Certain distal humerus fractures and elbow fracture dislocations warrant early fixation with an external fixator.
The distal humerus is close to the radial nerve and a hazardous area for the placement of an external fixator. No
known safe zone for the placement of an external fixator has been identified on the lateral border of the humerus.
We record the incidence of radial nerve damage following external pin fixation and note the relation of the radial
nerve to each pin.
A total of 39 cadavers were dissected for this study. Two 4 mm pins were placed with a multi-pin clamp into the
lateral border of the right and left humerus at 100 mm and 70 mm proximal to the lateral epicondyle. We dissected
the upper limbs and recorded the incidence of radial nerve damage and the position of the nerve in relation to
the two pins. Data for right and left sides were combined. The radial nerve was damaged by the proximal and
distal pin in 56.4% and 20.5% respectively. The radial nerve was located anterior to the proximal pin (41%) and
distal pin (79.5%). The radial nerve was located posterior to the proximal pin (2.6%) and distal pin (0.0%). We
were unable to identify a safe zone from this study. We propose that pins should be placed less than 100 mm
proximally from the lateral epicondyle and as posterior as possible to minimise the risk of radial nerve damage.