Abstract
Malpositioning of the component of a total knee implant and malalignment of the leg is one of the significant factors for the outcome after Total Knee Arthroplasty.
Previous studies have shown that the use of a navigation system can improve these. This article presents the initial results of a prospective and non-randomised study describing navigated implantation in TKA with special reference to soft tissue balancing in knees with posttraumatic deformity. The secondary objective is to found out reproducibility of the software.
Methods: Since January 2004, 15 patients with post-traumatic arthrosis of the knee and axial malalignment of more than 15 degrees, pre operative arc of motion 75 degrees admitted to our senior author for TKA have been followed up prospectively. The data were collected over a period of 25 months. Apart from the usual clinical evaluations, no patients had CT of the leg prior to the operation & postoperatively. Intra-operative and peri-operative morbidity data were collected and blood loss measured.
Results: A postoperative leg axis between 3 degrees varus and 3 degrees valgus was obtained in all of the navigated knees after soft tissue balancing. The alignment of the components using computer-assisted surgery in regard to femoral varus/valgus, femoral rotation, tibial varus/valgus, tibial posterior slope, tibial rotation are reproducible and consistent. Computer-assisted surgery took longer with a mean increase of 31 minutes for kinematic data acquition. Intraoperatively we achieved range of motion more than 120 degrees. No patient required manipulation postoperatively for improving range of motion
Conclusion: These results support that the precise surgical reconstruction of the mechanical axis of the knee and proper alignment of the component is achievable in patients who suffered posttraumatic deformities and secondary arthrosis by using an intraoperative navigation system.
It has been mentioned in the literature that minor deviations in the insertion point of Intramedullary instrumentation during TKA may result in malalign-ment of several degrees [Nuno-Siebrecht 2000], which can be avoided with these soft ware.
Correspondence should be addressed to Mr Carlos Wigderowitz, Senior Lecturer, University Department of Orthopaedic and Trauma Surgery, Ninewells Hospital and Medical School, Dundee DD1 9SY.
