The Impact of Bone Deformity on Osteoarthritic Varus Knee Correctability

Background Bone deformities in the varus osteoarthritic knee may influence soft-tissue balancing and therefore knee correctability. The hypothesis of the present study was that the grade of coronal plane knee deformity may influence directly knee correctability along the entire range of motion from 0° to 90°. Tibial and femoral epiphyseal bone deformities were also analyzed to determine which kind had the greater impact on knee correctability. Methods A coronal plane deformity radiographic assessment and an intraoperative correctability assessment using computer-assisted surgery were performed on 118 varus osteoarthritic knees undergoing total knee arthroplasty. Knees were divided into groups taking into account the kind of bone deformity (tibial, femoral, and combined). Results A significant inverse correlation was found between coronal plane deformity and knee correctability at every 10 degrees of flexion. Correlation was strong at 0° and progressively got weaker at further flexion angles. According to literature, knees with a varus deformity >10° were rarely correctable in full extension, but often correctable in flexion, whereas knees with varus deformity >15° showed to be almost never correctable. Combined deformity group had a significantly lower rate of correctability along the entire range of motion. Conclusion The severity of varus knee malalignment always influenced knee correctability with the knee in full extension, in further flexion (20°-60°), correctability was mildly affected. Isolated tibial epiphyseal deformity and combined epiphyseal deformity have the greatest impact on knee correctability.