Medial Approach to the Knee and Its Supporting Structures

Medial Approach to the Knee and Its Supporting Structures ‌

The medial approach16 provides the widest possible exposure of the ligamentous structures on the medial side of the knee. Although it is used mainly for the exploration and treatment of damage to the superficial medial (collateral) ligament and medial joint capsule, the approach also can be used for a medial meniscectomy in conjunction with ligamentous repair and for the repair of a torn anterior cruciate ligament. (See the section regarding the lateral approach to the distal femur.)

Position of the Patient

Place the patient supine on the operating table. Exsanguinate the limb and apply a tourniquet. Flex the affected knee to about 60 degrees. Abduct and externally rotate the hip on that side, placing the foot on the opposite shin. Various thigh rests have been designed to make it easier to maintain this position (Fig. 10-24).

Landmark and Incision

Landmark

Palpate the adductor tubercle on the medial surface of the medial femoral condyle. It lies on the posterior part of the condyle in the distal end of the natural depression between the vastus medialis and hamstring muscles.

Incision

Make a long, curved incision, beginning at a point 2 cm proximal to the adductor tubercle of the femur. Curve it anteroinferiorly to a point 6 cm below the joint line on the anteromedial aspect of the tibia. The middle of this incision runs parallel to the medial border of the patella about 3 cm medial to it (Fig. 10-25).

Internervous Plane

There is no true internervous plane in this approach. Because the nerves at the level of the knee pass posterior to the approach in the popliteal fossa,

dissection is quite safe. The only cutaneous nerve that may be damaged is the saphenous nerve and its branches.

Superficial Surgical Dissection

Raise the skin flaps to expose the fascia. The exposure should extend from the midline anteriorly to the posteromedial corner of the knee posteriorly (Fig. 10-26).

Figure 10-24 Position for the medial approach to the knee.

Figure 10-25 Make a long, curved incision. The middle of this incision runs parallel and about 3 cm medial to the medial border of the patella.

The infrapatellar branch of the saphenous nerve crosses the operative field transversely and is sacrificed; however, the saphenous nerve itself, which emerges from between the gracilis and sartorius muscles, must be preserved, as must the long saphenous vein in the posteromedial aspect of

the dissection. (The infrapatellar branch of the saphenous nerve should be cut and the end buried in fat to diminish the chances of the formation of a painful neuroma.)

Deep Surgical Dissection

Exposing the deep structures within the knee involves incising the layers that cover them, either in front of or behind the superficial medial ligament (the medial collateral ligament). These separate incisions provide access to the anterior and posterior parts of the medial side of the joint, respectively.

Anterior to the Superficial Medial Ligament

Use the anterior approach to expose the superficial medial ligament, the anterior part of the medial meniscus, and the cruciate ligament.

Incise the fascia along the anterior border of the sartorius muscle in line with the muscle’s fibers, starting from its attachment to the subcutaneous surface of the tibia and extending proximally to a point 5 cm above the joint line (see Fig. 10-26). The anterior border of the sartorius is hard to define at the level of the knee joint, so it should be sought either at the muscle’s tibial insertion or at the proximal end of the wound. Now, flex the knee further to allow the sartorius muscle to retract posteriorly, uncovering the other two components of the pes anserinus, the semitendinosus and gracilis muscles, which lie beneath and behind the sartorius (Fig. 10-27).

Figure 10-26 Retract the skin flaps to expose the fascia of the knee. Note that the infrapatellar branch of the saphenous nerve crosses the operative field transversely. Incise the fascia along the anterior border of the sartorius.

Retract all three muscles posteriorly to expose the tibial insertion of the superficial medial ligament, which lies deep and distal to the anterior edge of the sartorius. Note that the ligament inserts some 6 to 7 cm below the

joint line, not close to it (Fig. 10-28). Apply a gentle valgus force to the superficial medial ligament to reveal its point of injury.

Make a longitudinal medial parapatellar incision to gain access to the inside of the front of the joint. To avoid damage to the underlying medial meniscus, begin the incision well above the joint line and cut down carefully (Fig. 10-29).

Posterior to the Superficial Medial Ligament

The posterior approach exposes the posterior third of the meniscus and the posteromedial corner of the knee.

Incise the fascia along the anterior border of the sartorius muscle in the same way as for the anterior approach (see Fig. 10-26). Retract the muscle posteriorly, together with the semitendinosus and gracilis muscles (Fig. 10-30 ). In cases of damage to the posteromedial joint capsule, the back of the medial femoral condyle usually will be seen, with its underlying meniscus visible through the torn posteromedial joint capsule. If the capsule is intact, expose the posteromedial corner of the joint by separating the medial head of the gastrocnemius muscle from the semimembranosus muscle. Although both muscles are supplied by the tibial nerve, this intermuscular plane is a safe area for dissection, because the semimembranosus receives its nerve supply well proximal to the approach and the gastrocnemius receives it well distal.

Figure 10-27 Flex the knee and retract the sartorius posteriorly to uncover the remaining components to the pes anserinus.

Finally, separate the medial head of the gastrocnemius muscle from the posterior capsule of the knee joint almost to the midline by blunt dissection (Fig. 10-31). Full exposure allows the posteromedial corner of the capsule to be inspected for damage. A second arthrotomy posterior to the superficial medial ligament (the tibial collateral ligament) permits inspection or treatment of posterior intra-articular or periarticular

pathology (see Fig. 10-31). Repair of the posteromedial comer of the joint also is possible.

Figure 10-28 Retract all three muscles (sartorius, semitendinosus, and gracilis) posteriorly to expose the tibial insertion of the superficial medial ligament.

Dang

Nerves

The cut end of the infrapatellar branch of the saphenous nerve should be buried in fat to prevent the formation of a painful postoperative neuroma.

The saphenous nerve emerges from between the gracilis and sartorius muscles, and runs with the long saphenous vein. It provides sensation for some of the non–weight-bearing portions of the foot and should be preserved (Fig. 10-32; see Fig. 10-35).

Vessels

The saphenous vein appears in the posterior corner of the superficial dissection. Because it may be required for future vascular procedures, it should be preserved (see Fig. 10-35).

The medial inferior genicular artery curves around the upper end of the tibia. It may be damaged when the medial belly of the gastrocnemius muscle is lifted off the posterior capsule: The damage may go unnoticed until the wound is closed and the tourniquet is released (see Figs. 10-38 and 10-39).

Figure 10-29 Make a longitudinal medial parapatellar incision to gain access to the inside of the front of the knee joint.

The popliteal artery lies against the posterior joint capsule in the midline and is adjacent to the medial head of the gastrocnemius muscle. Take care to avoid injuring the vessel during separation of the gastrocnemius from the joint capsule (see Figs. 10-58 and 10-61).

Special Problems

Hematomas under the skin flap that develop postoperatively can cause skin necrosis. Therefore, the large skin flaps that are created in this approach should be drained well.

How to Enlarge the Approach

The incision already is extensive, providing exposure to all the medial structures of the knee, and cannot be extended usefully in either direction. (For repair of the anterior cruciate ligament, see the section describing the lateral approach to the distal femur.)

Figure 10-30 Retract the sartorius, semitendinosus, and gracilis posteriorly to expose the posteromedial corner of the joint. Orientation of the knee (inset).

Figure 10-31 Expose the posteromedial corner of the knee joint by first separating the gastrocnemius muscle and the posterior capsule of the joint, and then performing a capsulotomy posterior to the tibial collateral ligament.