RESUMO
In implant research, a central objective is to optimize the osseous integration of implants according to their function and scope of application. In the preclinical stage, the animal model is commonly used to study implants for in vivo host tissue response and biomechanical tests are a frequently applied method for characterization of contact phenomena. However, the individual parameters and options for both the animal model and the biomechanical test arrangements vary widely, which can negatively affect the reliability and comparability of the results. In the present method description, we focus on implants for trabecular bone replacement and outline differentiated considerations for optimizing the animal model and the biomechanical test arrangement best suited for the area of application described. In addition, our aim was to present an optimized and strict study protocol for biomechanical push-out tests and step-by-step instructions in order to achieve precise and comparable results.â¢The rabbit model and the distal femur as an implantation site are ideal for biomechanical assessment of implant osseointegration.â¢Push-out tests are recommended, in which conformity of the axis is mandatory.â¢Sequential examination periods are beneficial, e.g. after 4 weeks for osseohealing and after 12 weeks for osseoremodeling.
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Porous structure properties are known to conduct initial and long-term stability of titanium alloy implants. This study aims to assess the histomorphometric effect of a 3-D porosity in Ti-6Al-4V implants (PI) on osseointegration in comparison to solid Ti-6Al-4V implants (SI). The PI was produced in a spaceholder method and sintering and has a pore size of mean 400 µm (50 µm to 500 µm) and mimics human trabecular bone. Pairs of PI and equal sized SI as reference were bilaterally implanted at random in the lateral femoral condyle of 16 Chinchilla-Bastard rabbits. The animals were sacrificed after 4 and 12 weeks for histomorphometric analysis. The histomorphometric evaluation confirmed a successful short-term osseohealing (4 weeks) and mid-term osseoremodeling (12 weeks) for both types of implants. The total newly formed bone area was larger for PI than for SI after 4 and 12 weeks, with the intraporous bone area being accountable for the significant difference (p<0.05). A more detailed observation of bone area distribution revealed a bony accumulation in a radius of +/- 500 µm around the implant surface after remodeling. The bone-to-implant contact (BIC) increased significantly (p<0.05) from 4 to 12 weeks (PI 26.23 % to 42.68 %; SI 28.44 % to 47.47 %) for both types of implants. Due to different surface properties, however, PI had a significant (p<0.05) larger absolute osseous contact (mm) to the implant circumference compared to the SI (4 weeks: 7.46 mm vs 5.72 mm; 12 weeks: 11.57 mm vs 9.52 mm [PI vs. SI]). The regional influences (trabecular vs. cortical) on bone formation and the intraporous distribution were also presented. Conclusively, the porous structure and surface properties of PI enable a successful and regular osseointegration and enhance the bony fixation compared to solid implants under experimental conditions.
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Osso Esponjoso/fisiologia , Fêmur/fisiologia , Osseointegração/fisiologia , Próteses e Implantes , Ligas , Animais , Remodelação Óssea/fisiologia , Teste de Materiais , Porosidade , Coelhos , TitânioRESUMO
In the present study, we analyzed the histological characteristics of osseointegration of an open-porous Ti-6Al-4V material that was produced in a space holder method creating a 3-D through-pores trabecular design that mimics the inhomogeneity and size relationships of trabecular bone in macro- as well as microstructure. Pairs of cylindrical implants with a porosity of 49 % and an average pore diameter of 400 µm (PI) or equal sized solid, corundum blasted devices (SI) as reference were bilaterally implanted press fit in the lateral condyles of 16 rabbits. Histological examination was performed after 4 weeks of short-term osseohealing and 12 weeks of mid-term osseoremodeling and we summarized the criteria for sequential osseointegration. After 4 weeks, osteoid had already been largely replaced by mineralized woven bone in both types of implants but was only represented to a greater extent in the deeper pores of PI. The cortical as well as trabecular region showed regular osseohealing with excessive and spatially undirected formation of immature woven bone. A dense bone mass was found in the cortical area, while in the trabecular region the bone mass was reduced distinctly, presenting large lacuna-like recesses and a demarcating trabecular structure. The pores near the implant surface contained more mineralized woven bone than the deeper pores. After 12 weeks, the osseoremodeling was largely completed with a physiological maturation to lamellar bone. The newly formed bone mass increased for PI and SI compared to the 4-week group and osteoid was only detectable in the deeper pores. The inhomogeneous trabecular design of the pores enables an excellent ingrowth of mineralized lamellar bone after remodeling to a pore depth of 1800 µm, which proves a functional load transfer from the surrounding bone into the implant. According to the concept of osseointegration by Branemark and Albrektsson, the histological evaluation confirms a successful, superior osseointegration of the presented porous properties improving long-term implant stability. The presented study protocol allows an excellent evaluation and comparison of the sequential osseointegration from short-term osseohealing to mid-term osseoremodeling.
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Ligas , Remodelação Óssea/fisiologia , Osseointegração/fisiologia , Próteses e Implantes , Titânio , Ligas/química , Animais , Teste de Materiais , Porosidade , Coelhos , Titânio/química , Cicatrização/fisiologiaRESUMO
In rotator cuff repair, strong and reliable suturing is necessary to decrease failure rates. The biomechanics of two self-cinching stitches - the single-loop knot stitch (SLKS) and the double-loop knot stitch (DLKS) - and the modified Mason-Allen stitch (mMAS) were compared. Twenty-seven porcine infraspinatus tendons were randomized among the three stitches. Each was cyclically loaded (10-80-200 N for 50 cycles each) while the gap formation was measured. Next, ultimate load to failure was tested. The gap widths after cyclic loading were 8.72 ± 0.93 mm for the DLKS, 8.65 ± 1.33 mm for the mMAS, and 9.14 ± 0.89 mm for the SLKS, without significant differences. The DLKS showed the highest ultimate load (350.52 ± 38.54 N) compared with the mMAS (320.88 ± 53.29 N; p = 0.304) and the SLKS (290.54 ± 60.51 N; p < 0.05). The DLKS showed similar reliability and better strength compared with the mMAS, while the SLKS showed a slight but not significant decrease in performance. In our experience, the DLKS and SLKS have clinical advantages, as they are easy to perform and the self-cinching loop knot allows the surgeon to grasp degenerative tendon tissue. Initial intraoperative tightening of the suture complex (preloading) before locking is important in order to decrease postoperative elongation.
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Porosity in titanium alloy materials improves the bony integration and mechanical properties of implants. In certain areas of application such as vertebral spacers or trabecular bone replacement (e.g. wedge augmentation in prosthetics), surface structures are desirable that promote bone integration and have biomechanical properties that are resistant to intraosseous load transfers and at the same time resemble the stiffness of bone to possible reduce the risk of stress shielding. In the present study, we investigated the biomechanical push-out behavior of an open-porous Ti-6Al-4V material that was produced in a space-holder and sintering method creating a 3-D through-pores trabecular design that corresponds with the inhomogeneity and size relationships of trabecular bone. The short-term and mid-term effects of the material properties on osseointegration in a biomechanical push-out study were compared to those of to a conventional solid Ti-6Al-4V material. In order to raise the measurement accuracy we implemented a strict study protocol. Pairs of cylindrical implants with a porosity of 49% and an average pore diameter of 400 µm and equal sized solid, corundum blasted devices as reference were bilaterally implanted press fit in the lateral femoral condyles of 14 rabbits. After sacrifice at 4 and 12 weeks, a push-out test was performed while the test set-up was designed to ensure conformity of implant axes and direction of applied force. Maximum holding force, Young's modulus, and mode of failure were recorded. Results of maximum push-out force (F-max) revealed a significant material effect (p < 0.05) in favor of porous implants after 4 weeks of osseohealing (6.39 vs. 3.36 N/mm2) as well as after 12 weeks of osseoremodeling (7.58 vs. 4.99 N/mm2). Evaluation of the failure mode resulted in three different types of displacement characteristics, which revealed a different mechanism of osseous anchoring between the two types of implants and substantiate the F-max and Young's modulus results. Conclusively, the porous implant offers surface properties that significantly improve its osseous stability compared to solid material under experimental conditions. In addition, we have optimized our study protocol for biomechanical push-out tests to produce precise and comparable results.
Assuntos
Osseointegração , Titânio , Animais , Teste de Materiais , Porosidade , Próteses e Implantes , Coelhos , Propriedades de SuperfícieRESUMO
Tendon elongation after Achilles tendon (AT) repair is associated with the clinical outcome. Reliable suture techniques are essential to reduce gap formations and to allow early mobilization. Cyclic loading conditions represent the repetitive loading in rehabilitation. The aim of this study was to compare the Kessler stitch and double loop knot stitch (DLKS) in a cyclic loading program focussing on gap formation. Sixteen human cadaveric ATs were transected and sutured using either the Kessler stitch or DLKS (eight matched pairs). The suture-tendon configurations were subjected to cyclic loading and additional ultimate load to failure testing using the Zwick 1446 universal testing machine. Each AT survived cyclic loading, with a mean gap formation less than 5 mm after 1000 cycles. The mechanical properties of the Kessler stitch and DLKS were not significantly different after cyclic loading with a mean displacement of 4.57 mm (± 1.16) for the Kessler stitch and 4.85 mm (± 1.14) for the DLKS (P = .76). There were no significant differences in the ultimate load testing (P = .85). Both bioprotective techniques prevent excessive gaping in cyclic testing when tendon loading is moderate. Our data and those from literature of gap formation in cyclic and ultimate loading allow the conclusion, that early aggressive AT loading after repair (e.g. full weightbearing) overstrain simple as well as complex suture configurations. Initial intraoperative tightening of the knots (preloading) before locking is important to decrease postoperative elongation.
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Tendão do Calcâneo , Procedimentos Ortopédicos , Técnicas de Sutura , Suturas , Resistência à Tração , Tendão do Calcâneo/lesões , Tendão do Calcâneo/cirurgia , Humanos , Masculino , Suporte de CargaRESUMO
BACKGROUND: Osteolysis which leads to aseptic loosening of implants is a fundamental problem in joint replacement surgery (arthroplasty) and the leading cause for implant failure and revision surgery. Metal (CoCr) particles separated from implants by wear cause osteolysis and the failure of orthopedic implants, but the molecular mechanism is not clear. The chemokine receptor CXCR4 has been shown to play a pivotal role in periprosthetic osteolysis. The aim of this study was to determine which signal transduction pathway (PLC-DAG-PKC or MAPK/ERK) induces CXCR4 expression in osteoblast-like cells (MG63) cells. METHODS: MG63 and Jurkat cells were stimulated with different amounts of particles (107 , 106 , and 105 ) for different time periods (30 min to 24 h), in the presence and absence of specific inhibitors (chelerythrine for the PLC-DAG-PKC pathway and PD98059 for the MAPK/ERK pathway). The expression of CXCR4-specific mRNA was determined by real-time polymerase chain reaction (PCR), and the PKC activity was measured by Western Blot using an antibody specific for PKC-related phosphorylation. RESULTS: Real-time PCR data showed that CXCR4 mRNA expression in MG63 cells induced by CoCr particles was significantly diminished by the PKC-specific inhibitor chelerythrine. This effect was not observed with the MAPK/ERK inhibitor PD98059. The involvement of PKC was also confirmed by an intensified phosphorylation pattern after stimulation with CoCr particles. In Jurkat cells, none of the inhibitors exhibited any effect. CONCLUSION: The induction of CXCR4-specific mRNA expression in MG63 cells after stimulation with CoCr particles is regulated by the PLC-DAG-PKC pathway and not by the MAPK/ERK pathway. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2326-2332, 2017.
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Ligas de Cromo/efeitos adversos , Regulação da Expressão Gênica/efeitos dos fármacos , Sistema de Sinalização das MAP Quinases/efeitos dos fármacos , Próteses Articulares Metal-Metal/efeitos adversos , Osteólise , Receptores CXCR4/biossíntese , Artroplastia/efeitos adversos , Interface Osso-Implante/patologia , Linhagem Celular , Ligas de Cromo/farmacologia , Humanos , Células Jurkat , Osteoblastos/patologia , Osteólise/induzido quimicamente , Osteólise/metabolismo , Osteólise/patologiaRESUMO
In a previous failure analysis performed on femoral components of cemented total hip replacements, we determined high volumes of abraded bone cement. Here, we describe the topography of the polished surface of polymethyl methacrylate (PMMA) bone cement containing zirconia radiopacifier, analyzed by scanning electron microscopy and vertical scanning interferometry. Zirconia spikes protruded about 300nm from the PMMA matrix, with pits of former crystal deposition measuring about 400nm in depth. We deduced that the characteristically mulberry-shaped agglomerates of zirconia crystals are ground and truncated into flat surfaces and finally torn out of the PMMA matrix. Additionally, evaluation of in vitro PMMA-on-PMMA articulation confirmed that crystal agglomerations of zirconia were exposed to grain pullout, fatigue, and abrasion. In great quantities, micron-sized PMMA wear and zirconia nanoparticles accumulate in the cement-bone interface and capsular tissues, thereby contributing to osteolysis. Dissemination of nanoparticles to distant lymph nodes and organs of storage has been reported. As sufficient information is lacking, foreign body reactions to accumulated nanosized zirconia in places of long-term storage should be investigated. STATEMENT OF SIGNIFICANCE: The production of wear particles of PMMA bone cement in the interface to joint replacement devices, presents a local challenge. The presence of zirconia particles results in frustrated digestion attempts by macrophages, liberation of inflammatory mediators, and necrosis leading to aseptic inflammation and osteolyses. Attempts to minimize wear of articulating joints reduced the attention to the deterioration of cement cuffs. We therefore investigated polished surfaces of retrieved cuffs to demonstrate their morphology and to measure surface roughness. Industrially admixed agglomerates of the radiopacifier are abraded to micron and nano-meter sized particles. The dissemination of zirconia particles in the reticulo-endothelial system to storage organs is a possible burden. Research to replace the actual contrast media by non-particulate material deserves more attention.
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Artroplastia de Quadril/métodos , Cimentos Ósseos/química , Metais/química , Células-Tronco/citologia , Zircônio/química , Idoso , Idoso de 80 Anos ou mais , Meios de Contraste/química , Cristalização , Reação a Corpo Estranho , Prótese de Quadril , Humanos , Interferometria/métodos , Microscopia Eletrônica de Varredura , Nanopartículas/química , Osteólise/patologia , Tamanho da Partícula , Polimetil Metacrilato/química , Pós/química , Desenho de Prótese , Falha de Prótese , Propriedades de SuperfícieRESUMO
During the loosening cascade of cemented rough femoral stems, the destruction of the mantle and the production of cement and metal wear debris occur after the loss of constraint at the interface. Two-dimensional (2D) measurements (light microscopy based morphometry on fragments of mantles and vertical scanning interferometry of femoral stems) permitted mathematical 3D-extrapolations to estimate the wear volumes. Fragments of the cement mantles available lost volumes from 0.85 mm(3) to 494.10 mm(3) (median amount of bone cement wear = 178,426 mg). The harder metal surfaces lost between 1.459 mm(3) and 5.688 mm(3) of material (the median amount of metal wear per surface = 1.504 mg/100 mm(2)). Compared to the loss of material due to the fretting of stems, the abrasion of metal, and cement in defective cement mantles produced wear volumes sufficiently high to induce osteolysis. Though the design of the femoral stem and the handling of bone cement do not represent contemporary design and clinical practice, respectively, an extremely high number of joint replacements still in daily use may be impacted by this study because of possible predicted failures. Once the processes of fragmentation, abrasion, and osteolysis have been realized, the time until revision surgery should not be unduly prolonged.
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Artroplastia de Quadril , Cimentos Ósseos/efeitos adversos , Prótese de Quadril/efeitos adversos , Recall de Dispositivo Médico , Osteólise/patologia , Polimetil Metacrilato/efeitos adversos , Falha de Prótese , Idoso , Idoso de 80 Anos ou mais , Análise de Falha de Equipamento , Humanos , Masculino , Pessoa de Meia-Idade , Osteólise/etiologiaRESUMO
PURPOSE: In rotator cuff repair, strong and long-lasting suturing techniques that do not require additional implants are needed. This study examines the ultimate load to failure and the Young's modulus at the suture-tendon interface for a novel single-loop knot stitch and double-loop knot stitch. These values are compared to those of the modified Mason-Allen stitch. METHODS: Twenty-four infraspinatus muscles with tendons were dissected from porcine shoulders (twelve Goettingen minipigs). The preparations were randomly allocated to three groups of eight samples. Load-to-failure testing of the single-loop knot stitch, the double-loop knot stitch and the mMAS were performed using a Zwick 1446 universal testing machine (Zwick-Roell AG, Ulm, Germany). RESULTS: The highest ultimate load to failure for the three techniques occurred with the double-loop knot stitch with a median value of 382.2 N (range 291.8-454.2 N). These values were significantly higher than those of the single-loop knot stitch, which had a median value of 259.5 N (range 139.6-366.3 N) and the modified Mason-Allen stitch, which had a median value of 309.3 N (range 84.55-382.9 N). The values of the single-loop knot stitch and the modified Mason-Allen stitch did not differ significantly. Regarding the Young's modulus, no significant differences were found between the double-loop knot stitch with a median value of 496.02 N/mm² (range 400.4-572.6 N/mm²) and the modified Mason-Allen stitch with 498.5 N/mm² (range 375.5-749.2 N/mm²) with respect to the stiffness of the suture-tendon complex. The median value for the Young's modulus of the single-loop knot stitch of 392.1 N/mm² (range 285.7-510.6 N/mm²) was significantly lower than those of the double-loop knot stitch and modified Mason-Allen stitch. CONCLUSION: This in vitro animal study demonstrated that both the single-loop knot stitch and the double-loop knot stitch have excellent ultimate load-to-failure properties when used for rotator cuff repair. The introduced single-loop knot stitch and double-loop knot stitch offer an alternative to other common used stitch techniques in rotator cuff repair.
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Artroscopia/métodos , Manguito Rotador/cirurgia , Técnicas de Sutura/instrumentação , Suturas , Animais , Modelos Animais de Doenças , Desenho de Equipamento , Feminino , Lesões do Manguito Rotador , Suínos , Porco MiniaturaRESUMO
CXCR4, the chemokine receptor for CXCL12, also known as SDF-1 (stromal cell derived factor-1), has been shown to play a pivotal role in bone metastasis, inflammatory, and autoimmune conditions but has not been investigated in periprosthetic osteolysis. We co-cultured osteoblast-like cells with increasing concentrations of metallic (Co-35Ni-20Cr-10Mo and Co-28Cr-6Mo) and Co-ions simulating wear debris. Real-time polymerase chain reaction (RT-PCR) and Western blotting were used to quantify gene and protein expression of CXCR4. The expression of tumor necrosis factor-alpha (TNF-α) and the effects of AMD3100 (bicyclam) on both CXCR4 and TNF-α expression among these cells was investigated. RT-PCR showed an increase in CXCR4 mRNA (7.5-fold for MG63 and 4.0-fold for SaOs-2 cells) among cells co-cultured with metal alloy particles. Western blotting showed a time-dependent increase in protein expression of CXCR4. The attempted blockade of CXCR4 by its known competitive receptor agonist AMD3100 led to a significant inhibition TNF-α mRNA expression. Immunohistochemistry showed CXCR4 positivity among patients with failed metal-on-metal hip replacements and radiographic evidence of osteolysis. Our data collectively suggest that the CXCR4 chemokine is upregulated in a dose- and time-dependent manner in the presence of metallic wear debris.
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Metais/efeitos adversos , Próteses e Implantes/efeitos adversos , Receptores CXCR4/metabolismo , Idoso , Ligas/farmacologia , Western Blotting , Linhagem Celular , Cobalto/farmacologia , Demografia , Feminino , Regulação da Expressão Gênica/efeitos dos fármacos , Humanos , Imuno-Histoquímica , Masculino , Próteses Articulares Metal-Metal/efeitos adversos , Pessoa de Meia-Idade , Osteoblastos/metabolismo , Receptores CXCR4/genéticaRESUMO
The era of metal-on-metal (MoM) total hip arthroplasty has left the orthopaedic community with valuable insights and lessons on periprosthetic tissue reactions to metallic debris. Various terms have been used to describe the tissue reactions. Sometimes the nomenclature can be confusing. We present a review of the concepts introduced by Willert and Semlitsch in 1977, along with further developments made in the understanding of periprosthetic tissue reactions to metallic debris. We propose that periprosthetic tissue reactions be thought of as (1) gross (metallosis, necrosis, cyst formation and pseudotumour); (2) histological (macrophage-dominated, lymphocyte-dominated or mixed); and (3) molecular (expression of inflammatory mediators and cytokines such as interleukin-6 and tumor necrosis factor-alpha). Taper corrosion and modularity are discussed, along with future research directions to elucidate the antigen-presenting pathways and material-specific biomarkers which may allow early detection and intervention in a patient with adverse periprosthetic tissue reactions to metal wear debris.
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PURPOSE: To investigate the biomechanical and magnetic resonance imaging (MRI)-derived morphologic changes between single- and double-row rotator cuff repair at different time points after fixation. METHODS: Eighteen mature female sheep were randomly assigned to either a single-row treatment group using arthroscopic Mason-Allen stitches or a double-row treatment group using a combination of arthroscopic Mason-Allen and mattress stitches. Each group was analyzed at 1 of 3 survival points (6 weeks, 12 weeks, and 26 weeks). We evaluated the integrity of the cuff repair using MRI and biomechanical properties using a mechanical testing machine. RESULTS: The mean load to failure was significantly higher in the double-row group compared with the single-row group at 6 and 12 weeks (P = .018 and P = .002, respectively). At 26 weeks, the differences were not statistically significant (P = .080). However, the double-row group achieved a mean load to failure similar to that of a healthy infraspinatus tendon, whereas the single-row group reached only 70% of the load of a healthy infraspinatus tendon. No significant morphologic differences were observed based on the MRI results. CONCLUSIONS: This study confirms that in an acute repair model, double-row repair may enhance the speed of mechanical recovery of the tendon-bone complex when compared with single-row repair in the early postoperative period. CLINICAL RELEVANCE: Double-row rotator cuff repair enables higher mechanical strength that is especially sustained during the early recovery period and may therefore improve clinical outcome.
Assuntos
Imageamento por Ressonância Magnética , Lesões do Manguito Rotador , Manguito Rotador/cirurgia , Animais , Fenômenos Biomecânicos , Modelos Animais de Doenças , Feminino , Manguito Rotador/patologia , Manguito Rotador/fisiopatologia , OvinosRESUMO
Two series of cementless total hip arthroplasty with acetabular sockets of a threaded truncated cone design were compared regarding volumetric wear rates. The first series included all-polyethylene acetabular sockets of the type Endler (E-PE); in the second series, a nonmodular titanium metal-backed polyethylene (E-MB) socket with an identical outer shape to E-PE was implanted. Bearings were articulated with alumina 32-mm diameter ball heads. Ninety-five retrieved devices were examined with a modified fluid displacement method using dental self-polymerizing precision casts. The sockets had to be revised mainly because of wear-induced osteolysis: E-PE after 10.6 years on average and E-MB after 7.8 years (P = .002). Comparison with unused sockets showed mean wear rates of 63 mm(3)/y for E-PE and 120 mm(3)/y for E-MB (P = .0008). Increased contact stress and load deformation due to reduction of polyethylene thickness in E-MB compared to E-PE were identified as predominant reasons for higher wear rates.
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Acetábulo , Artroplastia de Quadril/instrumentação , Prótese de Quadril , Metais , Polietileno , Desenho de Prótese , Acetábulo/diagnóstico por imagem , Acetábulo/cirurgia , Adulto , Idoso , Óxido de Alumínio , Remoção de Dispositivo , Feminino , Articulação do Quadril/diagnóstico por imagem , Articulação do Quadril/cirurgia , Humanos , Masculino , Pessoa de Meia-Idade , Falha de Prótese , Radiografia , ReoperaçãoRESUMO
The aim of the study was to evaluate the time-zero mechanical and footprint properties of a suture-bridge technique for rotator cuff repair in an animal model. Thirty fresh-frozen sheep shoulders were randomly assigned among three investigation groups: (1) cyclic loading, (2) load-to-failure testing, and (3) tendon-bone interface contact pressure measurement. Shoulders were cyclically loaded from 10 to 180 N and displacement to gap formation of 5- and 10-mm at the repair site. Cycles to failure were determined. Additionally, the ultimate tensile strength and stiffness were verified along with the mode of failure. The average contact pressure and pressure pattern were investigated using a pressure-sensitive film system. All of the specimens resisted against 3,000 cycles and none of them reached a gap formation of 10 mm. The number of cycles to 5-mm gap formation was 2,884.5 + or - 96.8 cycles. The ultimate tensile strength was 565.8 + or - 17.8 N and stiffness was 173.7 + or - 9.9 N/mm. The entire specimen presented a unique mode of failure as it is well known in using high strength sutures by pulling them through the tendon. We observed a mean contact pressure of 1.19 + or - 0.03 MPa, applied on the footprint area. The fundamental results of our study support the use of a suture-bridge technique for optimising the conditions of the healing biology of a reconstructed rotator cuff tendon. Nevertheless, an individual estimation has to be done if using the suture-bridge technique clinically. Further investigation is necessary to evaluate the cell biological healing process in order to achieve further sufficient advancements in rotator cuff repair.
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Análise de Falha de Equipamento , Manguito Rotador/fisiologia , Manguito Rotador/cirurgia , Âncoras de Sutura , Técnicas de Sutura , Animais , Fenômenos Biomecânicos , Cadáver , Ovinos , Resistência à TraçãoRESUMO
INTRODUCTION: Intervertebral spacers are made of different materials, which can affect the postfusion magnetic imaging (MRI) scans. Susceptibility artifacts especially for metallic implants can decrease the image quality. This study aimed to determine whether magnesium as a lightweight and biocompatible metal is suitable as a biomaterial for spinal implants based on its MRI artifacting behavior. MATERIALS AND METHODS: To compare artifacting behaviors, we implanted into one porcine cadaveric spine different test spacers made of magnesium, titanium, and carbon-fiber-reinforced polymers (CFRP). All test spacers were scanned using two T1-TSE MRI sequences. The artifact dimensions were traced on all scans and statistically analyzed. RESULTS: The total artifact volume and median artifact area of the titanium spacers were statistically significantly larger than magnesium spacers (p < 0.001), while magnesium and CFRP spacers produced almost identical artifacting behaviors (p > 0.05). CONCLUSION: Our results suggest that spinal implants made with magnesium alloys will behave more like CFRP devices in MRI scans. Given its osseoconductive potential as a metal, implant alloys made with magnesium would combine the advantages to the two principal spacer materials currently used but without their limitations, at least in terms of MRI artifacting.
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Artefatos , Materiais Biocompatíveis , Imageamento por Ressonância Magnética/métodos , Próteses e Implantes , Coluna Vertebral/patologia , Animais , Carbono , Fibra de Carbono , Compostos de Magnésio , Polímeros , Suínos , TitânioRESUMO
BACKGROUND: The optimal method for rotator cuff repair of the shoulder is not yet known. The aim of this study was to compare the time-dependent biomechanical properties of the traditional open transosseous suture technique and modified Mason-Allen stitches (group 1) versus the double-loaded suture anchors technique and so-called arthroscopic Mason-Allen stitches (group 2) in rotator cuff repair. METHODS: Eighteen adult female sheep were randomized into two groups: in an open approach in which the released infraspinatus tendon was repaired with group 1, and with group 2. Animals were sacrificed at 6, 12, or 26 weeks; shoulders were harvested and magnetic resonance imaging was performed. Eight untreated contralateral shoulders served as controls. Tendons of 16 additional unpaired cadaver shoulder joints of adult female sheep were identically treated for analysis at time zero. In a biomechanical evaluation all specimens were loaded to failure at a constant displacement rate using a standard universal testing machine. The load-to-failure and stiffness of the healed bone-tendon interface were calculated. RESULTS: Magnetic resonance imaging analysis showed cuff integrity in all cases, and no evidence of foreign body reaction to the anchors. Load-to-failure and stiffness data did not indicate any significant difference between the two treatment groups, neither at 6 weeks nor at 12 or 26 weeks. However, at time zero the group 2 had a higher load-to-failure in comparison to the group 1 (P<0.010), but there was no difference for the stiffness (P<0.121). CONCLUSIONS: This in vivo study showed that, postoperatively, the group 2 technique provides superior stability and after healing would gain strength comparable to the group 1 technique.
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Desenho Assistido por Computador , Modelos Animais de Doenças , Análise de Falha de Equipamento , Modelos Biológicos , Lesões do Manguito Rotador , Manguito Rotador/cirurgia , Âncoras de Sutura , Implantes Absorvíveis , Animais , Fenômenos Biomecânicos/métodos , Simulação por Computador , Elasticidade , Desenho de Equipamento , Feminino , Ovinos , Estresse Mecânico , Resistência à TraçãoRESUMO
BACKGROUND CONTEXT: Image quality and implant detectability by conventional imaging methods are suboptimal for perioperative spinal diagnostics, primarily limited by implant-related artifacts. PURPOSE: To evaluate the imaging quality of various intervertebral spacers examined by flat-panel detector-based volumetric computed tomography (FD-VCT) versus magnetic resonance imaging (MRI). STUDY DESIGN/SETTING: A preclinical comparative study on an experimental porcine model. The study was performed at a university research facility. METHODS: Three different intervertebral spacer types (titanium, carbon fiber-reinforced polymer, cobalt-chrome-molybdenum) were implanted in a cadaveric porcine spine and then examined by MRI using T1-weighted spin echo (T1w-SE) and turbo spin echo (T1w-TSE) sequences. Comparative imaging was performed with an experimentally approved FD-VCT prototype featuring two-dimensional and three-dimensional imaging and high isotropic spatial resolution. Data analysis focused on spacer shape, implant positioning, and implant-bone interface. RESULTS: Compared with MRI, and despite the use of T1w-SE and T1w-TSE sequences, the image quality and detectability of all target characteristics were better with FD-VCT absent the usual artifacts. Using its option for implant-specific imaging, the experimental FD-VCT imager allowed reliable determination of additional variables such as dimension and volume. CONCLUSIONS: This experimental study provides initial evidence that FD-VCT produces excellently sharp, high-accuracy, artifact-free imaging quality that is superior to MRI in distinguishing key characteristics of intervertebral implants in a preclinical setting.
Assuntos
Imageamento por Ressonância Magnética , Dispositivos de Fixação Ortopédica , Coluna Vertebral/diagnóstico por imagem , Coluna Vertebral/cirurgia , Tomografia Computadorizada por Raios X , Animais , Processamento de Imagem Assistida por Computador , Imageamento Tridimensional , SuínosRESUMO
BACKGROUND CONTEXT: Interbody spacers for anterior spine fusion are made of different materials, which can affect the postfusion magnetic resonance imaging (MRI) scans. Susceptibility artifacts specially for metallic implants can decrease the image quality. PURPOSE: This study focused on the influence of determined implant parameters like shape, implant volume, and implant material in MRI artifacting with regard to solid geometrical titanium and carbon test spacers. STUDY DESIGN/SETTING: A comparative study on an in vitro spine model. The study was performed at a university research facility. METHODS: In this study we evaluated the postimplantation MRI scans of three determined cuboids and six cylinders, which were made of titanium alloy and carbon fiber reinforced polymer. MRI scans were carried out by using T1 turbo spin echo (TSE) sequences. The total artifact volume (TAV) as well as median artifact area (MAA) were calculated. Additionally the implant volume (IV)/TAV and cross-sectional area (CSA)/MAA relation were determined. Statistical analyses were calculated with the t test and Newman-Keuls test for multiple comparisons. RESULTS: Considering all test implants with an increasing implant size, the TAV and the MAA became significantly larger (p<.001) with simultaneous reduction of the IV/TAV and CSA/MAA relation. In contrast to the carbon implant group, for titanium cylinders with an implant volume equivalent to the cuboids significant differences in MRI artifacting (p<.05) could be demonstrated. CONCLUSIONS: Susceptibility artifacts were clearly affected by the implant material, shape, and implant volume. Independent of the implant material, with regard to a more advantageous IV/TAV and CSA/MAA relation, for larger implants the artifact rate was more limited to the implant's direct surroundings. On the basis of a high magnetizability for titanium implants with an equal IV, the range of implant-related susceptibility artifacts was influenced by the material as well as implant shape in favor of cylindric implants. According to the very low MRI artifact rate of carbon implants, the implant shape did not have any significant effect on the artifact behavior.
Assuntos
Artefatos , Imageamento por Ressonância Magnética , Próteses e Implantes , Animais , Carbono , Técnicas In Vitro , Disco Intervertebral/cirurgia , Fusão Vertebral/instrumentação , Coluna Vertebral , Suínos , TitânioRESUMO
The purpose of this study was to investigate how different materials affect the magnetic resonance imaging (MRI) detectability of interbody test spacers (ITS). We evaluated the post-implantation MRI scans with T1 TSE sequences for three different ITS made of titanium, carbon fibre-reinforced polymers (CFRP) and titanium-coated CFRP, respectively. The main target variables were total artefact volume (TAV) and median artefact area (MAA). Additionally, implant volume (IV)/TAV and cross section (CS)/MAA ratio were determined. The t test and Newman-Keuls test for multiple comparisons were used for statistical analysis. TAV and MAA did not differ significantly between CFRP and titanium-coated CFRP, but were approximately twice as high for the titanium ITS (p < 0.001). MRI detectability was optimum for CFRP and titanium-coated CFRP, but was limited at the implant-bone interface of the titanium ITS. The material's susceptibility and the implant's dimensions affected MRI artefacting. Based on TAV, the volume of titanium surface coating in the ITS studied has no influence on susceptibility in MRI scans with T1 TSE sequences.