Anteromedial approach to the femur

Introduction

The anteromedial approach to the femur provides excellent exposure of the lower two-thirds of the femur and the knee joint.

Indications

The anteromedial approach to the femur is used for:

1. Open reduction and internal fixation (ORIF) of distal femoral fractures, particularly those with intra-articular extension requiring a medial plate.
2. Open reduction and internal fixation of femoral shaft fractures (limited to the distal two-thirds of the femur due to the presence of the femoral neurovascular bundle).
3. Treatment of chronic osteomyelitis.
4. Biopsy and treatment of bone tumors of the femur.
5. Quadricepsplasty.

Patient Positioning

• Position the patient supine on the operating table.
• Consider placing a lift under the contralateral hip to facilitate access to the medial femur.

Landmarks and Incision

Landmarks

• Vastus medialis muscle.

Incision

• Make a 10 to 15 cm longitudinal incision on the anteromedial side of the thigh, over the interval between the rectus femoris and vastus medialis muscles.
• If the knee joint needs to be opened, extend the incision distally along the medial border of the patella to the knee joint line.
• The exact length of the incision depends on the pathology being treated.

Internervous Plane

• There is no true internervous plane for the anteromedial approach to the femur. The dissection proceeds between the vastus medialis and rectus femoris muscles, both of which are innervated by the femoral nerve.
• The intermuscular plane can be safely used to expose the distal two-thirds of the femur, as both muscles receive their nerve supply high in the thigh.

Superficial Dissection

• Incise the fascia lata (deep fascia) along the skin incision and identify the interval between the vastus medialis and rectus femoris muscles. Develop this plane by retracting the rectus femoris laterally.

Deep Dissection

• Begin distally and open the knee joint capsule along the skin incision by cutting through the medial patellar retinaculum.
• Proceed proximally and split the quadriceps tendon near its medial border.
• Open the plane with sharp dissection, staying within the substance of the quadriceps tendon and leaving a small cuff of tendon attached to the vastus medialis.
• This preserves the insertion of these fibers and allows for easy closure. If the vastus medialis is detached from the quadriceps tendon, reattachment is very difficult and muscle function is impaired.
• Next, continue to develop the interval between the vastus medialis and rectus femoris muscles proximally to expose the vastus intermedius muscle.
• Split the vastus intermedius along its fibers. Directly beneath it lies the periosteum-covered femoral shaft. Continue the dissection in the epiperiosteal plane to reach the bone.

Approach Extension

Proximal Extension

• The anteromedial approach to the femur can be extended proximally along the same interval between the rectus femoris and vastus medialis muscles.
• To lengthen the deep dissection, split the vastus intermedius further.
• This extension provides excellent exposure of the lower two-thirds of the femur.

Distal Extension

• Continue the skin incision distally, curving it laterally to end just below the tibial tubercle.
• Incise the medial retinaculum along the skin incision. This makes the patella more mobile and allows for lateral subluxation to fully expose the knee joint.
• Be careful not to avulse the quadriceps tendon from its insertion during this maneuver.

Dangers

Structures at risk during the anteromedial approach to the femur include:

1. Medial Superior Genicular Artery:
   • The medial superior genicular artery crosses the field just proximal to the knee joint.
2. Vastus Medialis Muscle:
   • Distal fibers of the vastus medialis muscle insert directly onto the medial border of the patella.
   • These fibers are disrupted during exposure.
   • Careful closure is required to prevent lateral patellar subluxation.

References

• Surgical Exposures in Orthopaedics – 4th Edition
• Campbell’s Operative Orthopaedics, 12th Edition