Arthroscopy update #9. Posterior compartment observation and instrumentation in the knee using anteromedial and anterolateral portals and an interchangeable cannula system.

The technique for routine posterior compartment observation in the knee described here uses cannulae that are 75 mm long and either 4.6 mm or 5.6 mm in diameter. Once they have been introduced, they remain in place while instruments and the arthroscope are interchanged within them. The arthroscope is attached to a bridge that connects to either cannula. Anteromedial and anterolateral portals are used with the interchangeable cannulae system. Once the arthroscope has been attached to the cannula in the anterolateral portal, an identical cannula with a blunt obturator is passed from the anteromedial portal into the posterolateral compartment under direct vision. The position of the arthroscope and blunt obturator are then reversed so that the arthroscope views the posterolateral compartment. To view the posteromedial compartment, the maneuver is repeated with the arthroscope in the anteromedial portal. The cannula with the blunt obturator is then advanced from the anterolateral portal under direct vision into the posteromedial compartment, and the position of the arthroscope and obturator are again interchanged. Hypertrophic synovium and osteophytes in the notch can be removed by passing shavers or burrs through the cannulae. Posteromedial and posterolateral portals are established with the 70 degree arthroscope under direct vision; once a cannula has been placed in a posterior portal, instrumentation and observation through the posterior cannula can be performed. The cannula from the opposite anterior portal remains in the posterior compartment. Hand and power instruments can be passed safely across the notch and into the posterior compartments while viewing the procedure through the posteriorly positioned arthroscope. The posterior cruciate ligament is then observed from the posteromedial portal while palpating the ligament with instruments entering the posterior compartment from the anterolateral portal.