Computer-aided preoperative planning in knee osteotomy.

It has been demonstrated that osteoarthritis (OA) is activity related and may worsen when joint contact stress becomes excessive due to overloading. Hence, joint alignment and loading are considered to be the key biomechanical determinants for OA. The initiation of pathologic changes in the knee has been described by the mechanism termed, "vicious cycle" in which joint axial malalignment creates excessive stresses to the localized joint cartilage/subchondral bone regions and the surrounding soft tissue which in turn produces more laxity and joint deformity and thus repeats the cyclic degradation mechanism. If this degenerative cycle can be broken with joint alignment surgery such as osteotomy, a procedure to realign the knee joint and thus redistribute joint forces applied to each compartment, performed properly and at the appropriate time, the osteoarthritic disease process can be decelerated and even reversed. The main goals of this paper are to emphasize the importance of accurate preoperative planning for osteotomy in order to properly correct joint alignment, and to justify the application of an existing computer program, OASIS (Osteotomy Analysis and Simulation Software) using plain radiographs to perform appropriate surgical planning. Normal subjects and knee osteotomy patients were studied to establish a database for the purpose of establishing the utility and efficacy of the presently proposed concept. We wish to rationalize knee osteotomy as a preferred and cost-effective treatment for patients with early symptoms of OA in the knee. This paper presents a new concept of preoperative planning for knee osteotomy based on the underlying etiology of the disease and biomechanical viewpoint with strong emphasis on surgical treatment rationales. The established principles in this paper can be applied to other joints of the body and will help implement preventive measures and other non-surgical means to manage patients with axial malalignment or early degenerative changes.