Orthopaedic surgical approaches 2022, Nov, 21 | 12:00 am

Approaches for External Fixation Pelvis-Femur-Tibia and Fibula-Ankle

The Pelvis

External fixation of the pelvis is used in life-threatening situations to achieve hemodynamic stability. The anterior pelvis is accessible in the supine trauma patient, and the anterior superior iliac spine is the most useful landmark for pin placement. Fluoroscopy should be used.

Two techniques are available for pin placement.

 

Iliac Crest

 

Place two external fixation pins immediately posterior to the anterior superior iliac spine through the subcutaneous surface of the iliac crest. Only drill the outer cortex and introduce the pins by hand, allowing them to slide between the two tables of the iliac wing. Be aware that the plane of the iliac wing is difficult to assess, particularly when the bone is displaced by trauma. Introducing long needles on either side of the iliac wing, keeping them in contact with the bone, provides a useful guide to correct pin placement (Fig. 13-5A–E).

The lateral femoral cutaneous nerve of the thigh is vulnerable at the level of the anterior superior iliac spine; therefore, pins should always be inserted under direct vision through small incisions rather than through blind stab incisions.

Anterior Inferior Iliac Spine External Fixation

This technique provides more stability than the iliac crest technique but is much more technically demanding.

Identify the anterior inferior iliac crest using a C-arm image intensifier and mark the skin. Make a 2-cm longitudinal incision centered over the anterior inferior iliac spine. Deepen the incision down to the deep fascia. Divide the fascia in line with the skin incision and identify the interval between the sartorius muscle and the tensor fasciae latae (Fig. 13-6B). Explore the intermuscular interval with a finger and palpate the bone. Insert a K-wire into the bone and check its position with the image intensifier. The wire should be at least 2 cm above the joint line to avoid inadvertent penetration of the hip joint capsule.

Alternatively make a stab incision over the anterior superior iliac crest and insert a pin down to bone through muscle under image intensifier control.3–5

 

 

 

 

 

 

 

Figure 13-5 A: Incision for iliac crest external fixation pins. B: Two wires placed on either side of the iliac crest mark the dissection for the unicortical drill hole. C:

The pin will find its way between the inner and outer table of the ilium using this open technique. D: The pins should be in the thick iliac tubercle. E: Two pins in place in the iliac wing.

 

Drill the outer cortex using fluoroscopy and introduce the pin by hand allowing it to slide into the supra-acetabular region (Fig. 13-6A–E).

The hip joint capsule is the structure that is most at risk during this procedure. The lateral cutaneous nerve of the thigh is always close but the main neurovascular bundle is always well medial to the approach.

 

 

 

 

 

 

Figure 13-6 A: A small stab 3 cm distal to the anterior superior iliac spine over the anterior inferior iliac spine. B: Small open incision using fluoroscopy. C: Blunt dissection finds the anterior inferior iliac spine. D: Unicortical drilling establishes a portal for the pin above the hip joint in the supra-acetabular region. E: Pin in place above the hip joint in the anterior inferior iliac spine.

 

The Femur

The femoral artery enters the thigh in direct anterior relationship to the head of the femur (the femoral pulse). The artery courses down the limb, passing to the medial side of the bone in its middle third, and crosses the knee joint in direct posterior relationship to the distal femur. The sciatic nerve enters the thigh posterior to the femoral head and maintains this posterior relationship as it runs distally. At a variable point in the thigh, the nerve splits into its tibial and common peroneal components. The tibial nerve joins the femoral artery in the back of the knee joint. The common peroneal nerve runs with the tendon of the biceps muscle posterolateral to the bone.

Half pins can be inserted laterally throughout the entire length of the femur without damage to any of the neurovascular structures. These pins

do tether the fascia lata and vastus lateralis muscles, however, and it often is not possible to mobilize the knee successfully with them in position. In the distal third of the femur, laterally inserted half pins can be extended medially to transfix the limb. Be aware that these pins may penetrate the knee joint occasionally, resulting in leakage of synovial fluid and possible septic arthritis of the knee.

In the middle third of the bone, anteriorly inserted half pins also are safe. Care should be taken not to penetrate the posterior cortex too deeply, though, to avoid damage to the tibial nerve (Fig. 13-7).

 

 

 

Figure 13-7 The variable relationship of the femoral artery to the femur dictates different pin positions depending on the level of pin placement. A: Proximal third: Insert half pins from the lateral surface of the bone. Avoid penetrating the medial cortex too deeply to avoid damage to the profunda femoris artery and its tributaries. B: Middle third: Place laterally inserted half pins. Avoid penetrating the medial cortex too far to avoid damage to the femoral artery. Alternatively, place anteriorly inserted half pins. Avoid penetrating the posterior cortex too deeply to prevent damage to the sciatic nerve. C: Distal third: Place transfixion pins through the bone in a medial to lateral direction. Be aware that transcondylar pins will penetrate the knee joint synovium.

The Tibia and Fibula

The anterior and posterior neurovascular bundles course down the leg on either side of the interosseous membrane lying between the tibia and fibula.

 

Fibula

 

The intimate relationship of the common peroneal nerve to the neck of the fibula makes pin insertion into the upper third of the fibula hazardous. Fortunately, this rarely is necessary.

 

Tibia

 

The tibia has a broad subcutaneous surface throughout its entire length. Because the bone is triangular in shape, the middle of this surface lies anterior to both neurovascular bundles. The subcutaneous surface of the bone can be used throughout its entire length for the placement of half pins. This route allows good bony anchoring without the risk of soft tissue tethering (Fig. 13-8).

 

 

 

Figure 13-8 Because the neurovascular bundles lie largely posterior to the tibia and it has a subcutaneous surface, pin placement is relatively straightforward. A:

Proximal third: Insert anterior half pins through the subcutaneous surface of the bone. If half pins are used, avoid penetrating the bone too far to protect the posterior neurovascular bundle—the posterior tibial artery and the tibial nerve. B: Middle third: Insert anterior half pins through the subcutaneous surface. C: Distal third: Insert anteriorly placed half pins.

 

The Ankle

The bony prominences of the distal tibia, calcaneus, and first metatarsal provide access for pin placement. The neurovascular bundle running behind the medial malleolus should be avoided (Fig. 13-9). Half pins should be used, except in the calcaneus, where transfixion pins provide a very stable pin construct to be placed for trauma-related problems.

Half pins are placed in the distal tibia and in the first metatarsal using a mini-open technique. The calcaneal pin is a transfixion pin posterior and distal to the neurovascular bundle. The calcaneal pin should be placed from medial to lateral to avoid injury to the neurovascular bundle. The pin in the first metatarsal is placed perpendicular to the long axis of the first ray but distal to the tibialis anterior tendon.

 

 

Figure 13-9 Pin placement for external fixation around the ankle.

 

REFERENCES

  1. MITTELMEIER W, BRAUN C, SCHäFER R: The Kapandji technique for fixation of distal radius fractures—a biomechanical comparison of primary stability. Arch Orthop Trauma Surg. 2001;121(3):135–138.

  2. MCQUEEN MM: Non-spanning external fixation of the distal radius.

    Hand Clin. 2005;21(3):375–380.

  3. KIM WY, HEARN TC, SELEEM O ET AL: Effect of pin location on stability of pelvic external fixation. Clin Orthop Relat Res. 1999; (361):237–244.

  4. HAIDUKEWYCH GJ, KUMAR S, PRPA B: Placement of half-pins for supra-acetabular external fixation: an anatomic study. Clin Orthop Relat Res. 2003;(411):269–273.

  5. LIDDER S, HEIDARI N, GäNSSLEN A ET AL: Radiological landmarks for the safe extra-capsular placement of supra-acetabular half pins for external fixation. Surg Radiol Anat. 2013;35(2):131–135.