A fundamental model of quasi-static wheelchair biomechanics

The performance of a wheelchair system is a function of user anatomy, including arm segment lengths and muscle parameters, and wheelchair geometry, in particular, seat position relative to the wheel hub. To quantify performance, researchers have proposed a number of predictive models. In particular, the model proposed by Richter is extremely useful for providing initial analysis as it is simple to apply and provides insight into the peak and transient joint torques required to achieve a given angular velocity. The work presented in this paper identifies and corrects a critical error; specifically that the Richter model incorrectly predicts that shoulder torque is due to an anteflexing muscle moment. This identified error was confirmed analytically, graphically and numerically. The authors have developed a corrected, fundamental model which identifies that the shoulder anteflexes only in the first half of the push phase and retroflexes in the second half. The fundamental model has been extended by the authors to obtain novel data on joint and net power as a function of push progress. These outcomes indicate that shoulder power is positive in the first half of the push phase (concentrically contracting anteflexors) and negative in the second half (eccentrically contracting retroflexors). As the eccentric contraction introduces adverse negative power, these considerations are essential when optimising wheelchair design in terms of the user's musculoskeletal system. The proposed fundamental model was applied to assess the effect of vertical seat position on joint torques and power. Increasing the seat height increases the peak positive (concentric) shoulder and elbow torques while reducing the associated (eccentric) peak negative torque. Furthermore, the transition from positive to negative shoulder torque (as well as from positive to negative power) occurs later in the push phase with increasing seat height. These outcomes will aid in the optimisation of manual wheelchair propulsion biomechanics by minimising adverse negative muscle power, and allow joint torques to be manipulated as required to minimise injury or aid in rehabilitation.     

The Coffin-Siris syndrome: a proposed diagnostic approach and assessment of 15 overlapping cases

Coffin-Siris syndrome (CSS) is a rare, clinically heterogeneous disorder often considered in the setting of cognitive/developmental delay and 5th finger/nail hypoplasia. Due to the clinical variability of facial and other features, this diagnosis is often difficult to confirm clinically and the existence of this disorder as a specific diagnosis has been at times an issue of debate. In an effort to further delineate the spectrum and key phenotypic features, we reviewed 80 previously reported cases to define features in patients that most closely correlated with a convincing diagnosis. There appear to be two subtypes of CSS, one which displays the "classic" coarse facial features previously described; another displays "variant" facial features which are less striking. Using these features, we defined an algorithm to rank the confidence of diagnosis and applied it to 15 additional patients who had been previously characterized by chromosome microarray. This approach will also facilitate uniform categorization for whole-exome analysis.     

Survey of health status and complications among propionic acidemia patients

Propionic acidemia (PA) is a rare organic acidemia that is due to deficiency in the enzyme propionyl-coA carboxylase. Complications are currently described mostly in the form of case reports. We sampled a population of affected individuals in order to estimate the frequency of complications amongst the sample. The study is a cross-sectional retrospective review with a survey instrument and recruitment through the Propionic Acidemia Foundation. Responses for 58 individuals were tabulated for each question as how frequently the complication was reported among responders. Commonly reported findings included seizures, arrhythmia, leucopenia, and anemia. Developmental and cognitive disabilities were reported in the majority of individuals. Heart failure or cardiomyopathy was reported in over half of deceased individuals at time of death. Pancreatitis was reported in a minority of the sample, yet more than half of these reported a recurrence. These results update and extend our current knowledge of recognized complications among individuals with PA. The results also provide new information regarding developmental outcomes and previously unreported morbidity from cardiac and gastrointestinal complications. Longitudinal studies exploring associated biochemical and clinical parameters are necessary to further our understanding of the pathophysiology of PA and its complications.     

Misidentification of Candida parapsilosis as C famata in a clinical case of vertebral osteomyelitis

A case of vertebral osteomyelitis involving misidentification of Candida parapsilosis as C famata by the VITEK 2 compact is described. Species-specific primers were used in the polymerase chain reaction to correctly identify the clinical isolate. When uncommon species of Candida are reported using automated systems, heightened clinical suspicion is warranted.     

Changes in Satiety,Supra- and Infraband Transit,and Gastric Emptying Following Laparoscopic Adjustable Gastric Banding: A Prospective Follow-up Study

Background  

Laparoscopic adjustable gastric banding (LAGB) induces and sustains weight loss, likely by activating the peripheral satiety mechanism. Recent data suggests that food is not retained above the optimally adjusted LAGB, suggesting that an alternate mechanism is inducing satiety. How transit and gastric emptying change following LAGB and correlate with satiety and weight loss have not been adequately defined.     

The Effect of the Cam Deformity on the Insertion of the Femoral Component in Hip Resurfacing

Surface arthroplasty simulations were generated using 3-dimensional computed tomographic scans from 61 consecutive patients presenting with idiopathic osteoarthritis to evaluate the change in femoral component positioning that would allow optimal alignment when resurfacing a cam-type deformity. Anatomical parameters were measured to quantify the influence of the deformity on the insertion technique of the femoral implant. A modified femoral head ratio was initially calculated from plain radiographs to define the severity of cam deformity in these patients. A severe deformity required more superior translation of the entry point and greater reaming depth to allow safe insertion with optimal implant alignment. This could be achieved while preserving the leg length, minimizing the component size, and maximizing the amount of host bone contact, although the horizontal femoral offset was reduced. These findings suggest that the femoral component can be safely inserted by modifying the surgical technique despite progressive deformity of the femoral head.     

Impaired fibrinolysis and risk for cardiovascular disease in the metabolic syndrome and type 2 diabetes

Patients with the metabolic syndrome are insulin resistant and manifest a cluster of risk factors for cardiovascular disease. Impaired fibrinolysis and increased concentrations in blood of plasminogen activator inhibitor-1 (PAI-1) are related to insulin resistance and abdominal obesity and may contribute to the increased risk for cardiovascular disease in this group. Weight loss, metformin, and thiazolidinediones ameliorate insulin resistance and decrease concentrations of PAI-1. Thus, they may lower risk in patients with the metabolic syndrome.