Abstract
Introduction
There is a controversy with regard to the treatment of osteoarthritis (OA) of the knee in patients with considerable deformities of the femoral or tibial shafts. Some surgeons prefer to correct the deformity while performing TKA at the level of the knee joint. However, this technique requires accurate planning and execution of the planned cuts. In addition, the use of intramedullary guides in such cases may not be possible or desirable and may lead to complications. There is a strong indication for using navigation in such cases.
Methods
The navigation technique was used in both laboratory and clinical setting, First, we compared between navigational and conventional techniques in performing TKA in 24 plastic knee specimens (Sawbones, Sweden) that have osteoarthritic changes and complex tibial or femoral deformities. A demo kit for conventional instrumentation of posterior stabilised TKA (Scorpio, Stryker) was used for 12 cases and an image-free navigation system (Stryker) was used for a corresponding 12 cases. There were 4 different deformities; severe mid-shaft tibial varus, severe distal third femoral valgus, complex deformity distal femur and deformity following a revision TKA. The surgical procedures were performed by 3 arthroplasty surgeons, each surgeon operated on 8 knee specimens (4 knees in each arm of the study with 4 different deformities). Deformities were corrected at the level of the knee joint during TKA without prior osteotomies. For conventional techniques, surgeons used a combination of both intramedullary and extramedullary guides. Postoperative long leg radiographs were used to assess coronal alignment. Second, we used the same navigational technique clinically to perform TKA in patients with extra-articular deformities.
Results
Using both navigational and conventional techniques, it was possible to indirectly correct shaft deformities by adjusting the inclination of bone cuts at the level of the knee joint. The amount of bone cutting at distal femur and proximal tibia were variable depending on the location and direction of the deformity. There was no compromise of collateral ligaments or patellar tendons in both techniques. However, the accuracy of restoring normal alignment was better in navigational techniques. The results of the clinical cases are still in progress waiting analysis of a longer term follow up.
Discussion
Navigational techniques eliminated the use of both intramedullary and extramedullary guides. The improved accuracy with navigational techniques led to better alignment that can improve functional and survival outcome of similar cases of TKA in real patients.
