Reliability study of tibialis posterior and selected leg muscle EMG and multi-segment foot kinematics in rheumatoid arthritis associated pes planovalgus.
OBJECTIVE
To determine within- and between-day reliability characteristics of electromyographic (EMG) activity patterns of selected lower leg muscles and kinematic variables in patients with rheumatoid arthritis (RA) and pes planovalgus.


METHODS
Five patients with RA underwent gait analysis barefoot and shod on two occasions 1 week apart. Fine-wire (tibialis posterior [TP]) and surface EMG for selected muscles and 3D kinematics using a multi-segmented foot model was undertaken barefoot and shod. Reliability of pre-determined variables including EMG activity patterns and inter-segment kinematics were analysed using coefficients of multiple correlation, intraclass correlation coefficients (ICC) and the standard error of the measurement (SEM).


RESULTS
Muscle activation patterns within- and between-day ranged from fair-to-good to excellent in both conditions. Discrete temporal and amplitude variables were highly variable across all muscle groups in both conditions but particularly poor for TP and peroneus longus. SEMs ranged from 1% to 9% of stance and 4% to 27% of maximum voluntary contraction; in most cases the 95% confidence interval crossed zero. Excellent within-day reliability was found for the inter-segment kinematics in both conditions. Between-day reliability ranged from fair-to-good to excellent for kinematic variables and all ICCs were excellent; the SEM ranged from 0.60° to 1.99°.


CONCLUSIONS
Multi-segmented foot kinematics can be reliably measured in RA patients with pes planovalgus. Serial measurement of discrete variables for TP and other selected leg muscles via EMG is not supported from the findings in this cohort of RA patients. Caution should be exercised when EMG measurements are considered to study disease progression or intervention effects.
Institute for Applied Health Research, School of Health and Life Sciences, Glasgow Caledonian University, Glasgow, United Kingdom. ruth.barn@gcu.ac.uk
Ruth
R
Barn
Daniel
D
Rafferty
Deborah E
DE
Turner
James
J
Woodburn
D000328:Adult; D000368:Aged; D001172:Arthritis, Rheumatoid / Q000150:complications* / Q000175:diagnosis; D001696:Biomechanical Phenomena; D016001:Confidence Intervals; D004576:Electromyography; D005260:Female; D005528:Foot; D005531:Foot Deformities, Acquired / Q000209:etiology / Q000503:physiopathology*; D005684:Gait / Q000502:physiology*; D006801:Humans; D007866:Leg / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012494:Sampling Studies; D012720:Severity of Illness Index