Posterolateral Approach to the Femur
The posterolateral approach1–3 can expose the entire length of the femur. Because it follows the lateral intermuscular septum, it does not interfere with the quadriceps muscle. Although other lateral approaches involve splitting the vastus lateralis or vastus intermedius muscles, the functional results of the posterolateral approach do not differ significantly from those of other approaches, probably because the vastus lateralis originates partly from the lateral intermuscular septum. As a result, surgery still involves detaching a part of the muscle’s origin and does not use a true intermuscular plane.
The lateral intramuscular septum lies posterior to the femoral shaft at its proximal end. This septum overlies the middle of the shaft at its distal end. The posterolateral approach is therefore ideal for exposure of the distal one-third of the femur. The more proximal the approach, the greater the bulk of the vastus lateralis that will need to be retracted anteriorly and the more difficult the approach will be.
The uses of the posterolateral approach include the following:
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Open reduction and plating of femoral fractures, especially supracondylar fractures
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Open intramedullary nail placement for femoral shaft fractures if facilities for closed nailing do not exist
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Treatment of nonunion of femoral fractures
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Femoral osteotomy (which is performed rarely in the region of the femoral shaft)
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Treatment of chronic or acute osteomyelitis
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Biopsy and treatment of bone tumors
Position of the Patient
Figure 9-7 Position of the patient on the operating table for the posterolateral approach to the femur.
Figure 9-8 The internervous plane lies between the vastus lateralis (which is supplied by the femoral nerve) and the hamstring muscles (which are supplied by the sciatic nerve).
Landmarks and Incision
Landmarks
Palpate the lateral femoral epicondyle on the lateral surface of the knee joint. The epicondyle actually is a flare of the condyle. Moving superiorly, note that the femur cannot be palpated above the epicondyle.
Incision
Internervous Plane
The approach exploits the plane between the vastus lateralis muscle (which is supplied by the femoral nerve) and the lateral intermuscular septum, which covers the hamstring muscles (which are supplied by the sciatic nerve; Fig. 9-9).
Superficial Surgical Dissection
Incise the deep fascia of the thigh in line with its fibers and the skin incision (Fig. 9-10).
Deep Surgical Dissection
Identify the vastus lateralis under the fascia lata (Fig. 9-11). Follow the muscle posteriorly to the lateral intermuscular septum. Then, reflect the muscle anteriorly, dissecting between muscle and septum. Begin at the distal end of the incision where the plane is easiest to identify and develop. Numerous branches of the perforating arteries cross this septum to supply the muscle; they must be ligated or coagulated (Fig. 9-12). If the approach involves the supracondylar region, identify and ligate the numerous branches of the superior lateral geniculate vessels, which cross the operative fields. Failure to do so will result in profuse hemorrhage, which will be difficult to control.
Figure 9-9 Incision for the posterolateral approach to the thigh.
Figure 9-10 Incise the fascia of the thigh in line with its fibers and the skin incision.
Continue the dissection, following the plane between the lateral intermuscular septum and the vastus lateralis muscle, detaching those parts of the vastus lateralis that arise from the septum until the femur is reached
at the linea aspera (Fig. 9-13). Incise the periosteum longitudinally at this point and strip off the muscles that cover the femur, using epiperiosteal dissection. Detaching muscles from the linea aspera itself usually has to be done by sharp dissection (Fig. 9-14).
It is very easy to open up the plane between the vastus lateralis muscle and the lateral intermuscular septum in the distal third of the femur. Moving proximally, the muscle becomes thicker, and it becomes more difficult to lift the muscle bulk anteriorly to reveal the femoral shaft. To aid in this process, place a Hohmann or Bennett retractor over the anterior aspect of the femoral shaft, lifting the vastus lateralis forward. A retractor placed on the lateral intermuscular septum will help open up the gap and facilitate proximal dissection.
Figure 9-11 Identify the vastus lateralis under the incised fascia lata.
Figure 9-12 Elevate the vastus lateralis anteriorly, separating the muscle from the septum.
Dang
Vessels
The superior lateral genicular artery and vein cross over the lateral surface of the femur at the top of the femoral condyles. These vessels will need to be ligated for exposure to the bone.
Figure 9-13 Detach those portions of the vastus lateralis that arise from the septum until the femur and linea aspera are reached. Then, incise the periosteum longitudinally.
Figure 9-14 Expose the shaft of the femur.
How to Enlarge the Approach
Extensile Measures
The major value of this incision lies in its exposure of the distal two-thirds of the femur. It can be extended superiorly, however, up to the greater trochanter, to expose virtually the entire femoral shaft. Note that, superiorly, the tendon of the gluteus maximus muscle lies behind the lateral intermuscular septum.
The approach can be extended easily into a lateral parapatellar approach to the knee joint. This allows accurate visualization of the entire distal end of the femur. This extension is used to allow reduction and fixation of intra-articular fractures of the distal femur.
