[Value of absolute quantification of myocardial perfusion by PET in detecting coronary microvascular disease in patients with non-obstructive coronaries].

Objective: To compare the incidence of coronary microvascular disease (CMVD) between patients with non-obstructive and obstructive coronary arteries. Methods: We retrospectively analyzed 97 patients with angina pectoris, who underwent the absolute quantitative PET examination of myocardial perfusion and coronary anatomy examination within 90 days. All patients were divided into two groups: non-obstructive group (72 cases, no stenosis ≥50% in all three coronary arteries) and obstructive group (25 cases, at least one coronary stenosis ≥50%; and at least one coronary stenosis<50%). Quantitative parameters derived from PET including rest myocardial blood flow (RMBF), stress myocardial blood flow (SMBF), coronary flow reserve (CFR) and cardiovascular risk factors were compared between the two groups. CMVD was defined as CFR<2.90 and SMBF<2.17 ml·min(-1)·g(-1). Results: Incidence of CMVD was significant higher in the non-obstructive coronary arteries of the obstructive group than in the non-obstructive coronary arteries of non-obstructive group (47.1% (16/34) vs. 25.5% (55/216), χ(2)=6.738, P=0.009) while incidence of CMVD was similar between non-obstructive and obstructive patients ((44% (11/25) vs. 33.3% (24/72), χ(2)=0.915, P=0.339). RMBF ((0.83±0.14) ml·min(-1)·g(-1) vs. (0.82±0.17) ml·min(-1)·g(-1)), SMBF ((2.13±0.60) ml·min(-1)·g(-1) vs. (1.91±0.50) ml·min(-1)·g(-1)) and CFR (2.59±0.66 vs. 2.36±0.47) were similar between the two groups (all P>0.05). Conclusions: CMVD can occur in non-obstructive coronary arteries in both patients with non-occlusive coronary arteries and patients with obstructive coronary arteries. Prevalence of CMVD is significantly higher in patients with obstructive coronary arteries than in patients with non-obstructive coronary arteries. The CMVD severity is similar between the two groups.

Hoffa fracture: should precautions be taken during fixation and rehabilitation?

A coronal fracture of a femoral condyle (Hoffa fracture) is an unusual injury and there are only a handful of reports discussing it. We report a case of a 52-year-old worker who fell from a height, suffering lower limb injuries, including a Hoffa fracture with comminution, and had problems with malunion during the postoperative period. Clinicians should be aware that rehabilitation programmes need to be tailored to the method of fixation used to manage this uncommon fracture pattern.

Reproducibility of a task description questionnaire for working pregnant women.

The objective of this study was to evaluate the reproducibility of a Task Description Questionnaire that was designed to investigate exposures to, and influential factors for, problematic tasks experienced by working pregnant women. The questionnaire comprised questions concerning 22 task components (covering working posture, manual material handling, work pace, prolonged postures and others), eight influential factors contributing to problematic tasks, discomfort (measured using a body map) and level of effort to perform the tasks. Reproducibility of the questionnaire was assessed by interviewing participants on two occasions one week apart for interviews at both 20 and 34 weeks of pregnancy. Eleven and 13 problematic tasks were reported by 21 working pregnant women at 20 and 34 weeks of pregnancy, respectively. These tasks were surveyed using the Task Description Questionnaire. Kappa statistics and correlation coefficients (supplemented by paired t-tests) were used to examine the reproducibility of responses to the questionnaire. The results showed that most of the variables were measured with very good or satisfactory reproducibility. The reproducibility of exposure to work posture was higher than that of exposure to manual material handling. There was no significant difference between test and retest means for the discomfort scores measured on the body map, except for the maximum discomfort score for the whole body in the 34 weeks survey. The study suggests that the questionnaire can be reliably used in the study of problematic tasks experienced by pregnant women. But an initial preview of the questions by the subjects and explanation of the questions given to the subjects by the interviewer may help to produce more reliable results.

Determination of axial rotation angles of limb segments - a new method.

This paper describes a new method of determining the axial rotation angle of a limb segment during three-dimensional movement. Instead of describing the three-dimensional rotation by a three-step rotation (Euler/Cardan angles), a one-step rotation (instantaneous screw axis), or a non-step rotation (floating axis method), the new method uses a two-step rotation to describe the three-dimensional rotation of the limb segment: the rotation of the long axis of the limb segment about a specific axis passing through the proximal joint centre and perpendicular to the long axis of the limb segment, and the axial rotation about the long axis. A short review of previous methods followed by a full description of the principle of the new method with detailed derivation of some important equations (Appendices), comparison with Euler/Cardan angles and a simple experimental demonstration are given in this paper. A method of solving the gimbal-lock problem when using this method is also proposed.

Evaluation and calibration of an electromagnetic tracking device for biomechanical analysis of lifting tasks.

Electromagnetic motion tracking devices are increasingly used as a kinematic measuring tool. The aim of this study was to evaluate a long-range transmitter in an environment with a conventional force plate present in order to assess its suitability for further biomechanical applications. Using a calibration apparatus developed in our lab and Optotrack measurements, the performances of the Motion Star were evaluated. Positions and orientations were measured in a 140 x 80 x 120 cm(3) space centered on the force plate. Using a mathematical model developed at Queen's University, these data were calibrated. Errors on position and orientation were less than 150 mm and 10 degrees before calibration of the Motion Star, and less than 20mm and 2 degrees after calibration, with no differences between data collected with the force plate switched on/off. These errors did not depend on sensor orientation. Variability of the signal was small indicating minimal noise. Field distortion was the largest source of measurement error, which increased with the distance between the transmitter and the sensor and the proximity of the sensor to the force plate. Before its use for biomechanical analysis of lifting tasks and validation of dynamic models using force plate data, the data from electromagnetic motion tracking devices must be calibrated to decrease the errors due to electromagnetic field distortion.

A three-dimensional definition for the flexion/extension and abduction/adduction angles.

Flexion/extension and abduction/adduction, two major parameters for the description of joint rotations, are used to define planer anatomical orientations of body segments. These two-dimensional definitions have been used extensively in the biomechanical literature for reporting and representing both two-dimensional and three-dimensional joint rotations. Whether these traditional two-dimensional measurements represent true joint rotations in three dimensions has not been investigated. A quantitative error analysis is presented to show how large an error can be produced in the flexion/extension and abduction/adduction angles when using two-dimensional measurements to represent three-dimensional joint rotations. The results indicate that for an out-of-plane flexion the error in abduction angle measured by previous methods increases with both flexion and initial abduction angle and become very sensitive when the flexion angle exceeds 40 degrees. Although the error can be less than 2 degrees for flexion below 20 degrees when the initial abduction angle is at 30 degrees, it can be as large as 9 degrees for 60 degrees of flexion with an initial 10 degrees of abduction; nearly double the real abduction angle. Therefore, two-dimensional measurements of flexion/extension and abduction/adduction can be erroneous and overestimated for a three-dimensional joint rotation. To overcome the problem new definitions are proposed for the true flexion/extension and abduction/adduction angles as two independent parameters for three-dimensional joint rotation.

Graphical presentation of the range of hip and knee rotations for clinical evaluation of gait.

OBJECTIVE: This paper reports a method of using a multi-axis graph to represent the range of rotations at the hip and knee joints during gait for clinical evaluation of a patient's performance. DESIGN AND METHODS: The multi-axis graph uses 12 symmetrically arranged axes to represent each component of range of rotations at the hip and knee joints of both legs. The range of joint rotations of thirteen normal subjects and two patients were measured using an electromagnetic motion tracking system with four foot switches. RESULTS: The range of joint rotations of normal subjects shows a symmetrical star in the multi-axis graph. Abnormal function of a patient shows an asymmetrical star. CONCLUSIONS: This representation provides a simple way to examine a patient's performance in a time effective manner. Relevance. In clinical practice, the multi-axis representation of joint rotations can be used as an initial evaluation of a patient's performance to identify problems for further investigation.

Effects of discectomy on the stress distribution in the lumbar spine.

The change of the stress distribution of the lumbar spine after discectomy was analysed by the three-dimensional finite element method. It was shown that the stress level in the posterior element was higher, but that in the anterior element was lower than before disc excision. The most significant change of the stress distribution was found in the trabecular bone of the vertebral body. It is considered that in discectomy the normal disc tissue should be preserved as much as possible to maintain good function of the spine.

Three-dimensional clinical measurement of bilateral hip and knee rotations.

This paper reports a technique of using an electromagnetic system to measure three-dimensional bilateral hip and knee joint rotations during walking and of using peak cross-correlation between rotation angles to describe the pattern of rotations. Three-dimensional rotations of thigh and shank during gait were recorded using five receivers of the electromagnetic system synchronised with four foot-switches. Thirteen normal subjects were tested on two separate occasions to examine repeatability of the measurements. The relationship between the rotations was represented as lags at peak cross-correlation. Twelve parameters of the lags at peak cross-correlation were calculated. The analysis showed that the joint rotation could be measured reliably and the cross-correlation analysis provided parameters that were generally suitable for defining characteristics of hip and knee joint rotations during gait.

Analysis of self-reported problematic tasks for pregnant women.

The objective of this study was to identify major components of, and influential factors in, problematic tasks performed by pregnant women employed in education, health care and service areas. Seventy-two pregnant women were surveyed using specially designed questionnaires consisting of an Initial Survey, a Job Analysis Questionnaire and a Task Description Questionnaire. Forty-four subjects (60%) had difficulty performing at least one work task and reported 105 tasks that were problematic at work. Reaching above the head, bending forward, bending and twisting, pushing, repeating actions and working at a fast pace were identified as the task components requiring the greatest level of effort. Excessive effort, excessive time, getting tired, repetitive actions, stress and fear of injury were identified as factors that had strong associations with the six major task components. Findings of this study suggest that these task components and factors should be considered when designing, assigning or analysing tasks for working pregnant women.

A spherical rotation coordinate system for the description of three-dimensional joint rotations.

Three-dimensional joint rotations in human movement analysis have been mainly described by Euler/Cardan angles. Due to sequence dependence, each combination of three Euler/Cardan angles defines a single pattern of joint rotation. When the rotation pattern is unknown, it needs to be considered using a particular sequence of Euler/Cardan angles to represent joint rotations. In this paper a spherical rotation coordinate system is developed for describing three-dimensional joint rotations using a method of rotation involving two steps: a long axis rotation and a pure axial rotation. Two angles of the classical spherical coordinate system--longitude and latitude--are used to describe long axis rotations in this newly proposed coordinate system. The spherical rotation coordinate system uses a radial rotation angle to describe pure axial rotation of a limb segment whereas the classical spherical coordinate system uses a radial displacement to describe motion of a point. An application of the spherical rotation coordinate system is given to define three-dimensional rotations of the glenohumeral joint. A mathematical proof shows that the long axis rotation and axial rotation are sequence independent. Two numerical examples are investigated which demonstrate that the spherical rotation angles can be uniquely determined in both forward and inverse kinematics without considering sequences rotations.