Abstract
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.
Highlights
Distal humerus fractures are uncommon, comprising 2% of all fractures and a third of all humerus fractures.[1]
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
Multi-pin clamp. the pin on the right is used as a marker, making the pin of the left the proximal pin situated at 100 mm proximal to the lateral epicondyle and the middle pin would be situated 30 mm distal to the proximal pin
Summary
Distal humerus fractures are uncommon, comprising 2% of all fractures and a third of all humerus fractures.[1]. Artico et al.[11] performed a study on fresh cadavers and found that the mean distance between the lateral epicondyle and the point where the nerve pierces the lateral intermuscular septum was 110 mm.[11] Kamineni et al.[12] described the safe zone for placing pins in relation to the trans-epicondylar distance They concluded that 100% of the trans-epicondylar distance along the lateral border of the humerus was a safe zone for external fixation.[12] Clement et al.[13] stated the risk of radial nerve damage by external fixation may be due to the variation in the course of the nerve and that wide incision and blunt dissection to the cortex was necessary to prevent nerve damage. Multi-pin clamp. the pin on the right is used as a marker, making the pin of the left the proximal pin situated at 100 mm proximal to the lateral epicondyle and the middle pin would be situated 30 mm distal to the proximal pin
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