A synovectomy is a surgical procedure used to treat synovitis and some other conditions that affect the synovium, a thin membrane that lines the inside of certain joints (called "synovial joints"), such as your knee, shoulder or elbow. In a synovectomy procedure, much of the synovium is removed.
Painful and swollen joints characterize a number of orthopedic injuries and conditions, but in people with inflammatory arthritis, the immediate cause of the swelling and pain is usually inflammation and excessive growth of the synovium.
"A normal synovium, which is usually one or two cell layers thick, produces synovial fluid that helps lubricate the joint," explains Mark P. Figgie, MD, Chief Emeritus of the Surgical Arthritis Service at HSS. "When the synovium grows too bulky, it produces too much synovial fluid, which contains an enzyme that, in large quantities, ‘eats away’ at the articular cartilage on the joint surface."
In patients with inflammatory arthritis, excessive growth of synovium is part of an abnormal immune response in which the body recognizes cartilage as a foreign substance that must be attacked. Loss of cartilage eventually leads to damage to the joint surface as well as the stiffness and pain characteristic of all types of arthritis. (Osteoarthritis, the more common form of arthritis, does not involve this type of inflammatory response. Other causes, including injury, wear-and-tear, and heredity are thought to contribute to the degeneration of cartilage in osteoarthritis.)
Rheumatologists – doctors who specialize in the treatment of rheumatic conditions like inflammatory arthritis (which includes rheumatoid arthritis, psoriatic arthritis and juvenile idiopathic arthritis) – usually rely on a variety of medications to control abnormal growth of the synovium. These include:
Patients who don’t respond to medication treatments noted may be referred to an orthopedic surgeon to discuss synovectomy. The amount of inflamed synovium removed varies from patient to patient, depending on the amount of damage. Some patients require only a partical synovectomy, with a smaller amount of tissue removed. To eliminate pain, others may need a complete synovectomy, in which the entire synovium is removed.
(While the majority of patients who undergo synovectomy have one of these types of arthritis, synovectomy is also used to treat patients with synovial chondromatosis, a condition in which small calcifications develop in the synovium; individuals with pigmented villanodular synovitis, a rare condition in which very aggressive growth of the synovium occurs; and those with hemophilia. For more on the latter, please see the section below on radiation synovectomy.)
"Typically, we see patients who have had some improvement after six months of drug therapy but still have one inflamed joint that has not responded," says Dr. Figgie. In such cases, surgical reduction of the synovium can allow the medication to effectively control the condition. Other candidates for synovectomy are those for whom medication has provided no relief.
Synovectomies are commonly performed on the following synovial joints:
There are two basic forms of synovectomy. It may be performed either as an open surgical procedure or with the aid of an arthroscope, in which the orthopedic surgeon uses miniaturized instruments, fiberoptic technology and a tiny camera inserted through very small incisions in the skin. Magnified pictures from the camera are projected onto a television monitor in the operating suite, guiding the surgeon throughout the procedure.
At HSS, many synovectomies are performed arthroscopically, but the choice of technique is often dictated by the affected joint. Using arthroscopy avoids the need for large incisions – an advantage if repeat synovectomies are needed – and allows for a faster rehabilitation. "It probably offers a more thorough removal of synovial tissue, as well," says Dr. Figgie. "But it is considerably more time-consuming than open surgery, and in some joints, more technically difficult to perform."
Synovectomy can yield dramatic improvement in function and pain relief. Patients whose articular cartilage is largely intact usually experience the best outcomes. The surgery has low complication rates, although postoperative stiffness is common, and more likely to occur after open surgery than after arthroscopy. The stiffness is treated with physical therapy.
The process varies, depending on which joint is involved, and the size of the incisions required for the procedure. In the case of larger joints, such as a knee synovectomy, postoperative range-of-motion exercises are essential, and patients are started on continuous passive motion (CPM) machines as soon as possible after their procedure.
Physical therapy will usually begin after one or two days. Working with an appropriate rehabilitation therapist is important to regain flexibility in the joint. After surgery, the patient must continue to take medication to delay recurrence of synovial inflammation in the treated joint, as well as to protect other joints. In some cases, the medication dose may be reduced after successful synovectomy. "The goal is to slow the whole process of synovial overgrowth down and make the medication more effective," says Dr. Figgie. "Left untreated, the patient will develop more and more synovitis, which can eventually lead to complete destruction of articular cartilage and the need for joint replacement surgery."
Summary prepared by Nancy Novick.