Associate Professor of Orthopaedic Surgery, Weill Medical College of Cornell University
Overview
Knee arthroscopy is a minimally invasive technique that allows orthopaedic surgeons to assess - and in some cases, treat - a range of conditions affecting the knee joint. During the procedure, the orthopedic surgeon makes small incisions or portals in the affected joint, and then inserts a tiny camera and fiber optics to light the interior space. Pictures obtained with the camera are then projected onto a screen in the operating suite.
While many people are now familiar with the technique, it might come as a surprise that the first arthroscopic evaluation of a knee actually took place in 1918. (This involved the insertion of the scope into a joint, without benefit of additional lighting.) In the following decades, subsequent efforts to apply the technique met with limited success.
"It wasn't until the advent of fiber optics in the 1970s and 1980s, that arthroscopy became a useful and 'user-friendly' technique for physicians," explains Frank A. Cordasco, MD, who is an associate attending orthopaedic surgeon at HSS. Today, thanks to the availability of sophisticated instrumentation, use of arthroscopy, particularly in the knee, is widespread.
The primary advantage afforded by arthroscopy is the ability to gain multiple views inside the joint. In the past, gaining access to some of these areas required an arthrotomy - a surgery in which an open incision was made - and dislocation of the knee cap. "That procedure carried the risk of additional injury to the joint," explains Dr. Cordasco. In contrast, arthroscopic examination of the knee joint usually does little damage to surrounding soft tissues. While most orthopedic surgeons continue to rely on radiographs (x-rays) and MRI to provide important preliminary information, many agree that arthroscopy is the best diagnostic tool available. "Arthroscopy offers pieces of information that the other tests don't," says Dr. Cordasco, "including that which is derived by probing the affected tissue."
Therapeutic applications of arthroscopy can also eliminate the need for large incisions. Reconstruction of the ACL (anterior cruciate ligament) and repair of a torn meniscus are among the most commonly performed arthroscopic surgeries.
Click thumbnail to enlarge
Illustration of the knee showing menisci and major ligaments.
Within the knee, these structures perform distinct functions. The ACL helps stabilize and support the joint. There are two menisci in the knee. These c-shaped pads of cartilage help protect the articular cartilage, the lining of the bones that allows them to glide smoothly against one another during motion. (Injury or loss of articular cartilage results in arthritis.) These structures also act as shock absorbers, distributing load across the knee.
Injuries to both the ACL and the menisci are common, particularly in athletes. (Torn menisci are also seen in older patients as the result of a degenerative process.) Moreover, surgeons often see them in conjunction with one another. This may be the result of injuries suffered at the same time, or in sequence; that is, a person with a torn ACL is at greater risk of injuring the menisci. Statistics show that more than 60% of patients diagnosed with an ACL tear also have a torn meniscus.
Some ACL and meniscus injuries can be treated non-surgically with rest, physical therapy, and activity modification. However, in a young active person, choosing to forgo ACL reconstruction or meniscus repair is likely to result in persistent instability and pain in the knee, as well as setting the stage for degenerative arthritis.
Arthroscopic surgery takes place only after the immediate post-injury swelling and inflammation has gone down, and the patient has recovered almost complete range of motion - a period of a few weeks.
Arthroscopic photo showing meniscus tear.
Because the ACL is often irreparably damaged, the surgeon usually replaces it with either an autograft (taken from the patient's own tissue) or an allograft (donated tissue). This graft may be retrieved either from the patient's knee, a bone-patellar tendon-bone graft, or from the hamstring or quadriceps. (When an autograft is used, it is retrieved through a small open incision.) Many orthopaedic surgeons prefer the bone-patellar tendon-bone graft because of the associated rapid healing time -about 3-6 weeks, versus a tendon graft which can take 8 to 12 weeks. The general success rate following ACL reconstruction is 85 to 90%.
Recovery time from an ACL reconstruction varies, with a period from about 6 to 9 months representing an average. During that period the patient participates in a rehabilitation program designed to strengthen muscles and restore range of motion.
Arthroscopy photo showing meniscus tear.
The treatment goal for a torn meniscus is preservation of the structure. Where possible, the surgeon sutures the torn meniscus together using one of a variety of techniques. All sutures are placed using arthroscopic techniques. However, because there is a poor blood supply to most of the meniscus, treatment often involves a partial menisectomy, or removal of the damaged area, while preserving as much of the structure as possible. In some cases, when the tear is complex or severe, the orthopedic surgeon removes the meniscus and transplants an allograft meniscus from donor tissue.
Illustration showing tear and area of resection.
Approximately 80-90% of arthroscopic meniscus repairs are successful. Interestingly, those patients who have injured both their ACL and their meniscus, and who undergo treatment for both injuries at the same time, have higher success rates.
"In reconstructing an ACL," Dr. Cordasco explains, "small drill holes are placed in the tibia and the femur, which causes bleeding. Our belief is that the blood carries factors that may actually stimulate healing of the meniscus."
Recovery time for these surgeries varies, with an average range of 3 to 6 weeks with respect to partial meniscectomy and 12 to 16 weeks regarding meniscus repair. Patients are enrolled in a rehabilitation program during this period.
Looking to the future, Dr. Cordasco anticipates that most advances in these surgeries will involve ways of stimulating healing. For example, researchers are now looking at a technique in which the two edges of the torn meniscus would be "painted" with a growth factor that will promote healing. Another possible technique would involve creating a scaffold between the pieces and adding growth factor that would allow for regeneration of tissue.
In the case of ACL reconstruction, the use of osteoconductive screws (hardware impregnated with material that can stimulate healing of the tendon into the bone) may eventually accelerate healing and result in a more secure attachment. And as in the case of research on the meniscus, the concept of creating a scaffold treated with growth factor that would result in regeneration of ACL tissue could eliminate the need for grafts.
In addition to ACL reconstruction and meniscus repair, arthroscopy is used for:
Using arthroscopic techniques, the orthopaedic surgeon can smooth defects or remove small pieces of loose tissue that may be causing these problems.
Arthroscopy can also help in the treatment of fractures in combination with an open procedure to repair the bone. "When a patient has a fracture in the knee, arthroscopy allows us to see these areas without disrupting the joint," explains Dr. Cordasco. "We can set the bone and place any necessary pins with minimal risk of additional injury to the patient."
If you are considering an arthroscopic procedure, it's important to be sure that the orthopaedist is qualified. "Most orthopaedic surgeons have the appropriate training to perform diagnostic arthroscopy, that is the use of the technique to evaluate the knee," says Dr. Cordasco. "However, operations such as ligament reconstructions, meniscus repairs, meniscal allograft transplantations, and articular cartilage restoration techniques, require specialized training in sports medicine or arthroscopic surgery."
