Minimally Invasive Approach to the Distal Femur
The minimally invasive approach to the distal femur utilizes two windows. The distal window is in effect a lateral parapatellar approach to the knee and allows visualization of the articular surface of the distal femur. The proximal window provides access to the femoral shaft and is a portion of the lateral approach to the femoral shaft (see Fig. 9-6). The minimally invasive approach is indicated for open reduction and internal fixation of distal femoral fractures, especially those that involve intra-articular fractures associated with complex metaphyseal injuries.10–13
Position of the Patient
Place the patient supine on the table with a bolster under the thigh so that the knee rests in approximately 30 degrees of flexion (Fig. 9-30). This will relax the pull of the gastrocnemius muscles on the distal fragment of the fracture. If a tourniquet is to be used, place the tourniquet high on the patient’s thigh and exsanguinate the limb using a compressive bandage or elevate for 3 to 5 minutes before the tourniquet is inflated. Use a radiolucent table and ensure that adequate imaging can be obtained of the
knee and femoral shaft by using an image intensifier before prepping and draping.
Landmarks and Incisions
Palpate the lateral joint line of the knee by flexing and extending the joint. The lateral margin of the patella and anterior surface of the lateral femoral condyle are easily palpable. The femoral shaft, however, is merely felt as a resistance beneath the tight iliotibial band.
Incision
Make a 6- to 8-cm longitudinal incision over the anterior half of the lateral femoral condyle, extending upward from the joint line. Make a second proximal longitudinal incision overlying the lateral aspect of the shaft of the femur (Fig. 9-31). The positioning and length of this second incision will relate to the implant being used, and the site of the incision must be determined using image intensification.
Internervous Plane
Distally, the dissection explores the internervous plane between the vastus lateralis muscle supplied by the femoral nerve and the biceps femoris muscles supplied by the sciatic nerve. Proximally, no internervous plane is available for surgery, but splitting the vastus lateralis muscle usually does not result in significant denervation.
Superficial Surgical Dissection
Begin distally. Incise the skin and subcutaneous tissue in the line of the skin incision. Divide the lateral retinaculum to visualize the joint capsule. At the proximal end of the distal window, develop a plane between vastus lateralis anteriorly and the lateral intramuscular septum posteriorly. Numerous branches of the superior lateral genicular artery with associated veins cross the operating field at this point and will need to be ligated or diathermied.
Figure 9-30 Position for the lateral approach to the distal femur.
Figure 9-31 Distally make a 6- to 8-cm incision over the anterior half of the femoral condyle beginning at the joint line. Proximally make a longitudinal incision over the lateral aspect of the femoral shaft. The position and length of the proximal incision depend on the site of the pathology and the implant to be used for treatment.
Deep Surgical Dissection
Distally divide the knee joint capsule and synovium longitudinally to expose the entire distal end of the femur. Retract the patella using an appropriate retractor and visualize all aspects of the joint by flexing and extending the knee. Proximally split the vastus lateralis muscle in a line of
its fibers to give direct access to the periosteum on the lateral aspect of the femoral shaft (Fig. 9-33). Finally, develop an epiperiosteal plane between the two windows on the lateral aspect of the femur using a blunt dissector or the surgical implant (Fig. 9-34).
Dang
The superior genicular artery and veins need to be seen and ligated. These vessels tend to be numerous and are closely adherent to the periosteum. If these vessels are not controlled, a large hematoma will result postoperatively.
How to Enlarge the Approach
Local measures
An external fixator or a distraction clamp can be applied to the lateral aspect of the femoral shaft and the lateral aspect of the tibia. This will cause the lateral aspect of the knee to open up, facilitating visualization of the articular surface.
Extensile Measures
The two skin incisions can be united and the vastus lateralis divided in the line of its fibers to provide access to the entire lateral aspect of the shaft of the femur. This maneuver will, of course, increase the degree of soft tissue damage and will reduce the blood supply to the metaphyseal fracture fragments.
Figure 9-32 Distally incise the subcutaneous tissues in the line of the skin incision to reveal the fascia overlying the vastus lateralis and the lateral patellar retinaculum. Proximally incise the subcutaneous tissues in the line of the skin incision to reveal the fascia covering the vastus lateralis.
Figure 9-33 Distally incise the lateral patellar retinaculum and the underlying joint capsule to enter the knee joint and expose the distal end of the femur. More proximally, incise the deep fascia to reveal the lateral aspect of the distal femur.
Proximally incise the fascia overlying the vastus lateralis and split the fibers of that muscle to expose the periosteum covering the lateral aspect of the femoral shaft.
Figure 9-34 Connect the two incisions by developing an epiperiosteal plane along the lateral aspect of the femur using blunt dissection.
