Management of different forms of varus deformity during total knee arthroplasty

ABSTRACT

Varus deformity of the lower limb is a common association of knee arthritis. The deformity-and more precisely its apex-is usually situated at the level of the joint and results from wear of the articular cartilage and subchondral bone underneath. Less commonly this deformity-due to non-united fracture, or malperformed osteotomy-maybe situated away from the joint line along the axes of the tibia or the femur. Two types of varus knee deformity in knee arthritis are therefore distinguishable, the intraarticular and the extra-articular types. Each of these types requires and deserves special attention and different way of correction during replacement of the knee joint. In this article three groups of varus osteoarthritic knees are presented, evaluated and compared. The first group comprised 82 knees with intraarticular deformity that ranged from 17 to 32 degrees and treated with total replacement of the joint after adequate soft tissue release. In the second and third groups 22 osteoarthritic knees with extraarticular varus deformity that ranged from 18 to 35 degrees were presented and differentiated according to the mode of surgical correction of the varus deformity. In one group compensatory bone cuts were carried out ignoring and compensating for the extraarticular deformity and correcting at the same time the overall limb alignment and the inclination of the joint line. In the other group, a single stage procedure that included a separate osteotomy away from the joint level corrected the deformity prior to replacement of the knee. Comparison of the three groups in this study demonstrated that total knee arthroplasty in knees with intra-articular varus deformities was relatively a simpler procedure and had superior results to the arthroplasty of the knees with extraarticular varus deformity. This procedure however, necessitated special attention to soft tissue balancing and special care in the repair of the released tissue. In the groups with extraarticular deformity limb alignment was a major concern. The worst results however, were obtained when compensatory bone resection was the technique of correction of the extraarticular varus and this was mainly due to ligament laxity. In this group tibial compensatory resection had better results than femoral compensatory resection. It is therefore concluded that during total knee arthroplasty extraarticular varus deformity is best managed independently through a separate osteotomy situated at the apex of the deformity. Careful soft tissue release and adequate repair of the released tissues were necessary for the stability after total knee arthroplasty in knees with intraarticular varus deformity