Early passive mobilization after digital nerve repair and grafting in a fresh cadaver

In the clinical management of combined tendon and nerve injuries, there are competing treatment strategies. Isolated tendon injuries should be rapidly mobilized after repair to prevent adhesion formation, whereas isolated nerve repairs are usually immobilized to prevent disruption and to allow axon regrowth. Recommendations in the published literature for the management of combined tendon and nerve injuries are vague and advise up to 3 weeks of immobilization. The goals of this study were to determine which length of nerve gap resulted in rupture of a repair following postoperative mobilization with the modified Duran protocol and with unrestricted motion and to determine whether nerve grafts are at risk of rupture after mobilization. A total of 100 digital nerves from 10 cadaver hands were tested with the modified Duran and the unsplinted protocols. Each digital nerve on each hand was sequentially resected and repaired at five progressively larger gap lengths after testing with both protocols. The mean nerve gaps at which disruption occurred were significantly different between the splinted (9.7 +/- 0.8 mm, n = 100) and unsplinted (7.3 +/- 1.9 mm, n = 100) protocols (t test, p < 0.001). One hundred percent of repairs remained intact, with up to 5 mm of resection with the modified Duran protocol (n = 100) and with up to 2.5 mm of resection with the unsplinted protocol (n = 100). All nerve grafts remained intact after mobilization within a dorsal-blocking splint (n = 100). Considering mechanical integrity of the nerve repair only, these data suggest that early mobilization with tendon protocols may be considered after a nerve injury to avoid the detrimental tendon sequelae that result from immobilization. The adequacy of functional recovery of mobilized nerves is yet to be determined.     

"Donor" muscle structure and function after end-to-side neurorrhaphy

End-to-end nerve coaptation is the preferred surgical technique for peripheral nerve reconstruction after injury or tumor extirpation. However, if the proximal nerve stump is not available for primary repair, then end-to-side neurorrhaphy may be a reasonable alternative. Numerous studies have demonstrated the effectiveness of this technique for muscle reinnervation. However, very little information is available regarding the potential adverse sequelae of end-to-side neurorrhaphy on the innervation and function of muscles innervated by the "donor" nerve. End-to-side neurorrhaphy is hypothesized to (1) acutely produce partial donor muscle denervation and (2) chronically produce no structural or functional deficits in muscles innervated by the donor nerve. Adult Lewis rats were allocated to one of two studies to determine the acute (2 weeks) and chronic (6 months) effects of end-to-side neurorrhaphy on donor muscle structure and function. In the acute study, animals underwent either sham exposure of the peroneal nerve (n = 13) or end-to-side neurorrhaphy between the end of the tibial nerve and the side of the peroneal nerve (n = 7). After a 2-week recovery period, isometric force (F(0) was measured, and specific force (sF(0) was calculated for the extensor digitorum longus muscle ("donor" muscle) for each animal. Immunohistochemical staining for neural cell adhesion molecule (NCAM) was performed to identify populations of denervated muscle fibers. In the chronic study, animals underwent either end-to-side neurorrhaphy between the end of the peroneal nerve and the side of the tibial nerve (n = 6) or sham exposure of the tibial nerve with performance of a peroneal nerve end-to-end nerve coaptation approximately 6), to match the period of anterior compartment muscle denervation in the end-to-side neurorrhaphy group. After a 6-month recovery period, contractile properties of the medial gastrocnemius muscle ("donor" muscle) were measured. Acutely, a fivefold increase in the percentage of denervated muscle fibers (1 +/0 0.7 percent to 5.4 +/-2.7 percent) was identified in the donor muscles of the animals with end-to-side neurorrhaphy (p < 0.001). However, no skeletal muscle force deficits were identified in these donor muscles. Chronically, the contractile properties of the medial gastrocnemius muscles were identical in the sham and end-to-side neurorrhaphy groups. These data support our two hypotheses that end-to-side neurorrhaphy causes acute donor muscle denervation, suggesting that there is physical disruption of axons at the time of nerve coaptation. However, end-to-side neurorrhaphy does not affect the long-term structure or function of muscles innervated by the donor nerve.     

Mechanical function of muscle reinnervated by end-to-side neurorrhaphy.

End-to-side neurorrhaphy is a surgical technique for peripheral nerve reconstruction when end-to-end neurorrhaphy is not an option. To define the effectiveness of end-to-side neurorrhaphy as a method of nerve repair, the authors tested the null hypothesis: there is no difference in the mechanical function of skeletal muscle denervated and reinnervated by end-to-side versus end-to-end neurorrhaphy. Adult Lewis rats underwent either transection and end-to-end epineurial repair of the left peroneal nerve (n = 9) or end-to-side repair of the distal stump of the peroneal nerve to the side of the tibial nerve (n = 8). After a 6-month recovery period, isometric force (Fo) was measured, and specific force (sFo) was calculated for the extensor digitorum longus muscle of each animal. Immunohistochemical staining for neural cell adhesion molecule (NCAM) was performed to identify populations of denervated muscle fibers. The mean extensor digitorum longus muscle mass in the end-to-end group (195 +/- 32 g) was significantly greater than that of the end-to-side group (146 +/- 55 g) (p < 0.05). A significantly greater percentage of denervated fibers was identified in the extensor digitorum longus muscles of animals in the end-to-side group (9.4 +/- 3.2 percent) than in those in the end-to-end group (3.8 +/- 1.0 percent) (p < 0.05). Despite a lower muscle mass and a higher percentage of denervated fibers, neither Fo nor sFo was significantly different in the two groups. These data support the null hypothesis that, under appropriate circumstances, there is no difference in the recovery of whole muscle force and specific force production in muscles reinnervated by end-to-side versus end-to-end neurorrhaphy.     

Preliminary investigation of a polyethylene glycol hydrogel "nerve glue"

Background

Polyethylene glycol (PEG) hydrogel is a biocompatible semi-adherent gel like substance that can potentially augment nerve repair much like a fibrin sealant. Potential advantages of this substance include fast preparation and set up time, as well as adhesion inhibiting properties. The purpose of this study was to perform an initial evaluation of PEG hydrogel in this application.

Methods

The sciatic nerves of 29 rats were transected and repaired using two 10-0 nylon sutures and either PEG hydrogel or fibrin glue. After 10 weeks, contraction forces of the reinnervated muscles were evaluated and histological assessment of scar tissue performed.

Results

Muscle strength testing revealed the average ratio of experimental to control sides for the fibrin glue group was 0.75 and for the PEG hydrogel group was 0.72 (no significant difference). Longitudinal sections through the nerve repair site showed no significant difference in nerve diameter but did demonstrate a significant reduction in scar thickness in the PEG hydrogel group (p < 0.01).

Conclusion

Though further study is necessary to fully evaluate, PEG hydrogel results in less scar tissue formation and equivalent muscle recovery as fibrin sealant when applied as a nerve glue in a rodent sciatic nerve repair model.     

抑制瘢痕细胞中串珠素表达对Ⅰ型胶原蛋白生成量的影响

目的：硬膜外瘢痕,又叫硬膜外纤维化,是指在硬膜外腔的手术涉及范围内形成的瘢痕组织或纤维化,是机体对创伤的修复反应。瘢痕的粘连和收缩会牵拉硬膜和神经根,限制其活动,被瘢痕包绕的神经根受到非正常的牵拉和挤压,神经纤维的轴浆运输、动脉血供、静脉回流受阻,神经根和背侧神经节对机械压迫很敏感,会产生一系列症状,如疼痛、麻木及下肢肌力降低等。近年来,对硬膜外瘢痕防治的研究大多是椎板切除术后如何通过物理或化学屏障来减少术后因瘢痕粘连导致的并发症。但对通过瘢痕形成过程中抑制其主要构成成分的生成来减轻椎板切除术后硬膜外瘢痕形成的相关研究还较少。通过减少椎板切除术后硬膜外瘢痕主要成分Ⅰ型胶原蛋白的生成来实现抑制椎板切除术后硬膜外瘢痕的形成。方法：选用30只250克两月鼠龄的SD雄性大鼠随机按1、2、3、4、5、6周分为6组,行后路4、5腰椎全椎板切除术。术后1、2、3、4、5、6周时每周取一组大鼠全锥板切除术后硬膜后方瘢痕组织,分别行病理切片HE染色,组织块贴壁法细胞培养。筛选第三周瘢痕组织培养的成纤维细胞进行慢病毒干扰串珠素表达并设对照组,通过Western-blot、RT-PCR分析Ⅰ型胶原蛋白生成量与对照组的差别并进行统计学分析。结果：慢病毒干扰小组Ⅰ型胶原蛋白生成量较对照组及纯病毒组明显减少（RT-PCR F=509.331,q A,B=-43.371,P〈0.01,q A,C=-46.133,P〈0.01,Western-Blot F=337.578;q A,B=-112.433,P〈0.01,q A,C=-89.227,P〈0.01）。结论：干扰串珠素表达能有效减少术后硬膜外瘢痕成纤维细胞生成Ⅰ型胶原蛋白,对抑制椎板切除术后硬膜外瘢痕形成应有一定作用。通过慢病毒介导的shRNA干扰成纤维细胞中的串珠素后,其生成的Ⅰ型胶原蛋白量与对照组相比较差异有统计学意义（P〈0.05）,这说明通过抑制瘢痕成纤维细胞的串珠素表达能够有效减少Ⅰ型胶原蛋白的生成。这种方法不论从Ⅰ型胶原蛋白是瘢痕主要构成成分方面,还是Ⅰ型胶原蛋白在瘢痕生成过程中分泌胶原中占得比例增多导致机体由胎儿期的无瘢痕愈合转化至成体的瘢痕愈合这个方面来将,理论上都能够做到有效地抑制、减少硬膜外瘢痕的形成,因此通过干扰硬膜外成纤维细胞串珠素表达从而达到抑制硬膜外瘢痕的形成这一理论是可行的,为进一步进行椎板切除术后抑制硬膜外瘢痕形成的体内试验奠定了理论基础。     

Interposition of a pedicle fat flap significantly improves specificity of reinnervation and motor recovery after repair of transected nerves in adjacency in rats

Despite highest standards in nerve repair, functional recovery following nerve transection still remains unsatisfactory. Nonspecific reinnervation of target organs caused by misdirected axonal growth at the repair site is regarded as one reason for a poor functional outcome. This study was conducted to establish a method for preventing aberrant reinnervation between transected and repaired nerves in adjacency. Rat sciatic nerve was transected and repaired as follows: epineural sutures of the sciatic nerve (group A, n = 6), fascicular repair of tibial and peroneal nerves respectively (group B, n = 8), and, as in group B, separating both nerves using a pedicle fat flap as barrier (group C, n = 8). As control only, the tibial nerve was transected and repaired (group D, n = 5). Muscle contraction force of the gastrocnemius muscle was significantly higher in group C as compared with groups A and B after 4 months. Muscle weight showed significantly lower values in group A as compared with groups B, C, and D. Histologic examination in group C revealed little growth of axons from the tibial to the peroneal nerve and vice versa. This axon crossing was observed only when gaps between the fat cells were available. These findings were confirmed by a significantly lower rate of misdirected axonal growth as compared with groups A and B using sequential retrograde double labeling technique of the soleus motoneuron pool. We conclude that a pedicle fat flap significantly prevents aberrant reinnervation between repaired adjacent nerves resulting in significantly improved motor recovery in rats. Clinically, this is of importance for brachial plexus, sciatic nerve, and facial nerve repair.     

A comparative study of nerve healing in adult, neonatal, and fetal rabbits.

This experiment quantitatively compared the human equivalent of a nerve repair following surgical division in the fetal, adult, and early childhood period of development using a rabbit as an experimental animal model. Twelve time-dated pregnant New Zealand White rabbits at 24 days' gestation (term = 31 days) underwent hysterotomy; one hind limb was delivered through the uterine opening. The sciatic nerve was divided and repaired by primary neurorrhaphy using two 11-0 epineural sutures. Sciatic nerve repair was also performed in 10 neonatal and 10 adult New Zealand White rabbits. Following repair, each group was assessed using electromyography examination, measuring distal motor latency and amplitude at 1, 2, 3, and 4 months postrepair. There was no difference in any of the groups in distal motor latency. The amplitude rose incrementally in all groups, and the fetal group had significantly higher amplitudes (p < 0.02) at 1, 2, 3, and 4 months in comparison with the adult group. There was no statistically significant difference between fetal and neonatal nerve repairs at any of the time periods. At the completion of the study, the nerve repair sites were harvested for histologic estimation of mean myelinated fiber density and fiber diameter distribution distal and proximal to the repair site. A greater percentage of myelinated axons crossed the repair site in the fetal group (83 percent) in comparison with the adult group (63 percent) (p < 0.03). Our study also demonstrated significant increases in the number of larger myelinated fibers crossing the repair site in comparison with the neonatal and adult groups (p < 0.04). This study found that fetal nerve healing following surgical repair is superior to that found in adult animals and results in a higher number of larger myelinated fibers crossing the repair site in comparison with adult and neonatal repairs.     

Nerve regeneration through side-to-side neurorrhaphy sites in a rat model: a new concept in peripheral nerve surgery

Despite great improvement and refinements in nerve repair techniques, there were still problems in repair of peripheral nerve injuries for which proximal stumps were not available. In these circumstances for which classic end-to-end neurorrhaphy was impossible, new treatment modalities, benefiting by an adjacent healthy nerve, have been under investigation to overcome this problem. Therefore, end-to-side nerve repair with its modifications came to view and axonal passages through this site were shown. Moreover, the results were unsatisfactory or necessitating sacrifice of another healthy nerve. Three groups, containing 10 rats each, were included in the study. First was the control group, with end-to-end repair of the peroneal nerve. Second was the end-to-side repair group, in which the distal stump of the peroneal nerve trunk was anastomosed to the lateral side of the tibial nerve. The third was the side-to-side repair group. In this technique, 1-mm diameter epineural windows, both from peroneal and tibial nerve trunks facing each other, were removed and side-to-side neurorrhaphy was performed. After 3 weeks, as the second step, the peroneal nerve was sectioned proximally. At 2, 4, 8, 12, 20, and 28 weeks, functional assessment of nerve regeneration was performed by using walking track analysis. The number of myelinated fibers and fiber diameters were measured and an electron microscopic evaluation was carried out. Statistically, both in morphometric and gait analysis, the differences in values between the groups were significant in favor of the control group, followed by the side-to-side group. The study showed that axonal passage was possible with side-to-side technique and the functional results were satisfactory and superior to the end-to-side technique. Continuous supply of neurotrophic factors from their target cells was the probable cause of superior functional return in side-to-side repair, because both joining nerves were intact and healthy during the anastomosis procedure and after 3 weeks. It was concluded that this technique could be indicated in salvage of nerves in cases for which any intermediate segments would be removed, as in tumor ablation surgery, harvesting of nerve grafts, or both.     

Results of treatment of extensive volar wrist lacerations: the spaghetti wrist

A series of 38 volar wrist lacerations is reviewed with regard to epidemiologic aspects and results. In general, return of tendon function was quite good, and return of nerve function in this series was also satisfying. We attribute the generally good results to immediate repair of all structures, microscopic repair of significant arterial injuries, microscopic grouped fascicular nerve repair, early mobilization (dynamic splinting and intensive occupational therapy), and a generally youthful group of patients. Review of this series has strengthened our opinion that aggressive primary repair of all injured structures is appropriate for these extensive lacerations.     

Promotion of regeneration and axon growth following injury in an invertebrate nervous system by the use of three-dimensional collagen gels.

We describe the application of three-dimensional collagen matrices to the study of nerve cord repair in the leech. Our experiments show that ganglia and connectives of the leech ventral nerve cord can be maintained for up to four weeks embedded in 3D gels constructed from mammalian type I collagen. Severed nerve cords embedded in the collagen gel reliably repaired within a few days of culture. The gel was penetrable by cells emigrating from the cut ends of nerves and connectives, and we consistently saw regenerative outgrowth of severed peripheral and central axons into the gel matrix. Thus, 3D gels provide an in vitro system in which we can reliably obtain repair of severed nerve cords in the dish, and visualize cell behaviour underlying regenerative growth at the damage site: and which offers the possibility of manipulating the regenerating cells and their extracellular environment in various ways at stages during repair. Using this system it should be possible to test the effect on the repair process of altering expression of selected genes in identified nerve cells.     

The effect of two episodes of denervation and reinnervation on skeletal muscle contractile function.

Sensory or motor "baby-sitting" has been proposed as a clinical strategy to preserve muscle integrity if motion-specific axons must regenerate over a long distance to reach denervated target muscles. Denervated muscles are innervated temporarily by using axons from nearby sensory or motor nerves. After motion specific motor axons have reached the target, the baby-sitter nerve is severed and motion-specific axons are directed to the target. Although this strategy minimizes denervation time, the requisite second episode of denervation and reinnervation might be deleterious to muscle contractile function. This study was designed to test the hypothesis that two sequential episodes of skeletal muscle denervation and reinnervation result in greater force and power deficits than a single peripheral nerve injury and repair. Adult Lewis rats underwent either transection and epineurial repair or sham exposure of the left peroneal nerve. After a 4-month recovery period, the contractile properties of the extensor digitorum longus muscle of the sham exposure group (control, n = 9) and one of the nerve division and repair groups (repair group 1, n = 9) were evaluated with measurements of the maximum tetanic isometric force, peak power, and maximal sustained power. A third group of rats underwent a second cycle of nerve division and repair (repair group 2, n = 9) at this same time point. Four months postoperatively, contractile properties of the extensor digitorum longus muscles were evaluated. Maximum tetanic isometric force and peak power were significantly reduced in repair group 2 rats as compared with repair group 1 and control rats. Maximal sustained power was not significantly different between the groups. These data support our working hypothesis that skeletal muscle contractile function is adversely affected by two cycles of denervation and reinnervation as compared with a single episode of nerve division and repair.     

Studies in flexor tendon wound healing: neutralizing antibody to TGF-beta1 increases postoperative range of motion

The postoperative outcome of hand flexor tendon repair remains limited by tendon adhesions that prevent normal range of motion. Recent studies using in situ hybridization techniques have implicated transforming growth factor beta-1 (TGF-beta1) in both intrinsic and extrinsic mechanisms of repair. TGF-beta1 is a growth factor that plays multiple roles in wound healing and has also been implicated in the pathogenesis of excessive scar formation. The purpose of this study was to examine the effect of neutralizing antibody to TGF-beta1 in a rabbit zone II flexor tendon wound-healing model. Twenty-two adult New Zealand White rabbits underwent complete transection of the middle digit flexor digitorum profundus tendon in zone II. The tendons were immediately repaired and received intraoperative infiltration of one of the following substances: (1) control phosphate-buffered saline; (2) 50 microg neutralizing antibody to TGF-beta1; (3) 50 microg each of neutralizing antibody to TGF-beta1 and to TGF-beta2. Eight rabbits that had not been operated on underwent analysis for determination of normal flexion range of motion at their proximal and distal interphalangeal joints, using a 1.2-N axial load applied to the flexor digitorum profundus tendon. All rabbits that had been operated on were placed in casts for 8 weeks to allow maximal tendon adhesion and were then killed to determine their flexion range of motion. Statistical analysis was performed using the Student's unpaired t test. When a 1.2-N load was used on rabbit forepaws that had not been operated on, normal combined flexion range of motion at the proximal and distal interphalangeal joints was 93+/-6 degrees. Previous immobilization in casts did not reduce the range of motion in these forepaws (93+/-4 degrees). In the experimental groups, complete transection and repair of the flexor digitorum profundus tendon with infiltration of control phosphate-buffered saline solution resulted in significantly decreased range of motion between the proximal and distal phalanges [15+/-6 degrees (n = 8)]. However, in the tendon repairs infiltrated with neutralizing antibody to TGF-beta1, flexion range of motion increased to 32+/-9 degrees (n = 7; p = 0.002). Interestingly, a combination of neutralizing antibody to TGF-beta1 and that to TGF-beta2 did not improve postoperative range of motion [18+/-4 degrees (n = 7; p = 0.234)]. These data demonstrate that (1) the rabbit flexor tendon repair model is useful for quantifying tendon scar formation on the basis of degrees of flexion between proximal and distal phalanges; (2) intraoperative infiltration of neutralizing antibody to TGF-beta1 improves flexor tendon excursion; and (3) simultaneous infiltration of neutralizing antibody to TGF-beta2 nullifies this effect. Because TGF-beta1 is thought to contribute to the pathogenesis of excessive scar formation, the findings presented here suggest that intraoperative biochemical modulation of TGF-beta1 levels limits flexor tendon adhesion formation.     

The optimal sequence of microvascular repair during prolonged clamping in free flap transfer

During free flap transfer, the surgeon may decide to begin with repair of the artery or the vein(s) and to unclamp the first vessel as soon as repair is completed or maintain the clamping of both vessels until completion of all repairs. Complications can lead to prolonged clamping times, potentially increasing the risk of tissue ischemia, vascular damage, and thrombosis. The goals of the present study were to determine whether the sequence of vessel repair and the duration of clamping affect the success of free flap transfer in cases requiring prolonged clamping. Sixty abdominal fasciocutaneous free flaps based on the superficial inferior epigastric vessels were created in Sprague-Dawley rats. To model clinical situations in which prolonged clamping is necessary, the study used a 1-hour delay before the repair of the second vessel. Flaps were randomized into four groups. In group I (n = 15), the artery was repaired first, and the arterial clamp was removed immediately to allow arterial inflow. In group II (n = 15), the arterial repair was first, and the arterial clamp was maintained until completion of venous repair. In group III (n = 15), venous repair was first, with venous clamping maintained until completion of the arterial repair. In group IV (n = 15), initial venous repair was followed by immediate unclamping, before arterial repair. On release of all clamps, the patency of arteries and veins was confirmed immediately and after 1 hour using a "milking" test. On the fifth postoperative day, each flap was assessed for necrosis and for patency of the anastomoses. Of 15 flaps in each group, five (33 percent) failed in group I, four (27 percent) failed in groups II and III, and six (40 percent) failed in group IV. Differences between groups were not statistically significant (p = 0.8). These results demonstrate that in cases requiring prolonged occlusive clamping (2 to 3 hours), factors such as venous congestion, possible clamp injury, and presence of static blood in contact with the new anastomosis have relatively equivalent contributions to the risk of failure. Accordingly, no advantage seems to be gained by beginning with the artery or the vein or by using early or delayed unclamping of the first vessel repaired.     

骨髓干细胞动员对动脉粥样硬化破裂斑块的稳定与修复作用

目的研究自体骨髓干细胞动员对兔动脉粥样硬化（AS）破裂斑块的稳定与修复作用。方法用液氮冻伤术创建兔AS破裂斑块模型,动员组注射重组人粒细胞刺激因子（rhG-CSF）动员自体骨髓干细胞,对照组注射等量生理盐水,连续5 d。动员第5天抽血分离获取单个核细胞,BrdU标记后经静脉注入动物体内;分别于动员后3d和4周末抽血,ELISA法检测兔血清MMP-9、hsC-RP及PAI-1水平;动员后4周处死兔,HE染色和Masson三色染色观察斑块病理形态,免疫组化染色观察BrdU在斑块区表达情况。结果动员5 d后,动员组兔外周血有核细胞计数及单核细胞比例明显增高;动员后4周,动员组新生内皮细胞及胶原纤维明显增多,在斑块区发现有BrdU标记的阳性细胞,动员组血清MMP-9、hsC-RP及PAI-1水平明显降低。结论应用rhG-CSF动员自体骨髓干细胞能通过促进血管内皮细胞和胶原纤维再生,降低炎症因子及凝血纤溶因子而稳定与修复AS破裂斑块。     

Immobilization of the rabbit tibialis anterior muscle in a lengthened position causes addition of sarcomeres in series and extra-cellular matrix proliferation

Rabbits were immobilized for 3 weeks with the ankle in plantar flexion, midrange position or dorsal extension (n=15). The left leg was used as control. Sarcomere lengths were measured by laser diffraction in vivo in the tibialis anterior (TA) muscle. Legs immobilized in the midrange position showed coherent diffraction patterns through the range of motion, but in those immobilized with TA in the stretched position no diffraction patterns in vivo could be obtained. Morphological analyses revealed increased fibrosis and occurrence of whorled fibers in these muscles. On 15 more likewise immobilized rabbits, a technique of measuring sarcomere lengths in vitro by first digesting the collagen in nitric acid was developed. These in vitro measurements showed shorter sarcomeres in the muscles immobilized in a lengthened position compared to the control, indicating an addition of sarcomeres in series.     

Functional and morphometric evaluation of end-to-side neurorrhaphy for muscle reinnervation

This study was undertaken to quantify the effect of motor collateral sprouting in an end-to-side repair model allowing end organ contact. Besides documentation of the functional outcome of muscle reinnervation by end-to-side neurorrhaphy, this experimental work was performed to determine possible downgrading effects to the donor nerve at end organ level. In 24 female New Zealand White rabbits, the motor nerve branch to the rectus femoris muscle of the right hindlimb was dissected, cut, and sutured end-to-side to the motor branch to the vastus medialis muscle after creating an epineural window. The 24 rabbits were divided into two groups of 12 each, with the second group receiving additional crush injury of the vastus branch. After a period of 8 months, maximum tetanic tension in the reinnervated rectus femoris and the vastus medialis muscles was determined. The contralateral healthy side served as control. The reinnervated rectus femoris muscle showed an average maximum tetanic force of 24.9 N (control 26.2 N, p = 0.7827), and the donor- vastus medialis muscle 11.0 N (control 7.3 N, p = 0.0223). There were no statistically significant differences between the two experimental groups (p = 0.9914). The average number of regenerated myelinated nerve fibers in the rectus femoris motor branch was 1,185 +/- 342 (control, 806 +/- 166), and the mean diameter was 4.6 +/- 0.6 microm (control, 9.4 +/- 1.0 microm). In the motor branch to the vastus medialis muscle, the mean fiber number proximal to the coaptation site was 1227 (+/-441), and decreased distal to the coaptation site to 795 (+/-270). The average difference of axon counts in the donor nerve proximal to distal regarding the repair site was 483.7 +/- 264.2. In the contralateral motor branch to the vastus medialis muscle, 540 (+/- 175) myelinated nerve fibers were counted. In nearly all cross-section specimens of the motor branch to the vastus medialis muscle, altered nerve fibers could be identified in one fascicle distal and proximal to the repair site. The results show a relevant functional reinnervation by end-to-side neurorrhaphy without functional impairment of the donor muscle. It seems to be evident that most axons in the attached segment were derived from collateral sprouts. Nonetheless, the present study confirms that end-to-side neurorrhaphy is a reliable method of reconstruction for damaged nerves, which should be applied clinically in a more extended manner.     

Modulation of peripheral nerve regeneration: a tissue-engineering approach. The role of amnion tube nerve conduit across a 1-centimeter nerve gap

A new type of a biodegradable nerve graft conduit material, the amnion tube, has been developed in our laboratory. To test the tube in the peripheral nerve regeneration process, it was initially applied across a 1-cm sciatic nerve gap in rats and was compared with other nerve conduit materials. We used male Sprague-Dawley rats as our animal model. The experiment included 66 rats that were randomly assigned into five groups: autograft (n = 17), amnion tube (n = 19), silicone tube (n = 20), no repair (n = 7), and sham group (n = 3). The process of peripheral nerve regeneration was evaluated at 2, 4, 10, and 17 weeks following injury and repair by using morphologic and functional assessments of the outcome of nerve regeneration in each animal. Nerve regeneration across the amnion tube nerve conduit was comparable with that seen in autograft and superior to that of the silicone group. A uniform nerve tissue was seen filling and crossing the amnion conduit, and the regenerated nerve from the proximal stump reached the distal end and was undifferentiated from the normal nerve tissues. At 4 months, the amnion tube biodegraded and no longer could be identified and differentiated from the nerve tissues. The amnion tube animal group showed a number of axons very close to that in the nerve autograft group (37,157 versus 33,054). Functional recovery at a 2- to 4-week interval was significantly statistically higher only in the amnion tube animal group (p = 0.01). However, the improvement disappeared between 10 and 17 weeks. In conclusion, the amnion tube is a potential ideal nerve conduit material secondary to its unique characteristics: it contains important neurotropic factors, is biodegradable, provokes a very weak immune response, is semiflexible, is readily available, and is easily manufactured into different sizes and diameters.     

Functional assessment in the rat by ground reaction forces

Although the rat sciatic nerve model is used extensively in the investigation of repair techniques, and a variety of evaluation methods utilized to assess the results, a means to measure directly and accurately the return of function in these animals is absent. Histologic, histomorphometric, and electrophysiologic methods can be reliable indicators of nerve regeneration but do not correlate to functional recovery. The purposes of this study were to develop apparatus to continuously measure ground reaction forces (GRF) and use GRF parameters in the assessment of gait parameters in normal rats preoperatively and following peripheral nerve severance and repair. Three neurorrhaphy methods: direct sciatic nerve repair, direct tibial nerve repair and double sciatic nerve repair simulating autograft, as well as a non-repaired tibial nerve transection were evaluated. The testing apparatus was designed to measure the spontaneous and voluntary effort of the rat with objective data. Three orthogonal components - vertical, craniocaudal (braking and propulsion), and mediolateral - of the ground reaction force were measured. Preoperative data showed that vertical forces were comparable among the four limbs but propulsion and braking forces displayed significant differences. At 12 weeks, functional recovery was most evident in the direct tibial nerve repair group and absent in the non-repaired tibial defect group. Direct sciatic nerve repairs and sciatic nerve grafts resulted in lesser degrees of improvement. Results indicated that the propulsive force is the optimal GRF parameter for evaluating recovery of useful function.     

A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans

This article reports the first randomized prospective multicenter evaluation of a bioabsorbable conduit for nerve repair. The study enrolled 98 subjects with 136 nerve transections in the hand and prospectively randomized the repair to two groups: standard repair, either end-to-end or with a nerve graft, or repair using a polyglycolic acid conduit. Two-point discrimination was measured by a blinded observer at 3, 6, 9, and 12 months after repair. There were 56 nerves repaired in the control group and 46 nerves repaired with a conduit available for follow-up. Three patients had a partial conduit extrusion as a result of loss of the initially crushed skin flap. The overall results showed no significant difference between the two groups as a whole. In the control group, excellent results were obtained in 43 percent of repairs, good results in 43 percent, and poor results in 14 percent. In those nerves repaired with a conduit, excellent results were obtained in 44 percent, good results in 30 percent, and poor results in 26 percent (p = 0.46). When the sensory recovery was examined with regard to length of nerve gap, however, nerves with gaps of 4 mm or less had better sensation when repaired with a conduit; the mean moving two-point discrimination was 3.7 +/- 1.4 mm for polyglycolic acid tube repair and 6.1 +/- 3.3 mm for end-to-end repairs (p = 0.03). All injured nerves with deficits of 8 mm or greater were reconstructed with either a nerve graft or a conduit. This subgroup also demonstrated a significant difference in favor of the polyglycolic acid tube. The mean moving two-point discrimination for the conduit was 6.8 +/- 3.8 mm, with excellent results obtained in 7 of 17 nerves, whereas the mean moving two-point discrimination for the graft repair was 12.9 +/- 2.4 mm, with excellent results obtained in none of the eight nerves (p < 0.001 and p = 0.06, respectively). This investigation demonstrates improved sensation when a conduit repair is used for nerve gaps of 4 mm or less, compared with end-to-end repair of digital nerves. Polyglycolic acid conduit repair also produces results superior to those of a nerve graft for larger nerve gaps and eliminates the donor-site morbidity associated with nerve-graft harvesting.     

A long-term, controlled-outcome analysis of in utero versus neonatal cleft lip repair using an ovine model.

Successful open repair of a cleft lip in utero has the advantage of scarless wound healing in the fetus. Unfortunately, no long-term outcome studies have been performed to evaluate the efficacy of these repairs. Moreover, no study to date has compared the long-term results of an in utero cleft lip repair to a similar, control-matched, newborn cleft repair. This study was performed to evaluate the 9-month outcome of in utero cleft lip surgery compared with an identical cleft lip repair performed on infant lambs. In utero epithelialized cleft lips were created through an open hysterotomy in sixteen 65-day-old fetal lambs (term = 140 days) using methods described by Longaker et al. Eight of 16 animals underwent subsequent in utero repair of these clefts at 90 days gestational age. The repair of the remaining eight animals was delayed until 1 week postpartum. At 9 months, the animals were analyzed for changes in lip contour and for the degree of scarring by hematoxylin and eosin and Masson's trichrome collagen staining. Two animals in each group died from preterm labor. Of the animals that survived to term, all repaired lips had some degree of abnormality postoperatively. One of six lips repaired in utero dehisced before delivery. Three of six neonatal repairs dehisced in the first postoperative month. In the remaining animals with intact lip repairs, the vertical lip height on the repaired side was an average of 9 to 12 mm shorter than the normal lip in both the in utero and neonatally repaired animals. Phenotypically, the postnatally repaired animals had more lip distortion and visible notching. Histologically, the in utero repair was scarless and the neonatal repairs had scar throughout the entire vertical height of the lip with an associated loss of hair in this region. Maxillary growth was also evaluated. There was no inhibition of maxillary growth in the animals that underwent in utero cleft lip repair. However, in the neonatal repair group, significant maxillary retrusion was evident. Compared with the cleft side of the maxilla, horizontal growth was decreased by 11 percent (p = 0.01). Compared with the intrauterine repair group, there was a 17-percent decrease in horizontal maxillary width (p = 0.01). Straight-line in utero repair of a cleft lip produces a better long-term result in terms of maxillary growth than a similar repair performed postnatally in the ovine model. There was no diminution in maxillary growth in the animals treated in utero. Histologically, in utero repair of clefts was indeed scarless. However, both lip repairs produced lips that were significantly shorter than their contralateral noncleft sides. This degree of lip shortening would require a secondary lip revision, thereby defeating the purpose of performing an intrauterine repair. Comparisons now need to be made between in utero and neonatal repairs using a Millard-type rotation advancement technique before intrauterine treatment can be considered to be more beneficial than our current treatment modalities.