Challenges in sciatic nerve repair: anatomical considerations

Laboratory investigation

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Object

The object of this study was to highlight the challenge of insufficient donor graft material in peripheral nerve surgery, with a specific focus on sciatic nerve transection requiring autologous sural nerve graft.

Methods

The authors performed an anatomical analysis of cadaveric sciatic and sural nerve tissue. To complement this they also present 3 illustrative clinical cases of sciatic nerve injuries with segmental defects. In the anatomical study, the cross-sectional area (CSA), circumference, diameter, percentage of neural tissue, fat content of the sural nerves, as well as the number of fascicles, were measured from cadaveric samples. The percentage of neural tissue was defined as the CSA of fascicles lined by perineurium relative to the CSA of the sural nerve surrounded by epineurium.

Results

Sural nerve samples were obtained from 8 cadaveric specimens. Mean values and standard deviations from sural nerve measurements were as follows: CSA 2.84 ± 0.91 mm2, circumference 6.67 ± 1.60 mm, diameter 2.36 ± 0.43 mm, fat content 0.83 ± 0.91 mm2, and number of fascicles 9.88 ± 3.68. The percentage of neural tissue seen on sural nerve cross-section was 33.17% ± 4.96%. One sciatic nerve was also evaluated. It had a CSA of 37.50 mm2, with 56% of the CSA representing nerve material. The estimated length of sciatic nerve that could be repaired with a bilateral sural nerve harvest (85 cm) varied from as little as 2.5 cm to as much as 8 cm.

Conclusions

Multiple methods have been used in the past to repair sciatic nerve injury but most commonly, when a considerable gap is present, autologous nerve grafting is required, with sural nerve being the foremost source. As evidenced by the anatomical data reported in this study, a considerable degree of variability exists in the diameter of sural nerve harvests. Conversely, the percentage of neural tissue is relatively consistent across specimens. The authors recommend that the peripheral nerve surgeon take these points into consideration during nerve grafting as insufficient graft material may preclude successful recovery.

Abbreviations used in this paper:AGC = axon guidance channel; CSA = cross-sectional area; EHL = extensor hallucis longus.

Object

The object of this study was to highlight the challenge of insufficient donor graft material in peripheral nerve surgery, with a specific focus on sciatic nerve transection requiring autologous sural nerve graft.

Methods

The authors performed an anatomical analysis of cadaveric sciatic and sural nerve tissue. To complement this they also present 3 illustrative clinical cases of sciatic nerve injuries with segmental defects. In the anatomical study, the cross-sectional area (CSA), circumference, diameter, percentage of neural tissue, fat content of the sural nerves, as well as the number of fascicles, were measured from cadaveric samples. The percentage of neural tissue was defined as the CSA of fascicles lined by perineurium relative to the CSA of the sural nerve surrounded by epineurium.

Results

Sural nerve samples were obtained from 8 cadaveric specimens. Mean values and standard deviations from sural nerve measurements were as follows: CSA 2.84 ± 0.91 mm2, circumference 6.67 ± 1.60 mm, diameter 2.36 ± 0.43 mm, fat content 0.83 ± 0.91 mm2, and number of fascicles 9.88 ± 3.68. The percentage of neural tissue seen on sural nerve cross-section was 33.17% ± 4.96%. One sciatic nerve was also evaluated. It had a CSA of 37.50 mm2, with 56% of the CSA representing nerve material. The estimated length of sciatic nerve that could be repaired with a bilateral sural nerve harvest (85 cm) varied from as little as 2.5 cm to as much as 8 cm.

Conclusions

Multiple methods have been used in the past to repair sciatic nerve injury but most commonly, when a considerable gap is present, autologous nerve grafting is required, with sural nerve being the foremost source. As evidenced by the anatomical data reported in this study, a considerable degree of variability exists in the diameter of sural nerve harvests. Conversely, the percentage of neural tissue is relatively consistent across specimens. The authors recommend that the peripheral nerve surgeon take these points into consideration during nerve grafting as insufficient graft material may preclude successful recovery.

Sciatic nerve injuries are relatively uncommon among peripheral nerve injuries.2 Typically, injury to this nerve occurs with trauma to the buttock, hip, or posterior thigh. Iatrogenic injury can occur in the setting of injections in the gluteal region or after hip and knee surgery. The sciatic nerve is the largest peripheral nerve in both length and cross-sectional area (CSA), and its size presents anatomical challenges for repair. Furthermore, muscle and sensory targets can be located at considerable distances (for example, 90 cm) from the site of injury. As nerve regeneration progresses at a rate of only 2.5 cm per month—successful regeneration to distal targets is one of the most demanding in peripheral nerve repair. While neurotization techniques have revolutionized the surgical treatment of upper-extremity injuries (for example, brachial plexus injuries), repair of lower-extremity peripheral nerve defects involving a gap relies on more traditional sensory nerve autografts.

Transection of the sciatic nerve occurring distal to the innervation of the posterior thigh (Fig. 1) musculature spares knee flexion so that a patient's ability to ambulate is often preserved. Ambulatory function in these cases is contingent on a normally functioning quadriceps and an ankle foot orthosis. However, the loss of sensory innervation to the plantar aspect of the foot can lead to serious morbidity, including pressure sores.2,13 In addition to restoring motor and/or sensory function, nerve repair can mitigate and/or reduce the incidence and severity of neuroma formation and subsequent development of neuropathic pain.5 With recent advances in surgical technique and the use of tendon transfers, patients can expect better functional outcomes than ever before.2 When the damage to the sciatic nerve is extensive enough to preclude coaptation, nerve grafting techniques with autologous sensory nerve graft are used. With large gaps of the sciatic nerve, surgeons will face the challenge of insufficient donor nerve graft material.

Fig. 1.
Fig. 1.

Artist's image of sciatic nerve after transection with a gap at mid-thigh sparing branches to the knee flexor muscles (biceps femoris, semimembranosus, semitendinosus). Copyright Allan D. Levi. Published with permission.

In the following study we investigate the detailed anatomy of the sural nerve, which is the nerve most commonly used for autologous grafting. We explore the variability in the size, fascicular content, and amount of epineurium connective tissue in several cadaveric specimens and use these measurements to make assertions about the constraints of this graft material. To further illustrate anatomical constraints of sciatic nerve repair, we present a series of 3 cases in which sural nerve grafting was used to repair lacerating injuries to the sciatic nerve. We present these clinical data to highlight the important issue of insufficient graft material, which is often faced in peripheral nerve surgery. Strategies and future directions in the repair of nerve defects with significant segmental loss will be explored.

Methods

Obtaining Neural Tissue

Sciatic and sural nerve segments were harvested from cadavers with the permission of the University of Miami, Miller School of Medicine Anatomical Board. Sural nerves were identified at their retromalleolar location, and nerve samples were obtained in a location 8–12 cm superior to the lateral malleolus. The sciatic nerve was identified in the superior aspect of the popliteal fossa and was transected 6–10 cm proximal to where the nerve clearly bifurcated into tibial and common peroneal nerves.

Histological Analysis

The nerve samples were postfixed with 1% osmium tetroxide overnight. The fixative was removed, and the specimens were washed in buffer and dehydrated in a graded series of ethanols. The sural and sciatic samples were embedded by passage through propylene oxide and then propylene oxide/Epon-araldite (1:1). Polymerization of Epon-araldite was complete after 16 hours (overnight) at 64°C. The resulting blocks were cut using an ultramicrotome to obtain 1-μm semi-thin transverse sections of the peripheral nerves at their epicenter, which were then stained with toluidine blue. With the aid of a grid, sections were examined for the axonal and connective tissue and a ratio was determined relating the two. Camera lucida drawings were made of the transverse sections and colored for clarity. Measurements were carried out using widely available ImageJ software. The laboratory methods were adopted from Levi et al.25

The sural nerves were measured for total cross-sectional area (CSA), circumference, diameter, percentage of neural tissue, fat content, and number of fascicles. The percentage of neural tissue was defined as the CSA of fascicles lined by perineurium, or the intraperineural tissue, relative to the CSA of epineurium-lined sural nerve. The neuronal fat content was measured as separate globules, and the total fat CSA was then determined. Measurements were carried out by 2 members of the research team and subsequently validated by an independent observer.

Statistical Analysis

The mean fascicle content, diameter, circumference, and CSA for samples were obtained. The means and standard deviations are included in the analysis. Basic mathematical analyses were performed using Microsoft Excel.

Results

Nerve samples were obtained from total of 8 cadaveric specimens (Fig. 2A). Their ages ranged from 60 to 88 years. There were 5 males and 3 females.

Fig. 2.
Fig. 2.

A: Cross-sectional images of all 8 human sural nerve specimens obtained well above the medial malleolus. There is a significant degree of variability in overall cross-sectional area, fascicular anatomy, and amount of connective tissue and fat, as well as number of fascicles. Original magnification ×5. B: Toluidene blue–stained cross-section of a sciatic nerve obtained at mid-thigh. Bar = 1.0 mm.

The results of this analysis including means and standard deviations are displayed in Table 1. The mean CSA of the sural nerves was 2.84 ± 0.91 mm2. The average number of fascicles within the sural nerve was 9.88 (range 4–15 fascicles). Finally, the percentage of neural tissue was remarkably similar for each sural nerve, with a mean value of only 33.2% ± 5%. Thus, only a third of the cross sectional area of each sural nerve graft represents a regenerative environment for sciatic nerve axons. With a total CSA ranging from a low of 1.20 mm2 to a high of 3.75 mm2, the relative amount of neural tissue, which regenerating axons would encounter, was thus quite variable.

TABLE 1:

Anatomical measurements from sural nerve cross-sections*

NerveCSA (mm2)Circumference (mm)Diameter (mm)Fascicular CSA (mm2)Neural Tissue (%)No. of Fascicles
13.156.542.390.9731.3110
22.625.831.980.8632.867
33.759.872.961.1129.6815
43.717.302.871.1230.228
53.697.032.521.0227.6812
62.436.112.340.7831.9914
72.166.502.130.8840.799
81.204.201.680.4940.794
mean2.846.672.360.9033.179.88
SD0.911.600.430.214.963.68

Sural nerves were obtained from formalin-fixed cadaveric specimens 8–12 cm superior to the lateral malleolus. CSA = crosssectional area.

Some sural nerves have a remarkable amount of fat around and within the nerve. With regard to fat content, there was an average of 0.83 ± 0.91 mm2 of fatty tissue located within and outside of the epineurium. The average percentage of fat present within the epineurial borders was 18.18% ± 14.37%. Such measurements demonstrate the wide degree of variability in total fat content. Additionally, they suggest that location of fatty tissue is not uniform among sural nerves. These results are displayed in Table 2. Cross-sections of all 8 sural nerves are displayed in Fig. 1. The tabulated results and images demonstrate the fairly high degree of variability between sural nerve specimens.

TABLE 2:

Analysis of intraneural and extraneural fat content*

NerveExtraneural (mm2)Intraneural (mm2)Total (mm2)% Intraneural
10.160.020.189.00
20.200.040.2417.63
30.480.200.6829.70
42.150.522.6819.58
51.010.041.063.96
60.050.050.1047.22
71.480.101.576.13
80.110.020.1312.22
mean0.710.120.8318.18
SD0.770.170.9114.37

Displayed are the cross-sectional area measurements of fat globules present around and within the sural nerves. Fat was deemed to be intraneural when located within the epineurium of the sural nerve and extraneural when located outside of the epineurium.

We also evaluated one sciatic nerve cross-section (Fig. 2B). Here we calculated a total CSA of 37.50 mm2 and a fascicular CSA of 21.00 mm2, representing a nerve content of 56%. We then calculated the average length of sural nerve (y-axis) required to repair increasingly lengthy segmental defects within the sciatic nerve (x-axis). The large deviations in the error bars illustrates the enormous variability in the CSA of the sural nerve as well as the need for considering alternative measures for nerve graft material with even limited defects (see Fig. 4).

Fig. 3.
Fig. 3.

Repair of sciatic nerve with multiple sural nerve grafts. The images were obtained during surgical repair and correspond to the illustrative cases presented in this paper (Cases 1, 2, and 3, respectively, A–C). As can be seen, more attention was paid to the medial, tibial portion of the sciatic nerve in our repair due to the lack of autologous graft material and the relatively poor prognosis for peroneal nerve recovery.

Fig. 4.
Fig. 4.

Graph showing the length of sural nerve required to bridge sciatic nerve defects of different lengths. The plotted values are based on the means for the sural and sciatic nerve cross-sectional area (CSA) calculated from measurements performed in the cadaveric specimens used in this study. The error bars represent 95% confidence intervals, based upon variation in sural CSA.

Illustrative Cases

Case 1

A 52-year-old male sustained a deep posterior thigh injury resulting in near amputation of his right leg from a boat propeller. There was a deep soft tissue injury to the thigh and midshaft femoral fracture but no vascular injury present. Neurological examination demonstrated complete loss of motor function (0/5 strength) in foot dorsiflexion, eversion, and plantar flexion, as well as extensor hallucis longus (EHL) function. Loss of sensation was noted on dorsal and plantar aspects of the foot as well as lateral malleolus and posterior and lateral leg, while sensation was preserved on the medial malleolus and medial leg from the femoral nerve/saphenous branch. Knee flexion was 3/5, as the sciatic nerve injury was distal to the branches to the biceps femoris, and obturator nerve function was normal.

Surgical exploration demonstrated complete transection of the sciatic nerve 11 cm above the popliteal fossa, distal to hamstring innervation. Additional injuries to the leg were significant, and repair of the sciatic nerve was delayed for 12 days to allow for definition of the nerve ends. Intraoperatively, the proximal and distal ends of the sciatic nerve were identified, with an estimated 3.5 cm gap between them. After removal of obvious neuromatous portions on both ends the gap was measured as 6.5 cm in length. Bilateral sural nerve grafts were used to connect the sciatic nerve ends. Ultimately, 12 individual sural nerve fascicles were utilized to bridge the defect (Fig. 3A). Graft attachment was achieved with 8-0 nylon sutures supplemented with fibrin glue. Given the paucity of graft material, emphasis was placed on repair of the tibial division of the sciatic nerve.

Case 2

This 31-year-old man was injured when a mortar detonated 15 feet from his location. Metal fragments entered the posterior aspect of his left leg, and he immediately experienced paralysis of the lower leg, including foot dorsiflexion, plantar flexion, and EHL function. The injury was stabilized at a military facility in Iraq. Electromyographic studies performed 4 months postinjury revealed complete loss of function of the tibial nerve and moderate dysfunction of the common peroneal nerve. The hamstring musculature was intact. By this time the patient had regained some function in foot dorsiflexion (2/5 strength) as well as eversion of the foot. He also had increasing degrees of neuropathic pain over the entire lateral leg and foot.

Five months after injury the patient was taken to surgery. Intraoperatively, a large area of scar tissue was noted at the site of shrapnel penetration. After extensive resection of the neuroma, the tibial and common peroneal divisions were identified. Intraoperative nerve action potentials revealed weak conduction through the common perioneal nerve and no conduction through the tibial nerve. A 4-cm gap was left in the tibial portion of the sciatic nerve. A sural nerve graft was obtained from the right leg; the length of the harvested nerve tissue was measured 25 cm. Using 5 × 4-cm grafts, the gap in the tibial division was approximated (Fig. 3B). Anastomosis was achieved with 7-0 Prolene sutures.

Case 3

This 17-year-old male patient sustained a degloving injury to his posterior right thigh when a tile floor eroded beneath him. When seen in the emergency department, he had no sensation below the knee and 0/5 strength in dorsiflexion, plantar flexion, and EHL function. The patient was brought immediately to the operating theater for repair of an associated venous injury. There were no arterial or osseous injuries. Exploration of the sciatic nerve revealed a complete transection, and the nerve ends were anchored with epineurium tacking sutures.

After his skin, muscular, and venous injuries were stable, about 1 month after the initial injury, the patient underwent sciatic nerve repair. Intraoperatively, a large sciatic nerve neuroma was resected, revealing a 4.5-cm defect. Bilateral sural nerves provided 60 cm of autologous graft material;40 10 fascicular segments were applied to the tibial division and 4 to the peroneal division (Fig. 3C). Repair was accomplished with 8-0 nylon sutures.

Discussion

Repair of sciatic transection with the use of nerve grafting has yielded variable success in the past. Some of the largest published studies have been generated from data collected between 1968 to 1999 at Louisiana State University Hospital.20,21,34 Other notable studies include those of Gousheh et al.13 and Aydin et al.,2 representing primarily military-related injuries of the sciatic nerve. These studies show variable rates of success, depending on the level of injury and whether the tibial or peroneal branches were involved.2,13,20 Focusing on repair requiring autologous nerve graft, the worst outcomes are seen in the peroneal division of the sciatic nerve at the level of the buttock, with good outcomes being reported in 21.4%–24.3% of cases.13,20 In contrast, the highest rates of recovery were seen with tibial graft repairs in the mid-thigh, with good outcomes reported in approximately 80% of the cases reported.13,20 In addition to location and branch involved, other factors cited as affecting the success of nerve grafts include length of time to surgery (delay > 4 months being associated with worse outcomes), and length of the nerve defect (length > 5 cm being associated with worse outcomes).41

The anatomy of the sciatic nerve has been well described in the literature.1,13,14,20,33 The sciatic nerve originates from the anterior divisions of L-4 through S-3 and the posterior divisions of L-4 through S-2, thus forming the tibial and peroneal branches, respectively.20 The sciatic nerve begins as these fibers coalesce entering the gluteal region through the greater sciatic foramen below the piriformis muscle33 and then courses inferiorly at the midway point between the ischial tuberosity and greater trochanter of the femur. Running down the thigh, it lies just beneath the biceps femoris muscle.33 Along the entire length of the sciatic nerve, its tibial and peroneal branches are separate and distinct.2,13 The tibial and common peroneal nerves are technically formed as the sciatic nerve bifurcates, which is usually in the distal thigh.

The sural nerve, a common candidate for autologous grafting, has also been studied extensively.10,19,33,39,40 It is most frequently made up of medial and lateral components, which are branches from the tibial and common peroneal nerves, respectively.39 From its origination in the popliteal fossa, the sural nerve courses down the posterior leg to its, relatively nonvariable, destination at the retromalleolar region.39 Cadaveric studies have demonstrated a median sural nerve length of 43 cm (range 35–47 cm).40 In cases of lengthy (> 5 cm) sciatic defects it would be beneficial to know, given the length of the sural nerve, how much nerve tissue will be harvestable. Thus, a central factor would be the cross-sectional area (CSA) of both the sural and sciatic nerves in the patient.

According to our data, the CSA of a sural nerve ranges from 1.2 to 3.75 mm2; additionally, the percentage of the tissue that contains valuable neural structures, represented as the fascicles, averaged about 33%, with a relatively narrow range. To correlate our results with in vivo studies we reviewed ultrasound and MRI data from sciatic and sural nerves in healthy controls (Table 3).9,16,23,26,42,44 These studies also demonstrate a large variability with regard to CSA, especially of the sural nerve.9,15,16,26,44 Specifically, the sural nerve CSA as measured by ultrasound ranged from 1.44 to 5.3 mm2. When averaged, these in vivo measurements have a weighted mean of 3.79 mm2. Comparing this to our mean CSA value from the cadaveric studies, 2.84 mm2 ± 0.91 mm2, we see that the value obtained from ultrasonography is more than 1 standard deviation above that obtained in the laboratory. This may be explained in part by dehydration of the specimens in processing and fixation. Also, one would be more likely to capture fatty and connective tissue surrounding the epineurium when using ultrasound, and we did not include such tissue in our CSA calculation. Furthermore, data from our analysis of nerve-associated fatty tissue (Table 2) suggests that if fat is considered with sural CSA measurement there will be a further increase in the variability between samples. Notably, our cadaveric samples came from a group of donors with an advanced mean age, as would be expected from our method of collection. Although it is known that this type of traumatic injury most commonly occurs in younger adults, we do not believe age to be a factor affecting the measurements presented. While age typically equates to an increased CSA, this correlation has not been seen with the sural nerve near the ankle.8 Furthermore, at the level of the nerve fascicle; cadaveric data from individuals of various ages showed no correlation between fascicular diameter and age.35 On the other hand, at the level of individual myelinated axons, changes with age have been documented.35,36,43 It appears that these age-related changes do not affect the nerve CSA at the macroscopic level. To determine the theoretical maximum length of sciatic gap that could be bridged, one can calculate nerve volumes of the sural nerve with the CSA measurements that we have obtained. These results are displayed on Fig. 4. As can be seen, the length of bridgeable gap would be largely dependent on the CSA of the sural nerve and length of the harvested sample. Further extrapolating from these measurements, we estimate, using a 95% confidence interval, that sural nerves with a small CSA would only be able to cover 2.5 cm of sciatic nerve defect, whereas those with larger CSA may bridge up to an 8-cm gap. The calculation of the required sural nerve graft length was based on a volumetric analysis of the product of CSA and the length of the sural nerve needed to fill the 3-dimensional sciatic nerve defect. With the problem of insufficiency in mind, peripheral nerve surgeons can use preoperative imaging (MRI and ultrasonography) to better anticipate graft insufficiency. In such cases, surgeons could employ similar volumetric calculations to those presented here in developing their operative plan.

TABLE 3:

Sciatic and sural nerve cross-sectional areas as measured by other modalities*

NerveCSA (mm2)Variability of CSA (mm2)Sample SizeMeasurement ToolAuthors & Year
sciatic56range 28–10219ultrasoundLatzke et al., 2010
sciatic34.2SEM 558ultrasoundTagliafico et al., 2012
sciatic43.3IQR 19.910MRISinclair et al., 2011
sural3.6SEM 1158ultrasoundTagliafico et al., 2012
sural5.295% CI 4.7–5.725ultrasoundHobson-Webb et al., 2013
sural1.44SD 0.3450ultrasoundLiu et al., 2012
sural5.3SD 1.860ultrasoundCartwright et al., 2008

This table depicts the cross-sectional area of both sciatic and sural nerves as measured by various techniques. All sciatic measurements were obtained from the mid-thigh level and all sural nerve measurements were obtained at the level of the calf. SD = standard deviation; SEM = standard error of the mean; IQR = interquartile range.

In noted study the approximate CSA measurement was listed as a median.

With the challenges to sural nerve grafting in mind, it would be advantageous to consider the alternatives. One strategy has been to focus the repair on the tibial division of the sciatic nerve and not on the peroneal division.13 In this method more graft material will be used on the medial portion of the sciatic nerve. The rationale for this stems from a desire to restore plantar flexion and heel sensation as well as the historically poor success with peroneal branch repair.11,13,20 Another option, in line with the previous strategy, is to sacrifice the ipsilateral common peroneal nerve and use this in repair of the tibial branch.13 Doubt about peroneal branch sacrifice arises from concerns of vascularization of this relatively large-bore nerve.6 Furthermore, as improvements in peroneal branch restoration are made, this method will become less favorable. Heading in a different direction, an option would be to look for alternative autologous nerves. In the past, small sensory nerves of the forearm and dorsal foot have been harvested, but these nerves may not provide sufficient material for grafting. Use of intercostal nerves has been reported, but these nerves may be more difficult to obtain.12,31,46 Due to anatomical considerations, the lower extremity is less amenable to nerve transfer. After exploiting all autologous nerve sources, the next place to look might be cadaveric, allograft tissue.30,37,38 Such a strategy was explored in a case series published by Mackinnon et al.30 One of their 10 patients did have sciatic nerve injury, and in that case authors were able reconstruct the posterior tibial nerve with 230 cm of allograft tissue and restore protective sensation to the foot.30 Such an extensive amount of tissue would be impossible to obtain from autograft sources. Lastly, newer options include the use of axon guidance channels (AGCs).

AGCs can be made with either acellular autograft tissue or nonbiological material, such as silicone, polyglycolic acid, or collagen. Currently, the FDA has approved 11 types of conduits for clinical use.18 Many reports of successful nerve repairs using AGCs have been published, with a majority of data pertaining to their use in small-diameter nerves or very short gaps.7,17,27–29 As AGC technology advances, large-bore nerves with longer gap repairs are being attempted. A recent study addressed this issue of large-bore nerves in 4 patients with injuries of the median nerve (1 case), ulnar nerve (1 case), and brachial plexus (2 cases), using absorbable collagen or polyglycolic acid conduits.32 Authors followed the patients for variable lengths of time (range 9 months–4 years) and, unfortunately, observed relatively poor outcomes in all 4 cases.32 They went on to hypothesize that the larger diameter of the nerves grafted played a major role in their poor results. Regarding AGC improvement strategies, some approaches include incorporation of extracellular matrix proteins and/or neurotrophic factors.3,4,22,45 Another, more recent approach has been to incorporate autologous, cultured Schwann cells into the AGCs (Fig. 5).5,24 Results from animal models have been promising.5,24 As these supplementation strategies advance, the use of AGCs can be expected influence the repair of large-bore peripheral nerves more dramatically; however, AGCs appear poorly suited for the treatment of sciatic nerve injury at this time.

Fig. 5.
Fig. 5.

Schematic illustration of of auto-transplantation protocol that could potentially expand Schwann cells from a sural nerve biopsy and transplant them within a tube into a segmental defect within the sciatic nerve. Copyright Allan D. Levi. Published with permission.

Conclusions

When appraised collectively, the anatomical data along with the current literature offer much information about the potential for autologous grafting in large-bore peripheral nerve injury. Sciatic nerve injury, specifically, presents its own challenges for the peripheral nerve surgeon. When considering graft repair with sural tissue, several factors must be taken into consideration. In particular, the CSA and fascicular content should be considered, as variability here can preclude successful recovery.

Disclosure

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author contributions to the study and manuscript preparation include the following. Conception and design: all authors. Acquisition of data: all authors. Analysis and interpretation of data: all authors. Drafting the article: all authors. Critically revising the article: all authors. Reviewed submitted version of manuscript: all authors. Approved the final version of the manuscript on behalf of all authors: AD Levi.

References

  • 1

    Andersen HLAndersen SLTranum-Jensen J: Injection inside the paraneural sheath of the sciatic nerve: direct comparison among ultrasound imaging, macroscopic anatomy, and histologic analysis. Reg Anesth Pain Med 37:4104142012

  • 2

    Aydin AOzkan TAydin HUTopalan MErer MOzkan S: The results of surgical repair of sciatic nerve injuries. Acta Orthop Traumatol Turc 44:48532010

  • 3

    Battiston BGeuna SFerrero MTos P: Nerve repair by means of tubulization: literature review and personal clinical experience comparing biological and synthetic conduits for sensory nerve repair. Microsurgery 25:2582672005

  • 4

    Belkas JSShoichet MSMidha R: Peripheral nerve regeneration through guidance tubes. Neurol Res 26:1511602004

  • 5

    Berrocal YAAlmeida VWGupta RLevi AD: Transplantation of Schwann cells in a collagen tube for the repair of large, segmental peripheral nerve defects in rats. Laboratory investigation. J Neurosurg 119:7207322013

  • 6

    Best TJMackinnon SEEvans PJHunter DMidha R: Peripheral nerve revascularization: histomorphometric study of small- and large-caliber grafts. J Reconstr Microsurg 15:1831901999

  • 7

    Brooks DNWeber RVChao JDRinker BDZoldos JRobichaux MR: Processed nerve allografts for peripheral nerve reconstruction: a multicenter study of utilization and outcomes in sensory, mixed, and motor nerve reconstructions. Microsurgery 32:1142012

  • 8

    Cartwright MSMayans DRGillson NAGriffin LPWalker FO: Nerve cross-sectional area in extremes of age. Muscle Nerve 47:8908932013

  • 9

    Cartwright MSPassmore LVYoon JSBrown MECaress JBWalker FO: Cross-sectional area reference values for nerve ultrasonography. Muscle Nerve 37:5665712008

  • 10

    de Alvarenga Yoshida RYoshida WBSardenberg TSobreira MLRollo HAMoura R: Fibular nerve injury after small saphenous vein surgery. Ann Vasc Surg 26:729.e11729.e152012

  • 11

    Flores LP: Proximal motor branches from the tibial nerve as direct donors to restore function of the deep fibular nerve for treatment of high sciatic nerve injuries: a cadaveric feasibility study. Neurosurgery 65:6 Suppl2182252009

  • 12

    Gailliot RV JrCore GB: Serratus anterior intercostal nerve graft: a new vascularized nerve graft. Ann Plast Surg 35:26311995

  • 13

    Gousheh JArasteh EBeikpour H: Therapeutic results of sciatic nerve repair in Iran-Iraq war casualties. Plast Reconstr Surg 121:8788862008

  • 14

    Gustafson KJGrinberg YJoseph STriolo RJ: Human distal sciatic nerve fascicular anatomy: implications for ankle control using nerve-cuff electrodes. J Rehabil Res Dev 49:3093212012

  • 15

    Higgins JPFisher SSerletti JMOrlando GS: Assessment of nerve graft donor sites used for reconstruction of traumatic digital nerve defects. J Hand Surg Am 27:2862922002

  • 16

    Hobson-Webb LDMassey JMJuel VC: Nerve ultrasound in diabetic polyneuropathy: correlation with clinical characteristics and electrodiagnostic testing. Muscle Nerve 47:3793842013

  • 17

    Karabekmez FEDuymaz AMoran SL: Early clinical outcomes with the use of decellularized nerve allograft for repair of sensory defects within the hand. Hand (NY) 4:2452492009

  • 18

    Kehoe SZhang XFBoyd D: FDA approved guidance conduits and wraps for peripheral nerve injury: a review of materials and efficacy. Injury 43:5535722012

  • 19

    Kerver ALvan der Ham ACTheeuwes HPEilers PHPoublon ARKerver AJ: The surgical anatomy of the small saphenous vein and adjacent nerves in relation to endovenous thermal ablation. J Vasc Surg 56:1811882012

  • 20

    Kim DHMurovic JATiel RKline DG: Management and outcomes in 353 surgically treated sciatic nerve lesions. J Neurosurg 101:8172004

  • 21

    Kline DGKim DMidha RHarsh CTiel R: Management and results of sciatic nerve injuries: a 24-year experience. J Neurosurg 89:13231998

  • 22

    Kuffler DPReyes OSosa IJSantiago-Figueroa J: Neurological recovery across a 12-cm-long ulnar nerve gap repaired 3.25 years post trauma: case report. Neurosurgery 69:E1321E13262011

  • 23

    Latzke DMarhofer PZeitlinger MMachata ANeumann FLackner E: Minimal local anaesthetic volumes for sciatic nerve block: evaluation of ED 99 in volunteers. Br J Anaesth 104:2392442010

  • 24

    Levi ADBunge RP: Studies of myelin formation after transplantation of human Schwann cells into the severe combined immunodeficient mouse. Exp Neurol 130:41521994

  • 25

    Levi ADDancausse HLi XDuncan SHorkey LOliviera M: Peripheral nerve grafts promoting central nervous system regeneration after spinal cord injury in the primate. J Neurosurg 96:2 Suppl1972052002

  • 26

    Liu FZhu JWei MBao YHu B: Preliminary evaluation of the sural nerve using 22-MHz ultrasound: a new approach for evaluation of diabetic cutaneous neuropathy. PLoS ONE 7:e327302012

  • 27

    Lundborg GRosén BDahlin LDanielsen NHolmberg J: Tubular versus conventional repair of median and ulnar nerves in the human forearm: early results from a prospective, randomized, clinical study. J Hand Surg Am 22:991061997

  • 28

    Lundborg GRosén BDahlin LHolmberg JRosén I: Tubular repair of the median or ulnar nerve in the human forearm: a 5-year follow-up. J Hand Surg Br 29:1001072004

  • 29

    Mackinnon SEDellon AL: Clinical nerve reconstruction with a bioabsorbable polyglycolic acid tube. Plast Reconstr Surg 85:4194241990

  • 30

    Mackinnon SEDoolabh VBNovak CBTrulock EP: Clinical outcome following nerve allograft transplantation. Plast Reconstr Surg 107:141914292001

  • 31

    Mohammad JAHasaniya NShenaq S: Endoscopic technique for harvesting the intercostal nerve as a nerve graft: a feasibility preliminary study in cadavers. Plast Reconstr Surg 103:961001999

  • 32

    Moore AMKasukurthi RMagill CKFarhadi HFBorschel GHMackinnon SE: Limitations of conduits in peripheral nerve repairs. Hand (NY) 4:1801862009

  • 33

    Moore KLDalley AF: Clinically Oriented Anatomy ed 5PhiladelphiaLippincott Williams & Wilkins2006. 555724

  • 34

    Murovic JA: Lower-extremity peripheral nerve injuries: a Louisiana State University Health Sciences Center literature review with comparison of the operative outcomes of 806 Louisiana State University Health Sciences Center sciatic, common peroneal, and tibial nerve lesions. Neurosurgery 65:4 SupplA18A232009

  • 35

    Ochoa JMair WG: The normal sural nerve in man. II. Changes in the axons and Schwann cells due to ageing. Acta Neuropathol 13:2172391969

  • 36

    O'Sullivan DJSwallow M: The fibre size and content of the radial and sural nerves. J Neurol Neurosurg Psychiatry 31:4644701968

  • 37

    Pabari AYang SYSeifalian AMMosahebi A: Modern surgical management of peripheral nerve gap. J Plast Reconstr Aesthet Surg 63:194119482010

  • 38

    Ray WZMackinnon SE: Management of nerve gaps: autografts, allografts, nerve transfers, and end-to-side neurorrhaphy. Exp Neurol 223:77852010

  • 39

    Riedl OFrey M: Anatomy of the sural nerve: cadaver study and literature review. Plast Reconstr Surg 131:8028102013

  • 40

    Riedl OKoemuercue FMarker MHoch DHaas MDeutinger M: Sural nerve harvesting beyond the popliteal region allows a significant gain of donor nerve graft length. Plast Reconstr Surg 122:7988052008

  • 41

    Roganović ZPavlićević GPetković S: Missile-induced complete lesions of the tibial nerve and tibial division of the sciatic nerve: results of 119 repairs. J Neurosurg 103:6226292005

  • 42

    Sinclair CDMiranda MACowley PMorrow JMDavagnanam IMehta H: MRI shows increased sciatic nerve cross sectional area in inherited and inflammatory neuropathies. J Neurol Neurosurg Psychiatry 82:128312862011

  • 43

    Sunderland S: Nerves and Nerve Injuries ed 2EdinburghChurchill Livingstone1978. 621951955

  • 44

    Tagliafico ACadoni AFisci EBignotti BPadua LMartinoli C: Reliability of side-to-side ultrasound cross-sectional area measurements of lower extremity nerves in healthy subjects. Muscle Nerve 46:7177222012

  • 45

    Weber RABreidenbach WCBrown REJabaley MEMass DP: A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans. Plast Reconstr Surg 106:10361045discussion104610482000

  • 46

    Yim KKHui KCRamos DLineaweaver WC: Use of intercostal nerves as nerve grafts in hand reconstruction with rectus abdominis flaps. J Hand Surg Am 19:2382401994

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Article Information

Address correspondence to: Allan D. Levi, M.D., Ph.D., University of Miami Miller School of Medicine, Department of Neurological Surgery, Lois Pope Life Center, 1095 N.W. 14th Terrace (D4-6), Miami, FL 33136. email: alevi@med.miami.edu.

Please include this information when citing this paper: published online April 11, 2014; DOI: 10.3171/2014.2.JNS131667.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Artist's image of sciatic nerve after transection with a gap at mid-thigh sparing branches to the knee flexor muscles (biceps femoris, semimembranosus, semitendinosus). Copyright Allan D. Levi. Published with permission.

  • View in gallery

    A: Cross-sectional images of all 8 human sural nerve specimens obtained well above the medial malleolus. There is a significant degree of variability in overall cross-sectional area, fascicular anatomy, and amount of connective tissue and fat, as well as number of fascicles. Original magnification ×5. B: Toluidene blue–stained cross-section of a sciatic nerve obtained at mid-thigh. Bar = 1.0 mm.

  • View in gallery

    Repair of sciatic nerve with multiple sural nerve grafts. The images were obtained during surgical repair and correspond to the illustrative cases presented in this paper (Cases 1, 2, and 3, respectively, A–C). As can be seen, more attention was paid to the medial, tibial portion of the sciatic nerve in our repair due to the lack of autologous graft material and the relatively poor prognosis for peroneal nerve recovery.

  • View in gallery

    Graph showing the length of sural nerve required to bridge sciatic nerve defects of different lengths. The plotted values are based on the means for the sural and sciatic nerve cross-sectional area (CSA) calculated from measurements performed in the cadaveric specimens used in this study. The error bars represent 95% confidence intervals, based upon variation in sural CSA.

  • View in gallery

    Schematic illustration of of auto-transplantation protocol that could potentially expand Schwann cells from a sural nerve biopsy and transplant them within a tube into a segmental defect within the sciatic nerve. Copyright Allan D. Levi. Published with permission.

References

  • 1

    Andersen HLAndersen SLTranum-Jensen J: Injection inside the paraneural sheath of the sciatic nerve: direct comparison among ultrasound imaging, macroscopic anatomy, and histologic analysis. Reg Anesth Pain Med 37:4104142012

  • 2

    Aydin AOzkan TAydin HUTopalan MErer MOzkan S: The results of surgical repair of sciatic nerve injuries. Acta Orthop Traumatol Turc 44:48532010

  • 3

    Battiston BGeuna SFerrero MTos P: Nerve repair by means of tubulization: literature review and personal clinical experience comparing biological and synthetic conduits for sensory nerve repair. Microsurgery 25:2582672005

  • 4

    Belkas JSShoichet MSMidha R: Peripheral nerve regeneration through guidance tubes. Neurol Res 26:1511602004

  • 5

    Berrocal YAAlmeida VWGupta RLevi AD: Transplantation of Schwann cells in a collagen tube for the repair of large, segmental peripheral nerve defects in rats. Laboratory investigation. J Neurosurg 119:7207322013

  • 6

    Best TJMackinnon SEEvans PJHunter DMidha R: Peripheral nerve revascularization: histomorphometric study of small- and large-caliber grafts. J Reconstr Microsurg 15:1831901999

  • 7

    Brooks DNWeber RVChao JDRinker BDZoldos JRobichaux MR: Processed nerve allografts for peripheral nerve reconstruction: a multicenter study of utilization and outcomes in sensory, mixed, and motor nerve reconstructions. Microsurgery 32:1142012

  • 8

    Cartwright MSMayans DRGillson NAGriffin LPWalker FO: Nerve cross-sectional area in extremes of age. Muscle Nerve 47:8908932013

  • 9

    Cartwright MSPassmore LVYoon JSBrown MECaress JBWalker FO: Cross-sectional area reference values for nerve ultrasonography. Muscle Nerve 37:5665712008

  • 10

    de Alvarenga Yoshida RYoshida WBSardenberg TSobreira MLRollo HAMoura R: Fibular nerve injury after small saphenous vein surgery. Ann Vasc Surg 26:729.e11729.e152012

  • 11

    Flores LP: Proximal motor branches from the tibial nerve as direct donors to restore function of the deep fibular nerve for treatment of high sciatic nerve injuries: a cadaveric feasibility study. Neurosurgery 65:6 Suppl2182252009

  • 12

    Gailliot RV JrCore GB: Serratus anterior intercostal nerve graft: a new vascularized nerve graft. Ann Plast Surg 35:26311995

  • 13

    Gousheh JArasteh EBeikpour H: Therapeutic results of sciatic nerve repair in Iran-Iraq war casualties. Plast Reconstr Surg 121:8788862008

  • 14

    Gustafson KJGrinberg YJoseph STriolo RJ: Human distal sciatic nerve fascicular anatomy: implications for ankle control using nerve-cuff electrodes. J Rehabil Res Dev 49:3093212012

  • 15

    Higgins JPFisher SSerletti JMOrlando GS: Assessment of nerve graft donor sites used for reconstruction of traumatic digital nerve defects. J Hand Surg Am 27:2862922002

  • 16

    Hobson-Webb LDMassey JMJuel VC: Nerve ultrasound in diabetic polyneuropathy: correlation with clinical characteristics and electrodiagnostic testing. Muscle Nerve 47:3793842013

  • 17

    Karabekmez FEDuymaz AMoran SL: Early clinical outcomes with the use of decellularized nerve allograft for repair of sensory defects within the hand. Hand (NY) 4:2452492009

  • 18

    Kehoe SZhang XFBoyd D: FDA approved guidance conduits and wraps for peripheral nerve injury: a review of materials and efficacy. Injury 43:5535722012

  • 19

    Kerver ALvan der Ham ACTheeuwes HPEilers PHPoublon ARKerver AJ: The surgical anatomy of the small saphenous vein and adjacent nerves in relation to endovenous thermal ablation. J Vasc Surg 56:1811882012

  • 20

    Kim DHMurovic JATiel RKline DG: Management and outcomes in 353 surgically treated sciatic nerve lesions. J Neurosurg 101:8172004

  • 21

    Kline DGKim DMidha RHarsh CTiel R: Management and results of sciatic nerve injuries: a 24-year experience. J Neurosurg 89:13231998

  • 22

    Kuffler DPReyes OSosa IJSantiago-Figueroa J: Neurological recovery across a 12-cm-long ulnar nerve gap repaired 3.25 years post trauma: case report. Neurosurgery 69:E1321E13262011

  • 23

    Latzke DMarhofer PZeitlinger MMachata ANeumann FLackner E: Minimal local anaesthetic volumes for sciatic nerve block: evaluation of ED 99 in volunteers. Br J Anaesth 104:2392442010

  • 24

    Levi ADBunge RP: Studies of myelin formation after transplantation of human Schwann cells into the severe combined immunodeficient mouse. Exp Neurol 130:41521994

  • 25

    Levi ADDancausse HLi XDuncan SHorkey LOliviera M: Peripheral nerve grafts promoting central nervous system regeneration after spinal cord injury in the primate. J Neurosurg 96:2 Suppl1972052002

  • 26

    Liu FZhu JWei MBao YHu B: Preliminary evaluation of the sural nerve using 22-MHz ultrasound: a new approach for evaluation of diabetic cutaneous neuropathy. PLoS ONE 7:e327302012

  • 27

    Lundborg GRosén BDahlin LDanielsen NHolmberg J: Tubular versus conventional repair of median and ulnar nerves in the human forearm: early results from a prospective, randomized, clinical study. J Hand Surg Am 22:991061997

  • 28

    Lundborg GRosén BDahlin LHolmberg JRosén I: Tubular repair of the median or ulnar nerve in the human forearm: a 5-year follow-up. J Hand Surg Br 29:1001072004

  • 29

    Mackinnon SEDellon AL: Clinical nerve reconstruction with a bioabsorbable polyglycolic acid tube. Plast Reconstr Surg 85:4194241990

  • 30

    Mackinnon SEDoolabh VBNovak CBTrulock EP: Clinical outcome following nerve allograft transplantation. Plast Reconstr Surg 107:141914292001

  • 31

    Mohammad JAHasaniya NShenaq S: Endoscopic technique for harvesting the intercostal nerve as a nerve graft: a feasibility preliminary study in cadavers. Plast Reconstr Surg 103:961001999

  • 32

    Moore AMKasukurthi RMagill CKFarhadi HFBorschel GHMackinnon SE: Limitations of conduits in peripheral nerve repairs. Hand (NY) 4:1801862009

  • 33

    Moore KLDalley AF: Clinically Oriented Anatomy ed 5PhiladelphiaLippincott Williams & Wilkins2006. 555724

  • 34

    Murovic JA: Lower-extremity peripheral nerve injuries: a Louisiana State University Health Sciences Center literature review with comparison of the operative outcomes of 806 Louisiana State University Health Sciences Center sciatic, common peroneal, and tibial nerve lesions. Neurosurgery 65:4 SupplA18A232009

  • 35

    Ochoa JMair WG: The normal sural nerve in man. II. Changes in the axons and Schwann cells due to ageing. Acta Neuropathol 13:2172391969

  • 36

    O'Sullivan DJSwallow M: The fibre size and content of the radial and sural nerves. J Neurol Neurosurg Psychiatry 31:4644701968

  • 37

    Pabari AYang SYSeifalian AMMosahebi A: Modern surgical management of peripheral nerve gap. J Plast Reconstr Aesthet Surg 63:194119482010

  • 38

    Ray WZMackinnon SE: Management of nerve gaps: autografts, allografts, nerve transfers, and end-to-side neurorrhaphy. Exp Neurol 223:77852010

  • 39

    Riedl OFrey M: Anatomy of the sural nerve: cadaver study and literature review. Plast Reconstr Surg 131:8028102013

  • 40

    Riedl OKoemuercue FMarker MHoch DHaas MDeutinger M: Sural nerve harvesting beyond the popliteal region allows a significant gain of donor nerve graft length. Plast Reconstr Surg 122:7988052008

  • 41

    Roganović ZPavlićević GPetković S: Missile-induced complete lesions of the tibial nerve and tibial division of the sciatic nerve: results of 119 repairs. J Neurosurg 103:6226292005

  • 42

    Sinclair CDMiranda MACowley PMorrow JMDavagnanam IMehta H: MRI shows increased sciatic nerve cross sectional area in inherited and inflammatory neuropathies. J Neurol Neurosurg Psychiatry 82:128312862011

  • 43

    Sunderland S: Nerves and Nerve Injuries ed 2EdinburghChurchill Livingstone1978. 621951955

  • 44

    Tagliafico ACadoni AFisci EBignotti BPadua LMartinoli C: Reliability of side-to-side ultrasound cross-sectional area measurements of lower extremity nerves in healthy subjects. Muscle Nerve 46:7177222012

  • 45

    Weber RABreidenbach WCBrown REJabaley MEMass DP: A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans. Plast Reconstr Surg 106:10361045discussion104610482000

  • 46

    Yim KKHui KCRamos DLineaweaver WC: Use of intercostal nerves as nerve grafts in hand reconstruction with rectus abdominis flaps. J Hand Surg Am 19:2382401994

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