Can simultaneous bilateral movement involve the undamaged hemisphere in reconstruction of neural networks damaged by stroke?

Normalization of upper limb movement remains a difficult problem for a significant subpopulation of hemiplegic stroke patients. Clinical observations prompted investigation of a novel approach using simultaneous identical bilateral movements performed independently. We briefly report 12 controlled single-case experiments using multiple-baseline designs across three separate grasp/reach activities. Unilateral performance tests with the hemiplegic arm using the bilaterally trained actions demonstrated clinically and statistically significant improvements in movement patterns. These improvements were specific to the trained movement and well maintained. Using recent literature we develop a theoretical model proposing that bilateral simultaneous movement promotes interhemispheric disinhibition likely to allow reorganization by sharing of normal movement commands from the undamaged hemisphere. Disinhibition may also encourage recruitment of undamaged neurones to construct new task-relevant neural networks. The potential contribution of spared ipsilateral pathways in the damaged hemisphere, indirect corticospinal pathways and ipsilateral pathways from the undamaged hemisphere is discussed.     

Heterogeneity in patellofemoral cartilage adaptation to anterior cruciate ligament transection; chondrocyte shape and deformation with compression

OBJECTIVE: The purpose of this study was to determine if the opposing cartilages of the feline patellofemoral joint adapted differently to short-term anterior cruciate ligament transection (ACL-T) and if the magnitude of chondrocyte deformation upon tissue loading was altered under ACL-T conditions compared to contralateral controls. In situ static compression of physiological magnitude was applied to the feline patellofemoral cartilage 16 weeks post-ACL-T and cartilage and chondrocyte deformation were evaluated by histomorphometry. DESIGN: Six adult cats were euthanized 16 weeks after unilateral ACL-T. A peak surface pressure of 9 MPa was applied to the fully intact patella and femoral groove cartilages. After in situ fixation under compression, sections from the centre of the indent and from an adjacent unloaded area of the cartilages were analysed. Chondrocyte shape, size, clustering and volumetric fraction were quantified. RESULTS: Experimental patellar articular cartilage was thicker, contained larger chondrocytes that were more frequently arranged in clusters and had, on average, a larger chondrocyte volumetric fraction compared to contralateral controls. In contrast, the experimental femoral groove cartilage demonstrated little adaptation to ACL-T. CONCLUSIONS: The patellar articular cartilage adapts to short-term ACL-T to a greater extent than femoral groove cartilage. We speculate that differences in the histological parameters of control tissues, such as cartilage thickness and the magnitude and depth distribution of chondrocyte shape, size and volumetric fraction may contribute to predisposing patellar cartilage, and not femoral groove cartilage, to adaptation after ACL-T.     

Topographical variations of the strain-dependent zonal properties of tibial articular cartilage by microscopic MRI

The topographical variations of the zonal properties of canine articular cartilage over the medial tibia were evaluated as the function of external loading by microscopic magnetic resonance imaging (µMRI). T2 and T1 relaxation maps and GAG (glycosaminoglycan) images from a total of 70 specimens were obtained with and without the mechanical loading at 17.6?µm depth resolution. In addition, mechanical modulus and water content were measured from the tissue. For the bulk without loading, the means of T2 at magic angle (43.6?±?8.1?ms), absolute thickness (907.6?±?187.9?µm) and water content (63.3?±?9.3%) on the meniscus-covered area were significantly lower than the means of T2 at magic angle (51.1?±?8.5?ms), absolute thickness (1251.6?±?218.4?µm) and water content (73.2?±?5.6%) on the meniscus-uncovered area. However GAG (86.0?±?15.3?mg/ml) on the covered area was significantly higher than GAG (70.0?±?8.8?mg/ml) on the uncovered area. Complex relationships were found in the tissue properties as the function of external loading. The tissue parameters in the superficial zone changed more profoundly than the same properties in the radial zone. The tissue parameters in the meniscus-covered areas changed differently when comparing with the same parameters in the uncovered areas. This project confirms that the load-induced changes in the molecular distribution and structure of cartilage are both depth-dependent and topographically distributed. Such detailed knowledge of the tibial layer could improve the early detection of the subtle softening of the cartilage that will eventually lead to the clinical diseases such as osteoarthritis.     

Primary knee ligament repair--revisited

There were 4710 knee sprains resulting from skiing in the four Aspen ski areas between 1976 and 1979. Twenty percent of the patients (942) had complete tears. Of these, 302 elected to remain in Aspen for treatment. All were treated by primary ligament repair without augmentation. These cases were evaluated an average of 42 months after injury. Patients with isolated tears of the medial collateral ligament were found to be doing well; virtually all of them had returned to preinjury activity levels. Thirty-six percent of the isolated anterior cruciate repairs were rated failures, and 43% of the combination ACL-MCL injuries had failed because of anterior cruciate deficiency. Twenty-nine percent of the ACL and ACL-MCL injuries had meniscal tears. Cases that included meniscectomy had a failure rate twice as great as those in which the meniscus was preserved. The results following repair of anterior cruciate tears were not acceptable, and augmentation was indicated. Primary repair of medial collateral ligament tears produced excellent results. Meniscal tears were frequent in association with ligament disruption. Ligament repairs were less satisfactory when meniscectomy was performed at the time of the repair.     

Clinical measures of handgrip limitation relate to impaired pinch grip force control after stroke

This study examined whether clinical measures of handgrip limitation relate to laboratory measures of grip force impairment during a pinch grip, lift, and hold task post-stroke. Handgrip ability in 45 people with stroke who had residual grip ability was examined relative to 45 age-matched healthy adults. The clinical tests included items from a) the Jebsen Taylor Hand Function Test; b) the Motor Assessment Scale; c) the Functional Independence Measure (FIM); and d) a custom-designed survey about hand-use in daily life. The laboratory test was summarized by principal components: 1) Pre-Lift Delay and 2) Grip Force Dyscontrol. For the stroke group, a moderate to strong correlation was found between Pre-Lift Delay and each clinical measure of handgrip limitation (rs=0.70-0.85) except the FIM (rs=0.38-0.49). In contrast, Grip Force Dyscontrol was not associated with handgrip limitation on any of the clinical tests (rs=-0.08 to 0.18).