Ultrasound evaluation of radial nerve injuries by cortex overlapping screw tips after internal fixation of humeral fractures: a cadaveric study

TL;DR

This study shows that ultrasound can accurately detect how close screws are to the radial nerve after arm bone surgery, helping prevent nerve damage.

Contribution

The study demonstrates that ultrasound can reliably visualize screw placement relative to the radial nerve in humeral fractures.

Findings

Ultrasound correctly identified all screw tips and their relation to the radial nerve in cadaveric humeral bones.

Ultrasound accurately measured the overlapping length of screw tips, unlike fluoroscopy which underestimated it in half the cases.

Seven out of eight screw tips had direct contact with the radial nerve, as confirmed by anatomical dissection.

Abstract

The radial nerve may be painfully irritated or damaged by open reduction and internal fixation (ORIF) of humeral fractures. Secondary radial nerve lesions after ORIF of humeral shaft fractures are described in up to 16%. Not only peripheral nerves but also orthopaedic instruments and osteosynthesis material are well visible by ultrasound. The aim of this study was to evaluate the accuracy of ultrasound in assessing the relation between the bone overlapping screw tips and the radial nerve close to the humeral bone.

Ultrasound-guided drilling was used to place screws as close as possible to the radial nerve in 8 humeral bones of four cadavers. The relation between the radial nerve and the screw tips was assessed by high-resolution ultrasound, and the overlap of all screw tips over the bone was measured by ultrasound and fluoroscopy. Thereafter, the findings were validated by anatomical dissection.

We could correctly identify all screw tips and their relation to the radial nerve by ultrasound. In 7 of 8 cases, the screw tip had direct contact with the radial nerve. The overlaying length of the screw tip was accurately measured by using ultrasound in all cases. In contrast fluoroscopy underestimated this length in 50% of cases.

With this study, we show that ultrasound can reliable visualize the screw tips and its relation to the radial nerve. Ultrasound is a promising diagnostic tool to evaluate patients with radial nerve irritations or lesions after ORIF of humeral fractures. Furthermore, ultrasound could be an adequate tool to guide drilling.

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