Arthroscopic Approaches to the Knee
Arthroscopic Approaches to the Knee
The knee is a large unconstrained hinge joint that is often described as subcutaneous. Its anteromedial and anterolateral coverings consist largely of fibrous tissue—the patellar retinaculum and joint capsule (see Figs. 10-32 and 10-33). Incisions through these coverings can be safely made without endangering any vital structures.
Arthroscopy of the knee has largely replaced open procedures for the following:
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Meniscal resection or repair
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Removal of loose bodies
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Anterior or posterior cruciate ligament reconstruction
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Synovial biopsy
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Synovectomy
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Debridement of early osteoarthritic knees, including microfracture
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Treatment of osteochondritis dissecans
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Arthroscopically assisted repair of tibial plateau fractures
Numerous arthroscopic portals have been described in knee arthroscopy surgery.1,2 The two most frequently used will be described.
The anterolateral portal is the one most commonly used for diagnostic
purposes; it is nearly always used in conjunction with the anteromedial portal. The combination of these approaches allows the use of the arthroscope along with arthroscopic instruments. Usually the arthroscope is inserted via the anterolateral portal and instruments are inserted via the anteromedial portal. However, either portal can be used for either purpose. These two approaches are described in this section.
Position of the Patient
Place the patient supine on the operating table. Apply a well-padded tourniquet to the mid-thigh. Exsanguinate the limb and inflate the tourniquet. Remove the end of the table (Fig. 10-1; see Figs. 10-9 and 10-41). Prep and drape the limb so that you are able to manipulate the knee during surgery. The use of an arthroscopic clamp placed around the tourniquet allows the surgeon to apply a valgus and external rotation force to the knee, facilitating access to the medial compartment. The use of a clamp, however, makes it more difficult to place the knee in the figure-of-eight position (placing the lateral malleolus of the involved extremity on the opposite thigh; see Figs. 10-8, inset to allow access to the lateral compartment of the knee. If a surgical assistant is available to provide the appropriate forces, the use of a clamp is not indicated.
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Figure 10-1 Place the patient supine on the operating table. Remove the end of the table so that you are able to manipulate the knee during surgery.
Landmarks and Incision
Lateral
Flex and extend the knee and use your thumb to palpate the lateral joint line. Move your thumb toward the midline. You will feel the resistance of the lateral edge of the patellar tendon. Flex the knee to 90 degrees. Place your forefinger in the recess created by the lateral border of the patellar tendon and the lateral joint space. This is the so-called soft spot. Make an 8-mm transverse stab incision approximately 5 mm proximal to your finger, 1 cm to 1½ cm above the joint line (Fig. 10-2).
Medial
Move your finger to palpate the medial joint line and the medial edge of the patellar tendon. Place your finger in the medial soft spot, and make an 8-mm stab incision some 1½ cm above the joint line. Note that because the lateral tibial plateau is slightly lower than the medial plateau, the lateral incision will be slightly lower than the medial one (see Fig. 10-2).
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Figure 10-2 Lateral incision: make a small 8-mm transverse stab incision 1½ cm above the lateral joint line. Medial incision: make an 8-mm stab incision 1½ cm above the medial joint line.
Internervous Plane
There is no internervous plane in these surgical approaches, which consist of incisions made in the medial and lateral patellar retinacula and joint capsule. No major nerves are present in these areas.
Surgical Dissection
With the knee flexed to 90 degrees, deepen the anterolateral skin incision using a sharp-ended blade. As you incise the retinaculum, you will suddenly feel a decrease in resistance. Withdraw the blade and insert the arthroscopic sheath and blunt trochar. Push the sheath and trochar into the anterolateral portion of the knee, taking care not to hit the underlying femur; then carefully extend the knee while advancing the arthroscopic sheath up into the suprapatellar pouch. Remove the trochar. Insert the 30-degree arthroscopic telescope. Switch on the irrigation fluid before switching on the light source to avoid thermal damage to the synovium.
Arthroscopic Exploration of the Knee
Although the use of a preoperative MRI identifies most pathologies within the knee, it is important to ensure that each arthroscopic exploration examines all portions of the knee and not merely the site of the presumed pathology.
Order of Scoping
Begin with placing a 30-degree arthroscope in the suprapatellar pouch (Fig. 10-3, view 1). The arthroscope should be easily mobile, allowing you to examine all portions of the suprapatellar pouch, noting especially the synovium and checking for the presence of any loose bodies.
Keeping the knee fully extended, withdraw the arthroscope into the patellofemoral joint, rotating the telescope to allow examination of both the femoral and patellar aspects of the joint (see Fig. 10-3, view 2). Manipulating the patella medially and laterally facilitates this procedure.
Keeping the leg extended, slide the tip of the arthroscope into the lateral recess or gutter of the knee, passing the scope between the lateral aspect of the femur and the lateral capsule of the joint (see Fig. 10-3, view 3). Observe the lateral surface of the femur, and ensure that you can see
the insertion of the popliteus muscle (see Fig. 10-3, view 4). The popliteal hiatus is a common recess for the presence of loose bodies.
Keeping the knee in full extension, sweep the arthroscope into the lateral portion of the knee, observing the anterior part of the lateral meniscus (Fig. 10-4, view 5). Pass the arthroscope medially, and rotate the scope so that you are looking posteriorly. This will allow you visualization of the medial femoral recess or gutter (see Fig. 10-4, view 6).
Withdraw the arthroscope into the center of the knee and gently flex to
90 degrees, allowing the tip of the arthroscope to enter the medial compartment of the knee. Observe the articular cartilage of the medial femoral condyle and medial tibial plateau. Also observe the medial meniscus and meniscal rim (Fig. 10-5, view 7). Apply a valgus and external rotation force to the knee, and rotate the scope so that it is looking laterally, to allow examination of the posterior horn of the medial meniscus (Fig. 10-6, view 8).
Withdraw the arthroscope into the intercondylar notch, observing the anterior and posterior cruciate ligaments (Fig. 10-7, view 9).
With the arthroscope in the area of the intercondylar notch, flex the knee to just over 90 degrees, abduct the hip, and place the lateral malleolus of the operative side on the anterior aspect of the contralateral knee (see Fig. 10-42). This is known as the figure-of-eight position and allows arthroscopic inspection of the entire lateral compartment (Fig. 10-8, inset). Observe the articular surfaces of the lateral femoral condyle and lateral tibial plateau. Examine the lateral meniscus in its entirety (see Fig. 10-8, view 10).
To allow inspection of the undersurface of the menisci and to assess the integrity of the cruciate ligaments, insert the arthroscopic hook through the anteromedial portal and use it under direct vision of the arthroscope to palpate these structures.
Dang
Articular Cartilage
The articular cartilage of the knee may be damaged at two stages during arthroscopy: By the incision into the joint capsule or by the forceful insertion of an arthroscope. If the incision is made carefully, this problem should not occur. Remember that if you meet with resistance when manipulating the arthroscope within the knee, then it is certain that you are damaging the articular cartilage. More posteriorly based incisions on the
medial side may easily damage the articular surface of the medial femoral condyle if performed blind. Therefore, it is recommended that more posterior medial or lateral incisions, if needed, should be made under direct arthroscopic control. Ten seconds of careless use of an arthroscope within the knee may create the equivalent of 10 years of wear in that joint.
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Figure 10-3 View 1: Begin with the arthroscope in the suprapatellar pouch and observe the synovium, checking for the presence of loose bodies. View 2: Withdraw the arthroscope into the patellofemoral joint. To observe the full extent of the joint, rotate the scope in both directions and move the patella medially and laterally. View 3: Slide the scope into the lateral recess of the knee and observe the lateral aspect of the lateral femoral condyle. View 4: Advance the arthroscope into
the lateral gutter to view the insertion of the popliteal muscle.
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Figure 10-4 View 5: With the knee in full extension, sweep the arthroscope into the lateral portion of the knee and observe the anterior horn of the lateral meniscus and the anterior part of the lateral femoral condyle. View 6: Advance the arthroscope medially and rotate it to look posteriorly. Observe the medial femoral recess.
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Figure 10-5 View 7: Withdraw the arthroscope into the center of the joint, and then flex the knee to allow the arthroscope to enter the medial compartment. Observe the rim of the medial meniscus, the medial femoral condyle, and the medial tibial plateau.
Meniscus
The meniscus may be damaged by the scalpel or the arthroscope if the incisions are made too close to the joint line.
How to Enlarge the Approach
Local Measures
Manipulation of the knee is the key to success in visualizing all portions of the joint. To allow complete inspection of the knee, apply a valgus external rotation force to assess the posterior aspect of the medial compartment of the knee. You will also need to apply a varus internal rotation stress to examine the lateral portions of the knee. Remember that the telescope you
use is angled at 30 degrees. Changing the direction of the telescope will therefore significantly change the view that you obtain (see Figs. 1-73 to 1-75). This is most important when examining the posterior third of the medial compartment of the knee.
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Figure 10-6 View 8: Apply a valgus/external rotation force to the knee, and rotate the arthroscope so that it is looking laterally. Observe the posterior horn of the medial meniscus.
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Figure 10-7 View 9: Withdraw the arthroscope into the intercondylar notch to observe the cruciate ligaments.
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Figure 10-8 (Inset) Flex the knee 90 degrees above the hip, and place the lateral malleolus of the operative side on the anterior aspect of the contralateral knee (figure-of-eight position). View 10: Advance the arthroscope into the lateral compartment of the knee to observe the lateral meniscus in its entirety.