Microwave-assisted digestion of organic samples: how simple can it become?

Advancements in sample preparation for performing trace analysis of inorganic analytes are coming from the dissemination of microwave-assisted procedures, but there is still room for improvements by looking for simple and easily applied procedures. Recently it was proposed a new approach called single reaction chamber with capability for digestions at high pressures and temperatures using simple vials and racks. This was a limitation of former cavity microwave ovens with closed vessels. It was demonstrated here that the use of single reaction chamber approach allows the implementation of efficient digestions using diluted solutions of nitric acid and also allows addressing a critical need of sample preparation for inorganic analysis by running mixed batches of samples. The feasibility of this procedure was demonstrated for organic samples and accuracy was proved by using certified reference materials of apple leaves, bovine liver and whole milk powder. Digestions performed of whole milk powder and bovine liver using 2.0 mol L(-1) nitric acid solution plus concentrated hydrogen peroxide at 240 °C led to residual carbon contents of 0.825 and 1.50% and residual acidities of 1.04 and 0.618 mol L(-1), respectively. These parameters are fully compatible with further measurements using ICP OES or ICP-MS. Al, Cu, Fe, Mn, Mo, Rb, Se, Sr, and Zn were accurately determined by ICP OES or ICP-MS depending on their concentrations in digests.

Effects of lateral-wedged insoles on kinetics at the knee.

Lateral-wedged insoles have been shown to help clinically alleviate pain associated with medial compartment osteoarthritis. This study analyzed the effects of lateral-wedged insoles on the gait and medial knee compartment load of 17 healthy subjects. Three-dimensional gait analysis was performed for each subject with and without wearing a 5 degrees lateral-wedged insole. Subjects walked at a constant velocity for both conditions. A motion analysis system and force plate were used to calculate temporal and spatial parameters, joint angles, moments, and powers. An analytical model was developed to estimate medial compartment loads at the knee for each subject during both conditions. Results were compared with a Student's paired t test. There were no significant differences in temporal and spatial parameters, joint angles at the hip, knee, and ankle, or kinetics at the hip and ankle. However, the external varus moment and estimated medial compartment load at the knee were reduced significantly with the addition of the lateral-wedged insole. These results suggest that the pain relief and improvement in function reported by patients with osteoarthritis while using lateral-wedged insoles may be achieved by a reduction in external varus moment and medial compartment load.

Walking, chair rising, and stair climbing after total knee arthroplasty: patellar resurfacing versus nonresurfacing.

During the past decade, the technology and design of knee joint prostheses has progressed considerably. However, there is still much controversy on whether resurfacing the patella during routine total knee arthroplasty (TKA) is necessary. This study compares the biomechanics of the lower limb in patients after TKA with and without patellar resurfacing during level walking, stair climbing, and chair rising. Eighteen patients who underwent TKA by two different surgeons using the same prosthesis were studied after full rehabilitation while walking, stair climbing, and chair rising. Patients were divided between those who were resurfaced and those who were not resurfaced. An aged-matched control population was recruited for comparison. The Hospital for Special Surgery Knee Rating Scale was used to gather clinical information. Kinematic and kinetic parameters were collected using a 5-camera Motion Analysis System and an AMTI OR6-5 force platform. For level walking, patients were asked to walk at a self-selected speed down an 8-m walkway. For stair climbing, patients were asked to climb a 4-step staircase without handrail support and for chair rising, patients were asked to rise from a chair that was positioned at the height of their knee joint line. Five trials for each side were recorded for averaging and statistical analysis. Temporal-spatial parameters and kinematic and kinetic variables at the knee joint were tested for significance using the repeated measures analysis of variance (ANOVA). There were no significant differences in the biomechanics of walking, stair climbing, or chair rising between patients after TKA with and without a resurfaced patella.

Functional outcome and gait analysis after triple or double arthrodesis.

Thirteen patients who had undergone unilateral triple or double arthrodesis were studied an average of 5.2 years after surgery. Patients with a neuromuscular disorder; inflammatory arthritis; or any other focus of lower extremity arthritis, deformity, or joint dysfunction were excluded from the study. Clinical and radiological assessment of the patients was performed in addition to three-dimensional kinematic and kinetic gait analysis. Objective clinical outcome based on the American Orthopaedic Ankle and Foot Society score was rated as good or excellent for 10 patients, fair for 2, and poor for 1. Two patients developed radiological evidence of arthrosis affecting other tarsal joints that was not apparent on preoperative radiographs. Two other patients had some progression of radiological arthrosis that was identified before the index surgery. The presence of radiological ankle or tarsal arthritis did not correlate with the level of the patient's pain or functional disability. Gait analysis demonstrated a 13% increase in range of flexion of the ipsilateral knee during the third rocker period of stance. At the ankle, range of motion during the same period of stance was reduced by 33%. This was mostly the result of a 6 degrees (53%) loss of plantarflexion at toe-off. Analysis of the ankle kinetic data identified a mean 13% reduction in the peak external ankle dorsiflexion moment and a 45% reduction in mean maximum power generation at the ankle in comparison to the normal side. Unilateral triple or double arthrodesis was shown to predictably result in decreased pain and increased function in otherwise normal individuals.

Walking boot design: a gait analysis study.

This study investigated the effect of various short-leg walking boot designs on walking. Four commercially available walking boots and a synthetic walking cast were tested using three-dimensional gait analysis to determine their effect on a normal individual's gait pattern. Temporal-spatial parameters and lower limb kinematics and kinetics were analyzed for 10 normal subjects. The synthetic walking cast was the most different when compared with the shoe condition with respect to the all parameters tested. The Bledsoe walking boot was the only boot that was not significantly different from the shoe condition for all parameters tested.

Effect of humeral head component size on hemiarthroplasty translations and rotations.

Glenohumeral translation and rotation were measured in 6 grossly normal, fresh frozen shoulder preparations while a manual load was applied to the humerus. The same tests (maximum elevation, total rotation, anterior/posterior (A/P) translation, and inferior translation) were repeated for each shoulder through 8 series: 1 with the shoulder intact, 1 with the shoulder vented, and 6 with progressively larger humeral head components after hemiarthroplasty. There was an inverse linear relation between humeral head component size and all 4 outcome variables. Replacing the native head with a component of equal diameter reduced elevation 20%, rotation 40%, A/P translation 50%, and inferior translation 60% in the vented shoulder. Replacing the native head with a component of equal effective volume decreased elevation 8%, rotation 20%, A/P translation 25%, and inferior translation 40% in the vented shoulder. Increasing humeral head component size decreased rotation, A/P translation, and inferior translation by similar percentages and elevation somewhat less. Humeral head component size is better described in terms of volume than in terms of diameter or offset.