Invited Discussion

I enjoyed reading this interesting article concerning vascularized sural nerve graft. This paper is well-written on the vascularity of sural nerve; however, clinical applications, as described in this article, have some difficulties.

Traditionally, satisfactory results have been achieved using nonvascularized interfascicular nerve in most clinical cases, except in heavily scarred, poorly vascularized recipient beds. Such beds are often encountered after replantations and diffuse crush injuries. In these situations, two conventional approaches should be preferred. Covering with well-vascularized tissue, such as free skin flap or muscle flap, promotes the vascularity of the conventional nerve graft, performed secondarily. The other method is to use the vascularized nerve graft with accompanying well-vascularized tissue, to cover the heavily scarred tissue or extensive skin defect.

It is well-known that the big and thick nerve graft, such as the ulnar nerve trunk graft easily results in central necrosis of the nerve, which blocks the growth of regenerating axons; however, a small and thin nerve graft such as the sural nerve has promoted a long-standing controversy on clinical indications. Vascularized nerve grafting should have proven clinical advantages, before changing its status from an experimental procedure to an acceptable clinical alternative for nerve reconstruction. The advantages must outweigh the inherent disadvantages of increased technical difficulty and length of the procedure. Although proof is lacking that vascularized nerve grafts are better than nonvascularized grafts, three pieces of experimental evidence, four clinical impressions from other authors, and our own clinical long-term results suggest that vascularized nerve grafts in poor recipient beds often improved functional recovery over nonvascularized grafts. However, these impressions must ultimately be substantiated by long-term follow-up studies.

At present, the vascularized ulnar nerve graft is the first representative of this procedure, although it is limited to use in reconstruction following complete paralysis of the brachial plexus. The vascularized sural nerve graft is used to repair nerve defects longer than 10 cm, and simultaneously to cover the accompanying skin defect. For a simple nerve defect, we use nonvascularized nerve graft, as long as the defect is covered with well-vascularized tissue, and satisfactory results were obtained without exception.

The small-caliber nerve graft such as the sural nerve can be easily revascularized without vascular anastomosis, when it is placed in a well-vascularized bed. The vascularity of the surrounding tissue is the most important factor for survival of the sural nerve graft. In case 1, the authors primarily covered the skin defect with the latissimus dorsi musculocutaneous flap. In this situation, the nerve was placed in well-vascularized tissue, and the vascularized nerve graft was not required; a simple conventional nerve graft would be sufficient.

The vascularized sural nerve graft, accompanied with the sural artery and its comitant vein, may have the most reliable vascularity, compared with the other distal blood supply, the peroneal artery system, which was described by us.[1] [2] [3] The authors' model cannot accompany the overlying skin flap, which is the most useful indication for this nerve graft to simultaneously cover the skin defect and to place the nerve graft in a well-vascularized bed. On the contrary, our graft model can accompany the skin flap. This is the most useful advantage of the vascularized sural nerve graft. In case 3, the nerve was also placed in well-vascularized tissue, and a conventional nerve graft would be sufficient.

As mentioned above, the vascularized sural nerve graft with a vascular pedicle of sural artery and vein has rare clinical indications, and is advantageous only as a long nerve graft in a poorly vascularized, scarred bed without skin defect; that is a rare occasion in clinical cases.

REFERENCES

• 1 Doi K, Kuwata N, Kawakami F. The free vascularized sural nerve graft.  Microsuregery . 1984;  5 175-184
• 2 Doi K, Kuwata N, Sakai K. A reliable technique of free vascularized sural nerve grafting and preliminary results of clinical applications.  J Hand Surgery . 1985;  12 677-684
• 3 Doi K, Tamaru K, Sakai K. A comparison of vascularized and conventional sural nerve grafts.  J Hand Surg . 1992;  17A 670-676