Lower Extremity

Femur: Given the medial and posterior location of neurovascular structures in the thigh, an anterolateral or lateral approach can be used with little risk to neurovascular structures. At the distal third of the femur, however, care should to be taken to avoid over-penetration of the posterior cortex, as this risks injury to the popliteal artery. Anterior pins placed in the distal femur should begin 7.5 cm above the superior pole of the patella to avoid inadvertent intraarticular placement.23

Knee: For distal femur and/or proximal tibia fractures including those involving the articular surfaces, a knee spanning fixator is most appropriate. Two pins each in the intact femur and tibia can be connected by bars. To maximize stability of this longer construct, good pin spread and/or multiple bars should be considered. As with other long bone fractures, longitudinal traction is used to correct coronal and sagittal alignment. The fixator should be locked with the knee in flexion. A posterior slab, short leg splint can be helpful to control ankle plantarflexion and provide additional soft tissue rest and pain control as the gastrocnemius muscle crosses the knee joint.

Tibia: The neurovascular bundle runs along the bone’s posterolateral surface. This leaves the anteromedial surface free for safe pin placement. The thin layer of subcutaneous tissue overlying the bone makes this surface easily palpable along its entire length. The direct anterior tibial crest should be avoided as it is significantly thicker than the rest of the bone, and pin placement is difficult even with a power drill. Pins should be placed about 1 cm medial to the anterior crest to avoid the crest as excessive drilling can result in thermal necrosis, pin loosening and eventual infection.

Fibula: External fixation of the fibula is not indicated despite any amount of associated tibia or soft tissue injury.

Ankle: To stabilize the ankle (typically in the setting of an unstable distal tibia fracture), two pins should be placed in the tibia proximal to the fracture site and be connected to a centrally-threaded transfixation pin (or pins) placed through the calcaneus using a medial-to-lateral approach to avoid injury to the neurovascular bundle located just posterior to the medial malleolus. (Figure 4a below) While a 4 mm pin can be placed in the first metatarsal to control ankle dorsiflexion, stable placement can be difficult and the tibialis anterior tendon at the base of the bone can be at risk. A calcaneal pin is more easily placed, and sufficient ankle dorsiflexion can be maintained with the addition of a posterior slab splint as necessary. Talar neck pins, with appropriate anatomic knowledge, can be useful to stabilize the distal tibia, particularly if a calcaneal fracture is present that precludes transfixation pin placement.