Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 4 de 4
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Knee ; 21(1): 224-31, 2014 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-23582376

RESUMO

PURPOSE: Periprosthetic distal femur fracture after total knee arthroplasty due to the stress-shielding phenomenon is a challenging problem. Retrograde intramedullary nail (RIMN) or locking plate (LP) fixation with/without a strut allograft has been clinically used via less invasive stabilization surgery (LISS) for the treatment of these periprosthetic fractures. However, their biomechanical differences in construct stability and implant stress have not been extensively studied, especially for the osteoporotic femur. METHODS: This study used a finite-element method to evaluate the differences between RIMN, LP, and LP/allograft fixation in treating periprosthetic distal femur fractures. There were sixteen variations of two fracture angles (transverse and oblique), two loading conditions (compression and rotation), and four bony conditions (one normal and three osteoporotic). Construct stiffness, fracture micromotion, and implant stress were chosen as the comparison indices. RESULTS: The LP/allograft construct provides both lateral and middle supports to the displaced femur. Comparatively, the LP and RIMN constructs, respectively, transmit the loads through the lateral and middle paths, thus providing more unstable support to the construct and high stressing on the implants. The fracture pattern plays a minor role in the construct stabilization of the three implants. In general, the biomechanical performances of the RIMN and LP constructs were comparable and significantly inferior to those of the LP/allograft construct. The bone quality should be evaluated prior to the selection of internal fixators. CONCLUSIONS: The LP/allograft construct significantly stabilizes the fracture gap, reduces the implant stress, and serves as the recommended fixation for periprosthetic distal femur fracture.


Assuntos
Placas Ósseas , Transplante Ósseo , Fraturas do Fêmur/cirurgia , Análise de Elementos Finitos , Fixação Intramedular de Fraturas , Modelos Biológicos , Fraturas Periprotéticas/cirurgia , Aloenxertos , Artroplastia do Joelho , Fraturas do Fêmur/fisiopatologia , Humanos , Masculino , Teste de Materiais , Pessoa de Meia-Idade , Osteoartrite do Joelho/fisiopatologia , Osteoartrite do Joelho/cirurgia , Fraturas Periprotéticas/fisiopatologia , Rotação , Estresse Mecânico
2.
BMC Musculoskelet Disord ; 14: 281, 2013 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-24088294

RESUMO

BACKGROUND: For anterior lumbar interbody fusion (ALIF), stand-alone cages can be supplemented with vertebral plate, locking screws, or threaded cylinder to avoid the use of posterior fixation. Intuitively, the plate, screw, and cylinder aim to be embedded into the vertebral bodies to effectively immobilize the cage itself. The kinematic and mechanical effects of these integrated components on the lumbar construct have not been extensively studied. A nonlinearly lumbar finite-element model was developed and validated to investigate the biomechanical differences between three stand-alone (Latero, SynFix, and Stabilis) and SynCage-Open plus transpedicular fixation. All four cages were instrumented at the L3-4 level. METHODS: The lumbar models were subjected to the follower load along the lumbar column and the moment at the lumbar top to produce flexion (FL), extension (EX), left/right lateral bending (LLB, RLB), and left/right axial rotation (LAR, RAR). A 10 Nm moment was applied to obtain the six physiological motions in all models. The comparison indices included disc range of motion (ROM), facet contact force, and stresses of the annulus and implants. RESULTS: At the surgical level, the SynCage-open model supplemented with transpedicular fixation decreased ROM (>76%) greatly; while the SynFix model decreased ROM 56-72%, the Latero model decreased ROM 36-91%, in all motions as compared with the INT model. However, the Stabilis model decreased ROM slightly in extension (11%), lateral bending (21%), and axial rotation (34%). At the adjacent levels, there were no obvious differences in ROM and annulus stress among all instrumented models. CONCLUSIONS: ALIF instrumentation with the Latero or SynFix cage provides an acceptable stability for clinical use without the requirement of additional posterior fixation. However, the Stabilis cage is not favored in extension and lateral bending because of insufficient stabilization.


Assuntos
Análise de Elementos Finitos , Vértebras Lombares/cirurgia , Modelos Biológicos , Dinâmica não Linear , Dispositivos de Fixação Ortopédica , Implantação de Prótese/instrumentação , Fusão Vertebral/instrumentação , Fenômenos Biomecânicos , Placas Ósseas , Parafusos Ósseos , Humanos , Vértebras Lombares/fisiopatologia , Teste de Materiais , Desenho de Prótese , Falha de Prótese , Amplitude de Movimento Articular , Reprodutibilidade dos Testes , Estresse Mecânico
3.
Spine (Phila Pa 1976) ; 38(13): E775-82, 2013 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-23486410

RESUMO

STUDY DESIGN: The pretension of the Dynesys cord was varied to evaluate its effects on both tissue responses and screw-spacer behaviors by the finite-element method. OBJECTIVE: This study aimed to provide detailed information about the motion-preserving and load-shielding mechanisms of the Dynesys screw-spacer joint. SUMMARY OF BACKGROUND DATA: Intuitively, higher cord pretension aims to ensure the occurrence of screw-spacer contact, thus making the spacer the transmitter of the vertebral loads. However, detailed investigations of the cord-pretension effects have not yet been carried out. METHODS.: Using a validated lumbosacral model, the moderately degenerative L4-L5 segment was instrumented by a static fixator and the Dynesys fixator was further used to bridge a mildly degenerative L3-L4 segment. The pre-tended cord was modeled as an elastic spring with 0- and 300-N pretensions. The disc range-of-motion, disc stress, facet force, bone-screw stress, and screw-spacer force were chosen as comparison indices. RESULTS.: At the transition and adjacent segments, the range-of-motion differences between the 2 pretensions were 7.7% and 2.0% on average, respectively. The mechanical differences at the transition and adjacent segments were 9.0% and 5.2% (disc stress) and 9.4% and 9.1% (facet force), respectively. The results indicated that the cord pretension has a minor effect on the adjacent segments in comparison with the transition segment. However, the stress at the screw hub and force of the screw-spacer contact of the 300-N pretension were increased by 33.7% and 316.5% on average than without pretension, respectively. CONCLUSION: The moment arm from the screw-cord center to the fulcrum is significantly less than that of vertebral loads. This leads to the minor effect of increasing the cord pretension on the responses of the adjacent segments. However, the cord pretension can significantly affect both screw-spacer force and bone-screw stress. LEVEL OF EVIDENCE: 4.


Assuntos
Parafusos Ósseos , Vértebras Lombares/cirurgia , Procedimentos Ortopédicos/instrumentação , Próteses e Implantes , Fenômenos Biomecânicos , Elasticidade , Humanos , Fixadores Internos , Disco Intervertebral/fisiopatologia , Vértebras Lombares/patologia , Vértebras Lombares/fisiopatologia , Região Lombossacral , Modelos Anatômicos , Procedimentos Ortopédicos/métodos , Amplitude de Movimento Articular , Estresse Mecânico , Articulação Zigapofisária/fisiopatologia
4.
J Chin Med Assoc ; 73(8): 435-7, 2010 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-20728856

RESUMO

Primary renal carcinoid tumors are extremely rare lesions of the kidney, with fewer than 60 cases reported previously. Here, we present the case of a 46-year-old man who had primary renal carcinoid tumor with multiple liver, para-aortic lymph node and bony metastases when he was diagnosed initially. In consideration of life quality, we performed cytoreductive surgery only. In the following year, the patient did not have any severe cancer-related morbidity.


Assuntos
Tumor Carcinoide/patologia , Neoplasias Renais/patologia , Neoplasias Ósseas/secundário , Humanos , Neoplasias Hepáticas/secundário , Metástase Linfática , Masculino , Pessoa de Meia-Idade
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...