A Kinematic approach to Knee Replacements

Knee is the largest and the most complex joint in the body. It is very much needed for any form of movement – such as running, walking, swimming and cycling.  On most occasions, knee replacement is usually done in people aged 60 and older. Knee replacement is a surgical procedure to resurface a knee damaged by arthritis. Various types of arthritis may be prevalent in people. Metal and plastic parts are used to cap the ends of the bones that form a knee joint. The goal of knee replacement surgery is to resurface the parts of the knee joint that have been damaged and to relieve knee pain that cannot be controlled by other treatments.

Prof. Dr. D Gokulraj, from Fortis Hospital, Vadapalani explains about the updated Kinematic alignment treatment in Knee Replacement and its difference with the regular replacement.

There are usually two main types of knee replacement: total and partial. Total replacement is when the entire joint is replaced with artificial surfaces; partial knee replacement, where only one damaged component of the knee is replaced.

What is Kinematic knee  alignment

‘Kinen’ in old Greek means to move and the word kinematics is the part of classical mechanics. Kinematic axes of movement depend upon how the flex rotates and flexes. Hence, the Kinematic alignment is a 3D alignment and cannot be studied as a whole only through an X-ray.

Process of Kinematic knee alignment

It is a customized method of positioning a knee replacement with the aim of restoring native, pre-arthritic joint lines and rotational axes of patients knee. This is not the traditional total knee replacement method. This is an alternative technique for positioning total knee arthroplasty (TKA). Knee replacements are aligned by a philosophy called Mechanical Alignment. In this alignment the leg is brought to look like a “straight” leg. But the difficulty here is that most of the knees are not naturally straight. Only 2% are naturally straight using hip-knee-angle method on X-ray.

Kinematic alignment is a relatively new surgical technique for implementing total knee replacement. Majority of the patients are eligible for this procedure and hence this is highly recommended by the Orthopaedic surgeons worldwide. This method of Kinematically aligning is a relatively easier and a straightforward method. It is used in the total knee replacement arthroplasty (TKA), which is a surgical technique that is developed recently aiming at anatomically positioning and kinematically align all the knee components. The process aims to resurface the knee joint by removing a cartilage and bone thickness equivalent to the implant thickness and where the knee implants are aligned on the knee kinematic axis that dictates the motion / movement.

The procedure

Here the implant is custom positioned right on the joint line of the knee to help it naturally align your knee with the implant. This customized position, kinematically aligned total knee replacement may bring your knee back to your healthier days. Patients who have undergone a kinematic alignment experienced better outcome and reported significant benefits like better pain relief, knee functioning, and bending of the knee when compared to patients who undergone mechanical knee replacement.

Many of these benefits are due to the fact that kinematically alignment uses caliper measurements to adjust the position of the implants to within 1/2 of a millimeter. Half millimeter adjustments are much more accurate than robotics and navigational instruments, which are used to perform mechanic alignment.

Advantages

• After surgery, patients who are aligned with kinematic knee replacement reported that their knee returned to normal functioning quickly. One can walk without a walker and be able to drive a car within 4 weeks of surgery.
• The risk of infection and complications are low in kinematically aligned knee replacements as the experts are using minimally invasive surgical (MIS) procedure.
• The risk of blood transfusion is also negligible as your knee ligaments are preserved and not release as they are done in mechanical alignment
• The time taken for a kinematically aligned total knee replacement surgery itself is short and typically takes less than 40 minutes.
• 90% of patients only require 2 days of stay at the hospital
• Kinematic alignment transports the deformed arthritic knee to its pre arthritic level i.e. returns to their normal knee. Hence the patient is active and mobile as their younger days.

Comparison

The knee kinematics of patients with kinematically aligned TKAs more closely resembled that of normal healthy controls than that of patients with mechanically aligned TKAs. This may be the result of a better restoration of the individual's knee anatomy and ligament tension. A return to normal gait parameters post-TKA will lead to improved clinical outcomes and greater patient satisfaction.

However, it is important to choose the surgeon with technical expertise and experienced in handling this kind of procedure specifically. Choosing the right surgeon is what makes all the difference.