Lateral Approach

LATERAL APPROACH

USES

This approach is used for lateral ligament reconstructions, open lateral patellar releases, iliotibial band surgery, and peroneal explorations. The approach varies in its anterior and posterior locations depending on the indication for surgery. It is the distal extension of the lateral approach to the femur discussed in Section 8.

ADVANTAGES

The approach can be shifted anteriorly or posteriorly, and extended proximally or distally, with ease.

DISADVANTAGES

This approach has no significant disadvantages for surgery on the lateral structures of the knee. A straight incision generally works well. It can be curved if necessary for open lateral meniscus repairs, as a longitudinal incision’s exposure is not as good unless it is quite extensive. For that procedure, an incision paralleling the joint line would be more suitable.

STRUCTURES AT RISK

The important structures that can be damaged with this approach include the fibular collateral ligament, the popliteus tendon, and the peroneal nerve. All of the other structures in the area are running parallel to the incision and will be split longitudinally if a cut is made inadvertently too deep. The key to identifying the lateral collateral ligament is its orientation, running from anterior to posterior with the knee flexed. With the knee extended, it runs on an oblique angle that is clearly heading posteriorly and is not parallel to the fibers of the iliotibial band.

The peroneal nerve is definitely at risk. It is always posterior to the biceps femoris tendon and crosses below the head of the fibula going around the neck of the fibula. However, as it crosses the posterolateral corner, it is in direct contact with the biceps tendon and is frequently very difficult to distinguish from the tendon on the basis of color or tightness. Therefore, it should always be approached from the tendon side, that is, anteriorly, and identified proximal to the knee, where it is separate from the biceps.

TECHNIQUE

Typically, the incision is straight, starting as far proximally as necessary and going as far distally as necessary for the structure in question. Once you are through the skin and subcutaneous tissue and you are looking at the fascia, it is necessary to palpate the various structures. The head of the fibula is easily palpated, as is Gerdy’s tubercle. The lateral collateral ligament can be felt running in a more direct anteroposterior direction. If the goal is to open the lateral knee capsule, then the patellar tendon should be palpated and the capsulotomy should be done 1 cm lateral to that. If the goal is to repair lateral ligaments, the dissection should stay anterior to the head of the fibula to protect the peroneal nerve. The iliotibial band is easily identified in the tissues because of the direction of its fibers. It can be split along its anterior or posterior borders or in the middle without risk to any significant structure. The vastus lateralis is directly beneath it anteriorly. Below the posterior edge of the iliotibial band, the short head of the biceps femoris will be seen. If the fascia connecting to the iliotibial band along its lower surface is cut in line with the fibers and the iliotibial band is lifted anteriorly, the lateral collateral ligament can be seen. The posterior capsule of the knee can be opened just anterior to that by cutting in line with the fibers of the ligament. If necessary, you can go behind the ligaments with equal facility.

If the goal is to expose the peroneal nerve, then the incision should be placed more posteriorly and carried more distally. Here, the key landmark is the head of the fibula. The nerve should be identified with a nerve stimulator. In this location, the biceps tendon is almost indistinguishable from the peroneal nerve but anterior to it. When approaching the biceps tendon, it is critical that the nerve be identified so that you can tell one from the other and protect the nerve.

TRICKS

A trick to identifying the fibular collateral ligament is flexing the knee and finding the tight structure running from anterior to posterior.

The main trick for finding the peroneal nerve is to dissect proximally until there is more separation between the nerve and the biceps tendon. Flexing the knee again helps to relax the structures so that there is more separation between the nerve and the biceps tendon. The safe direction to approach this nerve is always from anteriorly, identifying first the biceps tendon with its attached muscle.

HOW TO TELL IF YOU ARE LOST

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