Objectives

Infection of implants is a major problem in elective and trauma surgery. Heating is an effective way to reduce the bacterial load in food preparation, and studies on hyperthermia treatment for cancer have shown that it is possible to heat metal objects with pulsed electromagnetic fields selectively (PEMF), also known as induction heating. We therefore set out to answer the following research question: is non-contact induction heating of metallic implants effective in reducing bacterial load in vitro?

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.

When performing the Scandinavian Total Ankle Replacement (STAR), the positioning of the talar component and the selection of mobile-bearing thickness are critical. A biomechanical experiment was undertaken to establish the effects of these variables on the range of movement (ROM) of the ankle.

Six cadaver ankles containing a specially-modified STAR prosthesis were subjected to ROM determination, under weight-bearing conditions, while monitoring the strain in the peri-ankle ligaments. Each specimen was tested with the talar component positions in neutral, as well as 3 and 6 mm of anterior and posterior displacement. The sequence was repeated with an anatomical bearing thickness, as well as at 2 mm reduced and increased thicknesses. The movement limits were defined as 10% strain in any ligament, bearing lift-off from the talar component or limitations of the hardware.

Both anterior talar component displacement and bearing thickness reduction caused a decrease in plantar flexion, which was associated with bearing lift-off. With increased bearing thickness, posterior displacement of the talar component decreased plantar flexion, whereas anterior displacement decreased dorsiflexion.