Advantages and disadvantages of pinless external fixation

The AO pinless external fixator (PEF) uses trocar tipped clamps to grip the outer tibial cortex rather than pins to transfix it. Its main advantage is to avoid further contamination of the medullary canal in open tibial fract ures where a nail may subsequently be used. We tested the anatomical safety of this device and its effect on plastic surgical procedures compared with a standard unilateral external fixator (UEF). The PEF and UEF were placed on two amputated limbs which were then dissecte d. structures at risk were traced on ten cadaver limbs. We found that important anatomical structures were endangered by the PEF an d that safe zones could not always be defined. The UEF avoided these struct ures. Plastic surgical approaches were made more difficult by the PEF which imposed limitations on local flap design and endangered the arterial perfo rators which supply them. We conclude that safety is compromised by the PEF because margins for error are small. It poses additional problems in soft tissue reconstruction and highlights the need for co-operation between plastic surgical and orthopaed ic teams in choice of fixation device. (C) 2000 Elsevier Science Ltd. All r ights reserved.