A new motorized seat for a patient with juvenile polyarticular arthritis

Abstract

A 42-year-old patient with multiple joint involvement including bilateral hip replacement and no movement of the knees or ankles required a custom made chair to enable her to be seated from a standing position by only allowing flexion of both hips. A motorized chair was designed and made that had a moveable footrest and seat unit powered by a linear actuator that allowed the patient to stand on the footrests when this unit was vertical and the seat angled at 45°. On activating the actuator by a joystick mounted on the armrest the footrests rolled forward along the floor whilst the seat fell to the horizontal in the final seated position. Two moveable axilla supports allowed the patient to share the load du ring seating between the shoulders and feet and away from the hips and knees as well as providing assurance against falling forward during upward movement of the seat. The problemThe patient is a 42-year-old female with multiple joint involvement because of juvenile polyarticular chronic arthritis (Stills disease). She has a range of active flexion at the knees of 0-20° for the left and 5-10° for the right with a valgus angulation of 10° for the left and 2° for the right. Both hips have a range of flexion of 30-70°, both being replaced seven years ago using conventional Charnley procedures involving trochanteric osteotomy and a low friction arthroplasty. One year ago the left hip was revised due to pain caused by loosening which involved revision arthroplasty using a long stem design of prosthesis and further shortening of the left leg. Her left leg has always been shorter and is currently 5.75in (14.5cm) less than the right leg, the shoe has been raised by this amount. Both her ankles are limited and painful in movement with a plantar-dorsal range of flexion of 15° on both sides. Her upper limbs are also severely affected with a 70° limit of abduction on both sides, with little strength in both arms to aid sitting and rising from a chair.With these clinical features it has been impossible to match any of the existing electrically and mechanically operated chairs to her needs to sit and rise with no arm assistance, no knee flexion and provide stability during the sitting or raising action. The majority of the self-lift chairs had