We evaluated the injuries, survival rats, and secondary surgeries of patients who had undergone finger replantation or revascularization between October 2005 and July 2010. The 70 digits came from 43 patients (average age, 46 years; range, 19 to 78 years; 37 men). Overall replantation survival rate was 94%; 93% (27/29) for complete amputations and 95% (39/41) for near-amputations. In all, 39 digits from 21 patients required 48 secondary surgeries; skin grafts, tenolysis, joint fusion, bone graft, osteotomy, and web plasty. The more proximal or more severe the injuries, the higher the need of secondary surgeries. The most common surgery soon after replantation was skin coverage; the most common after two months was tendon surgery. Primary repair must be adequate to restore the function and appearance of amputated digits; however, the possible need for secondary surgeries must be kept in mind to avoid restricting the options for secondary procedures.

To understand the neural mechanisms underlying the therapeutic effects of crossing nerve transfer for brachial plexus injuries in human patients, we investigated the cortical responses after crossing nerve transfer in mice using conventional and tomographic optical imaging. The distal cut ends of the left median and ulnar nerves were connected to the central cut ends of the right median and ulnar nerves with a sciatic nerve graft at 8 weeks of age. Eight weeks after the operation, the responses in the primary somatosensory cortex (S1) elicited by vibratory stimulation applied to the left forepaw were visualized based on activity-dependent flavoprotein fluorescence changes. In untreated mice, the cortical responses to left forepaw stimulation were mainly observed in the right S1. In mice with nerve crossing transfer, cortical responses to left forepaw stimulation were observed in the left S1 together with clear cortical responses in the right S1. We expected that the right S1 responses in the untreated mice were produced by thalamic inputs to layer IV, whereas those in the operated mice were mediated by callosal inputs from the left S1 to layer II/III of the right S1. To confirm this hypothesis, we performed tomographic imaging of flavoprotein fluorescence responses by macroconfocal microscopy. Flavoprotein fluorescence responses in layer IV were dominant compared to those in layer II/III in untreated mice. In contrast, responses in layer II/III were dominant compared to those in layer IV in operated mice. The peak latency of the cortical responses in the operated mice was longer than that in the untreated mice. These results confirmed our expectation that drastic reorganization in the cortical circuits was induced after crossing nerve transfer in mice.

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