Denatured Muscle as a Nerve Conduit: A Functional, Morphologic, and Electrophysiologic Evaluation

ABSTRACT

This experimental study evaluated denatured skeletal muscle and denatured epineural basement membrane tube as conduits to bridge defects in rat sciatic nerve. A 1-cm segment of sciatic nerve was resected in 48 rats. In Group 1 (control), the segment was discarded; in Group 2, the segment was re-implanted orthotopically; in Group 3, the defect was bridged by denatured (liquid nitrogen frozen and thawed) muscle; and in Group 4, the resected nerve segment was denatured as in Group 3, the axons removed, and the resulting epineural basement membrane tube used as a conduit. Functional assessment was carried out with the sciatic functional index (SFI). Histologic examination of the graft was made at 1.5, 2, 2.5, 3, and 6 months postoperatively. At 6 months, a Grass neurostimulator was used to determine the minimal voltage necessary to elicit ankle motion.

Hind-foot ulceration and/or toe loss occurred in all groups, but less commonly in the rats with denatured muscle and denatured nerve conduits. Both Groups 3 and 4 achieved a macroscopic appearance of nerve at 45 days. However, the denatured conduits were longer and narrower than in standard nerve grafts. In the distal nerve, a mixture of axonal regeneration and degeneration was seen in Groups 2 to 4. By 6 months, the microscopic appearance of the nerve grafts, conduits, and distal nerves was that of normal nerve, with no differences between the groups. Active plantar flexion following electrical stimulation was observed in Groups 2 to 4 at 6 months. The voltage required to elicit ankle motion was greater in Groups 3 and 4 than in Group 2 (p <0.001). Gait was impaired (SFI = -100) in all four groups throughout the 6 months of observation. Results indicated that denatured skeletal muscle and denatured epineural basement membrane tubes can act as matrices for the growth of regenerating axons. They appear to facilitate protective sensory recovery more rapidly and motor recovery (as determined by electrical stimulation) less effectively than conventional nerve grafts.