Functional evaluation of gap vs. abutment repair of peripheral nerves in the rat

Various expressions of nerve regeneration specificity (tissue, target, and end-organ) have been demonstrated histologically, but the influence of nerve regeneration specificity on functional outcome remains to be investigated. Specificity expression appears to be dependent, to some extent, on the distance between the proximal and distal nerve stumps. Regeneration specificity is inhibited by end-to-end alignment. This study examined the effect of gap distance repair on the return of rat hind-limb function, as measured by the sciatic function index (SFI). Sixty-four Sprague-Dawley rats were randomized into three groups: 0-mm gap (abutment), 2-mm gap, and 5-mm gap repair. The sciatic nerve was divided and secured in a Silastic conduit to maintain the gap length. The SFI was measured preoperatively and then at postoperative weeks 2, 4, 8, 12, 16, and 20. Results showed no significant difference in functional return between the abutment and the two gap groups at any time period (SFI at 20 weeks = -73.9, 0 mm; -73.5 2 mm; -75.2, 5mm; p = 0.90). This lack of difference in functional outcomes suggested an insignificant functional influence of regeneration specificity within single chamber conduits. The study also demonstrated that small gaps between nerve ends within a conduit yielded functional results equal to end-to-end repair of rat sciatic nerves.