Total Knee Replacement Surgery (TKR)

The decision to undergo a total knee replacement (TKR) is significant and requires a thorough understanding of both the benefits and risks involved. This document outlines the essential factors, approaches, and rehabilitation expectations to help you make an informed decision. Advancements in technology, such as robotic-assisted surgery and computer navigation, are increasingly utilized to improve precision and outcomes in knee replacement procedures.

Surgical Approach and Techniques

Total knee replacement involves the removal of damaged cartilage and bone from the knee joint, which are then replaced with a prosthetic implant. Various surgical techniques and technologies aim to improve the accuracy of implant placement, alignment, and ultimately, patient outcomes. Dr. Spelman employs both traditional and advanced surgical methods, including robotic-assisted surgery and computer navigation.

Robotic-Assisted Surgery

Robotic-assisted surgery is a precise and customizable technique where a robotic arm assists the surgeon in accurately positioning and aligning the knee implant. Preoperative imaging helps create a detailed 3D model of the knee, allowing for a personalized surgical plan. Studies and data from the AOANJRR indicate that robotic-assisted knee replacements may lead to:

   - Improved implant positioning

   - Better soft tissue balancing

Computer Navigation

Computer navigation provides real-time data to guide implant positioning and alignment during surgery. Sensors placed around the knee transmit information to a computer, which helps the surgeon achieve optimal alignment and improve joint function. Computer navigation is especially beneficial for patients with complex knee anatomy, deformities, or prior surgeries. AOANJRR data shows that computer-navigated TKR has demonstrated a lower rate of revision in the long term, especially in younger and active patients.

Bearing Surface Options

The bearing surface, which refers to the materials used in the knee prosthesis, plays a crucial role in longevity and wear resistance:

   - Polyethylene (XLPE): Cross-linked polyethylene is commonly used as a spacer between the metal components in knee replacements. Advances in XLPE have increased its durability and wear resistance, resulting in improved outcomes as recorded in the AOANJRR.

   - Ceramic Components: Ceramic surfaces are less common in knee replacements than in hip replacements, but they may be considered in cases where minimal wear is essential, although they come with a risk of brittleness and fracture.

Implant Choice

There are various designs and types of knee implants, each selected based on patient-specific factors such as age, activity level, and anatomy. AOANJRR data highlights the importance of using implants with a strong history of success and low revision rates. Dr Spelman recommends implants with proven performance in the registry and may suggest different options based on individual needs, including cruciate-retaining, posterior-stabilized, or constrained designs.

Alignment Options in Total Knee Replacement

Correct alignment is crucial in total knee replacement (TKR) to ensure the prosthesis functions well, remains stable, and lasts as long as possible. There are two primary alignment philosophies in TKR—mechanical alignment and kinematic alignment—each with its advantages, surgical techniques, and potential outcomes. Dr. Spelman will choose the alignment method best suited to your knee anatomy, lifestyle, and expectations from surgery.

Mechanical Alignment

Mechanical alignment is the traditional approach and aims to place the knee prosthesis in a neutral position relative to the leg's mechanical axis (the line from the hip center to the ankle center). The goal is to create a straight line through the center of the hip, knee, and ankle, which distributes load evenly across the joint and improves implant longevity.

• Surgical Technique: Mechanical alignment requires adjusting the bone cuts to align the leg in a neutral position, which sometimes means sacrificing the natural alignment and soft tissue balance.

• Benefits: This approach has been widely used and documented with a successful track record over decades. It is ideal for patients with significant deformities or those at high risk of implant wear.

• Outcomes: Mechanical alignment provides stability and is supported by data from the Australian Orthopaedic Association National Joint Replacement Registry (AOANJRR), indicating lower revision rates in mechanically aligned TKRs, especially in patients with challenging anatomical variations.

Kinematic Alignment

Kinematic alignment aims to restore the knee's natural anatomy by aligning the prosthesis to the individual's pre-arthritic or natural joint lines and rotation, preserving the natural soft tissue balance. Instead of creating a neutral leg alignment, kinematic alignment seeks to match the unique alignment of each patient’s knee.

• Surgical Technique: Kinematic alignment is a more personalized approach and may involve making minimal adjustments to maintain the knee’s natural alignment. This method can be challenging for complex cases, but it can be aided by robotic-assisted technology, which enhances precision.

• Benefits: Kinematic alignment can result in a more natural-feeling knee postoperatively, as it preserves the natural alignment and soft tissue balance. This method may offer improved patient satisfaction, especially in terms of knee motion and comfort.

• Outcomes: Early studies suggest that kinematic alignment may improve knee function and patient satisfaction. However, it may be associated with a slightly higher risk of implant wear or loosening in certain cases, especially if alignment is substantially outside the standard mechanical axis. Dr. Spelman may recommend kinematic alignment for patients with stable knee anatomy and high expectations for natural knee function post-surgery.

What is the right alignment for you?

Dr. Spelman will discuss which alignment method best suits your anatomy, lifestyle, and surgical goals. Robotic-assisted and computer-navigated technologies are particularly beneficial in refining alignment accuracy in both kinematic and mechanical approaches. AOANJRR data on alignment outcomes indicates that while both methods have excellent results, specific patient characteristics may guide the choice of alignment for the best long-term outcomes.

Risks of Total Knee Replacement

TKR is a choice that should be considered carefully when the benefits of surgery outweigh the risks. Potential risks include infection, blood clots (DVT), implant loosening, instability, leg length discrepancy, wear, fracture, and the need for revision surgery. Dr Spelman will discuss these risks with you and answer any questions, ensuring that you are fully informed.

What to Expect from Your Total Knee Replacement Surgery

Initial Consultation

During your consultation, Dr Spelman will evaluate your knee pain, mobility, medical history, and previous treatments. He will discuss both surgical and non-surgical options, covering the benefits and risks of TKR. Preoperative planning may include imaging studies such as X-rays, CTs, EOS scan or MRIs to assist in surgical planning, especially for robotic-assisted procedures.

7 Days Prior to Surgery

You may need to stop certain medications, such as fish oil or blood thinners, as advised by Dr. Spelman. The anaesthetist will review your medical history and medication list to finalize the anaesthesia plan for surgery.

Day of Surgery

You will arrive at the hospital with relevant imaging studies and follow fasting instructions provided by Dr Spelman’s office. After preoperative preparations, you will proceed to surgery, which typically lasts 90-120 minutes. You will then be monitored in the recovery area before being transferred to the ward.

Day 1 Post-Surgery

Dr Spelman will assess your progress and begin mobilization with a physiotherapist. You will receive medications to prevent blood clots, along with compression stockings. You will get out of bed with the physiotherapist to walk and will be required to start performing exercises in bed between physiotherapy session

Days 2-5

Your activity level will gradually increase with the support of a physiotherapist, and you may use ice packs to manage swelling. The length of stay in the hospital varies, with most patients discharged within 2-5 days, depending on mobility and support available at home.

Week 2

You will have a follow-up appointment to assess the surgical incision, pain levels, and mobility. At this stage, many patients transition to using a walking aid such as a stick or single crutch.

Week 6-8

Dr Spelman will review your progress and assess an X-ray of the knee to confirm implant positioning and stability. Most patients are walking independently by this stage, and may begin driving around 6-8 weeks post-surgery.

Ongoing Follow-Up

Long-term follow-up will include periodic X-rays to monitor the implant, with appointments every 2-5 years, depending on individual factors.