Histomorphometry of the ulnar nerve and of its branches

A morphometric study has shown that 10% of the fibers of the ulnar nerve sh ould suffice to reinnervate the biceps muscle in brachial plexus palsies. T he aim of this study was to evaluate, by a morphometric study using compute rized microanalysis, the cross-sectional surface areas of the different col lateral and terminal branches of the ulnar nerve. This was expressed in ter ms of percentage of the cross-sectional surface area of the main trunk of t he 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-s ectional area of the ulnar nerve. Thus use of these fascicles destined for the flexor digitorum profundus, identified by intra-operative nerve stimula tion, 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 result s in patients operated upon using this technique.