DR. P.V.A. MOHANDAS
Computer navigated surgery reduces the scope of human error and increases the success rate of such operations.
REPLACING arthritic joints has come of age with the introduction of computer navigation. Sir John Charnley innovated joint replacement 40 years ago. Since then, there have been enormous changes in the materials used and the techniques of surgery and most of the technical problems have been overcome.The component material and the design have been changed considerably to prevent component wear. If joint replacement is so successful in giving patients complete relief from pain and restoration of function, then what is the problem? The problem is the long-term survival of these artificial joints.
Comprehensive follow-up of these patients over the last 40 years has shown that if the joints were placed very accurately, it contributed to the long-term survival of the joints. To eliminate human error in placing the joints accurately, we find that Computer Navigated Joint Replacement is the only recourse. Two MIRAS (Minimally invasive reflective arrays) are mounted - one on the thighbone (femur) and another on the leg bone below the knee (tibia) on Steinmannpins. The camera attached to the computer has two widely spaced lenses (like eyes) and looks at the patient and the two arrays. The instrument and cutting jigs also have reflective arrays. Infrared beams from the camera lenses are reflected by the MIRAS and the computer registers three dimensions the MIRAS, the instruments and patient's hip, knee and ankle.By moving the limb with these reflective arrays and by pointing out special area in the limb with the instruments, the computer establishes in three dimensions the patient's normal and anatomical axis of the knee. Using navigable cutting jigs the computer allows the surgeon to do the bony cuts, balance the soft tissues and implant the knee components with near zero degree error. Surgeons have today mastered the sophisticated cutting jigs to produce accurate bone cuts and implant the components regularly in an exact axis.
Bend the knee
In the Eastern countries deep knee flexion for kneeling, squatting or sitting cross-legged is vital for social, religious, or cultural activities. Muslims pray five times a day, which requires kneeling. Many Indians sit cross-legged on the floor.In the Western world, patients require deep knee flexion more for leisure and sports activities.The ultra modern design of the High Flexion Knee with refined cam and post-mechanism; refined Sagittal radius of the posterior condyles and patello-femoral design provides 155 degrees of knee flexion. This is the maximum flexion provided by a normal adult knee.
In these days of technology explosion, the surgeon and the patient prefer to have most surgical procedures done by a minimally invasive technique. With minimally invasive or keyhole surgery, special instruments like laproscopes are required for surgery.MITKR is done by computer navigation, which enables the computer to visualise those portions of the joint that can't be seen due to the small incision. The computer also enables the components to be placed in the exact anatomical axis thereby preventing wear and ensuring the longevity of the joint.Due to the extremely small skin incision, the damage to the muscles and tendons during implantation is very minimal. Therefore the pain is much less and the functional result much better. The cutting blocks for the surgery and also the use of special reciprocating saws to make the cuts enables the surgeon to perform this surgery through a small incision. Minimally invasive, computer navigated TKR (MITKR) is the future of knee replacement surgery.