Purpose: The purpose of this study was to evaluate and compare the risk of iatrogenic radial nerve injury between arm positionings of 45° and 60° abduction in anterolateral humeral plating using a 4.5-mm narrow dynamic compression plate.
Methods: Fifty-six humeri of cadavers in the supine position with 45° of arm abduction were exposed through the anterolateral approach. A hypothetical fracture line was marked at the middle of the humerus, and a precontoured ten-hole 4.5-mm narrow dynamic compression plate was applied and fixed to the anterolateral surface. After the fixation, the radial nerve was exposed through a triceps-splitting approach. Screws in contact with or which had penetrated the radial nerve were deemed to be injuries. Then, the screws and plate were removed, the arm changed to the 60° arm abduction position, and the steps of applying the plate and inserting the screws were followed as in the 45° arm abduction step.
Results: The screws which could potentially injure the radial nerve were those of the second to sixth screw holes in both the 45° and 60° of arm abduction positions. The incidences of iatrogenic radial nerve injury of the second to sixth screw holes in the 45° position were 5.36%, 39.29%, 80.36%, 60.71%, and 10.71%, respectively, and at the 60° position were 5.36%, 53.57%, 83.93%, 60.71%, and 7.14%, respectively. There were no statistically significant differences in risk of injury between the two positions in all screw holes (all P-values > 0.05).
Discussion: In anterolateral humeral shaft fixation, arm abduction position did not affect the risk of iatrogenic radial nerve injury, with the main risk from certain screw holes. The surgeon should be careful in screw insertion, especially at the fourth and fifth screw holes.
Level of evidence: IV; cadaveric study.
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