Posterior Approach to the Femur‌‌‌

The posterior approach4 is useful in patients who cannot undergo more anterior approaches because of local skin problems. It provides access to the middle three-fifths of the bone, as well as to the sciatic nerve. Although it is performed rarely, its uses include the following:

1. Treatment of infected cases of nonunion of the femur

2. Treatment of chronic osteomyelitis

3. Biopsy and treatment of bone tumors

4. Exploration of the sciatic nerve

Knowledge of the anatomy that underlies this approach is vital for exploration of wounds in this area.

The approach is unusual in that surgery remains lateral to the biceps muscle in its proximal half, but proceeds medial to it in its distal half. This is because of the relationship of the posterior aspect of the femur to the sciatic nerve.

 

Position of the Patient

 

Place the patient prone on the operating table, supporting the pelvis and chest on longitudinally placed pillows or thick foam pads to allow the abdomen and chest to move freely, ensuring adequate ventilation (Fig. 9-21).

 

Landmark and Incision

Landmark

The gluteal folds are visible clearly on the buttock.

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 (Fig. 9-22).

 

Internervous Plane

 

The plane of dissection lies between the lateral intermuscular septum, which covers the vastus lateralis muscle (which is supplied by the femoral nerve), and the biceps femoris muscle (which is supplied by the sciatic nerve; Fig. 9-23).

 

Superficial Surgical 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 (Fig. 9-24). 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 (Fig. 9-25).

 

Figure 9-21 Position of the patient on the operating table for the posterior approach to the femur.

 

Figure 9-22 Make a straight longitudinal incision in the midline of the posterior

aspect of the thigh.

 

Figure 9-23 The internervous plane lies between the vastus lateralis (which is supplied by the femoral nerve) and the biceps femoris (which is supplied by the sciatic nerve).

 

Figure 9-24 Incise the deep fascia of the thigh in line with the skin incision or just lateral to it, taking care not to damage the posterior femoral cutaneous nerve.

 

Deep Surgical 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 (see Fig. 9-25). 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 (Fig. 9-26).

In the distal half of the wound, retract the long head of the biceps laterally to expose the sciatic nerve (Fig. 9-27). 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 (Fig. 9-28). Develop an epiperiosteal plane between the periosteum and overlying soft tissues (Fig. 9-29; see Fig. 9-28).

 

Dang

 

Nerves

The sciatic nerve courses down the back of the thigh in the posterior compartment. Because it lies medial to the biceps muscle in the upper part of the incision, it is protected from damage during the proximal part of the approach as long as the correct intermuscular plane is maintained. Distally, the nerve must be identified and care taken not to retract it overzealously (see Fig. 9-53).

The nerve to the biceps femoris branches from the sciatic nerve and enters the biceps from its medial side well up in the thigh. Because the dissection is on the safe lateral side, the nerve cannot be damaged proximally.

 

How to Enlarge the Approach

 

The approach 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.

 

Figure 9-25 Identify the lateral border of the biceps femoris; develop the plane

between the biceps femoris and the vastus lateralis.

 

Figure 9-26 Detach the origin of the short head of the biceps from the femur by sharp dissection, and reflect it medially to expose the posterior aspect of the femur.

 

Figure 9-27 Retract the long head of the biceps laterally to expose the sciatic nerve.

 

Figure 9-28 Retract the sciatic nerve laterally to expose the posterior aspect of the femur. Incise the periosteum.

 

Figure 9-29 Develop the subperiosteal plane to expose the posterior aspect of the femur.