Managing Severe Deformities With Calipered Kinematic Alignment

Kinematically aligned (KA) total knee arthroplasty (TKA) for severe deformity is addressed exactly as commonly treated mild deformed knees. As opposed to mechanically aligned (MA) TKA for severe deformity, no releases of soft tissue are routinely used. We can achieve desired physiological correction of the HKA (hip knee ankle) angle toward the prediseased individual alignment with respect of natural joint-line obliquity restoration. It is our belief that reconstructing the knee toward its physiologic state improves patient pain and motion, without the sensation of a nonnatural knee we typically used to see when applying MA for severe deformity. The common principle we apply for all severe deformities originates from the understanding that restoring the patient alignment to its prearthritic state without manipulating the soft tissue envelope will result in a more natural joint. We do not differentiate between long-standing extraarticular deformities and arthritic severe deformities, in that we aim to restore the articular joint and its corresponding soft tissue and muscular structures to the state that is regular for the individual patient. We do not find this different to simple common minor arthritic deformity, where our KA TKA goal is the same. The main concern, which is related to the lack of long-term follow-up of patients, is theoretically related to survivorship of the prosthetic constructs under pronounced angulations, which are typically found with those severe deformities. This concern has been slowly but repeatedly challenged during the last decade, with more evidence to support the neglect of old dogmatic mechanical assumptions becoming evident.