Factors which may increase stresses at the pin-bone interface in external fixation: a finite element analysis study.

The pin-bone interface of the external fixation system has been studied using a finite element mode. The maximum stresses were observed in the near 'cortex' adjacent to the site of entry of the pin. This location coincides with the area where loosening is usually first observed radiologically. Other results indicate that the stress values are significantly increased by using deep threads and by using stainless steel instead of titanium.