Calipered Kinematically Aligned Total Knee Replacement

Instead of a traditional mechanically aligned total knee replacement, let’s consider a calipered kinematically aligned one.

The calipered kinematic alignment total knee was created to speed up recovery and give the knee a more natural feel after total knee replacement, unlike the ‘mechanical alignment’ technique that uses a one-size-fits-all approach. Dr. Sukin adopted this technique in 2020 from Dr. Stephen Howell. Since then, Dr. Sukin has worked with published studies, become an educator to other orthopedic surgeons interested in kinematic alignment, and recently collaborated with a team of orthopedic surgeons worldwide to develop an augmented reality-assisted kinematic alignment technique to help surgeons.

In contrast, mechanical alignment changes the patient’s joint lines, requiring the release of perfectly normal ligaments, which causes pain, stiffness, and instability.

Calipered kinematic alignment uses a series of intraoperative verification checks and caliper measurements of the small pieces of bone removed by the surgeon to make sure the total knee replacement fits perfectly. These steps restore the patient’s pre-arthritic joint surfaces within 0 ± 0.5 mm, which is more accurate than robotics and navigation instrumentation. The kinematic alignment of the prosthetic components with the three kinematic axes of the knee has a similar beneficial effect on function as aligning new tires on the axles of a car, giving the knee a smooth ride.

A simple caliper is the most important tool when performing a kinematically aligned total knee replacement. It measures the thicknesses of the small portions of bone removed from the femur and adjusts them until they are within ± 0.5 mm of the thickness of the replacement parts. These adjustments are recorded as verifications. Recent studies have shown that the caliper technique is more accurate than robotic surgery in restoring the patient’s joint lines.

Researchers conducted ten studies worldwide, comparing the outcomes of patients treated with a caliper-assisted kinematic alignment technique to those treated with mechanical alignment. The results showed that patients who received the caliper-assisted technique had better patient satisfaction, function, and recovery. They also had fewer ligament releases, improved motion and orientation of the knee components during weight-bearing, and better overall knee function compared to those who received mechanical alignment.

Choosing the right prosthetic is also crucial.  A prosthesis with medial ball-in socket stability provides ACL-like stability. Unconstrained lateral compartment;  replicates normal pre arthritic anatomy

The human knee works like a ball-and-socket mechanism on the inside, and it pivots on the same side.  Using a prosthetic implant that mimics this function is essential for stability and a knee-like function. This design ensures that the ACL stays in place and provides a knee-like function. As a result, it leads to a
more stable and athletic knee. Studies have shown that combining kinematic alignment with a ball-in-socket prosthesis resulted in higher function, as measured by the Forgotten Joint Score, compared to traditional components that function like a knee without an ACL and meniscus.

Caliper-kinematically aligned total knee replacement offers many advantages, including more precise implant alignment compared to robotic surgery, the use of a minimally invasive surgical (MIS) approach, a low risk of infection due to the short anesthetic and surgical time, a negligible risk of blood transfusion,
same-day discharge for most patients, and a low risk of readmission within 30 days of surgery. The implants have also been proven to be durable. Most patients aged 60 or older have a low probability of needing another operation in the same knee.

Key Points
• Kinematic Alignment Advantages: Speeds up recovery, provides a more
natural feel, and is more accurate than robotics.
• Mechanical Alignment Drawbacks: Can Cause pain, stiffness, and instability
due to ligament releases.
• Caliper Importance: Ensures a perfect fit for the total knee replacement by
measuring and adjusting bone thickness.
• Treatment Outcomes: Caliper-assisted kinematic alignment technique
leads to better patient satisfaction, function, recovery, and knee function
compared to mechanical alignment.
• Prosthetic Design: A prosthetic implant mimicking the ball-and-socket
mechanism of the human knee is crucial for stability and knee-like function.
• Advantages of Caliper-Kinematic Alignment: Offers precise implant
alignment, minimally invasive approach, low risk of infection and blood
transfusion, same-day discharge, and durable implant