Basics of Knee Arthroscopy

Preoperative Evaluation

Indications for knee arthroscopy continue to expand at a rapid rate. Each patient's unique anatomy must be considered before initiating arthroscopy. Systematic evaluation of the entire knee includes a thorough physical examination and history. Additional studies including radiographs and advanced imaging should be reviewed, and proper documentation must be performed. Preoperative consultation with appropriate medical specialties and an anesthesiologist help reduce perioperative complications. Postoperative prophylaxis for deep vein thrombosis (DVT) should be considered in at-risk patients. Local, regional, and general anesthetic considerations should be reviewed with the patient and the anesthesia team.

Indications

Arthroscopy has diverse application in various forms of knee disease. Diagnostic arthroscopy helps confirm suspected knee injuries. An arthroscopic synovectomy can be useful for synovial biopsies to aid in the diagnosis of rheumatologic disorders, to remove diseased synovium and loose bodies, and to resect synovial folds or plicae. Arthroscopic treatment of septic arthritis of the knee has increased in frequency. Treatment of meniscal disease is perhaps the most common application of arthroscopy. Meniscal tears and repairs account for about half of knee injuries that require surgery. Osteochondral lesions commonly are addressed arthroscopically. Microfracture, autologous chondrocyte implantation, and osteochondral plug transfers are also performed arthroscopically.

Injuries to the cruciate ligaments can be diagnosed easily with arthroscopy and subsequently treated. Arthroscopic-assisted reconstruction of these ligaments is one of the most common orthopaedic procedures today. Other procedures that sometimes are aided with arthroscopy include tibial plateau fracture reduction, reduction and fixation of tibial eminence fractures, loose body removal, anterior fat pad débridement, and lateral release for patellar malalignment.

Contraindications for knee arthroscopy must be considered as well. One such consideration includes local skin infections over the portal sites. In addition, alternative treatments should be considered for patients who have too high a risk for surgery and those who are not expected to be compliant with postoperative rehabilitation.

Positioning

Two different forms of positioning are commonly used for knee arthroscopy. The patient can be positioned supine on the operating table, and a lateral post can be used for countertraction. Alternatively, the operative leg can be positioned in a commercially available leg holder ( Fig. 92.1 ). The operative leg is allowed to hang freely over the end of the operating table, and the opposite leg is positioned in a well-padded leg holder, taking care not to compress the peroneal nerve.

Portal Placement

Landmarks, including the inferior pole of the patella and the joint line, are marked. Portal incisions are typically vertical, 1 cm in length, and made with a no. 11 blade while the knee is flexed. A spinal needle can be used for localization of the anteromedial portal ( Fig. 92.2 ). Portal placement is key to successful knee arthroscopy. Standard arthroscopic portals for knee arthroscopy have traditionally included a superomedial or superolateral portal for fluid inflow and outflow, and inferomedial and inferolateral portals positioned just above the joint line on both sides of the patellar tendon for arthroscopy and instrumentation ( Fig. 92.3 ). Typically the inferolateral portal is used for arthroscopic visualization and the inferomedial portal is used for instrumentation, although alternating instrumentation between the medial and lateral portal is often necessary to reach certain structures ( Fig. 92.4 ). Newer arthroscopic fluid control systems have now made the use of superior outflow portals optional. The use of a far proximal superior portal can still be helpful for the visualization of patellar tracking (see Fig. 92.3 ).

Accessory portals for the knee include the posteromedial, posterolateral, far medial and lateral, and proximal superomedial portals. The posteromedial portal is often helpful for visualizing the posterior cruciate ligament and the posterior horn of the medial meniscus ( Fig. 92.5 ). The posterolateral portal, located just posterior to the lateral collateral ligament between the iliotibial band and the biceps tendon, sometimes is helpful, but extreme care should be taken to ensure that the portal is anterior to the biceps tendon to avoid injury to the peroneal nerve ( Fig. 92.6 ). An accessory medial portal has been developed for obtaining access to the appropriate angle for anatomic femoral tunnel placement in anterior cruciate ligament (ACL) surgery. Other portals include the midpatellar portal, far medial and lateral portals (which are sometimes helpful for instrument placement in hard-to-reach areas), and the proximal superomedial portal, located 4 cm proximal to and in line with the medial edge of the patella (for assessment of patellar tracking).

Diagnostic Arthroscopy

As with any joint, systematic examination of the knee is appropriate. Before positioning the patient, a complete examination is conducted after induction of anesthesia to assess instability in all planes. An arthroscopic cannula is placed in the superomedial or superolateral portal for inflow and outflow (although the use of these superior portals is now optional with many of the new pump systems), and the obturator and sheath are introduced into the inferolateral portal after incision with the knee flexed at 60 to 90 degrees, angled toward the notch. As the knee is brought into extension, the obturator and sheath are advanced into the suprapatellar pouch and the obturator is replaced by a camera for visualization. The anteromedial portal can be made at the outset of the case or created under visualization with the spinal needle (see Fig. 92.2 ). Although many examination sequences are possible, it is important to visualize the suprapatellar pouch, patellofemoral joint ( Fig. 92.7 ), medial and lateral gutters, medial and lateral compartments (meniscus and articular cartilage), and intercondylar notch (cruciate ligaments) in all patients. Surgeons differ with regard to fat pad excision for visualization and therapeutic purposes.

The patellofemoral joint is inspected and articulation is examined, including the patella facets and trochlea. Engagement should be full at 40 degrees. The gutters are examined for loose bodies. The knee is flexed and the scope is brought down into the intercondylar notch. The ACL is inspected by directing the scope to view it laterally and by probing the ligament ( Fig. 92.8 ). The ACL is composed of the two separate bundles that are often not distinct but can occasionally be recognized. The posterior cruciate ligament is also evaluated, although often only the femoral side is examined, with the remainder hidden by the ACL. The medial compartment is then visualized with valgus stress and extension using an assistant or with the surgeon resting the ankle on his or her hip. The foot can be externally rotated to improve access. The meniscus and articular surfaces are examined. Once all lesions are characterized, the lateral compartment is visualized in the same fashion in the figure-of-four position.

Accessory viewing portals are established as necessary if other areas need to be evaluated. A posteromedial portal can be helpful whenever medial meniscus pathology is suspected but is unable to be identified from the anterior portals. This portal is established by introducing the arthroscopic cannula into the back of the knee by directing it from anterior to posterior on the notch side of the medial femoral condyle. Care must be taken to avoid the saphenous nerve and vein. A spinal needle is used to establish the position of the portal. Next, a small incision is made in the skin only, followed by spreading with a blunt instrument down to the capsule. Once the arthroscope is in the posterior aspect of the knee, the posterior horn of the medial meniscus can be visualized. Use of a 70-degree scope may be helpful. After a complete evaluation of the joint is performed, all surgical pathology is addressed accordingly.

Instrumentation

A 30-degree arthroscope is most commonly used, although a 70-degree scope may be helpful in the posterior corners. An arthroscopic probe can be used and provides a sense of touch to the arthroscopist. Instruments angled upward, including biters, are best for the medial compartment, whereas straight instruments often work best in the lateral compartment. Arthroscopic shavers are available in both large and small sizes and should be chosen on the basis of the dimensions of the compartment.