Total knee replacement (TKR) is a common surgical procedure for individuals experiencing severe knee arthritis. The management of the patella (kneecap) during TKR is a nuanced decision, and there is no single answer regarding its removal. The approach taken depends on several factors, leading to different surgical strategies.
Patella Management Options in Total Knee Replacement
Patellar Resurfacing
Patellar resurfacing is the most common approach. Here, the posterior surface of the patella is covered with a new component, typically made of plastic. This procedure aims to ensure smooth tracking of the kneecap against the new femoral implant, maintaining proper knee mechanics and reducing friction.
Patellar Retention
Patellar retention means the patella is left untouched. This option is considered when the cartilage on the back of the patella is healthy and shows minimal signs of arthritis or damage. Preserving the existing patella avoids additional surgical steps and potential complications associated with resurfacing. Good clinical results are reported with this approach.
Patellectomy
Patellectomy, the complete removal of the patella, is a rare occurrence in modern total knee replacement surgery. This drastic measure is typically reserved for highly complex cases, such as instances of severe patellar damage, significant bone loss, or complications from previous knee surgeries involving the patella. The patella plays an important role in knee function, and its complete removal can significantly impact the extensor mechanism, affecting the ability to straighten the leg. Therefore, surgeons generally try to avoid patellectomy due to its potential for adverse effects on knee kinematics.
Factors Influencing the Surgeon’s Decision
Cartilage Condition
The condition of the patella’s cartilage is a primary determinant. If the cartilage on the posterior aspect of the patella shows significant wear, degeneration, or severe arthritic changes, resurfacing is generally favored to alleviate pain and improve function. Conversely, if the cartilage is well-preserved, the surgeon might opt for patellar retention.
Arthritis Severity
The severity of arthritis affecting the patellofemoral joint, which is the joint between the kneecap and the thigh bone, also influences the decision. Extensive arthritis in this specific compartment often leads to a recommendation for patellar resurfacing to address the source of pain and ensure proper interaction with the new implant. Conversely, isolated arthritis in other compartments of the knee with a healthy patellofemoral joint might support patellar retention.
Surgeon Preference
A surgeon’s individual preference and training also play a role. Some surgeons routinely resurface the patella, with rates exceeding 80% in regions like the United States. Others, particularly in Norway and Sweden, are more inclined towards non-resurfacing. This variability stems from different philosophies and techniques acquired during their training and experience.
Knee Alignment & Patient Factors
Overall knee alignment and stability are also considered, as these biomechanical factors influence patella tracking after replacement. Proper alignment of new femoral and tibial components is important for accurate tracking. Patient-specific factors, including previous knee surgeries, deformities, or activity levels, can also influence the surgeon’s choice.