Total Knee Arthroplasty: Understanding the Most Common Surgical Approach

What is the most common approach to TKA?

The most common surgical approach for Total Knee Arthroplasty (TKA) is the medial parapatellar approach, which involves an incision along the inner side of the kneecap, allowing excellent visualization of the joint structures.

Understanding Total Knee Arthroplasty (TKA)

Total Knee Arthroplasty (TKA), often referred to as total knee replacement, is a highly successful surgical procedure designed to alleviate severe knee pain and restore function in individuals suffering from advanced knee degeneration. This procedure involves replacing the damaged cartilage and bone surfaces of the femur (thigh bone), tibia (shin bone), and sometimes the patella (kneecap) with artificial components made of metal alloys and high-grade plastics. The primary indications for TKA include severe osteoarthritis, rheumatoid arthritis, and post-traumatic arthritis, where conservative treatments have failed to provide adequate relief.

The Most Common Surgical Approach: Medial Parapatellar

Among the various surgical techniques available for TKA, the medial parapatellar approach stands out as the most widely adopted and established method. This approach is favored by the vast majority of orthopedic surgeons due to its excellent anatomical exposure and reproducibility.

The medial parapatellar approach involves:

• A curved skin incision typically made along the medial (inner) aspect of the patella, extending proximally (upwards) along the quadriceps tendon and distally (downwards) along the patellar tendon.
• Opening the joint capsule (arthrotomy) just medial to the patella. This incision runs through the medial retinaculum and the joint capsule, allowing access to the knee joint.
• Eversion of the patella: The kneecap is carefully moved laterally (outward) and rotated, exposing the femoral condyles and the tibial plateau. This maneuver provides the surgeon with a clear, unobstructed view of the entire joint space, which is critical for precise bone cuts and accurate implant placement.

Why the Medial Parapatellar Approach is Preferred

The widespread use of the medial parapatellar approach is attributed to several significant advantages:

• Excellent Visualization: It offers unparalleled exposure of the distal femur, proximal tibia, and posterior aspects of the joint, facilitating accurate bone resections and optimal alignment of the prosthetic components. This direct visualization is crucial for achieving precise knee mechanics and longevity of the implant.
• Reproducibility and Predictability: Being a well-established technique, surgeons are highly familiar with its nuances, leading to predictable outcomes and a lower learning curve compared to some newer, less common approaches.
• Preservation of Quadriceps Function (Relative): While it involves an incision through the quadriceps expansion, it generally preserves the integrity of the vastus medialis obliquus (VMO) muscle more effectively than some other approaches that might inadvertently damage this important medial stabilizer of the patella. This relative preservation can contribute to better post-operative quadriceps strength and function.
• Blood Supply Considerations: The incision path tends to minimize disruption to the patellar blood supply, which is important for healing and preventing complications like patellar avascular necrosis.
• Versatility: This approach is adaptable to various patient anatomies, including those with significant deformities, and can be used for both primary and revision TKA cases.

Key Steps in the Medial Parapatellar Approach

While specific techniques may vary slightly between surgeons, the general sequence of steps in a medial parapatellar TKA typically includes:

• Skin Incision: A longitudinal incision is made on the anterior aspect of the knee, usually slightly medial to the midline.
• Medial Parapatellar Arthrotomy: The joint capsule is opened along the medial border of the patella, carefully separating the soft tissues from the bone.
• Patellar Eversion: The patella is gently displaced laterally to fully expose the femoral and tibial articular surfaces.
• Bone Resection: Specialized cutting guides are used to make precise cuts to the distal femur and proximal tibia, removing damaged bone and preparing the surfaces for the implants.
• Trial Reduction: Temporary trial components are inserted to assess the knee's stability, range of motion, and alignment. Adjustments are made as necessary.
• Component Implantation: The final prosthetic components (femoral, tibial, and often patellar) are secured in place, typically using bone cement, though some components may be press-fit.
• Closure: The patella is returned to its anatomical position, and the joint capsule, retinaculum, and overlying soft tissues are meticulously closed in layers. The skin incision is then closed with sutures or staples.

Other Surgical Approaches

While the medial parapatellar approach is dominant, other approaches exist, each with specific indications and potential advantages/disadvantages:

• Subvastus Approach: This "quads-sparing" approach avoids incising the quadriceps tendon or muscle, potentially leading to faster initial recovery and less post-operative pain. However, it offers more limited exposure, making it technically more challenging, especially in patients with larger limbs or significant deformities.
• Midvastus Approach: A compromise between the medial parapatellar and subvastus, this approach involves a small incision into the vastus medialis obliquus muscle but generally provides better exposure than the subvastus while being less invasive than the full medial parapatellar approach.
• Lateral Parapatellar Approach: Rarely used for primary TKA, this approach is typically reserved for revision surgeries or specific complex cases involving lateral deformities or previous lateral surgical scars.

These alternative approaches are less common for routine primary TKA due to potential challenges in exposure, increased technical difficulty, or specific patient factors that might contraindicate their use.

Post-Surgical Rehabilitation and Recovery

Regardless of the surgical approach used, successful TKA outcomes heavily rely on a comprehensive and diligent post-operative rehabilitation program. This typically begins immediately after surgery with:

• Pain Management: To facilitate early mobilization.
• Early Mobilization: Gentle range of motion exercises, often aided by a continuous passive motion (CPM) machine, and initial weight-bearing as tolerated.
• Physical Therapy: A structured program focusing on restoring knee range of motion, strengthening the quadriceps, hamstrings, and gluteal muscles, improving balance, and gait retraining.
• Home Exercise Program: Patients are provided with exercises to continue independently to maintain progress and ensure long-term recovery.

Adherence to the rehabilitation protocol is paramount for regaining strength, flexibility, and functional independence, ultimately allowing patients to return to their desired activities.

Conclusion

The medial parapatellar approach remains the most common and widely accepted surgical technique for Total Knee Arthroplasty. Its superior visualization, reproducibility, and favorable outcomes have solidified its position as the gold standard. While other approaches exist, they are typically reserved for specific circumstances or surgeon preference. Ultimately, the success of a TKA procedure hinges not only on the chosen surgical approach but also on the surgeon's expertise, meticulous technique, and the patient's commitment to a rigorous post-operative rehabilitation program.