Knee osteoarthrosis with extra-articular femoral deformity treated with total knee arthroplasty: A case series

Abstract

A successful Total knee arthroplasty (TKA) procedure requires restoration of mechanical axis and soft tissue balancing. Deformity of tibia and femur occurs with history of trauma or osteotomy, infection, metabolic bone disease and excessive bowing. Tackling pre-existing extra-articular deformity of lower limbs during total knee arthroplasty can be challenging due to difficulty in restoring alignment axis and soft tissue balancing. We have recorded 6 patients underwent total knee arthroplasty with preexisting extra-articular femoral deformity by intra-articular correction from 1995 to 2017. All patients had extra-articular deformity of the femur due to fracture malunion which were treated either conservatively, plating or intra-medullary nail. Coronal deformity is corrected from an average of 15.5 degrees to 4.6 degrees from neutral axis. Sagittal deformity is corrected from average of 6.8 degrees to 3.6 degrees. One patient developed progressive genu recurvatum at 7 years follow-up with range of motion at 25 degrees extension and 110 degrees flexion. The average pre-operative Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score was 68.5 (range 51−87) decreased to 50.7 (range 21–71) at 12 months post-operative and Knee score averaged 53.3 (range 51–55) increased to an average of 88.5 (range 82–94). There was only one revision for aseptic loosening 16 years after total knee replacement (TKR) and no other cases of radiological sign of aseptic loosening. In conclusion, Intra-articular correction of an extra articular femoral deformity for TKR is an attractive approach in mild to moderate deformity further from the knee joint.