Authors of section

Authors

Arnold Besselaar, Daniel Green, Andrew Howard

Executive Editor

James Hunter

General Editor

Fergal Monsell

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Safe zones for pin placement

1. Introduction

Inserting percutaneous instrumentation through safe zones reduces the risk of damage to neurovascular structures.

2. Upper leg

Anatomy

The thigh is covered by a circumferential muscular envelope and the diaphysis of the femur by a thick periosteum.

The major neurovascular structures are located medially and posteriorly, and, therefore, the femur can safely be approached over the anterolateral region.

Neurovascular structures of the upper leg

Safe zone in the middle of the shaft

The safest anatomical zones for pin insertion are the anterolateral and direct lateral regions of the femur.

Areas of soft-tissue damage should be avoided, to minimize the risk of subsequent pin-track infection.

See diagrams of cross-sections of the thigh to appreciate the location of muscle groups and neurovascular bundles at each level.

The anatomy in the area between the two solid green lines has a consistent cross-section.

Safe zone for pin insertion in the middle of the shaft
Anterolateral approach

Palpate vastus lateralis and rectus femoris with the patient in the supine position. The direction of the pin should be in the plane between these two muscles, as shown in the cross-section.

Avoid perforation beyond the medial femoral cortex to prevent injury to the neurovascular structures.

Anterolateral approach
Direct lateral approach

Palpate the vastus lateralis muscle belly and insert the pins in the direction shown in the diagram, aiming to obtain purchase in both cortices.

Avoid inserting pins laterally through the iliotibial tract to reduce the risk of pin loosening and pin-track infection.

Direct lateral approach

Safe zone in the distal third

Direct lateral approach

The lateral area of the distal part of the femur is easily accessible for pin insertion. The distal part of vastus lateralis is the only structure of the soft-tissue envelope to avoid.

The pin should be positioned at least 2 cm proximal to the growth plate.

Safe zone for pin insertion in the distal third

3. Lower leg

Neurovascular structures

Common peroneal nerve

The common peroneal nerve runs from the center of the popliteal fossa laterally and curves distally around the fibular head in an anterolateral direction. It separates into a superficial and a deep branch. Injury of this nerve will result in loss of ankle and toe extension, often causing severe functional deficit.

Neural structures of the lower leg
Saphenous nerve

The saphenous nerve runs distally along the anteromedial aspect of the thigh. The infrapatellar nerve branches as it passes the knee joint.

Injury of this nerve will not result in motor deficit but can cause cutaneous sensory loss.

Popliteal artery

The popliteal artery runs through the center of the popliteal fossa. It separates into the anterior tibial artery, the fibular artery and the posterior tibial artery at the level of the proximal tibial shaft (the trifurcation).

Popliteal artery

Safe zone in the midshaft of the tibia

The neurovascular bundle contains the anterior tibial artery and vein, together with the deep peroneal nerve, and runs close to the posterolateral border of the tibia.

These structures are at risk if a pin is inserted in the direction indicated by the red dotted line.

The pins should be inserted approximately 1 cm medial to the tibial crest, on the anteromedial aspect of the tibia, and are angled approximately 20° from the sagittal plane.

Safe zone for pin insertion in the midshaft of the tibia