Evaluating intratester reliability of manual masking of plantar pressure measurements associated with chronic gout.

BACKGROUND: Plantar pressure measurements are commonly used to evaluate foot function in chronic musculoskeletal conditions. However, manually identifying anatomical landmarks is a source of measurement error and can produce unreliable data. The aim of this study was to evaluate intratester reliability associated with manual masking of plantar pressure measurements in patients with gout. METHODS: Twenty-five patients with chronic gout (mean disease duration, 22 years) were recruited from rheumatology outpatient clinics. Patients were excluded if they were experiencing an acute gout flare at the time of assessment, had lower-limb amputation, or had diabetes mellitus. Manual masking of peak plantar pressures and pressure-time integrals under ten regions of the foot were undertaken on two occasions on the same day using an in-shoe pressure measurement system. Test-retest reliability was assessed by using intraclass correlation coefficients, SEM, 95% limits of agreement, and minimal detectable change. RESULTS: Mean peak pressure intraclass correlation coefficients ranged from 0.92 to 0.97, with SEM of 8% to 14%. The 95% limits of agreement ranged from-150.3 to 133.5 kPa, and the minimal detectable change ranged from 30.8 to 80.6 kPa. For pressure-time integrals, intraclass correlation coefficients were 0.86 to 0.94, and SEM were 5% to 29%, with the greater errors observed under the toes. The 95% limits of agreement ranged from -48.5 to 48.8 kPa/sec, and the minimal detectable change ranged from 6.8 to 21.0 kPa/sec. CONCLUSIONS: These findings provide clinicians with information confirming the errors associated with manual masking of plantar pressure measurements in patients with gout.

Functional and biomechanical characteristics of foot disease in chronic gout: A case-control study.

OBJECTIVES: despite the predilection of gout to the feet, the impact of gout on foot function and biomechanics is currently unknown. The aim of this study was to describe the effects of chronic gout upon function and selected biomechanical parameters associated with gait. METHODS: twenty-five patients with a history of gout were compared with 25 age and gender matched control participants with no history of gout or other forms of arthritis. General function, foot specific disease activity and lower limb activities were determined using the Health Assessment Questionnaire, Foot Function Index (pain domain), and Leeds Foot Impact Scale respectively. Each patient also underwent a gait assessment that included plantar pressure measurements and an evaluation of temporal-spatial gait parameters. FINDINGS: patients with chronic gout had higher levels of general and foot-specific disability, pain and impairment (P ≤0.001). Significantly lower peak plantar pressures were observed in the hallux of patients with chronic gout (P ≤0.05). Significantly higher pressure-time integrals were observed in the cases at the midfoot (P ≤0.05), but lower values were observed at the hallux (P ≤0.05). Patients with chronic gout walked slower, with longer step and stride lengths compared to the controls. INTERPRETATION: patients with chronic gout experience pain and disability associated with their feet. Different toe-off strategies may account for functional changes and pain associated with foot problems in chronic gout.

Development of a computed tomography method of scoring bone erosion in patients with gout: validation and clinical implications.

OBJECTIVES: To develop a method of scoring bone erosion in the feet of patients with gout using CT as an outcome measure for chronic gout studies, consistent with the components of the OMERACT filter. METHODS: Clinical assessment, plain radiographs and CT scans of both feet were obtained from 25 patients with chronic gout. CT scans were scored for bone erosion using a semi-quantitative method based on the Rheumatoid Arthritis MRI Scoring System (RAMRIS). CT bone erosion was assessed at 22 bones in each foot (total 1100 bones) by two independent radiologists. A number of different models were assessed to determine the optimal CT scoring system for bone erosion, incorporating the frequency of involvement and inter-reader reliability for individual bones. RESULTS: An optimal model was identified with low number of bones required for scoring (seven bones/foot), inclusion of bones over the entire foot, high reliability and ability to capture a high proportion of disease. This model included the following bones in each foot: first metatarsal (MT) head, second to fourth MT base, cuboid, middle cuneiform and distal tibia (range 0-140). Scores from this model correlated with plain radiographic damage scores (r = 0.86, P < 0.0001) and disease duration (r = 0.42, P < 0.05). Scores were higher in those with clinically apparent tophaceous disease than in those without tophi (P < 0.0001). CONCLUSIONS: We have developed a preliminary method of assessing bone erosion in gout using conventional CT. Further testing of this method is now required, ideally in prospective studies to allow analysis of the sensitivity to change of the measure.