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1.
BMC Musculoskelet Disord ; 24(1): 65, 2023 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-36694156

RESUMO

BACKGROUND: Correctly identifying patients at risk of femoral fracture due to metastatic bone disease remains a clinical challenge. Mirels criteria remains the most widely referenced method with the advantage of being easily calculated but it suffers from poor specificity. The purpose of this study was to develop and evaluate a modified Mirels scoring system through scoring modification of the original Mirels location component within the proximal femur. METHODS: Computational (finite element) experiments were performed to quantify strength reduction in the proximal femur caused by simulated lytic lesions at defined locations. Virtual spherical defects representing lytic lesions were placed at 32 defined locations based on axial (4 axial positions: neck, intertrochanteric, subtrochanteric or diaphyseal) and circumferential (8 circumferential: 45-degree intervals) positions. Finite element meshes were created, material property assignment was based on CT mineral density, and femoral head/greater trochanter loading consistent with stair ascent was applied. The strength of each femur with a simulated lesion divided by the strength of the intact femur was used to calculate the Location-Based Strength Fraction (LBSF). A modified Mirels location score was next defined for each of the 32 lesion locations with an assignment of 1 (LBSF > 75%), 2 (LBSF: 51-75%), and 3 (LBSF: 0-50%). To test the new scoring system, data from 48 patients with metastatic disease to the femur, previously enrolled in a Musculoskeletal Tumor Society (MSTS) cross-sectional study was used. The lesion location was identified for each case based on axial and circumferential location from the CT images and assigned an original (2 or 3) and modified (1,2, or 3) Mirels location score. The total score for each was then calculated. Eight patients had a fracture of the femur and 40 did not over a 4-month follow-up period. Logistic regression and decision curve analysis were used to explore relationships between clinical outcome (Fracture/No Fracture) and the two Mirels scoring methods. RESULTS: The location-based strength fraction (LBSF) was lowest for lesions in the subtrochanteric and diaphyseal regions on the lateral side of the femur; lesions in these regions would be at greatest risk of fracture. Neck lesions located at the anterior and antero-medial positions were at the lowest risk of fracture. When grouped, neck lesions had the highest LBSF (83%), followed by intertrochanteric (72%), with subtrochanteric (50%) and diaphyseal lesions (49%) having the lowest LBSF. There was a significant difference (p < 0.0001) in LBSF between each axial location, except subtrochanteric and diaphyseal which were not different from each other (p = 0.96). The area under the receiver operator characteristic (ROC) curve using logistic regression was greatest for modified Mirels Score using site specific location of the lesion (Modified Mirels-ss, AUC = 0.950), followed by a modified Mirels Score using axial location of lesion (Modified Mirels-ax, AUC = 0.941). Both were an improvement over the original Mirels score (AUC = 0.853). Decision curve analysis was used to quantify the relative risks of identifying patients that would fracture (TP, true positives) and those erroneously predicted to fracture (FP, false positives) for the original and modified Mirels scoring systems. The net benefit of the scoring system weighed the benefits (TP) and harms (FP) on the same scale. At a threshold probability of fracture of 10%, use of the modified Mirels scoring reduced the number of false positives by 17-20% compared to Mirels scoring. CONCLUSIONS: A modified Mirels scoring system, informed by detailed analysis of the influence of lesion location, improved the ability to predict impending pathological fractures of the proximal femur for patients with metastatic bone disease. Decision curve analysis is a useful tool to weigh costs and benefits concerning fracture risk and could be combined with other patient/clinical factors that contribute to clinical decision making.


Assuntos
Doenças Ósseas , Fraturas do Fêmur , Neoplasias , Humanos , Estudos Transversais , Fêmur/diagnóstico por imagem , Fêmur/patologia , Fraturas do Fêmur/diagnóstico por imagem , Fraturas do Fêmur/etiologia , Fraturas do Fêmur/patologia , Doenças Ósseas/patologia , Análise de Elementos Finitos
2.
J Arthroplasty ; 32(7): 2289-2300, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28285038

RESUMO

BACKGROUND: Loss of mechanical interlock between cement and bone with in vivo service has been recently quantified for functioning, nonrevised, cemented total knee arthroplasties (TKAs). The cause of interlocking trabecular resorption is not known. The goal of this study is to quantify the distribution of PE debris at the cement-bone interface and determine if polyethylene (PE) debris is locally associated with loss of interlock. METHODS: Fresh, nonrevised, postmortem-retrieved TKAs (n = 8) were obtained en bloc. Laboratory-prepared constructs (n = 2) served as negative controls. The intact cement-bone interface of each proximal tibia was embedded in Spurr's resin, sectioned, and imaged under polarized light to identify birefringent PE particles. PE wear particle number density was quantified at the cement-bone interface and distal to the interface, and then compared with local loss of cement-bone interlock. RESULTS: The average PE particle number density for postmortem-retrieved TKAs ranged from 8.6 (1.3) to 24.9 (3.1) particles/mm2 (standard error) but was weakly correlated with years in service. The average particle number density was twice as high as distal (>5mm) to the interface compared to at the interface. The local loss of interlock at the interface was not related to the presence, absence, or particle density of PE. CONCLUSION: PE debris can migrate extensively along the cement-bone interface of well-fixed tibial components. However, the amount of local bone loss at the cement-bone interface was not correlated with the amount of PE debris at the interface, suggesting that the observed loss of trabecular interlock in these well-fixed TKAs may be due to alternative factors.


Assuntos
Artroplastia do Joelho/efeitos adversos , Interface Osso-Implante , Polietileno , Falha de Prótese , Tíbia/cirurgia , Adulto , Idoso , Idoso de 80 Anos ou mais , Cimentos Ósseos , Reabsorção Óssea , Feminino , Humanos , Joelho/patologia , Masculino , Pessoa de Meia-Idade , Próteses e Implantes
3.
Calcif Tissue Int ; 98(6): 619-30, 2016 06.
Artigo em Inglês | MEDLINE | ID: mdl-26847434

RESUMO

Radiation therapy for soft tissue sarcoma or tumor metastases is frequently associated with damage to the underlying bone. Using a mouse model of limited field hindlimb irradiation, we assessed the ability of parathyroid hormone (1-34) fragment (PTH) delivery to prevent radiation-associated bone damage, including loss of mechanical strength, trabecular architecture, cortical bone volume, and mineral density. Female BALB/cJ mice received four consecutive doses of 5 Gy to a single hindlimb, accompanied by daily injections of either PTH or saline (vehicle) for 8 weeks, and were followed for 26 weeks. Treatment with PTH maintained the mechanical strength of irradiated femurs in axial compression for the first eight weeks of the study, and the apparent strength of irradiated femurs in PTH-treated mice was greater than that of naïve bones during this time. PTH similarly protected against radiation-accelerated resorption of trabecular bone and transient decrease in mid-diaphyseal cortical bone volume, although this benefit was maintained only for the duration of PTH delivery. Overall, PTH conferred protection against radiation-induced fragility and morphologic changes by increasing the quantity of bone, but only during the period of administration. Following cessation of PTH delivery, bone strength and trabecular volume fraction rapidly decreased. These data suggest that PTH does not negate the longer-term potential for osteoclastic bone resorption, and therefore, finite-duration treatment with PTH alone may not be sufficient to prevent late onset radiotherapy-induced bone fragility.


Assuntos
Densidade Óssea/efeitos dos fármacos , Osso e Ossos/efeitos dos fármacos , Osso e Ossos/efeitos da radiação , Hormônio Paratireóideo/farmacologia , Lesões Experimentais por Radiação/prevenção & controle , Animais , Modelos Animais de Doenças , Feminino , Fêmur/efeitos dos fármacos , Fêmur/efeitos da radiação , Camundongos , Camundongos Endogâmicos BALB C , Microtomografia por Raio-X
4.
Clin Orthop Relat Res ; 472(1): 304-13, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23975251

RESUMO

BACKGROUND: Aseptic loosening continues to be a short- and long-term complication for patients with cemented TKAs. Most studies to this point have evaluated tibial component fixation via radiographic changes at the implant-bone interface and quantification of component migration; direct assessment of morphologic features of the interface from functioning TKAs may provide new information regarding how TKAs function and are fixed to bone. QUESTIONS/PURPOSES: In a postmortem retrieval study, we asked: (1) What are the morphologic features at the cement-trabecular bone interface in retrieved tibial components? (2) Do constructs with greater time in service have less cement-trabecular bone interlock? (3) Do constructs with more estimated initial interlock sustain more interlock with in vivo service? METHODS: Fourteen postmortem retrieved tibial components with time in service from 0 to 20 years were sectioned and imaged at high resolution, and the current contact fraction, estimated initial interdigitation depth, current interdigitation depth, and loss of interdigitation depth were quantified at the cement-bone interface. Estimated initial interdigitation depth was calculated from the initial mold shape of the cement mantle that forms around the individual trabeculae at the time of surgery. Loss of interdigitation depth was the difference between the initial and current interdigitation depth. RESULTS: There was resorption of trabeculae that initially interlocked with the cement in the postmortem retrievals as evidenced by the differences between current interdigitation and the estimated original interdigitation. The current contact fraction (r(2) = 0.54; p = 0.0027) and current interdigitation depth (r(2) = 0.33; p = 0.033) were less for constructs with longer time in service. The current contact fraction for implants with 10 or more years in service (6.2%; 95% CI, 4.7%-7.7%) was much less than implants with less than 10 years in service (22.9%; 95% CI, 8.9%-37%). Similarly, the current interdigitation depth for implants with 10 or more years in service (0.4 mm; 95% CI, 0.27-0.53 mm) was much less than implants with less than 10 years in service (1.13 mm; 95% CI, 0.48-1.78 mm). The loss of interdigitation depth had a strong positive relationship with time in service (r(2) = 0.74; p < 0.001). Using a two-parameter regression model, constructs with more initial interdigitation depth had greater current interdigitation depth (p = 0.011), but constructs with more time in service also had less current interdigitation depth (p = 0.008). CONCLUSIONS: The cement-trabecular bone interlock obtained initially appears to diminish with time with in vivo service by resorption of the trabeculae in the cement interlock region. CLINICAL RELEVANCE: Our study supports the surgical concept of obtaining sufficient initial cement interlock (approximately 3 mm), with the acknowledgment that there will be loss of interlock with time with in vivo service.


Assuntos
Artroplastia do Joelho , Prótese do Joelho , Falha de Prótese , Tíbia/cirurgia , Idoso , Idoso de 80 Anos ou mais , Cimentos Ósseos , Cimentação , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Desenho de Prótese
5.
J Arthroplasty ; 29(9): 1863-70, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24845717

RESUMO

Aseptic loosening of total knee arthroplasty (TKA) components is the foremost cause of implant failure in the long term. While tibial component loosening is of primary concern, femoral loosening may become a clinical problem due to younger, more active patients seeking TKA, and also high-flexion designs. In this study, we analyzed the fixation for 19 non-revised, postmortem retrieved, femoral components of TKA with time in service ranging from 1 to 22 years. We found that the average total contact fraction for cemented components was 9.5% and had a power law response (decrease) with years in service. The average initial interdigitation depth was 0.7mm, and the average current interdigitation depth was 0.13mm. Loss of interdigitation was 81%. Over all, minimal fixation seems necessary for long-term success of TKA femoral components.


Assuntos
Artroplastia do Joelho/efeitos adversos , Artroplastia do Joelho/métodos , Fêmur/cirurgia , Prótese do Joelho/efeitos adversos , Osseointegração , Falha de Prótese/etiologia , Idoso , Idoso de 80 Anos ou mais , Cimentos Ósseos/uso terapêutico , Cadáver , Feminino , Humanos , Masculino , Metais , Pessoa de Meia-Idade , Desenho de Prótese , Amplitude de Movimento Articular , Tíbia/cirurgia
6.
J Orthop Res ; 41(1): 94-103, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-35332943

RESUMO

The mechano-biologic environment associated with aseptic loosening of cemented joint replacements is not fully understood. The goal of this study was to use a preclinical rat knee arthroplasty model to explore the changes in cement-bone morphology and micromotion that occur with in vivo service. Narrow gaps between cement and bone under the tibial tray were present at early time points, and with even small magnitude micromotion, resulted in large micromotion-to-gap width ratios. These data were then used to develop models of fluid flow in the cement-bone gaps to estimate potential for high fluid shear stress (FSS). Modeling results revealed supraphysiologic (>4 Pa) FSS were possible, particularly for cases in which eccentric loading applied to the implant and if the fluid in the gap consisted of marrow or synovial fluid. The early, high FSS environment, could cause fluid-induced periprosthetic osteolysis locally, resulting in progressive loss of cement-bone fixation.


Assuntos
Ratos , Animais
7.
J Mater Sci Mater Med ; 23(8): 2023-35, 2012 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-22678039

RESUMO

In finite element analysis (FEA) models of cemented hip reconstructions, it is crucial to include the cement-bone interface mechanics. Recently, a micromechanical cohesive model was generated which reproduces the behavior of the cement-bone interface. The goal was to investigate whether this cohesive model was directly applicable on a macro level. From transverse sections of retrieved cemented hip reconstructions, two FEA-models were generated. The cement-bone interface was modeled with cohesive elements. A torque was applied and the cement-bone interface micromotions, global stiffness and stem translation were monitored. A sensitivity analysis was performed to investigate whether the cohesive model could be improved. All results were compared with experimental findings. That the original cohesive model resulted in a too compliant macromechanical response; the motions were too large and the global stiffness too small. When the cohesive model was modified, the match with the experimental response improved considerably.


Assuntos
Cimentos Ósseos/química , Articulação do Quadril/patologia , Articulação do Quadril/fisiopatologia , Prótese de Quadril , Modelos Biológicos , Modelos Químicos , Idoso , Idoso de 80 Anos ou mais , Cimentos Ósseos/análise , Cadáver , Simulação por Computador , Feminino , Análise de Elementos Finitos , Dureza , Articulação do Quadril/cirurgia , Humanos , Masculino , Propriedades de Superfície , Resistência à Tração
8.
J Arthroplasty ; 27(2): 238-245.e1, 2012 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-21723696

RESUMO

Axial torsional loads representative of gait and stair climbing conditions were applied to transverse sections of 8 uncemented postmortem retrievals and a high-resolution imaging system with digital image correlation was used to measure local micromotion along the bone-implant interface. For 7 components that were radiographically stable, there was limited micromotion for gait loading (1.42 ± 1.33 µm) that increased significantly (P = .0032) for stair climb loading (7.32 ± 9.96 µm). A radiographically loose component had motions on the order of 2.3 mm with gait loading. There was a strong inverse relationship between the amount of bone-implant contact (contact fraction) (P = .001) and micromotion. The uncemented components had greater contact fraction (41.8% ± 14.4% vs 11.5% ± 10.2%, P = .0033) and less median micromotion (0.81 ± 0.79 µm vs 28.8 ± 51.1 µm) compared to a previously reported study of cemented retrievals.


Assuntos
Artroplastia de Quadril/instrumentação , Fêmur/cirurgia , Prótese de Quadril , Movimento (Física) , Desenho de Prótese , Autopsia , Fenômenos Biomecânicos , Remoção de Dispositivo , Fêmur/patologia , Marcha , Humanos , Modelos Biológicos , Análise de Regressão , Suporte de Carga
9.
J Orthop Res ; 40(12): 2843-2855, 2022 12.
Artigo em Inglês | MEDLINE | ID: mdl-35266584

RESUMO

Postradiotherapy bone fragility fractures are a frequent late-onset complication in cancer survivors. There is a critical need to develop preventative interventions, and the use of Food and Drug Administration-approved drugs remains an attractive option. Prior data from our lab and others have shown that parathyroid hormone [1-34] mitigates radiotherapy-induced bone loss, but only for the duration of drug delivery. Utilizing a murine hindlimb radiotherapy model, we investigated whether orchestrated delivery of single-dose zoledronic acid could extend these anabolic benefits after cessation of parathyroid hormone delivery. We then explored the potential use of parathyroid hormone as a bone marrow radioprotectant. While the addition of zoledronic acid to parathyroid hormone increased irradiated bone mass, there was no increase in femur bending strength. In this model, the parathyroid hormone was not effective as a marrow radioprotectant, although this could be due to the short course of parathyroid hormone treatment. Marrow repopulation kinetics differed from those in total body irradiation, with hematopoietic stem cell repopulation occurring relatively early at four weeks postirradiation. Furthermore, we found radiation induced a loss of marrow stromal cells and an increase in inflammatory monocytes. Statement of Clinical Significance: Staged delivery of parathyroid hormone and zoledronic acid shows promise as an off-the-shelf intervention to mitigate post-radiotherapy bone damage in cancer patients, but parathyroid hormone is unlikely to function as a broad-spectrum marrow radioprotectant.


Assuntos
Conservadores da Densidade Óssea , Doenças Ósseas Metabólicas , Humanos , Camundongos , Animais , Ácido Zoledrônico/farmacologia , Medula Óssea , Conservadores da Densidade Óssea/farmacologia , Hormônio Paratireóideo , Densidade Óssea , Doenças Ósseas Metabólicas/tratamento farmacológico
10.
Vet Comp Orthop Traumatol ; 35(1): 1-9, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34547789

RESUMO

OBJECTIVE: The aim of this study was to evaluate the effect of stem positioning on the biomechanical performance of a novel, collared, short-stem total hip implant under compression and torsion ex vivo. STUDY DESIGN: Six canine cadaveric femurs were implanted with a collared short-stem femoral implant. Canal flare index (CFI), stem angle, absolute and relative cut heights and relative size were measured radiographically and used as independent variables. Biomechanical performance of the construct was evaluated using physiologic loading (loading) and supraphysiologic loading (failure) protocols. RESULTS: During loading protocols, compressive stiffness was influenced by absolute cut height (p = 0.018). During failure protocols, peak torque was influenced by CFI (p = 0.004) and craniocaudal relative size (p = 0.005). Peak load and torsional stiffness were not impacted by any of the radiographic variables (p > 0.05). Three of six femurs developed longitudinal fractures originating at the medial calcar at the time of failure. CONCLUSION: The biomechanical performance of the collared short-stem implant was positively impacted by preserving more of the femoral neck, having a higher CFI and using a smaller implant size relative to the femoral neck isthmus.


Assuntos
Artroplastia de Quadril , Prótese de Quadril , Animais , Artroplastia de Quadril/veterinária , Fenômenos Biomecânicos , Cães , Fêmur/diagnóstico por imagem , Fêmur/cirurgia , Colo do Fêmur , Prótese de Quadril/veterinária , Desenho de Prótese/veterinária , Torque
11.
Adv Orthop ; 2021: 5591715, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34221514

RESUMO

One of the key roles of an orthopedic surgeon treating metastatic bone disease (MBD) is fracture risk prediction. Current widely used impending fracture risk tools such as Mirels scoring lack specificity. Two newer methods of fracture risk prediction, CT-based structural rigidity analysis (CTRA) and finite element analysis (FEA), have each been shown to be more accurate than Mirels. This case series illustrates comparative Mirels, CTRA, and FEA for 8 femurs in 7 subjects. These cases were selected from a much larger data set to portray examples of true positives, true negatives, false positives, and false negatives as defined by CTRA relative to the fracture outcome. Case illustrations demonstrate comparative Mirels and FEA. This series illustrates the use, efficacy, and limitations of these tools. As all current tools have limitations, further work is needed in refining and developing fracture risk prediction.

12.
J Orthop Res ; 39(4): 750-760, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-32965711

RESUMO

Post-radiotherapy (RTx) bone fragility fractures are a late-onset complication occurring in bone within or underlying the radiation field. These fractures are difficult to predict, as patients do not present with local osteopenia. Using a murine hindlimb RTx model, we previously documented decreased mineralized bone strength and fracture toughness, but alterations in material properties of the organic bone matrix are largely unknown. In this study, 4 days of fractionated hindlimb irradiation (4 × 5 Gy) or Sham irradiation was administered in a mouse model (BALB/cJ, end points: 0, 4, 8, and 12 weeks, n = 15/group/end point). Following demineralization, the viscoelastic stress relaxation, and monotonic tensile mechanical properties of tibiae were determined. Irradiated tibiae demonstrated an immediate (day after last radiation fraction) and sustained (4, 8, 12 weeks) increase in stress relaxation compared to the Sham group, with a 4.4% decrease in equilibrium stress (p < .017). While tensile strength was not different between groups, irradiated tibiae had a lower elastic modulus (-5%, p = .027) and energy to failure (-12.2%, p = .012) with monotonic loading. Gel electrophoresis showed that therapeutic irradiation (4 × 5 Gy) does not result in collagen fragmentation, while irradiation at a common sterilization dose (25 kGy) extensively fragmented collagen. These results suggest that altered collagen mechanical behavior has a role in postirradiation bone fragility, but this can occur without detectable collagen fragmentation. Statement of Clinical Significance: Therapeutic irradiation alters bone organic matrix mechanics and which contribute to diminished fatigue strength, but this does not occur via collagen fragmentation.


Assuntos
Doenças Ósseas Metabólicas/diagnóstico por imagem , Doenças Ósseas Metabólicas/radioterapia , Radioterapia/efeitos adversos , Tíbia/efeitos da radiação , Animais , Densidade Óssea , Colágeno/química , Elasticidade , Feminino , Análise de Elementos Finitos , Fraturas Ósseas/diagnóstico por imagem , Camundongos , Camundongos Endogâmicos BALB C , Estresse Mecânico , Resistência à Tração , Tíbia/diagnóstico por imagem , Viscosidade , Microtomografia por Raio-X
13.
J Orthop Res ; 39(11): 2353-2362, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-33382095

RESUMO

Aseptic loosening of total knee arthroplasty continues to be a challenging clinical problem. The progression of the loosening process, from the initial well-fixed component, is not fully understood. In this study, loss of fixation of cemented hemiarthroplasty was explored using 9-month-old Sprague-Dawley rats with 0, 2, 6, 12, 26 week end points. Morphological and cellular changes of cement-bone fixation were determined for regions directly below the tibial tray (epiphysis) and distal to the tray (metaphysis). Loss of fixation, with a progressive increase in cement-bone gap volume was found in the epiphysis (0.162 mm3 /week), but did not progress appreciably in the metaphysis (0.007 mm3 /week). In the epiphysis, there was an early and sustained elevation of osteoclasts adjacent to the cement border and development of a fibrous tissue layer between the cement and bone. There was early formation of bone around the cement in the metaphysis, resulting in a condensed bone layer without osteoclastic bone resorption or development of a fibrous tissue layer. Implant positioning was also an important factor in the cement-bone gap formation, with greater gap formation for implants that were placed medially on the tibial articular surface. Loss of fixation in the rat model mimicked patterns found in human arthroplasty where cement-bone gaps initiate under the tibial tray, at the periphery of the implant. This preclinical model could be used to study early biological response to cemented fixation and associated contributions of mechanical instability, component alignment, and periprosthetic inflammation.


Assuntos
Artroplastia do Joelho , Reabsorção Óssea , Prótese do Joelho , Animais , Artroplastia do Joelho/métodos , Cimentos Ósseos , Falha de Prótese , Ratos , Ratos Sprague-Dawley , Tíbia/cirurgia
14.
Calcif Tissue Int ; 87(3): 263-72, 2010 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-20563797

RESUMO

Many patients with symptomatic bone metastases receive radiation therapy, even though radiation is known to have potential adverse effects on bone. We hypothesized that the concurrent use of a bisphosphonate drug (zoledronic acid, ZA) or a combination of ZA plus an anabolic agent (parathyroid hormone, PTH) would lead to improvements in the microarchitecture and mechanical properties of irradiated bone. Human breast cancer cells were injected into the distal femur of 56 female nude mice, which were then divided into four groups: no treatment (0 Gy), radiation administered 4 weeks postinjection (20 Gy), radiation plus ZA (12.5 microg/kg weekly from weeks 4 to 12) (20 Gy + ZA), and radiation followed by ZA (25 microg/kg weekly from weeks 4 to 8) and PTH(1-34) (100 microg microg/kg daily from weeks 8 to 12) (20 Gy + ZA + PTH). Left limbs served as normal control bones. Bone loss over the 12-week study was tracked with serial radiography and bone densitometry. At the end of the study, micro-computed tomography and mechanical testing were used to quantify bone microarchitecture and bone strength. Radiation alone failed to prevent tumor-induced decreases in bone mineral density (BMD), trabecular bone volume, and bone strength. Treatment with 20 Gy + ZA or 20 Gy + ZA + PTH as adjuncts to radiation was effective at preserving trabecular bone architecture and bone strength at normal levels. ZA reduced the risk of mechanical fragility following irradiation of a lytic bone lesion. Supplemental use of PTH did not result in further increases in bone strength but was associated with significant increases in BMD and bone mass, suggesting that it may be beneficial in enhancing bone architecture following radiation therapy.


Assuntos
Anabolizantes/administração & dosagem , Conservadores da Densidade Óssea/administração & dosagem , Carcinoma/radioterapia , Difosfonatos/administração & dosagem , Neoplasias Femorais/radioterapia , Imidazóis/administração & dosagem , Osteólise/prevenção & controle , Hormônio Paratireóideo/administração & dosagem , Animais , Densidade Óssea/efeitos dos fármacos , Osso e Ossos , Carcinoma/patologia , Quimioterapia Combinada , Feminino , Neoplasias Femorais/patologia , Camundongos , Camundongos Nus , Osteólise/patologia , Ácido Zoledrônico
15.
J Mater Sci Mater Med ; 21(4): 1385-92, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19946736

RESUMO

The importance of the conditions at the stem-cement interface in cemented total joint replacements (THRs) with regard to the in vivo longevity of the implant is well recognized. In the present study, we used a simplified model of one part of a cemented THR (alloy rectangular beam bonded to rectangular cement plate) to study the influence of surface finish of the alloy beam (stem) on two measures of the evolution of random damage at the alloy beam-cement plate interface (stem-cement interface), under quasi-static direct shear load. Three surface finishes of the beams were used: satin-finish, grit-blasted, and plasma-sprayed. The random damage events were monitored from the emitted acoustic signals, with the two measures computed from these signals being the intensity of random damage events (IRDE) and the mean damage event energy (MDEE). Large number of random damage events (higher values of IRDE and low value of MDEE) occurred with grit blasted specimens, suggesting a high probability for the generation of debris particles at the interface. These findings, in conjunction with details on the size and shape of the debris particles, obtained using scanning electron microscopy, lead to the suggestion that satin-finish stems are desirable for use in cemented THRs.


Assuntos
Artroplastia de Quadril , Cimentos Ósseos/efeitos adversos , Nanopartículas Metálicas/efeitos adversos , Nanopartículas Metálicas/análise , Falha de Prótese , Resíduos/efeitos adversos , Artroplastia de Quadril/efeitos adversos , Artroplastia de Quadril/reabilitação , Fenômenos Biomecânicos , Cimentos Ósseos/química , Cimentação/efeitos adversos , Análise de Falha de Equipamento , Fricção/fisiologia , Microscopia Eletrônica de Varredura , Modelos Biológicos , Tamanho da Partícula , Porosidade , Fatores de Risco , Resistência ao Cisalhamento , Propriedades de Superfície
16.
J Mater Sci Mater Med ; 21(11): 2915-22, 2010 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-20857320

RESUMO

The failure of brittle and quasi-brittle polymers can be attributed to a multitude of random microscopic damage modes, such as fibril breakage, crazing, and microfracture. As the load increases, new damage modes appear, and existing ones can transition into others. In the example polymer used in this study--a commercially available acrylic bone cement--these modes, as revealed by scanning electron microscopy of fracture surfaces, include nucleation of voids, cracking, and local detachment of the beads from the matrix. Here, we made acoustic measurements of the randomly generated microscopic events (RGME) that occurred in the material under pure tension and under three-point bending, and characterized the severity of the damage by the entropy (s) of the probability distribution of the observed acoustic signal amplitudes. We correlated s with the applied stress (σ) by establishing an empirical s-σ relationship, which quantifies the activities of RGME under Mode I stress. It reveals the state of random damage modes: when ds/dσ > 0, the number of damage modes present increases with increasing stress, whereas it decreases when ds/dσ < 0. When ds/dσ ≈ 0, no new random damage modes occur. In the s-σ curve, there exists a transition zone, with the stress at the "knee point" in this zone (center of the zone) corresponding to ~30 and ~35% of the cement's tensile and bending strengths, respectively. This finding explains the effects of RGME on material fatigue performance and may be used to approximate fatigue limit.


Assuntos
Teste de Materiais , Polimetil Metacrilato/análise , Estresse Mecânico , Acústica , Entropia , Fraturas Ósseas/terapia , Testes de Dureza , Microscopia Eletrônica de Varredura , Modelos Estatísticos , Polimetil Metacrilato/química , Polimetil Metacrilato/uso terapêutico , Distribuição Aleatória , Propriedades de Superfície , Resistência à Tração
17.
Acta Orthop ; 81(3): 308-17, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20367421

RESUMO

BACKGROUND AND PURPOSE: Despite the longstanding use of micromotion as a measure of implant stability, direct measurement of the micromechanics of implant/bone interfaces from en bloc human retrievals has not been performed. The purpose of this study was to determine the stem-cement and cement-bone micromechanics of functionally loaded, en-bloc retrieved, cemented femoral hip components. METHODS: 11 fresh frozen proximal femurs with cemented implants were retrieved at autopsy. Specimens were sectioned transversely into 10-mm slabs and fixed to a loading device where functional torsional loads were applied to the stem. A digital image correlation technique was used to document micromotions at stem-cement and cement-bone interfaces during loading. RESULTS: There was a wide range of responses with stem-cement micromotions ranging from 0.0006 mm to 0.83 mm (mean 0.17 mm, SD 0.29) and cement-bone micromotions ranging from 0.0022 mm to 0.73 mm (mean 0.092 mm, SD 0.22). There was a strong (linear-log) inverse correlation between apposition fraction and micromotion at the stem-cement interface (r(2) = 0.71, p < 0.001). There was a strong inverse log-log correlation between apposition fraction at the cement-bone interface and micromotion (r(2) = 0.85, p < 0.001). Components that were radiographically well-fixed had a relatively narrow range of micromotions at the stem-cement (0.0006-0.057 mm) and cement-bone (0.0022-0.029 mm) interfaces. INTERPRETATION: Minimizing gaps at the stem-cement interface and encouraging bony apposition at the cement-bone interface would be clinically desirable. The cement-bone interface does not act as a bonded interface in actual use, even in radiographically well-fixed components. Rather, the interface is quite compliant, with sliding and opening motions between the cement and bone surfaces.


Assuntos
Artroplastia de Quadril , Fêmur , Idoso , Idoso de 80 Anos ou mais , Artroplastia de Quadril/efeitos adversos , Artroplastia de Quadril/métodos , Cimentos Ósseos , Cimentação , Feminino , Fêmur/patologia , Fêmur/fisiologia , Fêmur/cirurgia , Prótese de Quadril , Humanos , Masculino , Falha de Prótese , Manejo de Espécimes , Propriedades de Superfície
18.
J Orthop Res ; 38(6): 1175-1190, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32162711

RESUMO

Metastatic breast, prostate, lung, and other cancers often affect bone, causing pain, increasing fracture risk, and decreasing function. Management of metastatic bone disease (MBD) is clinically challenging when there is potential but uncertain risk of pathological fracture. Management of MBD has become a major focus within orthopedic oncology with respect to fracture and impending fracture care. If impending skeletal-related events (SREs), particularly pathologic fracture, could be predicted, increasing evidence suggests that prophylactic surgical treatment improves patient outcomes. However, current fracture risk assessment and radiographic metrics do not have high accuracy and have not been combined with relevant patient survival tools. This review first explores the prevalence, incidence, and morbidity of MBD and associated SREs for different cancer types. Strengths and limitations of current fracture risk scoring systems for spinal stability and long bone fracture are highlighted. More recent computed tomography (CT)-based structural rigidity analysis (CTRA) and finite element (FE) analysis methods offer advantages of increased specificity (true negative rate), but are limited in availability. Other fracture prediction approaches including parametric response mapping and positron emission tomography/computed tomography measures show early promise. Substantial new information to inform clinical decision-making includes measures of survival, clinical benefits, and economic analysis of prophylactic treatment compared to after-fracture stabilization. Areas of future research include use of big data and machine learning to predict SREs, greater access and refinement of CTRA/FE approaches, combination of clinical survival prediction tools with radiographically based fracture risk assessment, and net benefit analysis for fracture risk assessment and prophylactic treatment.


Assuntos
Neoplasias Ósseas/complicações , Neoplasias Ósseas/secundário , Tomada de Decisão Clínica , Fraturas Espontâneas/etiologia , Medição de Risco , Neoplasias Ósseas/epidemiologia , Análise de Elementos Finitos , Humanos , Morbidade , Tomografia Computadorizada por Raios X
19.
J Orthop Res ; 38(7): 1529-1537, 2020 07.
Artigo em Inglês | MEDLINE | ID: mdl-32167182

RESUMO

A preclinical rat knee replacement model was recently developed to explore the biological and mechanobiological changes of trabecular resorption for cement-bone interdigitated regions. The goal here was to evaluate the relevance of this model compared with human knee replacement with regards to functional micromechanics. Eight nonsurvival, cemented knee replacement surgeries were performed, the interdigitated gap morphology was quantified, and interface micromotion between cement and bone was measured for 1 to 5 bodyweight loading. Computational fluid dynamics modeling of unit cell geometries with small gaps between trabeculae and cement was used to estimate fluid flow. Gap width (3.6 µm) was substantially smaller compared with cement-bone gaps reported in human knee replacement (11.8 µm). Micromotion at the cement-bone border was also decreased for the rat knee replacement (0.48 µm), compared with human (1.97 µm), for 1 bodyweight loading. However, the micromotion-to-gap width ratio (0.19 and 0.22 for, rat and human), and estimated fluid shear stress (6.47 and 7.13 Pa, for rat and human) were similar. Replicating the fluid dynamic characteristics of cement-bone interdigitated regions in human knee replacements using preclinical models may be important to recapitulate trabecular resorption mechanisms due to proposed supraphysiologic fluid shear stress. Statement of clinical significance: local cement-bone micromotion due to joint loading may contribute to the process of clinical loosening in total joint replacements. This work shows that while micromotion and gap morphology are diminished for the rat knee model compared to human, the motion-to-gap ratio, and corresponding fluid shear stress are of similar magnitudes.


Assuntos
Artroplastia do Joelho , Cimentos Ósseos , Interface Osso-Implante , Animais , Fenômenos Biomecânicos , Feminino , Humanos , Hidrodinâmica , Ratos , Ratos Sprague-Dawley
20.
Bone Rep ; 12: 100262, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32258252

RESUMO

BACKGROUND: Cancer patients receiving radiotherapy for soft tissue sarcomas are often at risk of post-irradiation (post-RTx) bone fragility fractures, but our understanding of factors controlling radiation-induced bone injury is limited. Previous studies have evaluated post-RTx changes to cortical bone composition in the periosteum of irradiated tibiae, but have not evaluated effects of irradiation in deeper tissues, such as endosteal or mid-cortical bone, and whether there are differential spatial effects of irradiation. In this study, we hypothesize that post-RTx changes to cortical bone composition are greater in endosteal compared to mid-cortical or periosteal bone. METHODS: A pre-clinical mouse model of limited field hindlimb irradiation was used to evaluate spatial and temporal post-RTx changes to the metaphyseal cortex of irradiated tibiae. Irradiation was delivered unilaterally to the hindlimbs of 12-wk old female BALB/cJ mice as 4 consecutive daily doses of 5 Gy each. RTx and non-RTx tibiae were obtained at 0, 2, 4, 8, and 12 wks post-RTx (n = 9 mice/group/time). Raman spectroscopy was used to evaluate spatial and temporal post-RTx changes to cortical bone composition in age-matched RTx and non-RTx groups. RESULTS: Significant early spatial differences in mineral/matrix and collagen crosslink ratios were found between endosteal and periosteal or mid-cortical bone at 2-wks post-RTx. Although spatial differences were transient, mineral/matrix ratios significantly decreased and collagen crosslink ratios significantly increased with post-RTx time throughout the entire tibial metaphyseal cortex. CONCLUSIONS: Irradiation negatively impacts the composition of cortical bone in a spatially-dependent manner starting as early as 2-wks post-RTx. Long-term progressive post-RTx changes across all cortical bone sites may eventually contribute to the increased risk of post-RTx bone fragility fractures.

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