[1] 10w A New Epineural Nerve Repair Technique with External Metallic Circle

[1] 26w BACKGROUNDDespite the existence of various nerve coaptation techniques, functional results of nerve repair are still inadequate. Potential benefits of developing modified coaptation techniques cannot be disregarded.

[1] 132w The mean Sciatic Function Index values in external metallic circle repair (n:11) and conventional epineural repair (n:10) groups were Ϫ42.35 Ϯ 22.95 and Ϫ69.34 Ϯ 17.96, respectively (p ϭ 0.020). Electrophysiological studies revealed that the duration of compound muscle action potentials (CMAP) was (p ϭ 0,012) shorter in conventional nerve repair group than it was in external metallic nerve repair. When external metallic circle repair and conventional epineural repair groups were examined for distal nerve segments, there were significant findings for the diameter of axons (p ϭ 0.005), diameter of nerves (p ϭ 0.000), and for G ratios (p ϭ 0.000). The mean intraepineural cross sectional areas of external metallic circle repair and conventional epineural repair groups were 3.57 Ϯ 0.21 and 2.92 Ϯ 0.23 mm 2 , respectively (p ϭ 0.000).

[2] 10w Functional and histologic results were obtained in a blind fashion.

[1] 78w Many different technical improvements have been aimed at achieving better coaptationin nerve repairs, such as CO 2 laser welding [7], ring coupling [23] fibrin glue [22], and freeze-trimming [31], but none of them proved to be superior over conventional epineural suture technique. The debate continues regarding epineural versus fascicular or group fascicular repair of major mixed nerves [19,28]. Nerve expansion [20] and end-to-side nerve coaptation [26] are other challenging alternative methods that have not found wide clinical application.

[2] 9w The idea of creating a larger coaptation area is

[3] 43w 1 Normalized Compound Muscle Action Potential Latency, Amplitude, and Duration (mean Ϯ S.D.) GROUPS ONSET LATENCY AMPLITUDE DURATION Conventional epineural repair 32.89% Ϯ 15.33 Ϫ33.44% Ϯ 13.91 Ϫ0.63% Ϯ 13.37 External metallic circle repair 32.91% Ϯ 20.58 Ϫ33.24% Ϯ 16.50 15.86% Ϯ 17.04

[4] 173w new and has not yet been investigated adequately [15]. Unlike the vessel walls, epineurium has limited expansion capacity. In using the circle either on the arteries or on the veins, we were able to have an expansion of about 20 to 50% of the diameter [11][12][13]. During the initial attempts, the nerve coaptation gets difficult with the placement of a ring on the coaptation line, and the technique certainly requires additional surgical expertise. The first important point is to choose the correct diameter of the ring to adapt the repair. Here we only aimed to have an expansion of 10 to 20%. We assure you that it is not more difficult than an ordinary epineural repair once you adapt to the procedure. In applying a circle in the nerve repair; apart from an initial dilatation effect, we hoped to have long term benefits because of the resistance of circle repair to known centrineural displacement of sutures by the invading epineural connective tissue [3]. The results proved that this long-term benefit could be achieved.

[5] 77w Walking track analysis performed during the course of a study provides the investigator the unique opportunity to assess specific aspects of nerve recovery in a noninvasive fashion. Because morphologic examination of the regenerated nerves does not necessarily provide functionally relevant information on the outcome of nerve regeneration, many authors have been using modifications of functional sciatic nerve indexes [2,8,17,25,30]. We obtained statistically significant results, and the results of our walking track analysis favored external metallic circle repair.

[6] 123w CMAP amplitude is known to be proportional to the number of conducting motor axons in the nerve, while the onset latency, a measure of the distal conduction velocity of the fastest motor fibers, represents the degree of myelination of those fastest axons. On the other hand, the duration of CMAP reflects the homogeneity of the degree of myelination among all of the motor axons in the nerve [15]. Thus, our findings indicate that, although the num-ber of regenerating axons were about the same in both of the groups, more fibers were myelinated to a better degree in external metallic circle repair group; suggesting that the technique of the external metallic circle repair may provide a faster functional recovery than the conventional epineural repair.

[7] 58w Morphometric analysis also favors circle nerve repairs. Many authors report an increase of the number of axons at the distal end of the nerve repair. Decreases in nerve diameters and myelin thickness between the proximal and distal samples of groups are also expected findings, but external metallic circle repair seems to favor better nerve diameters and myelinization [5,9,10,18,24,28].

[8] 82w Because the physiologic events at the coaptation line are the only determinant of the eventual nerve healing potential in the otherwise healthy individual, an increase in volume of this very critical zone may have potentially positive effects on nerve regeneration. We believe that the external metallic circle nerve repair technique may enhance nerve regeneration by creating a larger sprouting and contact area for nerve fibers, but further investigations are needed before we can rely on the results of this simple modification [14,27,29].

[1] 27w The external metallic circle repair technique enhances nerve regeneration by enabling a larger sprouting and contact area for nerve fibers. © 2004 Elsevier Inc. All rights reserved.

[1] 38w The authors report a new coaptation technique in which the epineural sutures were performed with an external metallic circle to increase the coaptation surface. The sciatic nerves of 30 male Wistar albino rats were used in the study.

[2] 345w A total of 30 adult male Wistar albino rats weighing 250 to 300 grams were used in the experiment. They were housed in a central animal care facility in ␤-chip lined iron cages and provided with water and rat chow ad libitum. The rats were anesthetized with ketamine hydrochloride 100 mg/kg (Ketalar, Eczacıbas ¸ı, Turkey) and xylazine 10 mg/kg (Rompun, Bayer, Germany) and were prepared in the prone position. After shaving the right and left gluteal regions, the sciatic nerves were dissected through a gluteal muscle-splitting incision. Every right leg was used for the nerve repairs while left legs constructed internal controls. After this stage, each rat was assigned randomly into 1 of the 2 groups and was selected alternatively for the surgical procedure. The sciatic nerves were mobilized, keeping its 3 major branches intact. Six rats were used to gain experience for external metallic nerve repair technique; the method described on vessels previously was modified [11]. Hand made silver rings of 1.2 mm of inner diameter were used in this experiment (Figure 1 A,B). All the nerves were coapted by the senior author (Kayıkc ¸ıog ˘lu A) with 8/0 epineural sutures (Ethicon, Edinburgh, UK) performing a total of 6 stitches for each coaptation. The rings were incorporated at the coaptation line and the first guide sutures were placed passing inside the circle and tied over the circle bringing the epineuriums of cut ends together. The second guide sutures were placed 120 degrees away from the first guide suture again passing inside the circle and tied. A third suture was placed in between around the circle according to the same principle. Then the nerves were rotated to place another guide suture 120 degrees away from the others. With the addition of 2 more sutures in between, the coaptations were achieved (Figure 2 A,B). The same coaptation procedure was applied without a ring for the control group rats. During follow-up period, 3 rats were excluded from the study because of cannibalization. Finally the groups were constructed as: External metallic circle repair (n:11); conventional epineural repair (n:10).

[3] 250w Nerve conduction studies were performed 1 year after the surgical procedure. A commercial electromyograph (EMG) device (Synergy, Medelec, UK) was used for all nerve stimulation and recording procedures. The electrophysiological procedure was used previously in another study performed by Demirci M et al [21]. After anesthesia with ketamine hydrochloride 100 mg/kg (Ketalar), sciatic nerves on both sides were exposed through a gluteal splitting incision. The nerve was stimulated at 3 mm proximal to the coaptation line on the experimental side, and at the corresponding location on the opposite (internal control) side. A custom-made bipolar electrode (a pair of tungsten wires of 0.3 mm in diameter, hooked at the tip of 2 mm length, interelectrode distance 3 mm, anode proximal), and 0.2 ms duration of constant current pulses were used for stimulation. Evoked compound muscle action potentials (CMAP) were recorded on the corresponding gastrocnemius muscle using a surface electrode (8 mm diameter disk electrode) held at the muscle end-plate zone ("muscle belly") that was referenced to a needle electrode placed at the dorsum of the hind-paw subcutaneously. The stimulus strength was adjusted to be 5% higher than the strength necessary to obtain a maximal CMAP. The supramaximal stimulation was repeated several times until a stable CMAP was obtained. The onset latency, negative peak's amplitude, and negative peak's duration of CMAPs were measured on both sides for each rat. The nerve conduction parameters measured on the experimental side were normalized as percentages of the corresponding values obtained from the control (opposite) side.

[4] 95w The rats were sacrificed and 3 cm of the sciatic nerve segment centered on the coaptation line was excised. The specimens were fixed in a solution of phosphate-buffered 3% gluteraldehyte and then fixed in a phosphate buffered 1% osmium tetroxide solution. The tissue was dehydrated through serial alcohols and embedded in Spurr's resin. Sections were obtained from the specimen 0.5 to 1 cm proximal and distal to the repair site. Three-millimeter long nerve segments were used to prepare plastic sections. Toluidine blue stained semithin (1 m thick) sections were prepared for light microscopy (LKB-Nova, Sweden).

[5] 60w Quantitative morphometric analysis was performed on semithin sections by computerized image analysis software KONTRON 400 (Kontron Electronics Gmbh, Eching, Germany). Measurements were conducted at a 100ϫ magnification. Per each cross section 5 random fields were chosen and myelinated fibers were counted. Additionally, axon diameter, nerve diameter and g-ratio (the ratio of the axon diameter to the fiber diameter) were determined.

[6] 33w Cross section of the coaptation line was used to calculate the area of nerve repair. Ten random diameters obtained by oculometer were averaged and used to calculate the intraepineural cross sectional nerve area.

[7] 28w Mann-Whitney U test was used to compare the results. A p value smaller than 0.05 was accepted to be statistically significant. Variability was expressed as Ϯ standard deviation.

[8] 62w The onset latencies were prolonged, and the amplitudes were decreased at the experimental sides compared to the normal sides in both of the surgical groups with no significant difference (p Ͼ 0.05) between the groups. However, the duration of CMAP was significantly (p ϭ 0.012) shorter in the conventional nerve repair group than it was in external metallic nerve repair (Table 1).

[9] 61w The sections taken from the sciatic nerve proximal to the nerve repairs were significantly indistinguishable between the groups. When external metallic circle repair and conventional epineural repair groups were compared for distal nerve segments, there were significant findings for the diameter of axons (p ϭ 0.005), diameter of nerves (p ϭ 0.000) and for G ratios (p ϭ 0.000) (Table 2).

[10] 31w The mean intraepineural cross sectional areas of external metallic circle repair and conventional epineural repair groups were 3.57 Ϯ 0.21 and 2.92 Ϯ 0.23 mm 2 , respectively (p ϭ 0.000).

[1] 7w Nerve repair, epineural repair, circle nerve repair.

[2] 152w A lthough meticulous nerve repairs are being performed under the operating microscope, clinical results may still have limitations. Ever since Heuter [6] used stitches anchored in the superficial layer of the epineurium to achieve trunk to trunk coaptation, this technique has become the classic method of repairing transected peripheral nerves, under the term "epineural nerve repair." The fascicular repair technique proposed by Langley and Hashimoto [16] and popularized by Sunderland [26] has been added to the surgeon's armamentarium as a technique that aims to provide a better coaptation of the cut edges. In the last 20 years, interest has been focused on cellular events occurring in the regenerating axon, rather than the nerve repair technique, but expectations on potential benefits of using modified coaptation techniques cannot be disregarded. Ring coupling [23], laser welding [7], fibrin glue [22], and freeze trimming [31] are all the results of search for a new repair technique.

[3] 27w We report a new epineural nerve repair technique in which the coaptation is performed with the use of an external metallic circle to increase the coaptation area.

[4] 135w Examination of the walking patterns, previously described as a method of assessing nerve lesions [4] was performed on 52 nd week. A plastic 10 ϫ 10 ϫ 100 cm corridor in which a piece of paper was placed in the bottom was used to obtain rat footprints. Each rat's hind paws were dipped in India ink, and the rat was allowed to walk down the corridor. The footprint length (PL), the toe spread between the first and fifth toes (TS) and the distance between the second and fourth toes (IT) were measured. These measurements were done both on normal and experimental sides (The prefixes N and E are added for normal and experimental measurements, respectively; e.g., normal footprint length is NPL). The sciatic function index (SFI) was then calculated according to the formula given below:

[5] 21w An index of 0 was accepted as completely normal while an index of Ϫ100 indicated total impairment of sciatic nerve function.

[6] 96w In 2 rats for which clear print images could not be obtained because of poor sciatic function or a marked eversion or inversion deformity resulting from imbalanced reinnervation of the posterior tib-ial and peroneal fascicles, maximal and intermediary toe spreads were measured manually. For this purpose, the rats were lifted by the skin on the back of the neck and held in a vertical position with the hind feet on a clear acetate sheet. The maximal and intermediary toe spreads were then marked with a pen. Two measurements were taken and the results were averaged [1].

[7] 33w The mean Sciatic Function Index values in external metallic circle repair and conventional epineural repair groups were Ϫ42.35 Ϯ 22.95 and Ϫ69.34 Ϯ 17.96, respectively. This finding was statistically significant (p ϭ 0.020).

[8] 80w PROXIMAL NERVE SEGMENTS DISTAL NERVE SEGMENTS CONVENTIONAL EPINEURAL REPAIR EXTERNAL METALLIC CIRCLE REPAIR CONVENTIONAL EPINEURAL REPAIR EXTERNAL METALLIC CIRCLE REPAIR Number of myelinated axons 11689 Ϯ 760 11821 Ϯ 800 15078 Ϯ 1506 15107 Ϯ 1062 Diameter of axon 3.70 Ϯ 0.28 3.69 Ϯ 0.30 2.77 Ϯ 0.16 3.05 Ϯ 0.24 Diameter of nerve 6.26 Ϯ 0.53 6.27 Ϯ 0.59 4.33 Ϯ 0.23 4.95 Ϯ 0.44 G ratio 0.59 Ϯ 0.01 0.59 Ϯ 0.01 0.64 Ϯ 0.01 0.62 Ϯ 0.01