Patient-Specific Knee Replacement –

Total knee replacement surgery has revolutionized the management of knee arthritis requiring replacement surgery. The number of patients undergoing knee replacements has increased drastically over the past decade. A number of young patients are undergoing knee replacement surgeries due to various knee conditions.

Over the past decade, several new techniques and technologies have emerged raising the patient satisfaction bar. Customized implants and customized instruments (cutting blocks) are two such surgical techniques designed to make knee replacements patient-specific. They both allow greater kinematic movement around the artificial knee joint.

The use of custom implants and instruments is associated with greater efficiency of the surgery and a reduction in operative time. The reduction in operative time is linked to decreased risk of thromboembolic disease, reduction in intraoperative blood loss, and decreased risk of infection. The increase in efficiency and kinematics of the prosthetic joint with custom implants and instruments is also linked with decreased need for revision surgeries.

X-ray showing a custom knee replacement.

Customized implants are 3D printed along with customized cutting blocks. The customized implants are made specific to the patient’s natural anatomy of the knee. Unlike generic off-the-shelf implants, these are tailored according to the patient’s biomechanics.

A preoperative CT scan of the patient’s knee and both lower extremities is obtained. A 3D model of the knee anatomy is created with the help of computer software. An assessment of the biomechanical axis of the lower limbs is also made.

Custom 3D printed cutting blocks.

The data is then used to create patient-specific cutting blocks to minimize bone loss and ensure accurate placement of the customized implants. The result is a more kinematic knee and patients may experience a more natural-feeling knee joint.

Another system utilizes customized instruments/cutting blocks without custom-made implants. The patient’s knee CT/MRI images are used to create 3D anatomy and assess the mechanics of the patient’s knees. The resulting cutting blocks are used to make accurate bone cuts and minimize bone loss. The implants used are off-the-shelf implants.

Although the customized cutting-blocks only system does not use customized implants it offers several benefits. The operating surgeons’ choice while fixing the implant is vastly reduced to only one or a few custom sizes.

The operating surgeon may face difficulties during the surgery while balancing the ligaments and structures around the knee. Some of the patients may have contractures of the knee joint where the knee may have a limited motion before the surgery. The surgeon utilizes specific cutting and loosening of the tissue to obtain full movements around the joint.

Intraoperative image showing custom cutting blocks.

The above intra-operative challenges may warrant additional bone cuts and may require additional sizes of the implants to fit the changed anatomy. Off-the-shelf implants come in various sizes that may fit the customized bone cuts.

Both customized cutting blocks and customized implants are aimed towards increasing the efficiency of the surgery and achieving better kinematic results of the surgery. While customized cutting blocks help in accurate cutting of the bone, the customized implants are designed according to the patient’s knee anatomy. Speak with your orthopedic surgeon what type of customized knee surgery is best suited in your case.