Posterior Approach to Femur

The posterior approach to femur involves dissection of the posterior compartment of the thigh, it’s performed with the patient in prone position.

The key to the approach lies in understanding the anatomy of the sciatic nerve and its relationship to the biceps femoris muscle.

The posterior approach to femur uses include:

1. Treatment of infected cases of nonunion.
2. Treatment of chronic osteomyelitis.
3. Biopsy and treatment of bone tumors.
4. Exploration of the sciatic nerve.

Position of the Patient

Place the patient in prone position on the operating table.

Landmarks and Incision

Landmarks:

• The gluteal folds.

Incision:

• Make a straight longitudinal incision about 20 cm long down the midline of the posterior aspect of the thigh.
• The incision should end proximally at the inferior margin of the gluteal fold, and its length will vary with surgical need.

Internervous plane

Internervous plane for the posterior approach to femur lies between:

• Lateral intermuscular septum which covers vastus lateralis muscle innervated by the femoral nerve.
• Biceps femoris muscle which is innervated by sciatic nerve.

Superficial dissection

• Incise the deep fascia of the thigh in line with the skin incision, or lateral to it, taking care not to damage the posterior femoral cutaneous nerve, which runs longitudinally under the deep fascia (and roughly in line with the fascial incision), in the groove between the biceps and semitendinosus muscles.
• Identify the lateral border of the biceps femoris in the proximal end of the wound by palpating it.
• Then, develop the plane between the biceps femoris and vastus lateralis muscles, which are covered by the lateral intermuscular septum.

Deep dissection

• Begin proximally, Retract the long head of the biceps femoris muscle medially and the lateral intermuscular septum laterally, developing the plane with a finger.
• Identify the short head of the biceps as it arises from the lateral lip of the linea aspera.
• Detach its origin from the femur by sharp dissection, and reflect it medially to expose the posterior aspect of the femur.
• In the distal half of the wound, retract the long head of the biceps laterally to expose the sciatic nerve. Be aware that the nerve may already have divided into its tibial and common peroneal branches in which case two “sciatic nerves” will be found running side by side.
• Gently retract the sciatic nerve laterally to reveal the posterior aspect of the femur, which is covered with periosteum.
• Develop an epiperiosteal plane between the periosteum and overlying soft tissues.

Approach Extension

• The Posterior Approach to Femur cannot be extended usefully either superiorly or inferiorly.
• It is valuable solely for its exposure of the middle three-fifths of the shaft of the femur.

Dangers

The structures at risk during the posterior approach to femur includes:

1. Posterior femoral cutaneous nerve.
2. Sciatic nerve.
3. Nerve to biceps femoris.

Related Anatomy

Semimembranosus Muscle

• The insertions of the semimembranosus muscle greatly reinforce the posterior and posteromedial joint capsule of the knee.
• The muscle may be transferred to the anterior surface of the lateral femoral condyle, together with the semitendinosus tendon, to correct internal rotation deformity of the hip in patients with a variety of neurologic lesions, a technique that is used only rarely.

Semitendinosus Muscle

• As its name implies, the semitendinosus muscle has an extremely long tendon in relation to the size of its
  muscle belly. The tendon is at least 13 cm long and can be used in a variety of surgical procedures.
• It may be left attached to the tibia, even as it is attached via a drill hole to the patella, to hold that bone medially in cases of recurrent dislocation.
• It also may be used for posterior and anterior cruciate reconstruction; in that procedure, the tendon is separated from the muscle at the musculotendinous junction and is threaded through the femur so that it mimics the function of the missing cruciate ligaments. In addition, it may be used to reinforce a torn medial collateral knee ligament.

References

• Surgical Exposures in Orthopaedics book – 4th Edition
• Campbel’s Operative Orthopaedics book 12th
• BOSWORTH DM: Posterior approach to the femur. J Bone Joint Surg 26:687, 1944.