Kinematics at the ankle joint complex in rheumatoid arthritis

Abstract

This thesis investigates the three-dimensional kinematics at the ankle joint complex in rheumatoid arthritis. Previous studies have identified the rearfoot as a common site for inflammatory activity in rheumatoid arthritis resulting in painful and disabling deformity for which there are no proven interventions. A generic electromagnetic tracking system was developed to undertake three-dimensional kinematics at the ankle joint complex in the bare and shod foot during gait. A joint simulator was designed, manufactured and commissioned in house to test the accuracy of the system. The results indicated errors of less than 1° in rotation and 1 mm in position measurements. Clinical testing of the measurement system was undertaken in both normal healthy adults and rheumatoid arthritis subjects. The technique was able to measure the characteristic three-dimensional kinematics for the ankle joint complex in the normal subjects and detected accurately abnormal angular rotations in the rheumatoid arthritis group. In both cohorts the within day repeatability of the measurements were good, and over a longer period data were stable in the rheumatoid arthritis group allowing the technique to be used in longitudinal studies. Finally, skin movement artefact where the electromagnetic sensor is attached on the heel was investigated using a magnetic resonance imaging technique and found to be less than 1° across the range of motion for the joint complex. Kinematic measurements were undertaken in two cohorts of rheumatoid arthritis subjects randomised to receive or not custom manufactured foot orthoses to correct early valgus heel deformity. The orthoses were constructed in rigid carbon graphite and modified to offer the correct degree of movement control for each patient. Kinematic data were compared between the rheumatoid arthritis groups and that measured from an age- and sex-matched healthy adult population. In both rheumatoid arthritis groups abnormal kinematics were easily detected with significant alteration of inversion/eversion and internal/external rotation. With foot orthoses the inversion/eversion angular rotations were almost fully restored to normal, but little effect was observed for internal/external rotation. The rheumatoid arthritis patients underwent repeat kinematic measurement over a period of 30-months. In the control group the angular rotations improved slightly from baseline, although in comparison with normal healthy population remained abnormal. In the intervention group the orthotic control of inversion/eversion was sustainable for 30 months. Furthermore, coupling between inversion/eversion and internal/external rotation was partially restored towards the end of the study. In barefoot walking the intervention group demonstrated a substantial correction of the deformity in the frontal plane. It was attempted to explain the results in terms of soft-tissue laxity and adaptation following correction of joint deformity. Three-dimensional kinematic measurements were also conducted at the knee and calcaneotalonavicular joint complex. Abnormal rotations and orthotic response were demonstrable at these joints but with less satisfactory results because of technical limitations of the measurement technique. Plantar pressure distribution was also studied using an in-shoe measurement technique. Custom designed orthoses were found to alter the pressure and force distribution at the interface with the foot. The largest effects were observed at the heel and midfoot regions and these were sustainable and significantly different from the non-intervention control group. The clinical effectiveness of the foot orthoses was also evaluated. A pragmatic randomised controlled trial was undertaken and serial measurements of foot pain and disability, using the Foot Function Index conducted at baseline and 3,6 12,18,24 and 30-months. The results revealed an immediate and significant reduction in foot pain and disability with foot orthoses. Minor adverse reactions were reported but overall comfort levels and compliance were high. The overall reduction in foot pain and disability was sustained up to 30 months