Lateral Approach to the Knee and Its Supporting Structures
The lateral approach provides access to all the supporting structures on the lateral side of the knee. It may be extended for intra-articular exploration of the knee’s anterior and posterior structures as well.
Normally, only part of the exposure is needed for any single surgical procedure. Its major use is in the assessment of ligamentous damage, a type of pathology that is more common on the medial side because valgus stress is more common than varus stress.
Position of the Patient
Place the patient supine on the operating table with a sandbag under the buttock of the affected side. This position rotates the leg medially to expose better the lateral aspect of the knee. Exsanguinate the limb either by elevating it for 3 to 5 minutes or by applying a soft rubber bandage then inflate a tourniquet (see Fig. 10-41). Flex the knee to 90 degrees.
Landmarks and Incision
Landmarks
Locate the lateral border of the patella and the lateral joint line.
Gerdy tubercle (the lateral tubercle of the tibia), a smooth, circular facet on the anterior surface of the lateral condyle of the tibia, marks the inferior attachment of the iliotibial band. Palpate it just lateral to the
patellar ligament.
Incision
A long, curved incision is needed for adequate exposure of all the lateral structures of the knee. Begin the incision at the level of the middle of the patella and 3 cm lateral to it. With the knee still flexed, extend the cut downward, over Gerdy tubercle on the tibia and 4 to 5 cm distal to the joint line. Complete the incision by curving its upper end to follow the line of the femur (Fig. 10-45).
Internervous Plane
The dissection exploits the plane between the iliotibial band and the biceps femoris muscle. The iliotibial band is the fascial aponeurosis of two muscles, the gluteus maximus and the tensor fasciae latae. The tensor fascia lata is supplied by the superior gluteal nerve and the gluteus maximus by the inferior gluteal nerve. The biceps femoris is supplied by the sciatic nerve. Although the iliotibial band itself has no nerve supply, the plane between it and the biceps femoris can be considered an internervous one because of the band’s muscular origin (Fig. 10-46).
Superficial Surgical Dissection
Mobilize the skin flaps widely. Underneath are two major structures: The iliotibial band, sweeping down to attach to the anterolateral border of the tibia and Gerdy tubercle, and the biceps femoris muscle, passing downward and forward to attach to the head of the fibula. Both these structures may be avulsed from their insertions during severe varus stress to the knee.
Incise the fascia in the interval between the iliotibial band and the biceps femoris muscle, avoiding the common peroneal nerve on the posterior border of the biceps tendon (Fig. 10-47). Retract the iliotibial band anteriorly and the biceps femoris muscle (with the peroneal nerve) posteriorly, uncovering the superficial lateral ligament (fibular collateral ligament) as it runs from the lateral epicondyle of the femur to the head of the fibula. The posterolateral corner of the knee capsule also is visible (Fig. 10-48).
Deep Surgical Dissection
Enter the joint either in front of or behind the superficial lateral ligament (see Fig. 10-48).
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Figure 10-45 Incision for the lateral approach to the knee joint. The incision should be made with the knee flexed.
Anterior Arthrotomy
To inspect the entire lateral meniscus, incise the capsule in front of the ligament. Make a separate fascial incision to create a lateral parapatellar
approach. To avoid incising the meniscus, begin the arthrotomy 2 cm above the joint line (see Fig. 10-47).
Posterior Arthrotomy
To inspect the posterior horn of the lateral meniscus, find the lateral head of the gastrocnemius muscle at its origin at the back of the lateral condyle of the femur. Dissect between it and the posterolateral corner of the joint capsule. The lateral inferior genicular arteries are in this area; they must be ligated or coagulated.
Note that the popliteus muscle inserts into the femur by way of a tendon that lies inside the joint capsule; the posterolateral corner of the knee may be hidden by the popliteus and its tendon. In cases of trauma, the dissection in this area already may have been done.
Make a longitudinal incision in the capsule, starting the arthrotomy well above the joint line to avoid damaging the meniscus or the tendon of the popliteus. An arthrotomy of the posterior half of the joint capsule must be performed carefully to avoid damaging the popliteus tendon, which lies outside the meniscus. The arthrotomy allows inspection of the posterior half of the lateral compartment behind the superficial lateral ligament (see Fig. 10-48).
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Figure 10-46 Internervous plane between the iliotibial band (which is supplied by the superior gluteal nerve) and the biceps femoris (which is supplied by the sciatic nerve).
Dang
Nerves
The common peroneal nerve is the structure most at risk during this approach. It lies on the posterior border of the biceps tendon and must be found early in the approach, as the supporting structures of the lateral side of the knee are being dissected; thereafter, it must be protected, because it is easy to damage. To safely identify the nerve begin your dissection well
proximal to any damage and trace it from a normal area into an abnormal one (Fig. 10-49).
Vessels
The lateral inferior genicular artery runs between the lateral head of the gastrocnemius muscle and the posterolateral capsule, and requires ligation for full exposure of that corner of the joint (Fig. 10-51). Because this vessel may cause a significant postoperative hematoma if it is not ligated adequately, it is advisable to remove the tourniquet before closing the incision to check that adequate hemostasis has been achieved.
Muscles and Ligaments
The popliteus tendon is at risk as it travels within the joint before it attaches to the posterior aspect of the meniscus and the femur. Take care when opening the posterior half of the knee joint capsule to avoid cutting the tendon (see Fig. 10-51).
Special Problems
The lateral meniscus or its coronary ligament may be incised accidentally if arthrotomy is performed too close to the joint line.
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Figure 10-47 Incise the fascia in the interval between the iliotibial band and the biceps femoris to uncover the superficial lateral (fibular collateral) ligament and the posterior joint complex. Make a separate fascial incision anteriorly to create a lateral parapatellar approach.
How to Enlarge the Approach
Local Measures
The approach as described gives a complete view of the lateral structures of the knee and cannot be improved usefully.
Extensile Measures
The exposure cannot be extended usefully.
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Figure 10-48 Make an incision into the joint capsule anterior to the superficial lateral ligament for a standard anterolateral approach. To enter the posterior portion of the joint, retract the iliotibial band anteriorly and the biceps femoris posteriorly, revealing the superficial lateral ligament and the posterolateral aspect of the joint. Incise the joint capsule posterior to the ligament to reveal the contents of the joint.
