Nerve Suture

NERVE SUTURE, a technical method for connecting a nerve trunk whose conductivity has been disrupted over a certain length as a result of injury or disease. The primary indication for nerve suture is disruption of the integrity of a nerve trunk of traumatic origin. In the second place, nerve suture is applied in cases of focal nerve injuries resulting from traumatic and inflammatory lesions of the nerve or its surroundings with subsequent compression of the nerve trunk. In the latter case, sometimes an operation to free the nerve (see Neurelysis) is sufficient, but often a segment of the nerve is found to have degenerated from compression by scar tissue, and then it is necessary to perform a nerve resection and then suture it. It should be noted that before the introduction of small-caliber rifles in armies, gunshot interruptions of nerves were rarely observed; but starting with the Anglo-Boer and especially the Russo-Japanese War, nerve injuries became common, and during the last world war, extensive material on such injuries was collected in all warring countries. By analogy with vascular injuries, the cause is the significant velocity developed by the projectile (bullet), which pierces the nerves (as well as vessels) rather than deflecting them to the side, as happened previously. In the Balkan War (according to Gerulanos and Exner), the percentage of nerve injuries reached 1.5-1.7%. According to materials from the world war, nerves of the upper extremity are affected much more often than nerves of the lower extremity (e.g., according to the collective statistics of Borchardt out of 3,872 cases - 179 times brachial plexus, 1,028 times radial nerve, 897 times sciatic nerve, 677 times ulnar nerve, 566 times median nerve, 297 cases of combined nerve injuries of the hand, and the remaining nerves gave only tens of cases). A distinction is made between primary nerve suture, which follows immediately after the injury as part of the primary treatment of the injury, and secondary suture, which is performed after the wound has healed. The technique of nerve suture is based not only on anatomical data but also on physiological data, as well as data on nerve regeneration. The function of a nerve can be restored only under one condition - the growth of axial cylinders from the central segment into the peripheral segment until they reach the terminal branches. Thus, the peripheral segment, while not itself a source of regeneration of axial cylinders, i.e., of the conductors themselves, is of great importance as the path of future regeneration. Experiments and practice on humans show that nevertheless, without a peripheral segment, one central segment cannot give regeneration valuable from a functional point of view; the latter, although locally manifested very vigorously, but individual fibers, growing, do not go in the peripheral direction for any considerable length, but turn sideways and backward and form together with other proliferating elements of the nerve trunk the so-called central neuroma, which appears as a club-shaped thickening at the end of the central segment of the injured nerve. From the foregoing, it follows that for the success of the suture, it is necessary to connect the central segment capable of regeneration with the peripheral one. However, after a certain period of time, measured in months, so-called Nissl's degeneration develops retrograde in the central segment. If this has occurred, then suturing the segments will no longer give regeneration, and consequently, functional results. This circumstance should be attributed to the fact that late suturing, especially several years after injuries, does not achieve its purpose. One more condition is required to obtain a functional result from the suture - this is taking into account when applying the suture the so-called intrastem topography of the nerve, the importance of which was particularly emphasized by Stoffel. The fact is that the arrangement of individual nerves emerging from one common trunk always occupies a definite place in this trunk (e.g., peroneal nerve in the sciatic nerve trunk); therefore, for the most successful course of regeneration, it is important when bringing the central and peripheral segments together to fix them mutually so that the parts of the central end coincide with the same parts of the peripheral one. True, later observations (Edinger, Kennedy) dispute the practical importance of strictly observing this condition, but the thicker the trunk and the more isolated its parts, the more practically desirable it is to take into account the intrastem topography and facilitate the possibility of regeneration. Finally, practice shows that the presence of scar tissue along the path of growth of axial cylinders presents a very significant obstacle to their growth. It is practically considered that a scar 1 mm thick already represents almost an insurmountable obstacle to the penetration of nerve fibers. Hence it follows that the suture itself should be performed in such a way that the inevitable scar at the site of nerve segment union is as thin as possible. From all the above conditions, the modern surgical technique of suture follows. After the usual preparation, a sufficiently long skin incision is made, for convenience of orientation it is better to be flap-shaped in order to avoid a continuous scar. In fresh cases, finding both segments does not present particular difficulty, but in old cases, the isolation of nerves from scar tissue can be quite difficult. Then it is useful for orientation to expose both segments at some distance from the site of injury and then gradually and carefully isolate them from scar tissue. One can use ordinary instruments, but one must use the most delicate and non-traumatizing tissue models. In particular, one should not grasp the nerve trunk roughly; if necessary, it can be carefully held - with a forceps by the neurilemma. During such operations, a sterilizable electrode is necessary to facilitate finding the nerve segments by direct stimulation. For stimulation, a faradic current can be used - then a double electrode is taken, or a galvanic current - then an needle-shaped cathode is used, while a plate serves as the anode, applied at some distance to the patient's body.-The first requirement is to suture the peripheral and central segments of the same nerve trunk where nerves form a plexus (for example brachial plexus). Both segments must be very carefully isolated from the surrounding scar tissue, which may present particular difficulties if the injury was accompanied by prolonged suppuration. Then before suturing, both segments must be refreshed, preferably by a transverse section, which is especially important in late suture. In fresh primary union of segments as part of the primary treatment of the injury, refreshing is undertaken in the presence of crushing of the edges, bruising, etc., circumstances that sharply reduce the possibility of regeneration and threaten the formation of a significant scar. The refreshing of the edges itself is done with a sharp scalpel, and certainly not with scissors, which crush the nerve, "53 as a result of which the conditions for regeneration of nerve fibers worsen. Furthermore, any bleeding in the wound requires the most careful attention and equally careful stopping. Vessels should preferably be ligated with catgut to reduce the development of connective tissue near the sutured nerve. The parenchymal bleeding often observed after excision of scars must be stopped by pressure. Any accumulation of blood around the nerve suture threatens then with abundant growth of connective tissue, which upon final shrinkage may exert pressure on the nerve trunk and reduce to zero the results achieved by suturing. Then both segments are brought close to each other and placed in the correct position relative to each other. In late nerve suture, scar tissue often as a result of damage to the nerve trunk itself penetrates into it - such areas require their removal, and in this moment of the operation itself the apparent continuity of the nerve may already be disturbed. From the above propositions, it is clear that only the continuity of nerve fibers has value for function; therefore, questionable areas should be resected. In practice, cases are not uncommon where the nerve undergoes not a complete interruption, but only in a certain part; then it is quite appropriate to make a resection only of the affected area, and leave the undamaged one without intervention, i.e., to perform a partial nerve suture.-After more or less extensive resections, bringing the central segment to the peripheral one may present considerable difficulties; however, taking into account that direct nerve suture for the reasons stated above gives much more hope for regeneration than any plastic method of closing the nerve defect, all measures should be taken to achieve the direct suturing of the segments. For this purpose, both segments can be mobilized, i.e., isolated from the surrounding tissues. If such mobilization is done carefully without crushing the nerve trunks, it is well tolerated.

Then, if the nerve suture is performed on a limb, as is often observed in practice, a rational position of the limb should be used to bring the segments together, not even hesitating to immobilize the limb in the required position if this is necessary to prevent the danger of the sutured segments diverging. When giving the limb the most advantageous position, it should be remembered that according to Stoffel's research, the greatest benefit in suturing the plexus brachialis is given by adduction of the arm; on the arm when suturing the n. mediani and radialis - adduction of the arm and maximum flexion of the forearm, n. ulnaris - extension of the forearm and adduction of the arm; on the forearm when suturing the n. mediani - flexion of the forearm at a right angle, supination and flexion of the hand, n. ulnaris - extension of the forearm, supination and flexion of the hand, n. radialis - flexion at a right angle, supination and hyperextension of the hand. When suturing the n. femoralis - flexion of the thigh, n. ischiadici (n. tibialis and n. peronaeus) - extension of the thigh, flexion of the leg, plantar flexion of the foot. Finally, the actual suturing of the nerve segments should be performed. Material for the suture can be thin silk or catgut; the latter, if it contains antiseptic substances, is less desirable, as it causes greater development of connective tissue. For the suture, the finest number of thread that can achieve secure suturing should be used. Needles for the suture should be taken round, intestinal type, as the least damaging to the nerve tissue; the actual suturing should be performed through the nerve sheath, however striving for the apposition of both sections to be as intimate as possible. It is often useful to place not just a few sutures in different places at once, rather than all together at once, in order to

jj || -^: in contact and fix them in this position. Otherwise, individual sutures can easily cut through and thus cause new trauma to the nerve. Through-and-through nerve suturing undoubtedly damages it, and this is resorted to only when peripheral sutures fail to bring the central portions of the nerve together (see figure). When applying a partial nerve suture, only the damaged part is sutured in the same way; if a partial resection of the nerve was performed, the undamaged portion may acquire a curved deformation after suturing, however such a change is quite acceptable and in itself does not lead to functional impairment. The careful approximation of nerve segments sometimes necessitates the application of a relatively large number of sutures on large nerves. Usually four are sufficient, on very thin nerves - two. After completion of the suture itself, the ends of the threads should be cut short, and the suture site itself requires special care to prevent the formation of extensive scars that could later compress the nerve trunk. Various methods have been proposed to protect the suture from being incorporated into the surrounding scar, in practice, wrapping the nerve at the suture site with tissue flaps taken from surrounding parts, free tissue flaps, and nerve transposition have been tested on extensive material. As proposed by Kirschner, free fascial plasty was also tested for wrapping the sutured portion of the nerve, however the results were unsatisfactory, and this method was then abandoned. Somewhat better results were obtained when wrapping the suture site with fat flaps, but even this method did not provide sufficient satisfaction. Non-free flaps, cut out from adjacent tissues, mostly fat, were preferred by many surgeons, but in the end it turned out that immersing the sutured nerve into the always adjacent muscles gave the best results. The question of the best protection of the nerve suture from subsequent incorporation into a scar required long-term observations and was discussed in the literature for quite some time. In view of the fact that nerve regeneration is a prolonged process, and consequently the clinical result of the operation is apparent only after several months, sufficient time and material are required to evaluate the results. Spielmeier, who studied extensive material after World War I, concluded that the rate of nerve regeneration after suturing is subject to significant fluctuations depending both on the affected nerve and on the general conditions of the body in which such regeneration occurs (site of injury, age, nutrition, etc.). According to Spielmeier, an average of 1 year is required for complete restoration of function of the n. radialis, often longer; for the n. ischiadicus - 2-3 years. However, initial signs of regeneration appear much earlier; for example, after suturing the n. radialis - already after several months. In the surgical literature, a number of cases of unusually rapid restoration of function after nerve suture are described, for example after several hours or days. Such cases in no way can be considered as a result of healing by first intention of the sutured nerve segments. It is more likely that they must be explained by the presence of collateral branches that escaped damage, the function of which was suppressed by the presence of constant irritation at the site of injury; with the elimination of the latter during the operation (excision of scars, removal of inflamed areas, etc.) such function is restored almost immediately (Oppel, Girgolaw). Oppel observed such "lightning-fast" restoration of function (first signs within a day after the operation) as a result not of suturing, but of excision of a rather large (several cm) segment of the nerve, i.e. under conditions when not only regeneration but even the direct conductivity of the nerve trunk was out of the question. It is by no means indifferent in what condition the nerves are after suturing, since the suturing itself must be considered from the point of view of the treatment results of a given patient only as the first step in treatment, only as the restoration of conditions under which restoration of function is possible. Healing of the surgical wound by first intention is a necessary condition for the ultimate success. Suppuration in the wound usually leads to abundant development of connective tissue, compression of the nerve by it during scar formation and absence of functional results. Attempts to correct the situation with a repeated operation (just as with secondary suture after suppuration in the wound) can be undertaken only after the inflammatory process has completely subsided, otherwise a flare-up of latent infection will again nullify the results of the intervention. Indeed, clinical observations show that cases where suppuration was limited to skin sutures can lead to successful restoration of function. But even in a wound healed by first intention, the sutured nerve should not be left without intervention throughout the entire regeneration process. Experiments by Deinek, as well as clinical observations, showed that regeneration under the influence of heat proceeds faster than without this factor. Thus, physical therapy treatment with heat, especially the application of various procedures, is an urgent indication throughout the entire long postoperative period. It often requires great patience from the physician and the patient, but is rewarded with results. At the same time, physical therapy methods aim to maintain the normal condition of the muscles innervated by the damaged nerve and to combat trophic disorders. Thus, along with the effect of heat procedures, indications for electrization and massage arise. The most ideal conditions for nerve suture in practice are those cases where the nerve is severed and subsequently sutured in one session during surgery, for example in operations on the hammer (see Neurectomy). Under such conditions, restoration of function occurs as a rule. The conditions for regeneration of sensory and motor fibers are far from identical in their results. While severing sensory nerves often and without suturing is accompanied by restoration of function and sometimes even requires special measures to prevent restoration (e.g. in the treatment of neuralgias, particularly of the n. trigemini), restoration of motor function requires particularly careful suturing followed by prolonged physical therapy treatment. Among mixed nerves, the best results have been achieved in suturing the n. radialis and the least favorable on the n. peronaeus. In the absence of results after nerve suture, Bruns recommends re-exposing the site of connection and, having determined the cause of failure, attempting to eliminate it. The overall results of nerve suture, according to Auffenberg, average 70% success. Spielmeier notes complete restoration of function in 23% and improvement in 36%, Ranschburg considers 44% recoveries. Other authors give approximately the same figures. According to the collective statistics of Stradyn (2,248 cases), a successful result was obtained in 59.5%. In view of the much greater difficulty and less favorable results of nerve plastic surgery, i.e. replacement of their defects (see nerve plastic surgery), one should strive by all means to achieve direct connection of nerve segments. The above-mentioned mobilization of the nerve can be increased by moving the mobilized trunk along the shortest path, not even stopping at the detachment of several branching branches from the main trunk (Wrede, Wollenberg). The first author managed to eliminate a defect of the nervi mediani of 10.5 cm and apply a direct suture. A number of authors (Lobker, Bergmann, Trendelenburg, Kirschner, etc.) to facilitate the possibility of nerve suture resorted to bone resection where shortening of the limb has no great practical significance (for example on the shoulder) and where it is dictated by a simultaneous defect of tendons, the presence of pseudarthroses. Also worthy of mention is the "distant" nerve suture, i.e. connection of nerve segments with threads of various materials, implantation into the defect of a vein, Foramitti tubes (preserved calf vessels), etc. Only isolated favorable results with these suture methods, however, did not contribute to their spread; thus the "distant" suture has no practical significance. Nerve plastic surgery. Despite all the measures usually taken to achieve direct suturing of the central and peripheral segments of the damaged or resected nerve, in a number of cases this still cannot be achieved, and then one has to resort to plastic closure of the defect of the nerve trunk. Attempts to achieve connection of nerve segments by cutting out flaps from the central or from the peripheral segments with subsequent turning them to contact with the opposite ones in the manner of tendon plastic surgery should be abandoned at present, as they do not create sufficient conditions for regeneration of nerve fibers (see Nerve fibers - regeneration of nerve fibers). The above-mentioned "distant suture" in essence already represents a transition to plastic surgery.

However, the best method for plastic closure of a nerve trunk defect is free transplantation of a nerve segment taken from another, usually sensory, trunk. Most often, a cutaneous sensory nerve can be used for this purpose. The ends of the transplanted nerve segment are sutured into the defect with the same care as described above, after freshening the central and peripheral segments. If the transplanted nerve does not match in caliber with the trunk where there is a defect, it is permissible to transplant two or more segments placed in parallel. According to general rules, autoplastic transplantation gives the best results here; homoplastic transplants fare somewhat worse. The axis cylinders of the transplant, of course, die in both cases, and the transplant serves only as a path along which regenerating nerve fibers from the central segment grow toward the periphery. Heteroplastic transplantation gives even less reliable results than homoplastic. Nageotte experimentally developed the replacement of nerve defects by transplanting segments of nerves preserved by various methods. However, despite the favorable histological data regarding regeneration described by him, this method is hardly recommendable for clinical use, and experimentally it requires further development. Thus, the most effective and essentially easily performed method is the replacement of nerve defects by autotransplantation of segments of cutaneous sensory nerves. Along with this method, the method of anastomosis and implantation of the damaged nerve into a nearby healthy nerve that is accessible during surgery can also find application. In the anastomosis method, the peripheral segment of the damaged nerve is sutured to the central segment of another nerve that has been severed for this purpose during surgery. Practice has shown (Spitzy) that there is no need to sever the main healthy trunk for anastomosis, but it is sufficient to take one of its branches. The drawback of this method is the necessity to sever a healthy nerve and thus sacrifice its function. To avoid this, the peripheral segment of the damaged nerve can be implanted into a neighboring healthy nerve; at the site of implantation, only a longitudinal slit is made in the nerve, to the edges of which the implanted segment is sutured. The implantation method was improved by Hofmeister in that both segments of the nerve with the defect—central and peripheral—are implanted into the neighboring healthy nerve. According to this author's idea, the healthy nerve in this case should serve as a convenient path along which the regeneration of axis cylinders from the central segment can reach the peripheral. Finally, based on experimental data (Heineke), it has been proposed to implant the central segment of the damaged nerve directly into the muscle that this nerve innervates. The indication for this method is cases where the peripheral segment is so thin or branched that direct connection with the central segment is technically impossible. The results of nerve plastic surgery are worse than those of direct suture of the central and peripheral segments of nerves, but they are by no means so hopeless as to make these methods unworthy of application. Thus, according to Huber, success is achieved in 37% of cases; according to Gosset and Charrier, out of 216 cases, success was noted in 117, improvement in 56, and failure in 26, with 17 cases where the result remained unknown. In particular, regarding implantation methods, it must be noted that successful results are still rare with them, and these methods require further development. The situation is better with the results of direct implantation of the nerve into the muscle. Here, clinical data confirm the experiments, and a number of undoubtedly successful results have been described (Forster, Haberland, Kolliker).