A Study on the Alignment of the Lower Extremity in Patients with Rheumatoid Arthritis before Total Knee Arthroplasty

摘要

Though it is believed that alignment of lower extremities in rheumatoid arthritis (RA) is characterized as valgus knee, there are few reports written about it including bowing deformity of femur and tibia in detail. The angles representing alignment of lower extremities were measured by standing full-length A-P X-ray films. Forty cases and 80 lower extremities were evaluated. All cases were diagnosed as RA by ACR criteria. All X-ray films were taken bofore total knee arthroplasty. The average age was 63.1 years old, the average onset of RA was at 48.8 years and the average duration of RA was 14.4 years. They were classified into three groups (valgus, neutral, varus) by femoro-tibial angle (FTA). Duration and onset were studied among the three groups. The femoral neck angles and the angle of bowing of distal femur, proximal tibia and distal tibia were compared between the three groups. The average FTA was 175.0°. The valgus group had longer duration of RA and a younger onset. In addition, femoral neck angles of the valgus group were larger and medial bowing of distal femur, proximal tibia and distal tibia were observed compared to other two groups. It was suggested that alignment of lower extremities in younger onset of RA showed valgus deformity in spite of the tendency of varus deformity due to aging. The lower extremities of valgus/varus deformity of RA showed bowing deformity of femur and tibia.