OBJECTIVE: To evaluate the physical characteristics (durability, calibration, creep and hysteresis) and the accuracy and repeatability of the F-Scan in-shoe sensor. DESIGN: Observations of the system in clinical use combined with material bench-test experiments. BACKGROUND: The F-Scan system is a commercially produced in-shoe force/pressure measurement system. Whilst useful clinical studies have been reported there is little information on the performance characteristics of the system. METHODS: Output mass error following calibration was directly measured from the F-Scan system. A jig-mounted force meter tested groups of individual sensing units (4 @ 1 cm(-2)) for within and between sensor accuracy in full size and adjusted sensors. An Instron servohydraulic materials testing unit was used to evaluate creep, hysteresis and the repeatability of output forces over repeated loading cycles for full size and cut sensors. RESULTS: The F-Scan system lacks durability and suffers significant calibration error. Creep (19%) and hysteresis (21%) properties were poor. Within and between sensor variability in output was demonstrated and overall repeatability was poor. Adjusting the sensor size adversely affects output. CONCLUSIONS: Our findings suggest the F-Scan system has a limited capability for absolute accuracy but could still be used for quantitative studies provided its limitations are noted. RELEVANCE: These findings may help F-Scan users evaluate the relevance of clinical data and refine measurement protocols in the context of their own field of work.

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The loss of cervical lordosis in radiographs of patients presenting with neck pain is sometimes ascribed to muscle spasm. We performed a cross-sectional study of the prevalence of 'straight' cervical spines in three populations: 83 patients presenting to an accident department with acute neck pain, 83 referred to a radiology department with chronic neck problems, and 80 radiographs from a normal population survey carried out in 1958. Curvature was assessed on lateral radiographs both subjectively and by measurement. The prevalence of 'straight' cervical spines was 19% in the acute cases and 26% in the chronic cases. The 95% confidence interval for the difference was-6.4% to +19.3%. In the normal population 42% showed a straight spine, but a further third of these films had been taken in a position of cervical kyphosis; this probably reflects a difference in positioning technique. Women were more likely than men to have a straight cervical spine, with an odds ratio of 2.81 (95% CI 1.23 to 6.44). Our results fail to support the hypothesis that loss of cervical lordosis reflects muscle spasm caused by pain in the neck.

People of South Asian ethnic status terminate DMARD therapy sooner than North Europeans. The reasons for this difference are not clear but may concern problems with effective communication, cultural differences in attitudes to chronic illness or genetic polymorphisms in drug metabolism.