HEALTH & MEDICINE :: JUNE/JULY 2007
Partial Knee Replacement
The surgical treatment of knee arthritis becomes an option when nonoperative treatment fails. Surgical options include arthroscopy, osteotomy and joint replacement. Arthroscopy involves inserting a camera through small incisions over the knee and debriding or “cleaning up” the joint by removing loose cartilage fragments or loose bodies. This is usually reserved for patients with mild to moderate arthritis and evidence of torn cartilage. Osteotomy involves cutting bone around the knee to realign the leg so that the arthritic portion of the knee is unloaded from the weight-bearing forces. This is considered in younger, very active patients, particularly males. Knee replacement involves replacing the cartilage surfaces of the knee with metal and plastic components. This is the most effective option for severe arthritis in older patients.
Knee replacement has traditionally involved re-placing all of the surfaces of the knee, thus the term total knee replacement (Figure 1). The knee joint is divided into three compartments: medial (inner half), lateral (outer half) and patellofemoral (knee cap). Some individuals have arthritis that only affects one compartment of the knee. Partial knee replacements were designed with these patients in mind. This technique involves replacing only the affected compartment of the knee without violating the rest of the joint. This can mean less postoperative pain, shorter hospital stays and quicker return to functional activities compared to total knee replacement.
Figure 1
Figure 2
Figure 3
This concept was initially developed in the 1970’s however, poor patient selection and flawed designs of the components led to early failure rates. Consequently, most orthopaedic surgeons abandoned partial replacements in favor of total knee replacements, which had a proven track record. Beginning in the 1990’s, the partial replacement concept was reintroduced with improved component designs and more strict patient selection criteria. As a result, these designs now have 10 year survivorship rates that are comparable to total knee replacement designs. Initially, partial replacements were used for isolated arthritis of the medial or lateral compartments of the knee (Figure 2). More recently, isolated patello-femoral replacements are now available for patients whose arthritis is isolated to the knee cap portion of the joint (Figure 3). Contraindications to partial knee replacement include rheumatoid arthritis, significant stiffness, deformity and most importantly, involvement of arthritis in more than one compartment of the knee.
Partial replacements can be particularly desirable in middle-age patients with arthritis isolated to one compartment of the knee. In the past, the only replacement option would have been a total joint replacement. The chance of these younger patients wearing out the components and requiring a revision procedure can be high. A revision knee re-placement can be technically demanding, can involve bone loss issues and can yield results that are subpar compared to first-time, or primary, total knee replacement. While younger patients can also wear out partial knee replacement components, the revision of these designs to a total knee replacement is straightforward, involves little or no bone loss, and can yield results comparable to those individuals having a first time total knee re-placement.
Knee replacement techniques and designs continue to strive to improve patient outcomes. Partial knee replacement is another option in the orthopaedic surgeon’s algorithm of treatment choices for patients with osteoarthritis of the knee. Approximately 10-15% of patients can be candidates for this procedure when nonoperative treatment fails. Partial knee replacement in the properly selected patient, particularly when combined with a minimally invasive technique, can provide long-term pain relief and early return to activities.
Dr Manifold is a board certified Orthopaedic surgeon in Dover, Delaware, specializing in knee and shoulder disorders. He completed his fellowship training in knee replacement and reconstruction at The Insall Scott Kelly Institute/Beth Israel Medical Center, New York, and completed an Orthopaedic residency at New York Orthopaedic Hospital/ Columbia-Presbyterian Medical Center, New York. He graduated medical school from Temple University School of Medicine, Philadelphia. Dr. Manifold’s office practice is at Tooze, Easter & Manifold, MD, PA 720 S. Queen St. Dover, DE. To schedule an appointment, call 302-735-8700.
