Posterolateral Approach to Femur

The posterolateral approach to femur can expose the entire length of the femur bone with less blood loss, minimum muscle damage.

The uses of the posterolateral approach to femur include the following:

1. Helpful for exposure of entire length of femur.
2. Open reduction internal fixation of femur fractures especially supracondylar femoral fractures.
3. Open reduction for intramedullary nail  passage for femoral shaft fractures.
4. Treatment of femoral nonunions.
5. Femoral osteotomies.
6. Treatment of chronic or acute osteomyelitis.
7. Biopsy and treatment of bone tumors.

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.

Position of the Patient

Place the patient supine on the operating table with a sandbag beneath the buttock on the affected side to elevate the buttock and to rotate the leg internally, bringing the posterolateral surface of the thigh clear of the table.

Landmarks and Incision

• Landmarks:
  1.  Lateral femoral epicondyle.
• Incision:
  • Make a longitudinal incision on the posterolateral aspect of the thigh. Base the distal part of the incision on the lateral femoral epicondyle and continue proximally along the posterior part of the femoral shaft. The exact length of the incision depends on the surgery to be performed.

Internervous plane

The internervous plane for the posterolateral approach to femur lies between:

• The vastus lateralis muscle which is supplied by the femoral nerve).
• The lateral intermuscular septum, which covers the hamstring muscles  which are supplied by the sciatic nerve.

Superficial dissection

Through tensor fascia lata in line with its fibers and the skin incision.

Deep dissection

• Identify the vastus lateralis under the fascia lata.
• 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.
• 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.

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• 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.
• Incise the periosteum longitudinally at this point and strip off the muscles that cover the femur, using subperiosteal dissection. Detaching muscles from the linea aspera itself usually has to be done by sharp dissection.
• 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 Homan 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.

Approach Extension

Proximal Extension:

• The posterolateral approach to femur can be extended superiorly 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.

Distal Extension:

• The posterolateral approach to femur can be extended distally 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 intraarticular fractures of the distal femur.

Dangers

The structures at risk during the posterolateral approach to femur include:

1. Perforating branches of profunda femoris artery:
   • Perforating branches of profunda femoris artery at risk as they pierce lateral intermuscular septum.
   • They should be ligated to prevent hematoma.
2. Superior lateral geniculate vessels:
   • Superior lateral geniculate vessels at risk distally near femoral condyles.
   • They should be ligated to prevent hematoma.

References

• Surgical Exposures in Orthopaedics book – 4th Edition