End-to-Side vs. Free Graft Nerve Reconstruction-Experimental Study on Rats

Abstract

The long history of regeneration nerve research indicates many clinical problems with surgical reconstruction to be resolved. One of the promising surgical techniques in specific clinical conditions is end-to-side neurorrhaphy (ETS), described and then repeated with different efficiency in the 1990s of the twentieth century. There are no reliable data on the quality of recipient nerve regeneration, possible donor nerve damage, and epineural window technique necessary to be performed. This research attempts to evaluate the possible regeneration after end-to-side neurorrhaphy, its quality, potential donor nerve damage, and the influence of epineural windows on regeneration efficiency. Forty-five female Wistar rats were divided into three equal groups, and various surgical technics were applied: A-ETS without epineural window, B-ETS with epineural window, and C-free graft reconstruction. The right peroneal nerve was operated on, and the tibial nerve was selected as a donor. After 24 weeks, the regeneration was evaluated by (1) footprint analysis every two weeks with PFI (peroneal nerve function index), TFI (tibial nerve function index), and SFI (sciatic nerve function index) calculations; (2) the amplitude and latency measurements of motor evoked potentials parameters recorded on both sides of the peroneal and tibial nerves when electroneurography with direct sciatic nerve electrical stimulation and indirect magnetic stimulation were applied; (3) histomorphometry with digital conversion of a transverse semithin nerve section, with axon count, fibers diameter, and calculation of axon area with a semiautomated method were performed. There was no statistically significant difference between the groups investigated in all the parameters. The functional indexes stabilized after eight weeks (PFI) and six weeks (TFI and SFI) and were positively time related. The lower amplitude of tibial nerve potential in groups A and B was proven compared to the non-operated side. Neurophysiological parameters of the peroneal nerve did not differ significantly. Histomorphometry revealed significantly lower diameter and area of axons in operated peroneal nerves compared to non-operated nerves. The axon count was at a normal level in every group. Tibial nerve parameters did not differ from non-operated values. Regeneration of the peroneal nerve after ETS was ascertained to be at the same level as in the case of free graft reconstruction. Peroneal nerves after ETS and free graft reconstruction were ascertained to have a lower diameter and area than non-operated ones. The technique of an epineural window does not influence the regeneration result of the peroneal nerve. The tibial nerve motor evoked potentials were characterized by lower amplitudes in ETS groups, which could indicate axonal impairment.

Keywords: electroneurography; end-to-side; histomorphometry; locomotion analysis; motor evoked potentials; nerve reconstruction; rat; walking track analysis.

Figure 1

The average number and standard deviation of fibers, diameter, and surface area of axons in the studied groups and in the non-operated peroneal nerve. Statistical significance between each group is presented, where * is p < 0.05.

Figure 2

Microphotographs of transverse sections of the peroneal nerve; 40× image magnification (left side—non-operated, right side—operated: example from group A). Histograms presenting the fiber count are presented below each of the photographs.

Figure 3

The average number and standard deviation of fibers, diameter, and surface area of axons in the studied groups and in the non-operated tibial nerve. Statistical significance between each group is presented, where * is p < 0.05.

Figure 4

Microphotographs of transverse sections of the tibial nerve; 40× image magnification (left side—non-operated, right side—operated: example from group A). Histograms presenting the fiber count are presented below each of the photographs.

Figure 5

The scheme presents the anatomical division of the sciatic nerve into three branches; its anatomical photograph is shown below. Three applied techniques of surgical procedures: A—peroneal nerve graft to a tibial nerve without window incision, B—the same procedure with window incision, C—free graft of peroneal nerve using same nerve when its part was rotated 180°and sutured again.

Figure 6

(A) Parameters measured in the footprint in the walking track analysis. (B) Example of the recording in walking track analysis of one animal from group A (end-to-side suture without an incision of the donor nerve epineurium) during locomotion. PL—print length, TS—toe spread, ITS—intermediate toe spread.

Figure 7

Examples of evoked potentials recorded from peroneal nerves and tibial nerves following electrical (A,B) and magnetic (C,D) stimulations in one of rats from experimental group A (end-to-side suture without an incision of the donor nerve epineurium). Calibration bars for amplification and time base presented in A are the same for all recordings. The first vertical cursor after the stimulus artifact indicates the latency onset of potential in ms for each recording. The strengths of applied stimulations are (A)—0.1 mA, (B)—0.1 mA, (C)—0.6 T, and (D)—0.7 T.

Figure 8

The algorithm of the microscopic photographs (40× image magnification) transformation being the histological transverse sections of the nerve aiming to evaluate the morphometric values (preliminary picture, conversion to 8-bit grayscale, threshold result, inversion, particle count, numerical results, respectively).