Risk of Radial Nerve Injury during Distal Interlocking of Short Humeral Nails

Abstract

In the treatment of humeral head fractures, as well in subcapital and very proximal shaft fractures of the humerus several short humeral nails are in use, such as, e. g., the Polaris nail or the short UHN with a spiral blade (PHN). In contrast to long humeral nails, here both distal bolts are placed through the same aiming device as for the proximal bolts. The positioning of these distal bolts on the diaphysis after latero-medial implantation requires an analysis of their spatial relation in regard to the radial nerve to avoid the risk of possible nerve damage. In this anatomic-morphologic study. 4 complete shoulder/arm-regions with intact soft tissues have been gained from human cadavers. The antegrade insertion of a short nail with a spiral blade (PHN: Proximal Humeral Nail, Synthes) has been performed according to the clinical practise through a lateral acromial incision with splitting of deltoid muscle fibres. The titanium-PHN has a length of 150 mm and a diameter of 7.5 mm. Through the aiming device proximally a spiral blade and a bolt, distally two interlocking bolts were placed. The radial nerve has been exposed and marked in its complete course, the spatial relation between nerve and implant was documented. On its path from the lateral skin incision towards the lateral cortical bone of the humerus there is no risk of injuring the radial nerve, since the nerve crosses the shaft 4-7 centimetres more distally, coming from cranial-medially towards caudal-laterally. On the other hand, the medial preparation of the proximal radial nerve shows that the tip of the most distal bolt points towards the nerve. Nevertheless, this region of the nerve is covered very well by fat tissue and separated from the shaft through muscle fibres. Still it could be possible to injure the radial nerve on the basis of too profound drilling or the use of a bolt that exceeds the medial cortex by 4 mm or more. In conclusion, when drilling the distal interlocking holes for short humeral nails, it is important, not to reach further medially than the medial cortex in order not to touch the radial nerve. Bolts should not exceed the medial cortex by more than 1 mm. The lateral path for incision and bolt placement is without risk to injure the radial nerve.

Key words

Radial nerve - humeral nail - distal interlocking - PHN

References

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