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This paper examines the question;“ does permanent laser marking affect the mechanical performance of a metallic medical component?” The literature review revealed the surprising fact that very little has been presented or studied even though intuition suggests that its effect could be detrimental to a component's fatigue life. A brief investigation...
Citations
... In addition, laser marking creates microscopic grooves or notches that can act as stress concentrators leading to early initial fracturing during cyclic loading. 12 Continuing with Ti6Al4V as an example, another intrinsic property of the alloy that can result in early fracture is what is called the Bauschinger effect. 11 The crystal structure of titanium is such that when the alloy is bent without proper heat treatment, its strength in bending the opposite direction is markedly diminished. ...
... Laser marking is something that has been theoretically suggested in a limited study to change the life expectancy of devices in vivo. 12 Rod laser marking in this study clearly changed the surface morphology Metallographic image showing a cross section. White is the brittle a-phase, black is the stronger, more ductile b-phase. ...
Introduction:
What is overlooked in clinical studies are the possibilities of manufacturing and design aspects of the instrumentation that could initiate rod fracture. Although revision because of hardware fracture is a small fraction of the overall revision rates (12.1% to 13.7%), there are sufficient numbers of revision cases where hardware removed can undergo a thorough metallurgic analysis. This study is unique in that rod characteristics, such as alloy, surface markings, and fracture type, seen at fracture surfaces are considered in the analysis.
Methods:
This work was conducted under both a retrospective and prospective IRB. Patients considered for this study were between the ages of 18 and 85 years who underwent or were undergoing revision spine surgery with previous instrumentation in the cervical, thoracic, or lumbar region and evidence of at least one of the following: catastrophic hardware failure, pseudarthrosis, implant loosening, or nonfusion. Inclusion criteria were determined through radiographic and medical records review.
Results:
Fifty-six patients who had revision procedures because of different indications were included; 101 rods were removed, tested for fracture, and included in the analysis. Laser marking is significantly (P < 0.0001) associated with rod fracture. Detailed analysis showed notable surface and subsurface changes as the result of the marking, such as surface melting, cracking, and notching, creating locations to initiate a fracture. The three most informative variables to clinical rod fracture using multiple regression modeling were body mass index, presence or absence of laser mark (yes/no), and length of posterior fusion (≤2 spinal levels/>2 spinal levels). It was found that the relative risk of rod fracture is 23 times higher during 20 postoperative years than in cases with this index <0.4.
Discussion:
For a patient with a given body mass index, if they require a multilevel fixation greater than two levels and rods with laser marks are used, the risk of early rod fracture increases by 40%.
... Permanent marking in metallic components is usually performed with a laser (Fig 14a) to add information such as the manufacturer, material, lot number, model number, implant size, and whether an implant is intended for right limb or left limb reconstruction [124]. However, it is important to take into account that the location of laser marking can have detrimental effects in the fatigue life of load bearing implants [125]. Therefore, marking location and its effects on implant's mechanical properties should be considered during the implant design process and in G-4. ...
... Permanent marking in metallic components is usually performed with a laser (Fig 14a) to add information such as the manufacturer, material, lot number, model number, implant size, and whether an implant is intended for right limb or left limb reconstruction [124]. However, it is important to take into account that the location of laser marking can have detrimental effects in the fatigue life of load bearing implants [125]. Therefore, marking location and its effects on implant's mechanical properties should be considered during the implant design process and in G-4. ...
... The brittleness is elevated and lowers the fatigue resistance is reduced due to oxygen diffusion into the surface [34]. The fatigue strength is decreased up to 20% for Ti6Al7Nb through partial surface melting during laser marking of prostheses in air following the oxygen diffusion or the cracks in the remelt surface [35]. These events are restricted in case of doing the process in an inert atmosphere by Argon or other shielding gasses. ...
Laser surface treatment is an effective method to improve the surface hardness and wear resistance of titanium and its alloys. Laser remelting in the open atmosphere was performed on bare beta titanium alloy with different a duty of cycles (40-60-80-100). Considering that all the laser treatment parameters were the same, variable duty of cycle can significantly affect on surface quality and thickness of treated layer. In this work, the composition, microstructure, micro-hardness, surface morphology and tribological properties, specially coefficient friction (COF) and size distribution of wear debris (DLS) were carefully characterized and compared. The experimental results showed that laser treated samples and bare beta titanium have considerable differences in the microstructure, and surface color and morphology. Between laser treated samples, by increasing duty of cycle, mechanical behavior due to increased thickness of the treated layer is improved. Moreover, tribological properties were strongly affected by the hardness and microstructure of laser treated beta titanium samples and laser remelting led to remarkable progress in their wear resistant properties.
... Black marking with picosecond pulses Studies have shown, that small groves with a depth of at least 25 µm caused by laser marking can reduce the fatigue life of a component [6]. Therefore for the heavily loaded spindle, an ablation-free black marking process is needed. ...
Black marking as micrometer scaled binary coding applied on shafts by ultrashort pulsed lasers with high contrast and without ablation as a non-contact sensor system for combined measurement of angular position and torque.
... This limit has been clearly outlined in a recent study regarding the feasibility of the production of customized hip stem prostheses through EBM. 47 Even with reference to traditionally made components, fatigue life has proved to be critical: consider for example recent findings on the influence of permanent laser markings, [48][49][50] or catastrophic exits of peculiar geometries, 51 fatigue failure due to microstructural changes in the material produced by highfrequency electrocautery 52 or fretting corrosion, 53,54 and premature failure due to overloads produced by an inadequate bone support. 55,56 As previously mentioned, additively produced materials have shown to have generally lower fatigue strength, therefore it is not surprising that this aspect is even more critical for these components. ...
Background
Additive manufacturing technologies are being enthusiastically adopted by the orthopaedic community since they are providing new perspectives and new possibilities. First applications were finalised for educational purposes, pre-operative planning, and design of surgical guides; recent applications also encompass the production of implantable devices where 3D printing can bring substantial benefits such as customization, optimization, and manufacturing of very complex geometries. The conceptual smoothness of the whole process may lead to the idea that any medical practitioner can use a 3D printer and her/his imagination to design and produce novel products for personal or commercial use.
Aims
Outlining how the whole process presents more than one critical aspects, still demanding further research in order to allow a safe application of this technology for fully-custom design, in particular confining attention to orthopaedic/orthodontic prostheses defined as components responding mainly to a structural function.
Methods
Current knowledge of mechanical properties of additively manufactured components has been examined along with reasons why the behaviour of these components might differ from traditionally manufactured components. The structural information still missing for mechanical design is outlined.
Results
Mechanical properties of additively manufactured components are not completely known, and especially fatigue limit needs to be examined further.
Conclusion
At the present stage, with reference to load-bearing implants subjected to many loading cycles, the indication of custom-made additively manufactured medical devices should be restricted to the cases with no viable alternative.
... Nous avons identifié comme facteurs de risque de rupture : le poids > 80 kg (p = 0,002) (OR = 5,7, IC 95 % [1,[9][10][11][12][13][14][15][16][17]), l'âge < 60 ans (p = 0,02) (OR = 3,4, IC 95 % [1-6,6-9]), le sexe masculin (p = 0,01) (OR = 14,8, IC 95 % [1,3,[9][10][11]) et l'utilisation d'un pivot latéralisé (p < 0,001) (OR = 6,5, IC 95 % [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]). ...
... Les mécanismes de survenue d'une rupture d'implant fémoral ont été étudiés par Galante [5] : il s'agit d'un excès de contrainte sur une zone en tension aboutissant à une rupture en fatigue. La zone de fracture en fatigue comporte 3 régions [6] : le point d'amorce, la zone de propagation (stries parallèles en microscopie) et la zone de « fast fracture » (rupture finale). ...
... Le marquage laser, situé sur une zone supportant une très forte charge (parties antérieures et latérales du pivot [29]), constitue la zone d'amorce de la rupture en fatigue de l'implant [7,18,30]. La profondeur du marquage est également en cause : à partir de 50 m, la résistance à la fatigue est réduite de 20 % et de 50 % pour 70 [6]. Lors de la réalisation de ce marquage, la microstructure du col a pu être modifiée car la température induite peut être supérieure au point de fusion de l'alliage [28]. ...
Résumé
Introduction
La fracture du col prothétique sur un pivot non modulaire est un évènement rare en arthroplastie primaire de hanche (PTH). Des cas sporadiques ont été déclarés sur le pivot Corail™ suite à un marquage laser, mais les facteurs défavorables n’ont pas été déterminés avec précision. Aussi, nous avons mené une étude rétrospective d’une série de pivots Corail™ avec marquage laser cervical afin : de préciser le taux exact de fracture de col prothétique à dix ans ; de rechercher les facteurs favorisants ces fractures.
Hypothèse
Le marquage laser expose à un taux élevé de fracture cervicale prothétique.
Matériels et méthodes
Entre octobre 2002 et décembre 2003, 295 PTH (286 patients) ont été consécutivement implantées utilisant le pivot Corail™ avec marquage laser sur le col. Il s’agissait de 151 hommes (53 %) et 135 femmes (47 %), d’un âge moyen de 63 ans (mini : 18 ans ; maxi : 89 ans) et avec un poids moyen de 73 kg (mini : 45 kg ; maxi : 120 kg). Un pivot standard était implanté dans 240 cas (81 %) et latéralisé dans 55 cas (19 %). Le critère de jugement principal était le changement de pivot pour fracture du col prothétique.
Résultats
Au recul de 10 ans (mini : 1 ; maxi : 11), il y avait 11 perdus de vue (4 %) et 35 décès (12 %) (pivot en place). Le taux de survie globale à 10 ans était de 91 % (IC 95 % [87 %–94 %]). Seize patients (5,4 %) ont été repris pour fracture du col prothétique, six patients (2 %) pour infection ostéoarticulaire et, dans 4 cas (1,3 %), le chirurgien avait décidé de changer de façon préventive le pivot considéré comme à risque de rupture lors de la reprise de la cupule. Toutes les ruptures étaient des fractures de fatigue liées au marquage laser sur le col prothétique. Ces fractures étaient survenues à un délai moyen de 4,5 ans (mini : 1,4 ; maxi : 9,8). Les facteurs de risque favorisant la survenue de ces fractures étaient : le poids > 80 kg (p = 0,002) (OR = 5,7, IC 95 % [1,9–17]), l’âge < 60 ans (p = 0,02) (OR = 3,4, IC 95 % [1–6,6–9]), le sexe masculin (p = 0,01) (OR = 14,8, IC 95 % [1,9–113]) et l’utilisation d’un pivot latéralisé (p < 0,001) (OR = 6,5, IC 95 % [2–18]).
Conclusion
Le taux de fracture (5,4 %) était supérieur à celui rapporté dans les registres (< 1 %). Le mécanisme de rupture correspondait à un excès de contrainte sur une zone en tension aboutissant à une rupture en fatigue. Le sexe masculin, le poids élevé et le jeune âge étaient des facteurs de risque et correspondaient à ceux retrouvés dans la littérature pour les ruptures en fatigue. La localisation ainsi que la profondeur du marquage laser constituent une amorce de fracture de fatigue. Notre étude montrait que le marquage laser créait une zone de faiblesse sur le col prothétique et devait donc être interdit dans cette zone du pivot fémoral.
Niveau de preuve
Niveau IV, étude rétrospective.
... The mechanisms underlying femoral implant fracture were studied by Galante [5], and implicate excessive stress in an area under tension, inducing fatigue fracture. The fatigue region comprises 3 zones [6]: starting point, propagation region (parallel striae seen on microscopy), and final "fast fracture" zone. ...
... Laser etching, situated in a region of very high loading (anterior and lateral parts of the stem [29]), constitutes a starting point for fatigue fracture [7,18,30]. Etching depth is a factor: as of 50 m, fatigue resistance is reduced by 20%, and by 50% at 70 m [6]. The etching process may alter the microstructure of the neck, the temperature exceeding the alloy fusion threshold [28]. ...
Introduction:
Implant neck fracture involving a non-modular femoral stem is rare in primary total hip arthroplasty (THA). Occasional cases have been reported following laser etching of the Corail(tm) stem, but risk factors have not been precisely determined. We therefore performed a retrospective study on a series of Corail(tm) stems with laser neck etching, in order to: (1) determine the exact implant neck fracture rate at 10 years, and (2) identify associated risk factors.
Hypothesis:
Laser etching increases the rate of implant neck fracture.
Materials and methods:
Between October 2002 and December 2003, 295 THAs were consecutively performed using the Corail(tm) stem with laser neck etching, in 286 patients: 151 male (53%), 135 female (47%); mean age, 63 years (range, 18-89 years); mean weight, 73kg (range, 45-120kg). Stems were standard in 240 cases (81%) and lateralized in 55 (19%). The main assessment criterion was stem replacement for implant neck fracture.
Results:
At a mean 10 years' follow-up (range, 1-11 years), 11 patients were lost to follow-up (4%) and 35 had died (12%) (with stem in situ). Overall 10-year stem survival was 91% (95% CI: [87-94%]). Sixteen patients (5.4%) underwent revision surgery for implant neck fracture, 6 (2%) bone and joint infection and in 4 cases (1.3%) the stem was replaced preventively for fracture risk suspected during a revision procedure on the cup. All fractures were of the fatigue type, implicating implant neck laser etching. Mean time to fracture was 4.5 years (range, 1.4-9.8 years). Risk factors comprised: weight>80kg (P=0.002) (OR=5.7; 95% CI: 1.9-17), age<60 years (P=0.02) (OR=3.4; 95% CI: 1.2-9.6), male gender (P=0.01) (OR=14.8; 95% CI: 1.9-113) and lateralized stem (P<0.001) (OR=6.5, 95% CI: 2.3-18).
Conclusion:
The present 5.4% fracture rate was higher than in registry data (<1%). Fracture mechanisms involved excessive stress in an area under tension, leading to fatigue fracture. Male gender, high weight and young age were risk factors, as in the literature for fatigue fracture. Location and depth of laser etching induced fatigue fracture. The study demonstrated that laser etching creates an area of weakness in the implant neck and should therefore be eschewed in this part of the femoral stem.
Level of evidence:
IV, retrospective study.
... During this process, especially such sort of engraving when much heat is emitted (for example electric engraving), the surface is affected what can provide to effect of structural notch. Even laser engraving or stamping can be detrimental to a component's fatigue life [4,5]. Marking should not be made on highly stressed areas, near edges or on sensitive seal surfaces. ...
In this paper dynamic properties of low-alloy boron steels – Hardox 500, B27 and HTK 900H in delivered state (after hardening and tempering) are considered. Charpy V-notch (CVN) test results in connection with fractography in the ductile-to-brittle transition temperature region were analyzed. Obtained from CVN test the impact transition curve, not always predicts properly a behavior of materials in conditions of dynamic loading. So an analyze of character of fracture helps to evaluate the real behavior of materials. Tested samples were cut out longitudinally in relation to cold work direction. The results of CVN test for selected steels, in temperatures: −40°C, −20°C, 0°C and +20°C are presented. Regarding ductile-to-brittle transition temperature, there is a significant difference taking into account values of Charpy V energy absorbed and a character of fracture.
... During this process, especially such sort of engraving when much heat is emitted (for example electric engraving), the surface is affected what can provide to effect of structural notch. Even laser engraving or stamping can be detrimental to a component's fatigue life [4,5]. Marking should not be made on highly stressed areas, near edges or on sensitive seal surfaces. ...
The quality of the surface of cyclically loaded components is very important. Many observations confirm that the root cause of the micro cracks (causing the fatigue fracture) are primarily a surface's defects appearing during production process. These surface defects can be also caused by engraving processes used to perform identification marks. This paper presents the failure analysis of broken blade of the cutter Ku 500VX. The blade was subject of standard metallographic examination, hardness measurements, fractography analysis and metallographic studies using stereoscopic, light and scanning electron microscopes. The damage of the blade was caused by changes of the structure (formation of the brittle micro dendritic structure) that occurred during manual electric engraving process when the material was heated till its melting point. As a result the stresses occurred in surface what provided to micro cracking and to propagate the fatigue fracture. The origin of this fatigue fracture was in the place where the inscription was made.KeywordsMetallographic studiesFatigue fractureEngravingHigh speed steel
