Nerve Suture

NERVE SUTURE, a technical method of joining a nerve trunk whose conductivity has been impaired to some extent as a result of injury or disease. Indications for a nerve suture are primarily disruptions of the integrity of the nerve trunk of traumatic origin. Secondly, a nerve suture is applied as a result of focal nerve injuries as consequences of traumatic and inflammatory lesions of the nerve or its surroundings, followed by compression of the nerve trunk. In the latter case, the operation of nerve release (see Neurolysis) sometimes proves sufficient, but frequently a section of the nerve turns out to be degenerated from scar compression, and then it is necessary to perform a nerve resection operation and subsequently suture it. It should be noted that before the introduction of the small-caliber rifle in armies, gunshot interruptions of nerves were observed rarely; starting from the Anglo-Boer and especially the Russo-Japanese wars, nerve injuries became a common occurrence, and in the last World War, extensive material on such injuries was gathered in all belligerent countries. By analogy with vascular damage, the cause is the very significant speed developed by the projectile (bullet) that nerves (like vessels) are penetrated by it rather than deflected 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 World War data, the nerves of the upper extremity are affected much more often than the nerves of the lower extremity (e.g., according to Borchardt's compilation statistics, 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 combined hand nerve injuries, while other nerves gave only tens of cases). A distinction is made between a primary nerve suture, following immediately after the injury in the order of primary wound treatment, and a secondary suture, performed after the wound has healed. The technique of nerve suture is based not only on anatomical but also on physiological data, as well as data on nerve regeneration. Nerve function can be restored under only one condition—the outgrowth of axis cylinders from the central segment into the peripheral one until they reach the terminal branches. Thus, the peripheral segment, not serving itself as a source of regeneration of axis cylinders, i.e., the conductors themselves, appears to be very important as the path of future regeneration. Experiments and practice on humans show that, nevertheless, without the peripheral segment, the central one alone cannot yield a functionally valuable regeneration; the latter, although locally manifesting itself very violently, individual fibers proliferating do not go in the peripheral direction for any significant length, but turn sideways and backward and form, together with other proliferating elements of the nerve trunk, the so-called central neuroma, appearing as a club-shaped thickening at the end of the central segment of the injured nerve. From what has been said, 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, measured in months, so-called retrograde Nissl degeneration develops in the central segment in turn. Once this has occurred, the suturing of the segments will no longer yield regeneration and, consequently, functional results. To this circumstance should be attributed the fact that late suturing, especially several years after injuries, does not achieve its goal. Another condition is required to obtain a functional result of the suture—taking into account during the application of the suture the so-called intraneural topography of the nerve, the importance of which was especially emphasized by Stoffel. The fact is that the arrangement of individual nerves emerging from a common trunk always occupies its own definite place in this trunk (e.g., the peroneal nerve in the trunk of the sciatic nerve); therefore, for the most successful course of regeneration, it is important when bringing the central and peripheral segments closer together to perform their mutual fixation so that the divisions of the central end coincide with the same divisions 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 the divisions in it, the more practically desirable it is to take intraneural topography into account and thereby facilitate the possibility of regeneration. Finally, practice shows that the presence of scar tissue along the path of axis cylinder growth presents a very significant obstacle to their growth. It is practically accepted to consider that a scar 1 cm in thickness is already an almost insurmountable obstacle to the sprouting of nerve fibers. Hence it follows that the suture itself must be performed in such a way that the scar inevitable at the site of fusion of the nerve segments is as thin as possible. From all the above-stated conditions arises the modern surgical technique of the suture. After routine preparation, a sufficiently long skin incision is made, preferably of a flap shape for ease of orientation in order to avoid a continuous scar. In fresh cases, the search for both segments does not present special difficulty, but in old cases, the isolation of nerves from scars 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 cautiously isolate them from the scar tissue. Instruments can be used as usual, but one must use the most delicate and non-tissue-traumatizing models. Especially, the nerve trunk should not be grabbed roughly; if necessary, it may be cautiously held with forceps by the neurilemma. During such operations, a sterilizing electrode is necessary to facilitate finding the nerve segments by direct stimulation of them. The faradic current can serve for stimulation—then a double electrode is taken, or the galvanic current—then they manipulate with a needle-shaped cathode, while the anode serves as a plate applied at some distance to the patient's body. The first requirement is the suturing of the peripheral and central segments of the same nerve trunk where the nerves form a plexus (e.g., brachial plexus). Both segments must be very carefully isolated from the surrounding scar tissue, which can present particular difficulties if the trauma was accompanied by prolonged suppuration. Then, before suturing, both segments must be refreshed, preferably by a transverse section, which is especially important in late suturing. With fresh primary connection of the segments in the order of primary treatment of the injury site, refreshing is undertaken in the presence of crushing of the edges, their contusion, and similar circumstances that sharply reduce the possibility of regeneration and threaten the formation of a significant scar. The refreshing of the edges itself is performed with a sharp scalpel, and by no means with scissors, which crush the nerve, leading to a deterioration of the conditions for nerve fiber regeneration. Further, any bleeding in the wound requires the most careful attention and equally careful stoppage. Ligation of vessels is better performed with catgut in order to reduce the development of connective tissue in the vicinity of the sutured nerve. Parenchymatous bleeding, frequently observed after excision of scars, must be stopped by pressure. Any accumulation of blood around the nerve suture threatens subsequent abundant proliferation of connective tissue, which during final shrinkage can exert pressure on the nerve trunk and reduce the results achieved by suturing to zero. Then both segments are brought together and placed in the correct position relative to each other. In late nerve suture, scar tissue often penetrates inside it as a result of damage to the nerve trunk itself—such areas require their removal, and at the same time, the apparent continuity of the nerve may already be disrupted at the moment of the operation itself. From the above provisions, it is seen that only the continuity of nerve fibers is of value for function; therefore, questionable areas are subject to resection. In practice, there are frequent cases where the nerve is subjected not to complete interruption, but only in a certain part; then it is entirely expedient to make a resection of only the affected area and leave the undamaged one without impacts, i.e., to perform a partial nerve suture. After more or less extensive resections, bringing the central segment closer to the peripheral one can present significant difficulties; however, taking into account that direct nerve suture for the aforementioned reasons gives much more hope for regeneration than any plastic method of closing a nerve defect along its length, all measures should be taken to implement precisely 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 performed cautiously and without mashing the nerve trunks, it is well tolerated.

Then, if a nerve suture is performed on a limb, as is frequently observed in practice, a rational position of the limb should be used to bring the ends closer together, without hesitating even to immobilize the limb in the required position if this is necessary to eliminate the danger of separation of the sutured ends. When giving the limb the most advantageous position, it should be remembered that, according to Stoffel's studies, the greatest advantage in suturing the brachial plexus is provided by adduction of the shoulder; on the arm, when suturing the median and radial nerves, by adduction of the shoulder and maximum flexion of the forearm; for the ulnar nerve, by extension of the forearm and adduction of the shoulder; on the forearm, when suturing the median nerve, by flexion of the forearm at a right angle, supination, and flexion of the hand; for the ulnar nerve, by extension of the forearm, supination, and flexion of the hand; for the radial nerve, by flexion at a right angle, supination, and hyperextension of the hand. When suturing the femoral nerve, flexion of the thigh; for the sciatic nerve (tibial and peroneal nerves), extension of the thigh, flexion of the lower leg, and plantar flexion of the foot. Finally, the actual suturing of the nerve ends should follow. The material for the suture can be fine silk or catgut; the latter, if it contains antiseptic substances, is less desirable, as it causes a greater development of connective tissue. For the suture, one should use the finest thread number with which a secure suture can be achieved. The needles for the suture should be round, intestinal type, as they cause the least damage to the nerve tissue; the suturing itself is best performed through the nerve sheaths, while striving to ensure that the apposition of both cross-sections is as intimate as possible. It is often useful to place several sutures at various...

...at once all together, so that...

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).