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Computer assisted surgery in Total Knee Replacement (CAS – TKA)

Introduction

As the name implies, this surgical technique, also referred to as 'CAS-TKR' (Computer Assisted Surgery - Total Knee Replacement) or 'computer navigation', involves the use of computer assistance to guide the surgeon to ensure accurate preparation of the thigh bone (femur) and shin bone (tibia) before positioning the artificial knee joint. Accurate positioning and alignment of the prosthetic knee joint components is a critical factor in ensuring good functional and clinical outcomes.

CAS-TKR is based on techniques first deployed in brain and spinal surgery (neurosurgery).

Studies indicate that this approach allows the surgeon to more accurately align the new prosthetic knee joint by giving more accurate guidance for preparing bone tissue and ligament balancing.

The technique is especially useful in patients with a larger body build and/or where there are bone deformities after trauma.

Procedure

Conventional knee replacement surgery involves the use of handheld jigs and rods to ensure accurate placement of the artificial joint components. CAS-TKR instead uses a computer connected to an infrared camera positioned above the patient and connected to 'trackers' fixed to the femur and tibia, and to the cutting blocks.

Real-time 3D images of the knee and the surgical instruments guide the surgeon during the procedure while preparing the femur and tibia prior to fitting the new joint and during the positioning of the joint. The technique is accurate to tolerances of 1mm and 1 degree.

A more recent development is surface - navigation technology, which is a set of wireless electronic pods which monitors the patient's exact anatomic axis prior to the procedure so that the new prosthesis matches this precisely.