Clinical Study On The Dorsal Branch Of The Digital Nerve For Sensory Reconstruction In The Hand And The Relative Experimental Study On Peripheral Nerve Repair And Regeneration

Objective: To evaluate the efficacy of the dorsal branch of the digital nerve usedas a donor nerve for sensory reconstruction of the hand. Based on the anatomicalfeatures of the the dorsal branch of the digital nerve and the blood supply of thedorsal skin of the finger, we modified two series (including seven therapies)reconstructive techniques for repairing the soft-tissue defects and digital nervedefects. At the final follow-up, the functional results were evaluated andcompared to these of the conventional techniques so as to know the efficacy of themodified therapies. The relative experimental studies on peripheral nerve repairand regeneration were performed so as to provide experimental evidence forsensory reconstruction in the hands.Methods: The study included the clinical and experimental studies. Clinical studywas divided into two sections.(1) The clinical study of the dorsal digital flapsincluding both dorsal branches of the digital nerves for sensory reconstruction ofthe finger. A retrospective study was conducted that included73patients who hadsoft-tissue defects of the finger treated with the dorsal digital flaps including bothdorsal branches. Three types of the therapies were used for covering thesoft-tissue defects and repairing the injured digital nerve in both sides.Reconstructive techniques included the cross-finger flap including both dorsalbranches in35cases, the dorsal digital island flap including both dorsal branchesin24cases and the free dorsal digital flap including both dorsal branches in14cases. To objectively evaluate the results, we selected a comparison group thatincluded42patients treated with the dorsal digital flaps including one dorsalbranch of the digital nerve. Postoperatively, sensory restoration, total activemotion, pain, Tinel’s sign and patient satisfaction were evaluated and compared to the comparison group.(2) The clinical study of the vascularized nerve graftharvested from the dorsal branch of the digital nerve used for reconstructing thedigital nerve defects. A retrospective study was conducted that included78patients who had digital nerve defects treated with the vascularized nerve graft.Four types of the therapies were used for reconstructing the digital nerve defects.Reconstructive techniques included the dorsal digital nerve flap in21cases,Boomerang nerve flap in18cases, the bipedicled nerve flap in16cases and thepedicle nerve graft based on the second dorsal metacarpal artery in23cases.Postoperatively, the functional results were evaluated and compared to the freenerve graft group. Relative experimental study was divided into two sections.(1)A study of the rapid regeneration pattern without distal Wallerian degeneration.We developed an implantable apparatus that allows direct observation ofindividual axons of the sciatic nerve and assessed axon’s dynamic behavior so asto understand the details of this rapid regeneration pattern.(2) A comparisonstudy of the vascularized and nonvascularized nerve grafts. To explore themechanism of nerve regeneration influenced by the blood supply of the nervegraft, the number and rate of the regeneration axons and the number of themacrophages were evaluated.Results: The results of the clinical study showed the modified techniques basedon the dorsal branch of the digital nerve presented better discriminatory sensation,lower the incidence of the pain and Tinel’s sign, and higher degree of satisfactionthan the comparison groups. Experimental studies:(1) After nerve crush, somesevered axons retained distal stump intact without Wallerian degeneration and theproximal stump extended across the injury site and re-connect with the distalstump within24to48hours.(2) At1week after nerve grafting, significantdifference was seen in the number and rate of the regeneration axons and thenumber of the macrophages between the two groups. However, no significantdifference was seen at3week.Conclusions:(1) The dorsal branch of the digital nerve is similar to the digital nerve in the diameter, which can be used as a donor for sensory reconstruction ofthe finger.(2) The clinical and experimental studies showed, compared to thenonvascularized nerve grafting, the vascularized nerve grafting can achieve betternerve regeneration.(3) When the trauma is minimized with preservation of thecontinuity of the Schwann cell tube, some axons regenerated in a novel modelwithout Wallerian degeneration.