Microsuture Repair Research Articles

Purposeful Misalignment of Severed Nerve Stumps in a Standardized Transection Model Reveals Persistent Functional Deficit With Aberrant Neurofilament Distribution.

Functional recovery following primary nerve repair of a transected nerve is often poor even with advanced microsurgical techniques. Recently, we developed a novel sciatic nerve transection method where end-to-end apposition of the nerve endings with minimal gap was performed with fibrin glue. We demonstrated that transected nerve repair with gluing results in optimal functional recovery with improved axonal neurofilament distribution profile compared to the end-to-end micro-suture repair. However, the impact of axonal misdirection and misalignment of nerve fascicles remains largely unknown in nerve-injury recovery. We addressed this issue using a novel nerve repair model with gluing. In our complete "Flip and Transection with Glue" model, the nerve was "first" transected to 40% of its width from each side and distal stump was transversely flipped, then 20 µL of fibrin glue was applied around the transection site and the central 20% nerve was completely transected before fibrin glue clotting. Mice were followed for 28 days with weekly assessment of sciatic function. Immunohistochemistry analysis of both sciatic nerves was performed for neurofilament distribution and angiogenesis. Tibialis anterior muscles were analyzed for atrophy and histomorphometry. Functional recovery following misaligned repair remained persistently low throughout the postsurgical period. Immunohistochemistry of nerve sections revealed significantly increased aberrant axonal neurofilaments in injured and distal nerve segments compared to proximal segments. Increased aberrant neurofilament profiles in the injured and distal nerve segments were associated with significantly increased nerve blood-vessel density and branching index than in the proximal segment. Injured limbs had significant muscle atrophy, and muscle fiber distribution showed significantly increased numbers of smaller muscle fibers and decreased numbers of larger muscle fibers. These findings in a novel nerve transection mouse model with misaligned repair suggest that aberrant neurofilament distributions and axonal misdirections play an important role in functional recovery and muscle atrophy.

Comparison of peripheral nerve repair using ethyl-cyanoacrylate and conventional suture technique in a rat sciatic nerve injury model.

The aim of this study was to compare the outcomes of primary nerve repair using either ethyl-cyanoacrylate or conventional microsuture technique in a rat peripheral nerve injury model. In this study, a total of 30 Wistar Albino rats weighing between 220 and 275 g were used. The rats were randomly divided into three groups (10 in each), including one control (group 1) and two experimental groups (group 2, conventional microsuture repair; group 3, cyanoacrylate repair). In each group, the sciatic nerve was identified and transected. No further intervention was performed in group 1. The nerve was repaired using the epineural technique with a 10/0 atraumatic nylon in group 2 and synthetic cyanoacrylate adhesive in group 3. At the fifth postoperative week, needle electromyography (EMG) was performed to measure distal latency, combined muscle action potential (CMAP), and motor nerve conduction velocity (MNCV). Following the EMG recordings, animals were euthanized. Nerve samples were collected to evaluate vacuolar degeneration, fibrosis, and foreign body reaction histopathologically. In the EMG analysis, mean distal latency was significantly shorter in group 1 (0.85±0.09 ms) than in groups 2 (1.17±0.25 ms) (p=0.0052) and 3 (1.14±0.14 ms) (p=0.0026) while no significant differences existed between groups 2 and 3 (p>0.9999). The mean CMAP was greater in group 1 (10.5±0.35 mV) than in groups 2 (2.86±1.28 mV) (p=0.011) and 3 (2.16±1.34 mV) (p=0.0002), but there was no significant difference between groups 2 and 3 (p>0.9999). The mean MNCV was 53.5±5.95, 39.62±7.31, and 39.84±4.73 mm/sec in groups 1, 2, and 3, respectively. There was a significant difference between groups 1 and 2 (p=0.0052) and between 1 and 3 (p=0.0026), but not between 2 and 3 (p>0.9999). In the histopathological evaluation, the mean vacuolar degeneration score was 0, 2.12, and 1.88 in groups 1, 2, and 3, respectively. No obvious difference was observed between groups 2 and 3 (p=0.743). The mean fibrosis score was 0, 1.62, and 1.77 in groups 1, 2, and 3, respectively. There was no significant difference between groups 2 and 3 (p=0.888). The mean foreign body reaction score was 0, 2.5, and 2.44 in groups 1, 2, and 3, respectively. No difference was present between groups 2 and 3 (p=0.743). Primary nerve repair using the cyanoacrylate adhesive may provide similar electrophysiological and histopathological results as compared to the conventional microsuture repair.

Laryngeal adductor function following potassium titanyl phosphate laser welding of the recurrent laryngeal nerve.

Recurrent laryngeal nerve (RLN) transection injuries may occur during thyroidectomy and other surgical procedures. Laser nerve welding has been shown to cause less technique-related axonal damage than the traditional suture method. We compared functional adductor results using these two methods of RLN repair. Animal model. Canine hemilarynges underwent pretreatment testing of laryngeal adductor function, followed by RLN transection and repair using potassium titanyl phosphate (KTP) laser welding (n = 8) or microneural suture (n = 16) techniques. Six months later, adductor function was measured again and expressed as a proportion of the pretreatment value. The mean laryngeal adductor pressure ratios were 82.4% (95% confidence interval [CI]: 72.8%-92.0%) for the laser repair group and 55.5% (95% CI: 49.4%-61.6%) for the suture control group, with a difference of 26.9% (95% CI: 15.3%-38.5%). Both spontaneous and stimulated glottic closure was observed in the laser welding and microsuture repair groups. Laser nerve welding resulted in greater strength of adduction than suture repair of an acutely transected RLN. Suture anastomosis may traumatize more axons than the laser. Stronger vocal fold adduction is associated clinically with better protection from aspiration and improved voice outcomes. KTP laser welding should be considered for anastomosis of the RLN and other nerves. NA Laryngoscope, 130:1764-1769, 2020.

Compound Motor Action Potential Quantifies Recurrent Laryngeal Nerve Innervation in a Canine Model.

The compound motor action potential (CMAP) is the summated action potential from multiple muscle fibers activated by a single nerve impulse. The utility of laryngeal muscle CMAP for quantifying innervation following recurrent laryngeal nerve (RLN) injury was investigated. In a series of 21 canine hemi-laryngeal preparations, RLNs were exposed and a stimulating electrode placed. Maximum CMAP amplitudes and area under the curve from the thyroarytenoid (TA) muscles were obtained at baseline and at 6 months following injury to the RLN. Injury mechanisms included crush, stretch, cautery, and complete transection with microsuture repair. Prior to injury, baseline CMAP amplitudes and area under the curve were 15.81 mV and 15.49mVms, respectively. Six months following injury, CMAP amplitude and area under curve were 105.1% and 102.1% of baseline for stretch, 98.7% and 112.7% for crush, 93.3% and 114.3% for cautery. The CMAP amplitude and area under the curve in the transection/repair group had a 54.3% and 69.4% recovery, respectively, which were significantly different than baseline (P < .01, P < .05). These values were correlated with vocal fold motion. The CMAP is a measure of vocal fold innervation. The technique could be further developed for clinical and experimental applications.

Fibrin glue repair leads to enhanced axonal elongation during early peripheral nerve regeneration in an in vivo mouse model.

Microsurgical suturing is the gold standard of nerve coaptation. Although literature on the usefulness of fibrin glue as an alternative is becoming increasingly available, it remains contradictory. Furthermore, no data exist on how both repair methods might influence the morphological aspects (arborization; branching) of early peripheral nerve regeneration. We used the sciatic nerve transplantation model in thy-1 yellow fluorescent protein mice (YFP; n = 10). Pieces of nerve (1cm) were grafted from YFP-negative mice (n = 10) into those expressing YFP. We performed microsuture coaptations on one side and used fibrin glue for repair on the contralateral side. Seven days after grafting, the regeneration distance, the percentage of regenerating and arborizing axons, the number of branches per axon, the coaptation failure rate, the gap size at the repair site and the time needed for surgical repair were all investigated. Fibrin glue repair resulted in regenerating axons travelling further into the distal nerve. It also increased the percentage of arborizing axons. No coaptation failure was detected. Gap sizes were comparable in both groups. Fibrin glue significantly reduced surgical repair time. The increase in regeneration distance, even after the short period of time, is in line with the results of others that showed faster axonal regeneration after fibrin glue repair. The increase in arborizing axons could be another explanation for better functional and electrophysiological results after fibrin glue repair. Fibrin glue nerve coaptation seems to be a promising alternative to microsuture repair.

The Comparison of Histological Results of Experimentally Created Facial Nerve Defects Repaired by 2 Different Anastomosis Techniques

The objective of this study was to compare the histological regeneration characteristics of nerve fibers at the anastomosis lines performed by classic suture technique or a tissue adhesive (N-butyl-2-cyanoacrylate). The control group consisted of 7 rabbits. The 21 rabbits were randomly divided into 3 groups based on the harvesting week. In the study group following preparation of facial nerve bilaterally, a 0.5-cm segment of facial dorsal buccal nerve was resected, and the defect was repaired with a nerve graft, which was harvested from sural nerve of the same side by 8-0 nylon suture technique and by application of N-butyl-2-cyanoacrylate on the other side. Electron microscopic examination at consecutive second, fourth, and sixth days (corresponding to 4th, 8th, and 12th week in human subjects) revealed increased nerve degeneration findings in N-butyl-2-cyanoacrylate group when compared with microsuture repair technique. We conclude that N-butyl-2-cyanoacrylate is not an appropriate material for nerve anastomosis.

Atorvastatin is beneficial for muscle reinnervation after complete sciatic nerve section in rats

Nerve regeneration and functional recovery are often incomplete after peripheral neurotmetic lesion. Atorvastatin has been shown to be neuroprotective after transient ischaemia or traumatic injury. The aim of this study was to establish if systemic administration of Atorvastatin could improve functional muscle reinnervation after complete sciatic nerve section. Sixteen female Sprague-Dawley rats were used in this study. After a complete right sciatic nerve section, end-to-end microsuture repair was performed and fibrin glue was added. Three groups were studied: (1) sutures (S) + fibrin glue (F) only + saline administration for 14 days; (2) S+F+Atorvastatin administration for 14 days; and (3) uninjured nerve. Five months later, the sciatic nerve and the gastrocnemius muscle were isolated to perform in vivo electrophysiological measurements. Better kinematics was observed in atorvastatin-treated rats 5 months after its administration. Indeed, a larger excursion of the hip-ankle-toe angle during walking was observed. This effect was associated with the preservation of electromyographic activity (2.91 mV vs 0.77 mV) and maximal muscle force (85.1 g vs 28.6 g) on stimulation of the proximal nerve section. Five months after a neurotmetic lesion, the recovery is incomplete when using suture and fibrin glue only. Furthermore, the systemic administration of Atorvastatin for 14 days after lesion was beneficial in improving locomotion capability associated with the re-establishment of muscle strength and EMG activity.

Blocking the P2X7 receptor improves outcomes after axonal fusion

BackgroundActivation of the P2X7 receptor on peripheral neurons causes the formation of pannexin pores, which allows the influx of calcium across the cell membrane. Polyethylene glycol (PEG) and methylene blue have previously been shown to delay Wallerian degeneration if applied during microsuture repair of the severed nerve. Our hypothesis is that by modulating calcium influx via the P2X7 receptor pathway, we could improve PEG-based axonal repair. The P2X7 receptor can be stimulated or inhibited using bz adenosine triphosphate (bzATP) or brilliant blue (FCF), respectively. MethodsA single incision rat sciatic nerve injury model was used. The defect was repaired using a previously described PEG methylene blue fusion protocol. Experimental animals were treated with 100 μL of 100 μM FCF solution (n = 8) or 100 μL of a 30 μM bzATP solution (n = 6). Control animals received no FCF, bzATP, or PEG. Compound action potentials were recorded prior to transection (baseline), immediately after repair, and 21 d postoperatively. Animals underwent behavioral testing 3, 7, 14, and 21 d postoperatively. After sacrifice, nerves were fixed, sectioned, and immunostained to allow for counting of total axons. ResultsRats treated with FCF showed an improvement compared with control at all time points (n = 8) (P = 0.047, 0.044, 0.014, and 0.0059, respectively). A statistical difference was also shown between FCF and bzATP at d 7 (P < 0.05), but not shown with d 3, 14, and 21 (P > 0.05). ConclusionsBlocking the P2X7 receptor improves functional outcomes after PEG-mediated axonal fusion.

Blocking the P2X7 Receptor in a Rat Nerve-Injury Model Improves Long Term Functional Outcomes

Activation of the P2X7 Receptor causes the formation of pannexin pores. These holes allow for the efflux of ATP and the influx of calcium across the cell membrane. Activated P2X7 receptors have been shown to cause cell death in enteric and retinal ganglion cells. Polyethlyene glycol (PEG) and methylene blue (MB) have previously been suggested to delay Wallerian degeneration through a receptor-independent manner if applied during microsuture repair of the severed nerve. Calcium modulation is a critical part of the PEG based axonal repair because once calcium enters the axon, the cut nerve ends seal, preventing PEG based axonal fusion. Our hypothesis is that by modulating calcium influx via the P2X7 receptor pathway, we could augment PEG based axonal repair. The P2X7 receptor can be stimulated or inhibited using bzATP or Brilliant Blue FCF, respectively.

Comparison of Microsuture, Interpositional Nerve Graft, and Laser Solder Weld Repair of the Rat Inferior Alveolar Nerve

Intraosseous repair of nerves involves difficulty of access and there is concern that bone healing may interfere with repair outcomes. The present report describes the effect of 3 separate repair techniques on recovery from section of the rat intraosseous inferior alveolar nerve, with reference to the mental nerve distal and the trigeminal ganglion proximal to the nerve section. Unilateral exposure of the inferior alveolar nerves of 28 rats was achieved through bone windows. Nerves were sectioned and rats were assigned to 1 of 4 groups (n = 7): untreated controls, microsuture repair, interpositional nerve grafts from the femoral nerve, or laser solder weld repair. Animals were sacrificed 1 year after surgery for histologic evaluation of the mental nerve, inferior alveolar nerve, and trigeminal ganglion compared with unoperated contralateral nerves. Compared with the unoperated contralateral nerves, nerve section substantially decreased mental nerve fiber number, mental nerve myelination, mental nerve fiber diameter, inferior alveolar nerve vascularity, trigeminal neuron number, and trigeminal neuron horseradish peroxidase tracer uptake and increased trigeminal ganglion degenerate neurons (P < .001). All 3 forms of repair substantially decreased these effects (P < .05). Interpositional nerve graft was least effective (P < .05). Nonetheless, mental nerve fiber diameter was significantly decreased compared with unsectioned nerves after microsuture and laser solder weld repair (P < .05). Intraosseous repair of the inferior alveolar nerve decreases peripheral and central signs of degeneration. Clinical hyperesthesia after repair may reflect a predominance of small fibers after recovery.

Microsuture repair of intra-operative ruptures of cerebral aneurysms of the internal carotid artery

We report on two patients with intra-operative rupture of cerebral aneurysms that were managed by microsuturing. This is one of only a few reports of successful direct repair using suturing. We found that stitching remains an option to repair a tear of a saccular part of an aneurysm and a torn neck of a blister-like aneurysm, and thus this technique can be considered before sacrificing the artery.

Chondroitinase ABC and acute electrical stimulation are beneficial for muscle reinnervation after sciatic nerve transection in rats

Nerve regeneration and functional recovery are often incomplete after peripheral nerve damage. The aim of this study was to determine if chondroitinase ABC injection at the lesion site, 1 hour of electrical stimulation and the combination of these treatments at the time of repair could be effective in promoting muscle reinnervation. The right sciatic nerve was completely sectioned in 32 female Sprague-Dawley rats. End-to-end microsuture repair was undertaken and fibrin glue was added. Five groups were studied: 1) suture (S) + fibrin glue (F) only; 2) S + F + chondroitinase ABC; 3) S + F + electrical stimulation; 4) S + F + chondroitinase ABC + electrical stimulation; 5) uninjured nerve. Post recovery kinematics showed larger excursion of the hip-ankle-toe angle during walking in groups 2, 3 and 4 than in group 1 (p < 0.05). In vivo electromyographic activity and maximal muscle force were similar between groups 2, 3, 4 and 5, with higher values in all of them compared to group 1 (p < 0.05). Also, the distal stump of the sciatic nerve was excised, and cross-sectioning revealed that the number of axons were similar in all groups. 150 days after nerve transection, recovery was incomplete with S and F only. Chondroitinase ABC injection at the lesion site and/or 1 hour of electrical stimulation of the proximal nerve stump were beneficial in promoting nerve regeneration and functional muscle reinnervation.

Endoscopic microsuture repair of vocal fold defects

The presence of a nonvibratory segment of vocal folds after microlaryngeal surgery is often a cause of poor voice result. The etiology of a nonvibratory segment is due to full thickness epithelial defect followed by secondary wound closure and scar contracture. To reduce scar contracture and nonvibratory segment of the vocal folds, primary repair with a 6-0 chromic endo-knot suture technique was used to close defects and approximate microflaps of the vocal folds. This was done in 18 patients with epithelial defects after resection of benign vocal fold lesions. The pathologic findings included severe polypoid degeneration (n = 7), fusiform laryngeal polyps (n = 5), sulcus vocalis (n = 2), cyst (n = 2), and keratosis (n = 2). Voice was improved in all patients after surgery. Comparison of vocal fold vibration before and after surgery showed improvements in configuration, amplitude, and mucosal wave. Vocal folds that were sutured all had good vibratory characteristics; none had a nonvibrating segment at the site of suture placement. Voice and healing after microsuture technique were near normal by Day 10 and return of mucosal wave was often complete by Day 14. Endoscopic microsuture closure of microflaps of the vocal folds edge is safe and affords the surgeon an opportunity for primary repair with improved functional result.

Laser tissue soldering in urinary tract reconstruction: First human experience

Objectives Laser tissue soldering (LTS) in the urinary tract provides an immediate leak-free seal and may avoid complications seen with conventional repair (such as fistula and stricture). We have begun a Phase I clinical trial investigating the use of LTS in performing urologic reconstructive surgery. Methods Ten patients (aged 3 months to 38 years) underwent urologic reconstruction using LTS with a protein solder composed of human albumin (42%) and indocyanine green dye. In each case standard microsuture repair preceded laser-soldered suture line reinforcement. Anastomotic closure time and immediate leak pressure were measured. Postoperatively, all patients were evaluated for evidence of complications, including stricture, fistula formation, or impaired healing. Results Using LTS as an adjunct to suturing added an average of 7.9 ± 3.0 minutes (28%) to the overall mean anastomotic time of 28.3 ± 9.4 minutes. Intraoperative leak pressure measurements for laser-soldered anastomoses (≥94.2 ± 24.2 mm Hg) were significantly higher ( P < 0.001) than primarily sutured anastomoses (20 ± 2.9 mm Hg). Two instances of suture disruption (20%) occurred during laser activation, neither of which were repaired with sutures. Average follow-up for all patients was 7.1 ± 2.2 months. There were no intraoperative or postoperative complications, including the 2 patients with suture disruption. Conclusions These initial clinical results indicate that LTS is safe, easy to perform, and, contrary to conventional suturing, provides an immediate leak-free closure. Follow-up in these and other patients, as well as those undergoing sutureless and stent-free procedures, will determine whether our method of LTS benefits patients undergoing urologic reconstruction.

CO 2 laser welding versus conventional microsuture repair in patch-graft urethroplasty

This study evaluates the repair of urethral tissue using microsurgery and a combination of laser welding techniques. Using the rat as a model, a patch-graft urethroplasty was performed with either conventional microsuture repair, laser-assisted microsuture repair, or laser-assisted microsuture with protein solder. Repairs were assessed at various time periods (days 0, 1, 7, and 21). Analysis of success rate, bursting strength, histology, and operative time were completed. The laser with protein solder had the highest success rate at each time period and demonstrated advanced healing with the least amount of inflammation. Operative time was decreased by 30 percent using the laser. In conclusion, the laser solder repair was significantly better than either laser alone or conventional microsutures.

Selective reinnervation: a comparison of recovery following microsuture and conduit nerve repair

Selective reinnervation was studied by comparing the regeneration across a conventional neurorraphy versus a conduit nerve repair. Lewis rats underwent right sciatic nerve transection followed by one of four different nerve repairs (n = 8/group). In groups I and II a conventional neurorraphy was performed and in groups III and IV the proximal and distal stumps were coapted by use of a silicone conduit with an interstump gap of 5 mm. The proximal and distal stumps in groups I and III were aligned anatomically correct and the proximal stump was rotated 180° in groups II and IV (i.e. proximal peroneal nerve opposite the distal tibial nerve and the proximal tibial nerve opposite the distal peroneal nerve). By 14 weeks, there was an equivalent, but incomplete return in sciatic function index (SFI) in groups I, III, and IV as measured by walking track analysis. However, the SFI became unmeasurable by 6 weeks in all group II animals. At 14 weeks, the percent innervation of the tibialis anterior and medial gastrocnemius muscles by the peroneal and tibial nerves respectively was estimated by selective compound muscle action potential amplitude recordings. When fascicular alignment was reversed, there was greater tibial ( P = 0.02) and lesser peroneal ( P = 0.005) innervation of the gastrocnemius muscle in the conduit (group IV) versus the neurorraphy (group II) group. This suggests that the gastrocnemius muscle may be selectively reinnervated by tthe tibial nerve. However, there was no evidence of selective reinnervation of the tibialis anterior muscle. Despite these differences, the functional recovery in both conduit repair groups (III and IV) was equivalent to a correctly aligned microsuture repair (group I) and superior to that in the incorrectly aligned microsuture repair (group II).

Morphofunctional Evaluation of Fibrin Glue Versus Microsuture Nerve Repairs

Complications of microsuture repair of peripheral nerves include mechanical trauma, foreign body reaction, impairment of vascularity, and possible obstruction to successful sprouting. In addition, there are occasions when it is virtually impossible to perform a suture repair because of limited exposure and/or very fine structures, such as are encountered in pediatric cases. These situations have continued to provide the impetus for evaluating alternative methods of nerve coaptation. Recently, the use of tissue glue has gained in popularity as a technique for sutureless nerve repairs. We decided to test the efficacy of fibrin glue repair versus microsuture coaptation in the rat sciatic model. The repair sites were assessed for tensile strength, by quantitative morphometry, and by electrophysiologic studies. Tensile strength findings revealed that at two, four, and eight weeks after surgery, there was no significant difference between the two repair techniques, although there was a trend toward a stronger hold in the microsuture repairs. Electrophysiologic recordings revealed that conventional microsuture repairs had significantly faster conduction velocities, larger area under the curve, and higher peak amplitudes. The onset and peak latencies were comparable, revealing that the axonal quality of at least a certain number of axons was similar electrically. Axonal counts both proximal and distal to the repair showed no significant difference, although there was an overall suggestion of superiority in the number of myelinated axons in the suture repair.

Laser Assisted Urethral Closure in the Rat: Comparison of CO2 and Neodymium-YAG Laser Techniques

In 65 male rats a comparative study was undertaken to investigate a Neodymium-YAG and CO2 laser system for the microsurgical repair of longitudinal incisions of the rat urethra. Postoperative investigations included patency tests, necropsy and light microscopy. Use of the laser systems did not reduce operation time. The highest rate of postoperative strictures (90%), urethral fistulas (30%), urinomas (20%) and postoperative deaths (70%) was seen in the Neodymium-YAG laser group. CO2 laser repair was almost as efficacious as microsuture repair, except for a higher rate of urethral fistulas resulting from the initially weak laser weld. Based on these findings, the Neodymium-YAG laser seems unsuitable for urethral repair. Further studies in larger animals are warranted using a CO2 laser in combination with postoperative cystostomy for urinary diversion in order to avoid fistulas in the early postoperative period. (J. Urol., 144: 1000–1003, 1990)

Laser Welding in Urethral Surgery: Improved Results with a Protein Solder

Reconstruction of the rat urethra using the CO2 laser and a protein solder has dramatically decreased the postoperative fistula rate and decreased surgical time over conventional microsurgical reconstruction. Using the rat as a model, a partial transection of the ventral urethra was repaired in one of three ways in 39 animals: conventional microsuture repair, laser assisted microsuture repair and laser assisted microsuture repair with a protein solder. The success rate in each group was 50%, 58% and 90% respectively. Therefore, the laser repair is as efficacious as conventional microsuture repair. More importantly, laser with solder is significantly better than either the conventional method or laser alone.