Histomorphometry of the ulnar nerve and of its branches

A morphometric study has shown that 10% of the fibers of the ulnar nerve should suffice to reinnervate the biceps muscle in brachial plexus palsies. The aim of this study was to evaluate, by a morphometric study using computerized microanalysis, the cross-sectional surface areas of the different collateral and terminal branches of the ulnar nerve. This was expressed in terms of percentage of the cross-sectional surface area of the main trunk of the ulnar nerve. The study revealed that the branch to the flexor digitorum profundus bellies to the ring and little fingers formed 9.5% of the cross-sectional area of the ulnar nerve. Thus use of these fascicles destined for the flexor digitorum profundus, identified by intra-operative nerve stimulation, at the level of the arm would be sufficient for neurotisation of the nerve to the biceps. This has been confirmed by the initial clinical results in patients operated upon using this technique.