Knee Replacement Surgery

Apr 20, 2021 | Articles

The knee or tibiofemoral joint consists of three bones: the femur, the tibia, and the patella. The trio acts as a hinge, allowing flexion between the thigh and the shin of up to130° and a small degree of rotation. The bones are held in place by ligaments, and their articulating surfaces have a coating of cartilage. The entire structure is bathed in a lubricating fluid and enclosed within a protective membrane. Damage to any of these components can be painful and impair movement. In severe cases, surgical knee replacement or arthroplasty may be the only viable remedy.

The earliest attempts to perform this type of surgery were on patients with tuberculous joints, a condition which, like pulmonary TB, was all too common at that time. Today, however, extrapulmonary tuberculosis (EPTB) is a relatively rare occurrence in developed countries. Now, the most common reason for performing arthroplasty is to treat the condition known as osteoarthritis. In affected patients, the protective cartilage covering the head of the femur or tibia becomes eroded, exposing the bone beneath. A knee replacement involves removing the damaged head of one or both long bones and replacing them with the appropriate prosthetic parts.

Outright failures and limited successes characterised the early history of arthroplasty. The problem was mainly the lack of sufficiently durable, biocompatible materials to create the prosthetic components. During the intervening decades, materials science has advanced by leaps and bounds. Surgeons now have the choice of stainless steel, titanium alloys, ceramics, and super-tough plastics to manufacture long-lasting prostheses for use in knee replacement surgery.

Today, these materials are used in various combinations depending on which joint is to be replaced. Though previously favoured, stainless steel corrodes over time and is now used mostly for temporary implants like screws and plates. Tantalum, titanium, titanium alloys, and cobalt-chromium (CoCr) alloys are common choices for the artificial joint’s femoral component. Polyethylene will often be the material of choice to create the patellar and tibial components of a replacement knee joint.

It is not only new materials that have helped with the development of tibiofemoral and other forms of arthroplasty. New tools have also played a significant part. First, the X-ray machine offered the orthopaedic surgeons a better idea of what may be happening beneath the soft tissues of the bones and joints. But it was the introduction of the arthroscope, around 25 years later, that, over time, has since proved to be the gamechanger for those surgeons who specialise in performing knee replacements.

By making a tiny incision and inserting an arthroscope, the orthopaedic specialist has access to a magnified, full-colour view of the selected joint’s interior displayed on a monitor. When adjusting the scope’s position, it becomes possible to inspect the bones and surrounding soft tissues in close-up detail. The fine details of damaged or diseased areas are far superior to those obtainable from an X-ray. Consequently, arthroscopy is also of greater value when deciding on the most appropriate form of intervention which might be anything from simple lavage or a meniscectomy to a total knee replacement.

Knee, hip and shoulder arthroplasty is undertaken routinely by a specialist orthopaedic team at the Wilgers Life Hospital in Pretoria.