[Proximal interlocking of humeral intramedullary nails and risk of axillary nerve injury].

QUESTION: Possible injuries to the axillary nerve are criticised in antegrade and retrograde endomedullary nailing of the humeral shaft during proximal interlocking. Clinical experience seems not to support the theory of a high risk of nerve injury. The real risk although remains unknown under anatomical-morphological aspects.

MATERIAL AND

METHODS

Eight complete human cadaveric shoulder-arm regions with original soft-tissue coverage had been used. Four times the unreamed humeral nail (UHN) had been inserted retrograde, and four times antegrade, distributed in each pair. Antegrade interlocking was performed after skin incision and spreading of soft tissues through the aiming devices. This involved one oblique bolt from lateral to medial. Retrograde proximal interlocking was performed under image intensifier. This involved triple interlocking, once dorso-ventrally and twice latero-medially. The incision paths have been marked. After preparation of the nerve stem in the lateral axillary portal the different branches have been searched and exposed. The spatial relations of bolts and nerve branches have been measured and the insertion path of the bolts has been revised, finally lesions of nerve structures have been documented.

RESULTS

We found the latero-medially inserted bolt heads of the retrograde approach and the oblique bolt head of the antegrade approach being placed in a safe distance from the medio-dorsally positioned stem of the axillary nerve. On the other hand the dorsoventrally inserted bolt head (retrograde approach) showed in most cases a very tight relation to the nerve stem. Exploring the axillary nerve and its branches showed in no case a direct nerve lesion.

CONCLUSIONS

We suggest to perform only a sharp cutaneous incision and then to prepare the muscle only by careful spreading until touching bone, with tissue retraction during drilling. In retrograde nailing the dorso-ventral bolt should only be used in extreme proximal fractures.