Wire crossing angle affects the stability of circular fine wire frames. Anatomical atlases document safe ‘corridors’ to avoid neurovascular structures, although this may limit crossing angle. In the distal tibia the furthest posteriolateral safe corridor described is through the fibula. The present study describes a new and safe ‘retro-fibular’ corridor for wire placement in the distal tibia that provides a greater crossing angle. Two different methods of wire insertion are considered to determine which provides greater protection to neurovascular structures.

A dissection based study of 20 embalmed lower limbs divided into two groups. 1.8mm wires were inserted at increments along the tibia, from posterolateral to antero-medial, at 30–45 degrees to the sagittal plane. In the first group wires were placed against the posterior surface of the fibula and ‘stepped’ medially onto the tibia. In the second wires were inserted midway between the border of the fibula and tendoachilles. Standard dissection techniques were used to identify the path of wires and distance from neurovascular structures.

In group one distal tibial wires avoided the posterior tibial neurovascular bundle (mean distance 21.7mm) although passed close to the peroneal artery (mean distance 1.2mm). In group two both the posterior tibial and peroneal structures were avoided (mean distances 15.5mm and 7.1mm respectively). Comparison of the two groups shows a significant difference (p< 0.001).

Retrofibular wire placement is safe in the distal quarter of the tibia and facilitates an optimal crossing angle, although is not described in standard atlases. Insertion of wires mid-way between the posteromedial border of the fibula and the tendoachilles appears the most reliable technique.

Anatomical atlases document safe corridors for placement of wires when using fine-wire circular external fixation. The furthest posterolateral corridor described in the distal tibia is through the fibula. This limits the crossing angle and stability of the frame. In this paper we describe a new, safe Retro-Fibular Wire corridor, which provides greater crossing angles and increased stability. In a cadaver study, 20 formalin-treated legs were divided into two groups. Wires were inserted into the distal quarter of the tibia using two possible corridors and standard techniques of dissection identified the distance of the wires from neurovascular structures.

In both groups the posterior tibial neurovascular bundle was avoided. In group A the peroneal artery was at risk. In group B this injury was avoided. Comparison of the groups showed a significant difference (p < 0.001).

We recommend the Retro-Fibular wire technique whereby wires are inserted into the tibia mid-way between the posteromedial border of the fibula and the tendo Achillis, at 30° to 45° to the sagittal plane, and introduced from a posterolateral to an anteromedial position. Subsequently, when using this technique in 30 patients, we have had no neurovascular complications or problems relating to tethering of the peroneal tendons.

Introduction: An important factor affecting the stability of circular fine wire frames is the wire crossing angle, where an angle of 90 degrees confers optimal stability. Safe anatomical ‘corridors’ have been described to avoid neurovascular structures, but often limit the crossing angle. In the distal tibia the posterior tibial artery and tibial nerve wind medially facilitating safe placement of a posterior to anterior ‘retrofibular’ wire. The present study aims to identify structures at risk during ‘retrofibular’ wire placement and determine the level at which this can be used safely.

Methods: A dissection based study of 10 embalmed lower limbs. Wires of 1.8mm diameter were inserted at increments along the tibia. These were placed against the posterior surface of the fibula and ‘stepped’ medially past the posteromedial border onto the tibia. Wires were introduced from posterior to anterior, between 30 degrees and 45 degrees to the sagittal plane. This angle is estimated, reproducing clinical practice. Standard dissection techniques were used to identify the path of wires and distance from neurovascular structures.

Results: In the distal quarter of the tibia wires avoided the posterior tibial neurovascular bundle (mean distance 21.7mm) although passed close to the peroneal artery (mean distance 1.2 mm). Of the 30 wires placed in the distal tibia, 29 (97%) passed through the leg without damage to any neurovascular structures. Anterior tendons were tethered by 13% of wires placed in the distal quarter of the tibia.

Discussion: Retrofibular wire placement facilitates an optimal crossing angle, although is not described in standard atlases. Use in the lower quarter of the tibia does not threaten the posterior tibial neurovascular bundle. However, peroneal artery injury is a possibility. The clinical significance of peroneal artery injury at this level is unclear but should be considered when using this technique.