The influence of fat tissue on neuroma formation

The proximal stumps of transected sciatic nerves were implanted into an abdominal pedicle flap of fat tissue in rats. Nerve stumps that had been transected without implantation into fat tissue served as control experiments. At 4, 8, or 24 weeks postoperatively, the rats were sacrificed and the neuromas at the transected nerve ends together with the adjacent fat tissue were studied after intra-aortal perfusion fixation. Light microscopy revealed no significant difference in neuroma size between the two groups. In most animals with fat implantation, however, infiltration of fat tissue beyond the margins of the solid neuromatous bulb by regenerating nerve fibers was limited to rare axons growing along blood vessels and connective tissue strands. In only a few instances was the fat tissue itself invaded by minifascicles as was usually seen in the connective tissue surrounding control neuromas. It is concluded that diffuse outgrowth of nerve fibers is limited to some extent by fat tissue, which, however, is not an impermeable barrier for regenerating nerve fibers. Nevertheless, in a fat tissue flap, the neuroma is placed in a "soft pressure-free bed" which might be a prerequisite for permanent diminution of pain sensitivity.