PARTIAL KNEE REPLACEMENT
The knee is divided into 3 compartments, the medial, lateral and patellofemoral compartments. When only one or two compartments are replaced a partial replacement is performed preserving the remainder of the knee. This surgery is less invasive than a total knee, with a quicker and less painful recovery and usually a more natural feel for the patient after recovery. This handout is intended to describe a single (unicompartmental medial or lateral replacement) and double (iDuo bicompartmental medial patellofemoral or lateral patellofemoral) partial replacement and an isolated patellofemoral compartment is described in a separate handout.
When a total knee replacement is performed it replaces all 3 compartments and removes the Anterior Cruciate Ligament (ACL) and frequently the Posterior Cruciate Ligament (PCL) as well as thick cuts of bone to resurface the entire damaged knee removing all the arthritis. Partial knee replacement in comparison removes minimal bone and preserves all the ligaments of the knee leaving all other anatomical structures intact, giving the knee a more natural feel.
Isolated unicompartmental replacement is a salvage procedure for isolated osteoarthritis that is confined in one or two compartments of the knee. This treatment is indicated after conservative measures have failed to provide the patient with a quality of life that allows him/her to perform ADL’s (activities of daily living). It is indicated when other treatment options are not indicated or have failed. It preserves the rest of the joint that must be normal for a patient to have significant improvement.
MEDIAL IDUO PRE-OPERATIVE X-RAYS
X-rays demonstrate osteoarthritis of the patella (knee cap) and in the medial compartment. The joint space of the patient's lateral compartment appears intact. Therefore, the patient is a candidate for a bicompartmental replacement (iDuo). The lateral compartment will be left alone and not replaced.
GOAL OF TREATMENT
Restore the patient’s ability to perform everyday activities such as stair climbing, walking on uneven ground, getting out of a low chair, a car, or sitting with the knees bent for a prolonged period of time. These activities are generally difficult to perform when there is osteoarthritis present.
This procedure will help patients feel very comfortable and pain-free, but it is not intended for return to high-level impact loading, twisting activities. Premature failure of the components by wear is likely in-patients who resume running and pivoting sports. The prosthesis is designed to restore quality of life with activities of daily living. It is designed so as to resurface the end of the bone and preserving as much bone stock for any future conversions that may be needed. It is expected to last between 10-15 years and would allow an easier conversion to a primary total knee replacement, if needed.
TYPES OF COMPONENTS
Dr. Minas has at his disposal different devices for this. This will help him to individualize your surgical needs and give you the best possible outcomes post operatively. The different types are ConforMIS iUni, ConforMIS iDuo and Zimmer Miller Galante high flex.
The iUni is a component produced by the company ConforMIS Inc. It stands for Individualized unicompartmental resurfacing device. It is designed for patients with arthritic damage located in either the medial or lateral compartment of the knee. It differs from traditional implants in that traditional implants require the surgeon to choose from a range of standard implants that require the surgeon to cut the bone to fit the implant. iUni offers a more unique approach by creating the implant to specifically fit your knee, mirroring the surface and contours of your anatomic knee. This provides a bone sparing approach to the surgery. It gives the patient a more natural feeling to the knee preserving bone, cartilage, and ligaments, allowing the patient to have a less traumatic surgery and quicker recovery.
The ConforMIS iDuo is a bicompartmental partial knee replacement system produced by ConforMIS Inc as well. It is designed to resurface the either the medial or lateral weight bearing surfaces along with the patello-femoral compartment. (knee cap and groove). This device conforms to your anatomic surfaces and curves with the knee to give the surgeon a way to preserve the bone stock and allow for easy conversion to total knee replacement in the future. (if needed). The recovery time is shortened and the procedure is less traumatic allowing for a shorter recovery and a procedure for younger, active patients.
The Zimmer Miller Galante high Flex is a component produced by the company Zimmer. This system provides the patient a normal biomechanical function, minimally invasive precise implantation. The components provide accurate reproduction of the anatomic curves and size of the weight bearing surfaces of the knee. It allows for the surgeon to make minimal cuts on the bone sparing more bone stock for possible future conversion (if needed) to a total knee arthroplasty.