Total knee replacement is one of the most commonly performed orthopedic procedures. As of 2010, about 600,000 total knee replacements were being performed annually in the United States and these numbers are rising. The normal knee joint functions as a complex hinge allowing primarily flexion and extension, rotation and gliding. The knee joint is made up of three compartments, the lateral, medial and anterior (patellofemoral). Damage to the cartilage of one or more compartments may be the result of osteoarthritis (idiopathic or post-traumatic), inflammatory arthritis (rheumatoid,psoriatic, etc.), a-vascular necrosis, tumors, or congenital deformities. Osteoarthritis and rheumatoid arthritis are the causes of the overwhelming majority of total joint arthroplasties.

A successful Total knee arthroplasty(TKA) surgery includes: an accurate alignment( the mechanical axis in axial and rotational planes), as well as significant pain relief which improves function and quality of life. Incorrect alignment can lead to abnormal wear, premature mechanical loosening of the components and patellofemoral problems.

The common techniques for Total knee replacement are:

1. Conventional method TKR
2. CT/MRI-based preoperative navigated TKR
3. Image-free intraoperative navigated TKR In our research we focus on the 3rd method using the Orthopilot navigation system Aesculap®, Tutlingen, Germany. This system is an active PC based guiding system that helps the surgeon decide on the accurate alignment and orientation of the implant and cutting surfaces of the bone and thus avoid incorrect alignment.

We aim to compare between pre-operative and post-operative lower limb alignment (mechanical axis) in Aesculap based TKA using serview CT. Furthermore, we will try to examine the existence of a correlation between the CT scans and the Orthopilot navigation system output and assess the clinical outcome of the patient postoperatively.

Our Hypothesis is that the intra-operative navigation system is accurate and correlated to CT images results, moreover, allows the surgeon to achieve a good mechanical axis and high clinical outcome,

Inclusion Criteria:

• age over 18
• severe osteoarthrosis of the knee
• failure of conservative treatment.

Exclusion Criteria:

• patients with severe vascular disease
• secondary knee deformation due to muscular atrophy or disease
• active infection
• morbid obesity
• neuropathic knee and osteomyelitis.

patients undergoing navigated total knee replacement