cadaveric comparison of two methods for isolated talonavicular arthrodesis: Two-screws versus plate with integrated compression screw. Foot Ankle Surg 2021; 27:405-411. [PMID: 32553424 DOI: 10.1016/j.fas.2020.05.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2020] [Revised: 05/06/2020] [Accepted: 05/18/2020] [Indexed: 02/04/2023]
Abstract
BACKGROUND This study compared stiffness between two constructs for talonavicular arthrodesis: a dorsomedial plating system and two partially threaded cannulated cancellous screws. We hypothesized that the plate would exhibit greater stiffness and resistance to deformation during cyclic loading. METHODS The constructs were implanted in eight matched pairs of cadaveric feet and subjected to axial torsion, cantilever bending in two directions, and cyclic loading to failure. RESULTS The two-screw constructs were significantly stiffer in plantar-dorsal bending (p = .025) and trended towards a higher number of cycles before failure than the plate group (p = .087). No significant differences were observed in internal torsion (p = .620), external torsion (p = .165), or medial-lateral bending (p = .686). CONCLUSIONS This study provided the first biomechanical assessment of a plating system with an integrated compression screw, which was significantly less stiff than a two-screw construct when loaded from plantar to dorsal.
Collapse
Affiliation(s)
- Danielle M Cristino
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, 10th Floor Suite 1050, Philadelphia, PA 19104, United States.
| | - Elaine C Schmidt
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, 10th Floor Suite 1050, Philadelphia, PA 19104, United States.
| | - Sreenivasulu Metikala
- Department of Orthopaedic Surgery, Pennsylvania Hospital, Farm Journal Building, 5th Floor 230 West Washington Square, Philadelphia, PA 19106, United States.
| | - Karim Mahmoud
- Department of Orthopaedic Surgery, Pennsylvania Hospital, Farm Journal Building, 5th Floor 230 West Washington Square, Philadelphia, PA 19106, United States.
| | - Michael W Hast
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, 10th Floor Suite 1050, Philadelphia, PA 19104, United States.
| | - Daniel C Farber
- Department of Orthopaedic Surgery, Pennsylvania Hospital, Farm Journal Building, 5th Floor 230 West Washington Square, Philadelphia, PA 19106, United States.
| |
Collapse
|
9
|
Baltes T, van der Veen A, Blankevoort L, Donders J, Kloen P. Locking plate constructs in subtrochanteric fixation: a biomechanical comparison of LCP screws and AO-nuts. J Clin Orthop Trauma 2020; 16:1-6. [PMID: 33717935 PMCID: PMC7919968 DOI: 10.1016/j.jcot.2020.12.026] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 11/30/2020] [Accepted: 12/26/2020] [Indexed: 11/28/2022] Open
Abstract
OBJECTIVES Various studies have reported the use of the 95-degree condylar blade plate in the treatment of a subtrochanteric fracture or non-union. However, the holding power of standard screws in the metaphyseal and diaphyseal area is often diminished due to osteopenia. The alternative in this area is the use of locking plates, Schühlis or AO-nuts. With the latter two, non-locking screws in the blade plate can be converted to a fixed angle fixation. The objective of this study was to compare the stiffness and strength of the AO-nut augmented 95-degree condylar blade plate construct with that of a locking plate construct. In addition, a clinical series of eight patients treated with the AO-nut augmented 95-degree condylar blade plate construct is presented. METHODS Single screw-plate constructs of a 5.0 mm locking screw/locking compression plate (LCP) and a 4.5 mm non-locking screw/4.5 mm dynamic compression plate (DCP), converted to a fixed-angle screw construct using AO-nuts, were tested by cantilever bending. During loading, force and displacement were recorded, from which the bending stiffness (N/mm) and the yield strength (N) were determined. Secondarily, all patients that underwent surgical treatment for subtrochanteric fracture, malunion or non-union by the senior author using this technique, underwent chart review. RESULTS The stiffness of the locking screws was about four times higher compared to the AO-nut augmented construct. The yield strength was 2.3 times higher for the locking screw construct. In none of the eight patients treated with the fixed-angle blade plate, failure of the AO-nut augmented construct occurred. CONCLUSIONS Although the stiffness and strength of the AO-nut augmented construct is less than of the locking screw, excellent clinical outcomes can be achieved utilizing this construct.
Collapse
Affiliation(s)
- T.P.A. Baltes
- Department of Orthopaedic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands,Corresponding author. Department of Orthopaedic Surgery, PO Box 22660, Amsterdam, 1100 DD, the Netherlands.
| | - A.J. van der Veen
- Department of Physics and Medical Technology, Amsterdam UMC, Vrije Universiteit Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands
| | - L. Blankevoort
- Department of Orthopaedic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands
| | - J.C.E. Donders
- Department of Orthopaedic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands
| | - P. Kloen
- Department of Orthopaedic Surgery, Amsterdam UMC, University of Amsterdam, Amsterdam Movement Sciences, Amsterdam, the Netherlands
| |
Collapse
|
10
|
Deltopectoral vs. deltoid split approach for proximal HUmerus fracture fixation with locking plate: a prospective RAndomized study (HURA). J Shoulder Elbow Surg 2020; 29:2190-2199. [PMID: 32650077 DOI: 10.1016/j.jse.2020.06.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 06/16/2020] [Accepted: 06/22/2020] [Indexed: 02/01/2023]
Abstract
BACKGROUND This study aimed to compare the functional and clinical outcomes between the deltoid split (DS) approach and the classic deltopectoral (DP) approach for locking plate fixation of proximal humerus fractures (PHF) in a prospective randomized multicenter study. METHODS From 2007 to 2015, all patients with a PHF Neer II/III were invited to participate. Exclusion criteria were pre-existing pathology to the limb, patient refusing or too ill to undergo surgery, patient needing another type of treatment (nail, arthroplasty), and axillary nerve impairment. After consent, patients were randomized to one of the 2 treatments using the dark envelope method. Functional outcome was evaluated by validated questionnaires (12-Item Short Form Health Survey: version 2, Quick-DASH) with a minimum follow-up of 12 months. Complications were noted. RESULTS A total of 85 patients (44 DS, 41 DP) were randomized (mean age of 62). Groups were equivalent in terms of age, gender, body mass index, severity of fracture, and preinjury scores. The mean follow-up was 26 months. All clinical outcome measures were in favor of the deltopectoral approach. Specifically, the Q-DASH and SF-12v2 were better in the DP group (12 vs. 26, P = .003 and 56 vs. 51, P = .049, respectively). There were more complications in DS patients, but they did not reach statistical significance. CONCLUSIONS The primary hypothesis on the superiority of the deltoid split incision was rebutted. On the basis of our study, the DP approach seems to offer better function compared with the DS approach for fixation of Neer 2 and 3 PHF fractures fixed with a locking plate.
Collapse
|
11
|
Muramatsu K, Gandionco JA, Suguitan AA, Tani Y, Iwanaga R, Hashimoto T, Sakai T. Unidirectional Porous β-Tricalcium Phosphate: A New Bone Filling Substitute for Treatment of Distal Radius Fracture in the Elderly Population. J Hand Surg Asian Pac Vol 2020; 25:59-66. [PMID: 32000605 DOI: 10.1142/s2424835520500083] [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: 11/18/2022]
Abstract
Background: A new beta-tricalcium phosphate with unidirectional pore structure (UDPTCP), Affinos® (Kurray, Okayama, Japan), has been in clinical use since 2015. To date, there have been only a few clinical studies using this material. We report here the first clinical study for distal radial fracture in the elderly population treated with UDPTCP. Methods: Consecutive patients aged 65 years or older with dorsally displaced unstable fracture of the distal radius (n = 36) were treated operatively in our department. Following reduction of the fracture site, a 7 mm size cube of UDPTCP was placed in the gap of the bony defect and the fracture stabilized with mono-axial or poly-axial type locking plates and screws. Remodeling of the UDPTCP was evaluated by plain radiograph and clinical outcomes were also assessed. Results: UDPTCP was significantly resorbed at 2 months after surgery, both at the center and periphery of the material. Complications were only observed in the post-operative period. Significant correction loss of radial alignment was seen in patients stabilized with poly-axial locking plate. The clinical outcome in all cases was excellent. Conclusions: Block UDPTCP is a safe and convenient material for the treatment of distal radius fracture and is replaced within a suitable time period after grafting into the fracture site. UDPTCP and stable internal fixation is therefore a reliable strategy for restoring and preserving anatomical position, especially in the elderly population.
Collapse
Affiliation(s)
- Keiichi Muramatsu
- Department of Orthopedic Surgery, Nagato General Hospital, Nagato, Yamaguchi, Japan.,Department of Orthopedic Surgery, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan
| | - Jessica A Gandionco
- Department of Orthopedic Surgery, Nagato General Hospital, Nagato, Yamaguchi, Japan
| | - Anthony A Suguitan
- Department of Orthopedic Surgery, Nagato General Hospital, Nagato, Yamaguchi, Japan
| | - Yasuhiro Tani
- Department of Orthopedic Surgery, Nagato General Hospital, Nagato, Yamaguchi, Japan
| | - Ryuta Iwanaga
- Department of Orthopedic Surgery, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan
| | - Takahiro Hashimoto
- Department of Orthopedic Surgery, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan
| | - Takashi Sakai
- Department of Orthopedic Surgery, Yamaguchi University School of Medicine, Ube, Yamaguchi, Japan
| |
Collapse
|
12
|
Pitfalls and limits of locking plates. Orthop Traumatol Surg Res 2019; 105:S103-S109. [PMID: 30130659 DOI: 10.1016/j.otsr.2018.04.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 04/06/2018] [Accepted: 04/12/2018] [Indexed: 02/02/2023]
Abstract
The use of locking plates relies on novel mechanical and biological concepts: the bone healing is endochondral because of the elasticity of the constructs. Preoperative planning is required to determine the fracture reduction strategy and select the implants. The type of plate and the type of screws and their position determine the mechanical properties of the construct. Failure of locking plate fixation is a new phenomenon that differs from conventional plate fixation. These are brought on by inadequate planning, which is made worse when minimally invasive surgery is performed. Often, the fracture is not reduced correctly (leading to malunion), the implant length is incorrect, or the screw type, number, location and implantation sequence are inappropriate. Together these can result in an overly rigid construct with poor healing and implant failure or the opposite, an overly flexible construct that can compromise healing. The return to weight bearing after fracture fixation must be adapted to the type of fracture and construct. While locking plates provide better bone purchase, especially in osteoporotic bone, "en bloc" pulling out of the implant is possible. Delayed fractures at the end of the plates are also possible but can be avoided by making the correct biomechanical choices during fixation. For epiphyseal fractures, there are risks of cut-out and impaction of locking screws in cancellous bone related to the fracture pathology. In the long-term, locking plates can be difficult to remove; however, specialized instrumentation can make this easier.
Collapse
|
13
|
Abstract
Locking plates have led to important changes in bone fracture management, allowing flexible biological fracture fixation based on the principle of an internal fixator. The technique has its indications and limitations. Most of the typical failure patterns arise from basic technical errors. Types of locking plates, material properties and the general principles of locking plate applications are reviewed together with their misapplication.
Collapse
Affiliation(s)
| | - Mark Lenz
- Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Jena, Germany
| |
Collapse
|
14
|
Ehlinger M, Niglis L, Favreau H, Kuntz S, Bierry G, Adam P, Bonnomet F. Vascular complication after percutaneous femoral cerclage wire. Orthop Traumatol Surg Res 2018; 104:377-381. [PMID: 29414721 DOI: 10.1016/j.otsr.2017.10.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 10/12/2017] [Accepted: 10/13/2017] [Indexed: 02/02/2023]
Abstract
Cerclage wire is an effective fracture fixation method. However, its mechanical benefits are countered by local ischemia. Its efficacy for treating femoral periprosthetic fractures has been demonstrated since femoral fixation is possible even there is a stem in the diaphysis. It securely holds the proximal femur typically with an additional plate. The development of minimally-invasive surgery with plate fixation has led to the cerclage wire being inserted percutaneously. Here, we report on a case of secondary femoral ischemia following percutaneous cerclage wire of a periprosthetic femoral fracture. This was a Vancouver type B1 fracture. On the 3rd day after admission, minimally-invasive fixation with a femoral locking plate was performed with five cerclage wires added percutaneously. During the immediate postoperative course, the patient developed ischemia of the operated leg that required vascular surgery after confirmation by CT angiography. An arterial stop was visible with deviation of the superior femoral artery, which was not properly surrounded by the cerclage wire. The latter pulled perivascular tissues towards the femur. When combined with reduced arterial elasticity due to severe atherosclerosis, it resulted in arterial plication. The postoperative course was marked by multiple organ failure and death of the patient. Percutaneous surgery is an attractive option but has risks. The presence of severe atherosclerosis is a warning sign for loss of tissue elasticity. This complication can be prevented by preparing the bone surfaces and carefully positioning the patient on the traction table to avoid forced adduction. The surgeon must also be familiar with alternative techniques to cerclage wire such as polyaxial screws and additional plates.
Collapse
Affiliation(s)
- M Ehlinger
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France.
| | - L Niglis
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| | - H Favreau
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| | - S Kuntz
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| | - G Bierry
- Service de radiologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| | - P Adam
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| | - F Bonnomet
- Service de chirurgie orthopédique et traumatologie, hôpital de Hautepierre, hôpitaux universitaires de Strasbourg, 1, avenue Molière, 67098 Strasbourg, France
| |
Collapse
|
15
|
Mehta S, Chin M, Sanville J, Namdari S, Hast MW. Calcar screw position in proximal humerus fracture fixation: Don't miss high! Injury 2018; 49:624-629. [PMID: 29452734 PMCID: PMC7413303 DOI: 10.1016/j.injury.2018.02.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 02/06/2018] [Indexed: 02/02/2023]
Abstract
INTRODUCTION In locked plate fixation of proximal humerus fractures, the calcar is an important anchor point for screws providing much-needed medial column support. Most locking plate implants utilize a fixed-trajectory locking screw to achieve this goal. Consequently, adjustments of plate location to account for patient-specific anatomy may result in a screw position outside of the calcar. To date, little is known about the consequences of "missing" the calcar during plate positioning. This study sought to characterize the biomechanics associated with proximal and distal placement of locking plates in a two-part fracture model. MATERIALS AND METHODS This experiment was performed twice, first with elderly cadaveric specimens and again with osteoporotic sawbones. Two-part fractures were simulated and specimens were divided to represent proximal, neutral, and distal plate placements. Non-destructive torsional and axial compression tests were performed prior to an axial fatigue test and a ramp to failure. Torsional stiffness, axial stiffness, humeral head displacement and stiffness during fatigue testing, and ultimate load were compared between groups. RESULTS Cadavers: Proximal implant placement led to trends of decreased mechanical properties, but there were no significant differences found between groups. Sawbones: Distal placement increased torsional stiffness in both directions (p = 0.003, p = 0.034) and axial stiffness (p = 0.018) when compared to proximal placement. Distal placement also increased torsional stiffness in external rotation (p = 0.020), increased axial stiffness (p = 0.024), decreased humeral head displacement during fatigue testing, and increased stiffness during fatigue testing when compared to neutral placement. DISCUSSION The distal and neutral groups had similar mechanical properties in many cadaveric comparisons while the proximal group trended towards decreased construct stiffness. RESULTS from the Sawbones model were more definitive and provided further evidence that proximal calcar screw placements are undesirable and distal implant placement may provide improved construct stability. CONCLUSION Successful proximal humerus fracture reconstruction is inherent upon anatomic fracture reduction coupled with medial column support. Results from this experiment suggest that missing the calcar proximally is deleterious to fixation strength, while it is safe, and perhaps even desirable, to aim slightly distal to the intended target.
Collapse
Affiliation(s)
- Samir Mehta
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, PA, United States
| | - Matthew Chin
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, PA, United States
| | - Jennifer Sanville
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, PA, United States
| | - Surena Namdari
- Rothman Institute, Thomas Jefferson University, Department of Orthopaedic Surgery, Philadelphia, PA, United States
| | - Michael W. Hast
- Biedermann Lab for Orthopaedic Research, University of Pennsylvania, Department of Orthopaedic Surgery, Philadelphia, PA, United States,Corresponding author at: Biedermann Laboratory for Orthopaedic Research, University of Pennsylvania, 3737 Market Street, Suite 1050,10th Floor, Philadelphia, PA 19104, United States. (M.W. Hast)
| |
Collapse
|
16
|
Schoch B, Hast MW, Mehta S, Namdari S. Not All Polyaxial Locking Screw Technologies Are Created Equal: A Systematic Review of the Literature. JBJS Rev 2018; 6:e6. [PMID: 29360670 DOI: 10.2106/jbjs.rvw.17.00049] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND Locking plate fixation strength relies on axial alignment of the screw axis and plate hole, with small deviations in alignment substantially decreasing the load to failure. In an effort to overcome this technical deficiency, polyaxial locking plates were designed to provide increased flexibility of screw positioning with the intent of not sacrificing fixation strength. The purpose of this article is to review the variety of polyaxial locking mechanisms currently available, to compare the biomechanical performance of these designs, and to highlight their differences, which may have clinical implications. METHODS A systematic review using the search terms "polyaxial locking," "variable angle locking," "polyaxial screws," and "variable angle screws" was conducted to identify all English-language articles assessing variable-angle locking screw technology. All articles directly comparing the biomechanical performance of polyaxial locking technologies were included. RESULTS Polyaxial locking is achieved by 5 described mechanisms: point-loading thread-in, cut-in, locking cap, expansion bushing, and screw-head expansion. With increasing insertion angulation, point-loading thread-in and cut-in designs demonstrate reduced failure strength. However, locking-cap fixation maintains consistent failure strength with increasing off-axis insertion angles. CONCLUSIONS Reports comparing polyaxial locking technologies are limited. The current biomechanical literature raises concerns that these mechanisms have various strengths and performance characteristics. Based on the results of the few studies that exist, it appears that locking-cap fixation provides superior biomechanical strength when compared with point-loading and cut-in designs. Additional studies are needed to assess variable-angle locking mechanisms more completely.
Collapse
Affiliation(s)
- Bradley Schoch
- Department of Orthopaedic Surgery, University of Florida, Gainesville, Florida
| | - Michael W Hast
- Biedermann Lab for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Samir Mehta
- Biedermann Lab for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Surena Namdari
- Biedermann Lab for Orthopaedic Research, Department of Orthopaedic Surgery, University of Pennsylvania, Philadelphia, Pennsylvania
- Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, Pennsylvania
| |
Collapse
|
17
|
Ulusoy R, Bilge A, Akalin Y, Akinci M, Ermutlu S. Placing a threaded plug in the hole of a locking plate at the fracture level can increase the resistance of the plate: A biomechanical study. SANAMED 2018. [DOI: 10.24125/sanamed.v13i3.256] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Objectives: This study aimed to evaluate whether placing a threaded plug in the hole of a locking plate at the fracture level is beneficial for increasing the resistance of the plate. Methods: This experimental study analyzed load and compression forces in sheep tibia bone models. The following groups were assessed: Group 1 (n = 4), control bone samples; Group 2 (n = 4), samples of screw plate fixation without threaded plug in the hole at the fracture level; and Group 3 (n = 4), samples of screw plate fixation with a threaded plug in the hole at the fracture level. Elastic force, bending moment, elastic compression, and rigidity were evaluated using a three-point bending test. Results: Group 1 showed the greatest elastic force and the least amount of compression. The rigidity and elastic force were better in Group 3 than in Group 2. The mean elastic force in Group 3 was 22.4% of that in Group 1, whereas the mean elastic force in Group 2 was 19% of that in Group 1. Rigidity in Group 3 was 24.7% of that in Group 1, whereas rigidity in Group 2 was 18.3% of that in Group 1. Improved results were obtained in Group 3 when compared with Group 2. Conclusions: Our results suggest that placing a threaded plug in the hole of the plate at the fracture level provides additional rigidity and stability by improving resistance to loading forces, but the differences were not statistically significant.
Collapse
|
18
|
Abstract
OBJECTIVES This study sought to examine fatigue characteristics of 2 polyaxial locking screw designs: locking cap (LC) and cross-threaded (CT). The goal was to compare LC and CT implants at 0, 10, and 15 degrees of angulation to determine the effect of locking mechanism on screw-plate interface failure. The hypothesis was that LC implants would have superior fatigue properties in comparison to CT designs and that increased angulation of the screw would have a negative impact on the fatigue life of CT implants, but would not have any effect on LC implants. METHODS A total of 72 screws were tested in 4 upper extremity implants. Implants were subjected to cyclic shear loads and subsequent ramp to failure. Performance characteristics were statistically compared using nonparametric statistical methods. RESULTS Fatigue testing demonstrated that LC designs were consistently able to sustain a significantly higher number of cyclic loads than CT designs. There were no significant differences in the number of cycles sustained by LC designs because of changes in screw angle, but CT implants exhibited decreases in screw stability with increasing angulation. CONCLUSIONS Likely because of the spherical screw head geometry, LC fatigue characteristics are not influenced by the orientation of the screw relative to the plate. Application of an LC in the operating room requires additional time, but provides significantly more robust fixation of the screw, especially at oblique angles to the plate and provides a more predictable and consistent biomechanical result.
Collapse
|
19
|
Tidwell JE, Roush EP, Ondeck CL, Kunselman AR, Reid JS, Lewis GS. The biomechanical cost of variable angle locking screws. Injury 2016; 47:1624-30. [PMID: 27324325 DOI: 10.1016/j.injury.2016.06.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/14/2016] [Revised: 05/27/2016] [Accepted: 06/01/2016] [Indexed: 02/02/2023]
Abstract
INTRODUCTION Variable angle (VA) locking plates in fracture fixation surgery allow screws to be fastened to the plate within a conical "locus of vectors" in order to avoid existing prostheses, joint surfaces, or poor quality bone. Clinical failures of VA constructs in which screws have rotated at the plate/screw interface have been reported raising the concern that there may be a biomechanical cost for the increased flexibility that VA provides. The objective of this study was to test the mechanical properties of one commonly used VA locking mechanism with screws placed in both nominal and off-axis trajectories and compare these against the standard locking mechanism. METHODS VA locking screws were inserted into plates for distal femur fractures (VA Curved Condylar) at various angles (0° to 15° away from perpendicular). A control group of standard locking screws/plates was also tested. Maximum moment at the screw/plate interface and moment at two reference displacements were determined. RESULTS VA screws locked perpendicular to the plate provided the greatest maximum moment and moment at the reference displacements when using the VA system, and demonstrated lower moments compared to standard locking screws/plates (p<0.001). Based on linear regression, there was an average decrease of approximately 0.4 Nm screw-plate interface strength for every 1° increase in screw-plate angle (p<0.001). Decreases (p<0.05) were discovered in both maximum moment and moment at the reference displacements for screws locked at 5° relative to those locked at 0°, 10° relative to 0°, and 15° relative to 10°. DISCUSSION Standard locking systems provided greater resistance to rotational failure at the screw/plate interface than variable angle locking systems. Variable angle systems provided the greatest resistance to rotation when the screw was inserted perpendicular to the plate. As the off-axis angle increased, the resistance to rotation at the screw/plate interface decreased almost linearly. It is unknown if these differences are clinically significant in an actual fracture construct, but recent reported failures in the distal femur suggest that they might be. CONCLUSION Surgeons should weigh the risks and benefits of VA systems and attempt to minimize the off-axis angle magnitude when VA systems are selected.
Collapse
Affiliation(s)
- John E Tidwell
- UCSF Fresno, Department of Orthopaedics, 2823 Fresno Street, Fresno, CA 93721, USA
| | - Evan P Roush
- Penn State College of Medicine and Hershey Medical Center, Department of Orthopaedics & Rehabilitation, 500 University Drive, Mail Code H089, Hershey, PA, 17033, USA
| | - Cassandra L Ondeck
- Penn State College of Medicine and Hershey Medical Center, Department of Orthopaedics & Rehabilitation, 500 University Drive, Mail Code H089, Hershey, PA, 17033, USA
| | - Allen R Kunselman
- Penn State College of Medicine and Hershey Medical Center, Department of Orthopaedics & Rehabilitation, 500 University Drive, Mail Code H089, Hershey, PA, 17033, USA
| | - J Spence Reid
- Penn State College of Medicine and Hershey Medical Center, Department of Orthopaedics & Rehabilitation, 500 University Drive, Mail Code H089, Hershey, PA, 17033, USA
| | - Gregory S Lewis
- Penn State College of Medicine and Hershey Medical Center, Department of Orthopaedics & Rehabilitation, 500 University Drive, Mail Code H089, Hershey, PA, 17033, USA.
| |
Collapse
|
20
|
Lenz M, Wahl D, Zderic I, Gueorguiev B, Jupiter JB, Perren SM. Head-locking durability of fixed and variable angle locking screws under repetitive loading. J Orthop Res 2016; 34:949-52. [PMID: 26580296 DOI: 10.1002/jor.23108] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 11/09/2015] [Indexed: 02/04/2023]
Abstract
Polyaxial locking screws are increasingly applied in fracture fixation. To investigate the durability of the head-locking mechanism, the removal torque of variable angle (VA) and fixed angle (FA) stainless steel and titanium locking screws was investigated without and after a cyclic loading test. Stainless steel (St) and titanium (Ti) 2.4 mm orthogonally inserted FA screws and 2.4 mm VA screws inserted in different inclinations (0°-15°) (n = 6 per group) were locked at 0.8 Nm. Removal torque was determined without (W) and after (A) cyclic loading (sinusoidal load, 5 Hz, constant amplitude of 25 N, up to 10'000 cycles, or failure). Significant differences in-between the groups were detected by Student's t-test (p < 0.05). Except VA Ti in 0deg and FA, all groups exhibited a drop in removal torque below the insertion torque without and after cyclic testing. The removal torque was (St: FA W:0.81 Nm ± 0.04 A:0.72Nm ± 0.04; VA0deg W:0.73 Nm ± 0.04 A:0.65 Nm ± 0.05; VA15deg W:0.51 Nm ± 0.05 A:0.50 Nm ± 0.08; Ti: FA W:0.82 Nm ± 0.03 A:0.70 Nm ± 0.04; VA0deg W:0.80 Nm ± 0.02 A:0.72 Nm ± 0.05; VA15deg W:0.55 Nm ± 0.03 A:0.54 Nm ± 0.06). In all groups, the removal torque after cyclic testing did not drop below 16% of the removal torque without cyclic testing. No head loosening was observed after cyclic testing. Stainless steel and titanium 2.4 mm fixed and variable angle locking screws provide a stable and lasting head-locking mechanism. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:949-952, 2016.
Collapse
Affiliation(s)
- Mark Lenz
- AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland.,Department of Trauma, Hand and Reconstructive Surgery, University Hospital Jena, Germany
| | - Dieter Wahl
- AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland
| | - Ivan Zderic
- AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland
| | - Boyko Gueorguiev
- AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland
| | - Jesse B Jupiter
- Department of Orthopaedic Surgery-Hand and Upper Extremity Service, Massachusetts General Hospital, Boston 02114, Massachusetts
| | - Stephan M Perren
- AO Research Institute Davos, Clavadelerstrasse 8, CH-7270 Davos, Switzerland.,Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
| |
Collapse
|
21
|
The influence of bone density and anisotropy in finite element models of distal radius fracture osteosynthesis: Evaluations and comparison to experiments. J Biomech 2015; 48:4116-4123. [PMID: 26542787 DOI: 10.1016/j.jbiomech.2015.10.012] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Revised: 10/07/2015] [Accepted: 10/10/2015] [Indexed: 11/23/2022]
Abstract
Continuum-level finite element (FE) models can be used to analyze and improve osteosynthesis procedures for distal radius fractures (DRF) from a biomechanical point of view. However, previous models oversimplified the bone material and lacked thorough experimental validation. The goal of this study was to assess the influence of local bone density and anisotropy in FE models of DRF osteosynthesis for predictions of axial stiffness, implant plate stresses, and screw loads. Experiments and FE analysis were conducted in 25 fresh frozen cadaveric radii with DRFs treated by volar locking plate osteosynthesis. Specimen specific geometries were captured using clinical quantitative CT (QCT) scans of the prepared samples. Local bone material properties were computed based on high resolution CT (HR-pQCT) scans of the intact radii. The axial stiffness and individual screw loads were evaluated in FE models, with (1) orthotropic inhomogeneous (OrthoInhom), (2) isotropic inhomogeneous (IsoInhom), and (3) isotropic homogeneous (IsoHom) bone material and compared to the experimental axial stiffness and screw-plate interface failures. FE simulated and experimental axial stiffness correlated significantly (p<0.0001) for all three model types. The coefficient of determination was similar for OrthoInhom (R(2)=0.807) and IsoInhom (R(2)=0.816) models but considerably lower for IsoHom models (R(2)=0.500). The peak screw loads were in qualitative agreement with experimental screw-plate interface failure. Individual loads and implant plate stresses of IsoHom models differed significantly (p<0.05) from OrthoInhom and IsoInhom models. In conclusion, including local bone density in FE models of DRF osteosynthesis is essential whereas local bone anisotropy hardly effects the models׳ predictive abilities.
Collapse
|
22
|
Ehlinger M, Scheibling B, Rahme M, Brinkert D, Schenck B, Di Marco A, Adam P, Bonnomet F. Minimally invasive surgery with locking plate for periprosthetic femoral fractures: technical note. INTERNATIONAL ORTHOPAEDICS 2015; 39:1921-6. [DOI: 10.1007/s00264-015-2928-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 05/15/2015] [Indexed: 10/23/2022]
|
23
|
Mechanical performance in axial compression of a titanium polyaxial locking plate system in a fracture gap model. Vet Comp Orthop Traumatol 2015; 28:88-94. [PMID: 25703709 DOI: 10.3415/vcot-14-03-0046] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2014] [Accepted: 12/11/2014] [Indexed: 11/17/2022]
Abstract
OBJECTIVE To evaluate the bending strength of the VetLOX® polyaxial locking plate system. MATERIALS AND METHODS Thirty-five 3.5 mm 12-hole titanium VetLOX® plates were used to stabilize seven different construct designs in a 1 cm fracture gap simulation model. Each construct was subjected to axial compression. Mean bending stiffness (BS) and yield load (YL) of each construct design were analysed using a one-way ANOVA and Tukey post-hoc analysis. Screw angulation was measured on reconstructed computed tomography (CT) images. RESULTS Reducing plate working length for fixed-angle constructs significantly increased BS (p <0.01) and YL (p <0.01). For a constant plate working length, increasing screw number did not significantly affect BS (p = 1.0) or YL (p = 0.86). Screw angulation measurement technique was validated by intra-class correlation coefficients (ICC) (ICC >0.9 for inter- and intra-observer measurements). An average screw angle of 13.2° did not significantly affect mechanical performance although incomplete screw head-plate engagement was noted on some reconstructed CT images when angulation exceeded 10°. Prefabricated screw-head inserts did not significantly increase mechanical performance. A 4 mm bone-plate stand-off distance significantly reduced BS and YL by 63% and 69% respectively. CLINICAL RELEVANCE The VetLOX® system allows the benefits of polyaxial screw insertion whilst maintaining comparable bending properties to fixed angle insertion. The authors recommend accurate plate contouring to reduce the risk of plate bending.
Collapse
|
24
|
Abstract
OBJECTIVES The purposes of this study were to evaluate the cantilevered bending strength and failure modes of locking screws inserted at various angles in a plate with fully circumferential threaded holes. As an additional measure, the amount of screw head prominence at these angles was also assessed. METHODS Standard 3.5-mm locking screws were inserted into round fully circumferential threaded holes through a standard straight 3.5-mm locking plate at various angles. The achieved angle of insertion and its prominence protruding from the far-bone side of the plate was measured using an optical luminescence technique. Each screw was then loaded at a constant rate until failure in a cantilevered bending scenario. The maximum cantilevered bending strength was measured, and the moment at failure was calculated. RESULTS There was a positive correlation between increasing insertion angle and increasing prominence; a higher screw insertion angle yielded greater prominence. Prominence values ranged from negligible to 2 mm. As screw insertion angle increased, the bending moment at failure decreased. Screws inserted to 3 degrees or below primarily failed through screw deformation at the minor diameter below the head, whereas screws inserted to greater than 3 degrees primarily failed through locking mechanism disengagement. CONCLUSIONS These findings indicate that cross threading may not be biomechanically advantageous and may change screw mode of failure. Based on these findings, screws inserted to 3 degrees or higher would reduce the bending moment at failure to approximately 50% of an orthogonally inserted screw.
Collapse
|