RESUMO
This study aimed to present a model of post-scratching locomotion with two intermixed central pattern generator (CPG) networks, one for scratching and another for locomotion. We hypothesized that the rhythm generator layers for each CPG are different, with the condition that both CPGs share their supraspinal circuits and their motor outputs at the level of their pattern formation networks. We show that the model reproduces the post-scratching locomotion latency of 6.2 ± 3.5 s, and the mean cycle durations for scratching and post-scratching locomotion of 0.3 ± 0.09 s and 1.7 ± 0.6 s, respectively, which were observed in a previous experimental study. Our findings show how the transition of two rhythmic movements could be mediated by information exchanged between their CPG circuits through routes converging in a common pattern formation layer. This integrated organization may provide flexible and effective connectivity despite the rigidity of the anatomical connections in the spinal cord circuitry.
RESUMO
OBJECTIVES: The biomechanical difficulty in fixation of a Vancouver B1 periprosthetic fracture is purchase of the proximal femoral segment in the presence of the hip stem. Several newer technologies provide the ability to place bicortical locking screws tangential to the hip stem with much longer lengths of screw purchase compared with unicortical screws. This biomechanical study compares the stability of 2 of these newer constructs to previous methods. METHODS: Thirty composite synthetic femurs were prepared with cemented hip stems. The distal femur segment was osteotomized, and plates were fixed proximally with either (1) cerclage cables, (2) locked unicortical screws, (3) a composite of locked screws and cables, or tangentially directed bicortical locking screws using either (4) a stainless steel locking compression plate system with a Locking Attachment Plate (Synthes) or (5) a titanium alloy Non-Contact Bridging system (Zimmer). Specimens were tested to failure in either axial or torsional quasistatic loading modes (n = 3) after 20 moderate load preconditioning cycles. Stiffness, maximum force, and failure mechanism were determined. RESULTS: Bicortical constructs resisted higher (by an average of at least 27%) maximum forces than the other 3 constructs in torsional loading (P < 0.05). Cables constructs exhibited lower maximum force than all other constructs, in both axial and torsional loading. The bicortical titanium construct was stiffer than the bicortical stainless steel construct in axial loading. CONCLUSIONS: Proximal fixation stability is likely improved with the use of bicortical locking screws as compared with traditional unicortical screws and cable techniques. In this study with a limited sample size, we found the addition of cerclage cables to unicortical screws may not offer much improvement in biomechanical stability of unstable B1 fractures.
Assuntos
Placas Ósseas , Parafusos Ósseos , Fraturas do Fêmur/fisiopatologia , Fraturas do Fêmur/cirurgia , Fixação Interna de Fraturas/instrumentação , Prótese de Quadril/efeitos adversos , Análise de Falha de Equipamento , Fraturas do Fêmur/etiologia , Humanos , Desenho de Prótese , Estresse Mecânico , Resistência à Tração , Resultado do TratamentoRESUMO
Patch tests in 1000 cases of contact allergic dermatitis observed between 1972 and 1978 are recorded in detail, and compared in general with patch tests in a previously recorded 1000 cases of contact allergic dermatitis between 1964 adn 1972. The routine use, since 1974, of patch tests as advised by the International Contact Dermatitis Research Group has increased the detection of dermatitis caused by nickel, paraphenylene-diamine and related dyes, formaldehyde and perfumes (balsam of Peru), which indicates that aimed patch tests alone may be inadequate. The number of cases of dermatitis caused by antifungal agents and topical antihistamines decreased after Commonwealth and State legislation prohibiting their use was passed.