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Comparing the locking screw direction of three locking plates for lateral clavicle fractures: a simulation study. BMC Musculoskelet Disord 2021; 22:812. [PMID: 34548051 PMCID: PMC8456609 DOI: 10.1186/s12891-021-04697-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2021] [Accepted: 09/08/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The locking plate is a useful treatment for lateral clavicle fractures, however, there are limits to the fragment size that can be fixed. The current study aimed to measure the screw angles of three locking plates for lateral clavicle fractures. In addition, to assess the number of screws that can be inserted in different fragment sizes, to elucidate the size limits for locking plate fixation. METHODS The following three locking plates were analyzed: the distal clavicle plate [Acumed, LLC, Oregon, the USA], the LCP clavicle plate lateral extension [Depuy Synthes, LLC, PA, the USA], and the HAI clavicle plate [HOMS Engineering, Inc., Nagano, Japan]. We measured the angles between the most medial and lateral locking screws in the coronal plane and between the most anterior and posterior locking screws in the sagittal plane. A computer simulation was used to position the plates as laterally as possible in ten normal three-dimensional clavicle models. Lateral fragment sizes of 10, 15, 20, 25, and 30 mm were simulated in the acromioclavicular joint, and the number of screws that could be inserted in the lateral fragment was assessed. Subsequently, the area covered by the locking screws on the inferior surface of the clavicle was measured. RESULTS The distal clavicle plate had relatively large screw angles (20° in the coronal plane and 32° in the sagittal plane). The LCP clavicle lateral extension had a large angle (38°) in the sagittal plane. However, the maximum angle of the HAI clavicle plate was 13° in either plane. The distal clavicle plate allowed most screws to be inserted in each size of bone fragment. For all locking plates, all screws could be inserted in 25 mm fragments. The screws of distal clavicle plate covered the largest area on the inferior surface of the clavicle. CONCLUSIONS Screw angles and the numbers of screws that could be inserted in the lateral fragment differed among products. Other augmented fixation procedures should be considered for fractures with fragment sizes < 25 mm that cannot be fixed with a sufficient number of screws.
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Jordan MC, Jäckle V, Scheidt S, Eden L, Gilbert F, Heintel TM, Jansen H, Meffert RH. [Outcome after plate stabilization of symphyseal diastasis]. Unfallchirurg 2020; 123:870-878. [PMID: 32347368 PMCID: PMC7653790 DOI: 10.1007/s00113-020-00804-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Hintergrund Die Symphysensprengung mit entsprechender Diastase kann durch eine Symphysenplatte stabilisiert werden. Fragestellung Welche Beckenverletzungen werden mit einer Symphysenplatte stabilisiert und wie ist das Outcome? Material und Methoden Retrospektive Auswertung von 64 Patienten über einen Untersuchungszeitraum von 24 Monaten. Ergebnisse Es waren 56 Patienten männlich, 8 weiblich und das mittlere Alter betrug 44 Jahre (SD ± 17). Unfälle im Straßenverkehr waren der führende Grund für die Beckenverletzung. Die Verteilung nach AO-Klassifikation zeigte sich wie folgt: 14-mal B1-, 10-mal B2-, 5‑mal B3-, 23-mal C1-, 9‑mal C2- und 3‑mal C3-Verletzungen. Die Verteilung nach Young und Burgess ergab: 9‑mal APC-I-, 18-mal APC-II-, 13-mal APC-III-, 9‑mal LC-I-, 3‑mal LC-II-, 2‑mal LC-III- und 10-mal VS-Verletzungen. Der mittlere Injury Severity Score (ISS) betrug 32 und die mittlere stationäre Verweildauer 29 Tage (pos. Korrelation p ≤ 0,001). Im Verlauf war eine radiologische Implantatlockerung bei 52 Patienten nachweisbar. Therapierelevante Komplikationen gab es in 14 Fällen. Hierbei war das Implantatversagen (n = 8) der Hauptgrund für eine operative Revision. Diskussion Obwohl die radiologische Implantatlockerung häufig beobachtet wird, ist sie nur selten Grund für einen Revisionseingriff. Kommt es hingegen zum vollständigen Implantatversagen, tritt dies meist innerhalb der ersten postoperativen Wochen auf und ist revisionsbedürftig. Eine frühzeitige Abklärung durch Röntgenbildgebung sollte bei Verdacht erfolgen.
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Affiliation(s)
- Martin C Jordan
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland.
| | - Veronika Jäckle
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
| | - Sebastian Scheidt
- Klinik für Orthopädie und Unfallchirurgie, Universitätsklinikum Bonn, Venusberg-Campus 1, 53127, Bonn, Deutschland
| | - Lars Eden
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
| | - Fabian Gilbert
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
| | - Timo M Heintel
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
| | - Hendrik Jansen
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
| | - Rainer H Meffert
- Klinik und Poliklinik für Unfall‑, Hand‑, Plastische und Wiederherstellungschirurgie, Universitätsklinikum Würzburg, Oberdürrbacher Straße 8, 97080, Würzburg, Deutschland
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Cucchi D, Arrigoni P, Luceri F, Menon A, Guerra E, Müller LP, Burger C, Eygendaal D, Wegmann K. Modified anteromedial and anterolateral elbow arthroscopy portals show superiority to standard portals in guiding arthroscopic radial head screw fixation. Knee Surg Sports Traumatol Arthrosc 2019; 27:3276-3283. [PMID: 30863912 DOI: 10.1007/s00167-019-05411-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 02/13/2019] [Indexed: 10/27/2022]
Abstract
PURPOSE Arthroscopic fixation of radial head radial head fractures is an appealing alternative to open reduction and internal fixation, which presents the advantage of minimal surgical trauma. The aim of this study was to evaluate if modifications to the standard anteromedial (AM) and anterolateral (AL) portals could allow screw placement for radial head fracture osteosynthesis closer to the plane of the radial head articular surface. METHODS Eight fresh-frozen specimens were prepared to mimic arthroscopic setting. Standard AL (ALst) and AM (AMst) and distal AL (ALdi) and AM (AMdi) portals were established. Eleven independent examiners were asked to indicate the optimal trajectory, when aiming to place a cannulated screw parallel to the radial head surface for radial head osteosynthesis. A three-dimensional digital protractor was used to measure the angle between the indicated position and a Kirschner wire placed parallel to the radial head articular surface (α). The Shapiro-Wilk normality test was used to evaluate the normal distribution of the samples. Means, standard deviations, and 95% confidence intervals (95% CI) were calculated for each portal. A coefficient of variation (CoV) was calculated to determine agreement among observers and intra-observer variability. RESULTS Mean α angles were 25.1 ± 11.5° for AMst, 13.8 ± 4.8° for AMdi, 17.1 ± 13.4° for ALst, -2.6 ± 9.2° for ALdi. No overlapping in the 95% CI of ipsilateral standard and distal portals was observed, indicating that the difference between these means was statistically significant. The distal portals showed smaller inter-observer CoV as compared to the standard ones (AMst: 10.0%; AMdi: 4.6%; ALst: 12.5%; ALdi: 10.6%). Intra-observer CoV was similar for all portals (AMst: 5.5%; AMdi: 6.1%; ALst: 7.7%; ALdi: 7.1%). CONCLUSIONS The use of distal AM and AL portals permits to obtain α angles closer to the radial head articular surface than standard AM and AL portals. This is expected to allow screw placement in a flatter trajectory, which should correlate with a superior biomechanical performance of fixation. Good reproducibility of Kirschner wire placement from distal portals was observer among different examiners. Modifications to the standard AM and AL elbow arthroscopy portals allow to place screws for radial head fracture osteosynthesis in a position which should guarantee superior biomechanical performance of fixation.
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Affiliation(s)
- Davide Cucchi
- Department of Orthopaedics and Trauma Surgery, Universitätsklinikum Bonn, Sigmund- Freud-Str. 25, 53127, Bonn, Germany. .,Laboratory of Applied Biomechanics, Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Mangiagalli 31, 20133, Milan, Italy.
| | - Paolo Arrigoni
- Laboratory of Applied Biomechanics, Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Mangiagalli 31, 20133, Milan, Italy.,U.O. Clinica Ortopedica e Traumatologica Universitaria CTO, Azienda Socio Sanitaria Territoriale Centro Specialistico Ortopedico Traumatologico Gaetano Pini-CTO, Piazza Cardinal Ferrari 1, 20122, Milan, Italy
| | - Francesco Luceri
- U.O. Clinica Ortopedica e Traumatologica Universitaria CTO, Azienda Socio Sanitaria Territoriale Centro Specialistico Ortopedico Traumatologico Gaetano Pini-CTO, Piazza Cardinal Ferrari 1, 20122, Milan, Italy.,Università degli Studi di Milano, Via Mangiagalli 31, 20133, Milan, Italy
| | - Alessandra Menon
- Laboratory of Applied Biomechanics, Department of Biomedical Sciences for Health, Università degli Studi di Milano, Via Mangiagalli 31, 20133, Milan, Italy.,1° Clinica Ortopedica, ASST Centro Specialistico Ortopedico Traumatologico Gaetano Pini-CTO, Piazza Cardinal Ferrari 1, 20122, Milan, Italy
| | - Enrico Guerra
- Shoulder and Elbow Unit, Ortopedico Rizzoli, Via Pupilli 1, 40136, Bologna, Italy
| | - Lars Peter Müller
- Center for Orthopedic and Trauma Surgery, University Medical Center, Kerpenerstrasse 62, 50937, Cologne, Germany
| | - Christof Burger
- Department of Orthopaedics and Trauma Surgery, Universitätsklinikum Bonn, Sigmund- Freud-Str. 25, 53127, Bonn, Germany
| | - Denise Eygendaal
- Department of Orthopaedic Surgery, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands.,Department of Orthopaedic Surgery, Upper Limb Unit, Amphia Hospital, Breda, The Netherlands
| | - Kilian Wegmann
- Center for Orthopedic and Trauma Surgery, University Medical Center, Kerpenerstrasse 62, 50937, Cologne, Germany
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Zderic I, Willhuber GC, Ahrend MD, Gras F, Barla J, Sancineto C, Windolf M, Richards G, Gueorguiev B. Biomechanical comparison between standard and inclined screw orientation in dynamic hip screw side-plate fixation: The lift-off phenomenon. J Orthop Translat 2018; 18:92-99. [PMID: 31508312 PMCID: PMC6718874 DOI: 10.1016/j.jot.2018.10.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/17/2018] [Revised: 10/17/2018] [Accepted: 10/24/2018] [Indexed: 11/28/2022] Open
Abstract
Background Common failure modes of dynamic hip screw are cut-out and lift-off. To minimize the latter, distal screws can be inserted in different orientations. However, the effectiveness remains controversial. The aim of this study was to biomechanically investigate the influence of distal screw orientation on construct stability. Methods Thirty artificial generic long bones were assigned to three groups (n = 10) and fixed with two-hole dynamic hip screw–plates, inserting distal cortical screws with neutral parallel screw orientation (A), divergent screw orientation (B) or convergent screw orientation (C). Starting at 60 N, cyclic loading was applied to the implant tip perpendicular to the lag screw axis with progressive peak load increase at a rate of 0.002 N/cycle until failure. Parameters of interest were construct stiffness and machine actuator displacement after 250, 1000 and 5000 cycles, as well as cycles to failure. Results Displacement after 250, 1000 and 5000 cycles was significantly higher in Group C than in Groups A and B, p < 0.01, whereas no significant differences were observed between Groups A and B, p = 0.20. Specimens in Group C failed after 11,584 [standard deviation (SD), 5924] cycles, significantly earlier than those in Groups A and B [A: 27,351 (SD, 12,509); B: 28,793 (SD, 14,764)], p ≤ 0.02. Cycles to failure were not significantly different between Groups A and B, p > 0.99. The translational potential of this article Parallel or divergent distal screw insertion provides similar construct stability in terms of resistance to plate lift-off. In contrast, converging screw insertion leads to inferior stability and is not advisable from a biomechanical point of view.
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Affiliation(s)
- Ivan Zderic
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Gaston C Willhuber
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland.,Hospital Italiano de Buenos Aires, Juan D. Perón 4190, C1199ABD Buenos Aires, Argentina
| | - Marc-Daniel Ahrend
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland.,Department of Traumatology and Reconstructive Surgery, BG Trauma Center Tübingen, Eberhard-Karls University of Tübingen, Tübingen, Germany
| | - Florian Gras
- Department of Trauma-, Hand- and Reconstructive Surgery, Friedrich-Schiller University, Bachstrasse 18, 07743 Jena, Germany
| | - Jorge Barla
- Hospital Italiano de Buenos Aires, Juan D. Perón 4190, C1199ABD Buenos Aires, Argentina
| | - Carlos Sancineto
- Hospital Italiano de Buenos Aires, Juan D. Perón 4190, C1199ABD Buenos Aires, Argentina
| | - Markus Windolf
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Geoff Richards
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
| | - Boyko Gueorguiev
- AO Research Institute Davos, Clavadelerstrasse 8, 7270 Davos, Switzerland
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Michelitsch C, Nguyen-Kim TDL, Jentzsch T, Simmen HP, Werner CML. Computed tomography-based three-dimensional visualisation of bone corridors and trajectories for screws in open reduction and internal fixation of symphysis diastasis: a retrospective radiological study. Arch Orthop Trauma Surg 2016; 136:1673-1681. [PMID: 27628459 DOI: 10.1007/s00402-016-2568-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/19/2016] [Indexed: 11/24/2022]
Abstract
INTRODUCTION Typical stabilisation of pelvic open book injuries consists of plate fixation of the symphysis. No previous literature has been published about the evaluation of screw placement and their trajectory with four oblique 4.5 mm screws using a four-hole plate in symphysis diastasis. The aim of this study was to define insertion points and angles of trajectory for crossed screw placement regardless of any plate design based on an analysis of three-dimensional computed tomography data sets. METHODS One hundred human pelvic CT data sets were collected. Unilateral and bilateral placements of crossed 4.5 mm screws were simulated. Primary outcome measure was successful simulated screw placement without cortical breach. Secondary outcome measures included the anatomical measurements of the screw positions. RESULTS Simulated screw placement of two oblique screws on each side of the pubic symphysis without cortical breach was achieved in all (100 %) cases. There were a total of 400 screw simulations. Medial screws were longer, lateral screws had higher coronal angles, and the distance between both screws was higher on the right side (p < 0.001 each). The lengths of the right lateral, right medial, left lateral, and left medial screws were 44.9, 65.8, 45.4, and 67.4 mm, respectively. The sagittal angles to the dorsal surface area of the pubic rami were 10.5°, 11.1°, 9.0°, and 11.0°. The coronal angles to the vertical axis of the symphysis measured 39.5°, 16.0°, 33.8°, and 16.8°. The distances between these screws and the medial edge of the pubic crest were 33.5, 8.6, 29.5, and 7.3 mm. Furthermore, certain sex- and side-related differences were noted. CONCLUSIONS This series provides results about the feasibility and a detailed anatomical description of crossed screw placement. This is of special interest in pelvic surgery for choosing the entry points, safe screw channel parameters, and trajectories.
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Affiliation(s)
- Christian Michelitsch
- Department of Surgery, Division of Trauma Surgery, University Hospital, Zurich, Switzerland.
| | - Thi Dan Linh Nguyen-Kim
- Department of Diagnostic and Interventional Radiology, University Hospital, Zurich, Switzerland
| | - Thorsten Jentzsch
- Department of Surgery, Division of Trauma Surgery, University Hospital, Zurich, Switzerland
| | - Hans-Peter Simmen
- Department of Surgery, Division of Trauma Surgery, University Hospital, Zurich, Switzerland
| | - Clément M L Werner
- Department of Surgery, Division of Trauma Surgery, University Hospital, Zurich, Switzerland
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Abstract
The technique of placing an oblique screw in the terminal hole of a plate to increase screw pullout strength is widely taught in the operating room. The origin of this technique is unclear; however, it may have been used simply as a means to identify radiographs and misinterpreted to have some biomechanical benefit. The objective of this study was to measure the structural effect of oblique terminal screw placement (OTSP) during plate osteosynthesis. Foam blocks and limited contact dynamic compression plates and screws were used along with a custom fixture device. The terminal screw was placed in either an oblique (30-degree angle outward) or perpendicular fashion. A load was applied perpendicular to the plate in cantilever bending until failure. The oblique screw construct was significantly weaker than the perpendicular screw construct (399N vs. 465N, P < 0.001), independent of the block of material used. Post hoc analysis showed that the screw angle (P < 0.001) was a significant determinant of the load required to cause screw pullout. OTSP led to a decrease in pullout strength compared with a perpendicular screw in a deformable foam medium similar in density to osteoporotic bone. In patients with poor bone quality, OTSP may create a suboptimal fracture fixation construct.
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Rawlings M, Knox D, Patel M, Ackland D. A hybrid approach to mid-shaft clavicle fixation. Injury 2016; 47:893-8. [PMID: 26944179 DOI: 10.1016/j.injury.2016.01.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 01/25/2016] [Accepted: 01/31/2016] [Indexed: 02/02/2023]
Abstract
BACKGROUND The purpose of this study was to demonstrate the strength characteristics of a hybrid uni-cortical construct for clavicle fixation. The technique reported aims to combine benefits of uni-cortical fixation with stability comparable to traditional bi-cortical fixation. The approach utilises long, oblique uni-cortical screws at the distal ends of the plate acting as surrogate bi-cortical screws. Locked uni-cortical screws positioned centrally provide bending and torsion strength to the construct. This alternative hybrid uni-cortical technique does not require far cortex screw or drill penetration required in bi-cortical fixation techniques, thus avoiding potentially catastrophic vascular and or neurologic injury. The purpose of this study was to compare the mechanical behaviour of the hybrid uni-cortical construct to standard bi-cortical fixations under both torsion and bending loads. METHOD Thirty osteotomized human cadaveric clavicles were randomly allocated to three surgical fixation techniques: bi-cortical locked screw fixation, bi-cortical non-locked screw fixation and hybrid uni-cortical screw fixation. Each clavicle construct was tested non-destructively under torsional loading, and then under cantilever bending to failure. Construct bending and torsional stiffness, as well as ultimate failure strength, were measured. RESULTS There were no significant differences between uni-cortical or bi-cortical fixation constructs in either bending stiffness or ultimate bending moment (p>0.05); however, there was a trend towards greater bending stiffness in the hybrid construct. The uni-cortical hybrid fixation technique displayed a significantly lower mean torsional stiffness value when compared with the bi-cortical locked screw fixation (mean difference: 134.4 Nmm/degrees, 95% confidence interval [32.3, 236.4], p=0.007). CONCLUSION A hybrid uni-cortical approach to clavicle plate fixation that may improve screw purchase and reduce risk of intra-operative vascular damage demonstrates comparable bending strength to current bi-cortical approaches.
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Affiliation(s)
- Mathew Rawlings
- Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria 3010, Australia
| | - David Knox
- Department of Orthopaedic Surgery, Epworth Healthcare, Richmond, Victoria 3121, Australia; Centre for Limb Reconstruction, The Epworth Centre, Richmond, Victoria 3121, Australia
| | - Minoo Patel
- Department of Orthopaedic Surgery, Epworth Healthcare, Richmond, Victoria 3121, Australia; Centre for Limb Reconstruction, The Epworth Centre, Richmond, Victoria 3121, Australia; Department of Surgery, Southern Clinical School, Monash University, Clayton, Victoria 3168, Australia
| | - David Ackland
- Department of Mechanical Engineering, University of Melbourne, Parkville, Victoria 3010, Australia.
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Wähnert D, Windolf M, Brianza S, Rothstock S, Radtke R, Brighenti V, Schwieger K. A comparison of parallel and diverging screw angles in the stability of locked plate constructs. ACTA ACUST UNITED AC 2011; 93:1259-64. [PMID: 21911539 DOI: 10.1302/0301-620x.93b9.26721] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
We investigated the static and cyclical strength of parallel and angulated locking plate screws using rigid polyurethane foam (0.32 g/cm(3)) and bovine cancellous bone blocks. Custom-made stainless steel plates with two conically threaded screw holes with different angulations (parallel, 10° and 20° divergent) and 5 mm self-tapping locking screws underwent pull-out and cyclical pull and bending tests. The bovine cancellous blocks were only subjected to static pull-out testing. We also performed finite element analysis for the static pull-out test of the parallel and 20° configurations. In both the foam model and the bovine cancellous bone we found the significantly highest pull-out force for the parallel constructs. In the finite element analysis there was a 47% more damage in the 20° divergent constructs than in the parallel configuration. Under cyclical loading, the mean number of cycles to failure was significantly higher for the parallel group, followed by the 10° and 20° divergent configurations. In our laboratory setting we clearly showed the biomechanical disadvantage of a diverging locking screw angle under static and cyclical loading.
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Affiliation(s)
- D Wähnert
- University Hospital Münster, Department of Trauma Surgery, Waldeyerstrasse 1, Münster 48149, Germany.
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Biomechanical Comparison of Conventional Technique Versus Oblique Screw Placement in Plate Fixation. ACTA ACUST UNITED AC 2011; 70:E84-7. [DOI: 10.1097/ta.0b013e318214094d] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Patel PSD, Shepherd DET, Hukins DWL. The effect of screw insertion angle and thread type on the pullout strength of bone screws in normal and osteoporotic cancellous bone models. Med Eng Phys 2010; 32:822-8. [PMID: 20558097 DOI: 10.1016/j.medengphy.2010.05.005] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2009] [Revised: 05/10/2010] [Accepted: 05/12/2010] [Indexed: 11/24/2022]
Abstract
Screw fixation can be extremely difficult to achieve in osteoporotic (OP) bone because of its low strength. This study determined how pullout strength is affected by placing different bone screws at varying angles in normal and OP bone models. Pullout tests of screws placed axially, and at angles to the pullout axis (ranging from 10° to 40°), were performed in 0.09 g cm(-3), 0.16 g cm(-3) and 0.32 g cm(-3) polyurethane (PU) foam. Two different titanium alloy bone screws were used to test for any effect of thread type (i.e. cancellous or cortical) on the screw pullout strength. The cancellous screw required a significantly higher pullout force than the cortical screw (p<0.05). For both screws, pullout strength significantly increased with increasing PU foam density (p<0.05). For screws placed axially, and sometimes at 10°, the observed mechanism of failure was stripping of the internal screw threads generated within the PU foam by screw insertion. For screws inserted at 10°, 20°, 30° and 40°, the resistance to pullout force was observed to be by compression of the PU foam material above the angled screw; clinically, this suggests that compressed OP bone is stronger than unloaded OP bone.
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Affiliation(s)
- Purvi S D Patel
- School of Mechanical Engineering, University of Birmingham, Edgbaston, Birmingham B15 2TT, West Midlands, UK.
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Zehnder S, Bledsoe JG, Puryear A. The effects of screw orientation in severely osteoporotic bone: a comparison with locked plating. Clin Biomech (Bristol, Avon) 2009; 24:589-94. [PMID: 19464094 DOI: 10.1016/j.clinbiomech.2009.04.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2008] [Revised: 04/21/2009] [Accepted: 04/21/2009] [Indexed: 02/07/2023]
Abstract
BACKGROUND Techniques such as varying screw insertion angles and the use of locked plating have been shown to improve the strength of fixation in bone. The effects of these methods is less clearly understood in bone of exceedingly poor quality. METHODS Forty plate-bone constructs were assembled and divided into four groups of ten. Perpendicularly placed screws were placed in one group, convergently placed crossing screws were placed in a second group, an oblique end screw was placed in a third group, and a fourth group utilized perpendicularly placed locking screws in a locking plate. All test subjects were mounted and loaded in cantilever bending to the point of failure. Stiffness, initial load to failure, and maximal load tolerated were all analyzed. FINDINGS All four groups demonstrated evidence of failure at similar loads (21.8-26.1N). The locked group was able to tolerate significantly higher loads overall (37.3N, P=.044). All three non-locked groups demonstrated similar failure patterns and load to failure. Locking constructs demonstrated a distinctly different failure pattern. No significant differences were detected with regard to screw orientation and load to failure. The group with an oblique end screw was significantly less stiff than the other three constructs (P=.017). INTERPRETATION In a severely osteoporotic model, failure in cantilever bending at low forces will take place regardless of fixation methods used. The mechanism of failure is different in locked constructs compared to traditional constructs. The added benefit of oblique screw placement observed in healthy bone is not observed in osteoporotic bone.
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Affiliation(s)
- Scott Zehnder
- St. Louis University School of Medicine, Department of Orthopedic Surgery, 3635 Vista at Grand Blvd, St. Louis, MO 63104, USA.
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