Abstract
Introduction
In total knee arthroplasty (TKA), the correct positioning of the components is a key element to obtain good functionality and durability of the implant. The use of computer-assisted surgery (CAS) in TKA ensure excellent limb alignment, components orientation and ligament balancing; however, it is still unclear whether this translates to better mid- to long-term clinical and functional outcomes. We present our clinical, functional and radiological results in a case series of two hundred implants at a medium follow up of 2.5 years.
Material and Methods
Between March 2008 and January 2013 we performed 200 computer navigated TKAs in 180 patients. The average age of the patients was 64 years. The average BMI was 28 kg/m2. In all cases we implanted a posterior stabilised, fixed bearing TKA and adopted a protocol of pre- and intra-operative administration of tranexamic acid. We never performed patellar prosthesis. A radiographic assessment was made to all patients with pre- and post-surgery X-ray in the antero-posterior, lateral and axial-patella projection. Coronal plane alignment was measured by standard weight-bearing anteroposterior radiographs including the femoral head, knee and ankle. Computed tomography (CT) with artifact reduction was also carried out to evaluate axial or rotational femoral and tibial alignment. Clinical and functional evaluations were effected on the basis of the Knee Society Scoring System (KSS) and Tegner activity level score. Blood loss and reduction in haemoglobin were considered too. The medium follow-up was 2.5 years (minimum 1 year; maximum 5 years).
Results
We got excellent limb alignment and ligament balancing, as well as a very accurate axial orientation of the components (as shown on CT scans). Mean KSS was 44,6 +− 13.7 preoperatively; 75,4 +− 13.5 at 6 months follow-up; 83.4 +− 18.5 at 1 year follow up; 80.4 +−16.4 at 2 years follow up. Mean Tegner score was 34.2 +− 6.9 preoperatively; 67.3+− 12.6 at 6 months follow-up; 72.8+− 9.2 at 1 year follow up; 71.4 +− 13.5 at 2 years follow up. We also noticed a reduction in blood loss, due to non-use of intramedullary nail and to pre- and intra-operative administration of tranexamic acid
Discussion and conclusions
Computer navigation provides reproducible results in terms of alignment and kinematics, as well as a considerable reduction of the outliers. Nowadays CAS can be used as a “kinematic tool”: it allows to evaluate and to quantify the biomechanical performance of the knee, throughout the range of motion, by comparing the kinematic pattern between the osteoarthritic knee and the prosthesised one. However, further investigations with longer follow-up are needed to establish a correlation between these results and the durablity of the implant.
