Our knee is the biggest and strongest hinge joint of the body. It connects the thigh bone (femur) to the shin bone (tibia).
The knee also contains cartilage, meniscus and ligaments, including ACL (Anterior Cruciate Ligament), PCL (Posterior Cruciate Ligament), LCL (Lateral Collateral Ligament) and MCL (Medial Collateral Ligament).
There is a natural gap in the knee joint that aids in flexion or extension of the knee. Knee flexion means bending of the knee, which is essential for sitting, squatting, climbing stairs, kneeling, etc.
Contrarily, knee extension refers to the straightening of the knee, which is crucial for walking, jumping, standing, running, etc.
Image of a balanced knee gap; Source: Hip & Knee Book
A balanced knee has a “rectangular” flexion and extension gap as mentioned in the above image. However, advanced stage osteoarthritis reduces this gap, which causes the thigh and lower leg components to rub against each other.
As a result, the patient experiences unbearable pain while doing daily chores. They may need to undergo a knee replacement procedure, which involves replacing the damaged part of the knee with a customised implant.
During surgery, the surgeon needs to ensure the proper balance in the surrounding soft tissues before cutting the bone and placing the implant.
Because an imbalance in the surrounding soft tissues can lead to trapezoidal (improper) flexion and extension gaps. In trapezoidal, either the lateral or medial compartment can be stretched. When one is stretched, the other compartment becomes tight, which leads to imbalance.
Thus, it becomes very important to ensure the proper gap between the femur and tibial components during the knee replacement procedure.
This is done through the gap balancing technique.
What is Gap Balancing Technique and How is it Performed?
Gap balancing has emerged as one of the most effective approaches to achieving correct limb alignment, which ultimately contributes to implant stability and longevity. Hence, better range of motion and long-term results.
Using this technique, we strive to stabilise the knee throughout the full range of motion (from 0 to 130 degrees). This is achieved by balancing the lateral and medial compartments in the knee. We use a spacer block to access the imbalanced gap.
Thereafter, tight ligaments from the shrunk compartment are released to make it match with the stretched compartment. Once this is done and the adequate gap is achieved, the bones are cut and further process is initiated.
There are two techniques to perform gap balancing. One involves balancing the flexion gap first and then extension. The other technique is a vice-versa of the former one. However, both techniques require sequential soft tissue balancing for a rectangular flexion and extension gap.
Advantages
The gap balancing technique recognizes the fact that everyone’s knee anatomy is unique and ensures an individualised approach for optimal results.
This technique is especially beneficial for obese patients with knee osteoarthritis because it significantly reduces the risk of early failure and the need for revision surgery
Patients who have been operated using gap balancing techniques are usually less vulnerable to implant instability, stiffness, prosthetic joint infection, extensor mechanism injury, aseptic loosening, periprosthetic fracture and hypersensitivity reactions.
This all results in faster ambulation, better gait and improved patient satisfaction…that’s all what we want.