Influence of Blood Flow on the Neuroma Formation after Transposition of the Nerve Stump into Vein: Experimental and Clinical Study.

We study the influence of blood flow on the neuroma formation after transposition of the nerve stump into a vein. A total of 30 rats were divided into two groups. In group (I), a 10-mm segment of the femoral vein was excluded from the blood stream. A venotomy was performed in the middle of this segment. The proximal nerve stump of femoral nerve was transposed into the lumen of the femoral vein via a venotomy and held with an epineural suture through the venous wall. In group (II), the same technique was used as in group (I) but without exclusion of the vein segment from blood flow. The control side of the femoral nerve was transected and then was left in place. All animals were sacrificed after 28 weeks. Histopathological evaluation was performed postoperatively; serial transverse sections were made to find the largest diameter of the neuroma. Selected specimens were processed for electron microscopy examination. The following parameters were assessed in both the groups: cross-sectional area of neuromas; myelinated axons; and neural tissue to connective tissue ratio. In group (I), the proximal end of the tibial nerve formed a nonclassic neuroma. In group (II), the proximal end of the tibial nerve formed a nonclassic neuroma smaller in diameter than group (I). The proximal end of the femoral nerve of the control sides in both groups formed a classic neuroma larger in diameter than the experimental sides in both the groups. A Kruskal-Wallis H test showed that there was a statistically significant difference in myelinated axons between the different groups, X2 (3) = 36.19, p < 0.001. The average neural tissue to connective tissue ratio in the control group (I) ranged from 39.2 to 85.8%, but on the experimental side, it was more or less equalized. The average of a neural tissue to connective tissue ratio of the group (II) ranged from 59.1 to 63.9% in the treatment sides as compared to 28.6 to 82.4% in the control sides. The clinical experience utilizing the same technique in the treatment of 10 patients of painful neuromas of the superficial radial nerve and digital nerves were presented with encouraging results. The blood flow has a considerable effect on neuroma formation. We recommend a further study to know the fine details about the exact role of blood as the bloodstream may carry away neurotrophic factors that may also be released by the nerve stump itself.