Peripheral nerve elongation with tissue expansion techniques

Vacuum Assisted Closure Therapy versus Standard Wound Therapy for Open Musculoskeletal Injuries

Background. This study was performed to evaluate the results of vacuum assisted wound therapy in patients with open musculoskeletal injuries. Study Design and Setting. Prospective, randomized, and interventional at tertiary care hospital, from 2011 to 2012. Materials and Methods. 30 patients of open musculoskeletal injuries underwent randomized trial of vacuum assisted closure therapy versus standard wound therapy around the upper limb and lower limb. Mean patient age was 39 ± 18 years (range, 18 to 76 years). Necrotic tissues were debrided before applying VAC therapy. Dressings were changed every 3 or 4 days. For standard wound therapy, debridement followed by daily dressings was done. Data Management and Statistical Analysis. The results obtained were subjected to statistical analysis. Results. The size of soft tissue defects reduced more than 5 mm to 25 mm after VAC (mean decrease of 26.66%), whereas in standard wound therapy, reduction in wound size was less than 5 mm. A free flap was needed to cover exposed bone and tendon in one case in standard wound therapy group. No major complication occurred that was directly attributable to treatment. Conclusion. Vacuum assisted wound therapy was found to facilitate the rapid formation of healthy granulation tissue on open wounds in the upper limb and lower limb, thus to shorten healing time and minimize secondary soft tissue defect coverage procedures.

New treatment for peripheral nerve defects: reconstruction of a 2 cm, monkey median nerve gap by direct lengthening of both nerve stumps

We have developed a new treatment for peripheral nerve defects: nerve-lengthening method, and confirmed the efficacy and safety of our method using cynomolgus monkeys. A 20-mm defect in the median nerve of monkey's forearms was repaired through the simultaneous lengthening of both nerve stumps with original nerve-lengthening device. To evaluate nerve regeneration after neurorrhaphy, electrophysiological, histological, and functional recovery were examined and compared to the standard autografting. Nerve conduction velocity, axon maturation, and the result of functional test were superior in the nerve-lengthening method than in the autografting. And there were no adverse events associated with our method. We concluded that this method is practical for clinical application.

[Vacuum-assisted closure therapy. Current status and basic research]

The gap between the broad clinical use of vacuum-assisted closure therapy (VT) and knowledge of the physiological mechanisms leading to its effectiveness is great. The value of the technique and its future development are dependent on research into these mechanisms. A meta-analysis evaluating the results of basic research on the effectiveness of VT was carried out based on peer reviewed publications. This is considered in relation to other therapeutic approaches of basic research to wound healing (growth factors etc.). Our study includes a concise description of the scientific background to the mechanisms of cell stimulation using basic work on tissue expansion, bone, vessel and nerve distraction as well as in vitro cell stimulation. Evaluation of the scientific data on all known effects of VT was made based on the results from experimental animal studies, the results of randomized clinical studies, observations on clinical applications and case reports. Assessment of the studies was based on design and significance as well as the appraisal of our own clinical experience. Data involving cellular effects (proliferation, synthesis, wound healing), systemic effects (mediators, systemic inflammatory disease), extracellular effects (perfusion, edema, local wound environment, stabilization, barriers) and complex effects of VT (inflammation, matrix function, blood supply) were examined. Systematic analysis of the data allows scientifically interested surgeons rapid access to the theme, the first, to this extent, extensive overview of the current scientific situation as well as a comprehensive bibliography for all areas involving the theme of mechanical cell stimulation. The authors list major areas for future research and encourage the development of multicenter studies.

Vacuum-assisted closure for the treatment of abdominal wounds

Abdominal wall defects pose a significant surgical challenge. The defect may result from trauma, infections, previous major surgery, or some combination of these etiologies. This article describes the Vacuum-Assisted Closure device (VAC, KCI, San Antonio, Texas) and how it can help in treating these defects.

Effects of antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure: An experimental study

BACKGROUND

Elongation of peripheral nerve by the use of a tissue expander is helpful to repair nerve defects. This study was designed to investigate the effects of some antineoplastic agents on the peripheral nerves under a surgical tissue expansion procedure.

MATERIALS AND METHODS

Twenty-five Wistar rats were used in this study. Following the exposition of the sciatic nerve and placement of two 10/0-nylon sutures in the epineurium 20 mm apart, a tissue expander was then placed under it. Inflation of the expander was immediately accomplished by the separate percutaneous injections of 6, 6, and 8 ml for every 3 min under general anesthesia. The expander was fully deflated at the end of each 3 min The distance between two sutures was measured 1 h later to measure the rate of elongation. Rats were randomly divided into five groups (according to the administered drugs), each consisting of five rats (10 sciatic nerves). Normal saline (1 ml) in the control group (group I), cyclophosphamide (15 mg/kg) in the group II, cisplatinum (3 microg/kg) in the group III, mitomycin-C (0.5 mg/kg) in the group IV and 5-fluorouracil (10 mg/kg) in the group V were injected intravenously. Intravenous injections of drugs were performed via the tail vein 30 min before expansion, 48 and 96 h after removal of expander. The incision was reopened on the third and seventh postoperative days, and five sciatic nerves of each group were exposed and then the pinching test was performed to measure regeneration distance. Electroneurographic changes were recorded. The expanded portion of the sciatic nerve between two sutures was harvested for histological evaluation.

RESULTS

There is no significant difference between the elongation rates of all groups (P < 0.05). Histologic evaluation showed that inflammatory changes, vacuolization, intraneural edema, demyelination, axonal changes in the control group, the cisplatinum group, and the mitomycin-C group. These changes were significantly decreased in the cyclophosphamide group and the 5-fluorouracil group. In the cyclophosphamide group and the 5-fluorouracil group, the amplitude of compound action potential (CAP) values were significantly higher and the latency was significantly shorter (P > 0.05).

CONCLUSION

We believed that cyclophosphamide and 5-fluorouracil may be helpful in tissue expansion of peripheral nerves, by decreasing the effects of the ischemia-reperfusion injury on the expanded peripheral nerves.

Maximum intraoperative elongation of the rat sciatic nerve with tissue expander: Functional, neurophysiological, and histological assessment

The purpose of this study was to assess the maximum rapid intraoperative elongation of the rat sciatic nerve with the use of tissue expander, and its possible functional recovery. One hundred and eight rats were divided into five groups, and their right sciatic nerves were expanded with a 10-cc, 12-cc, 14-cc, 16-cc, and 18-cc expander, respectively, for 1 h. The functional recovery of the nerve was assessed at intervals up to 3 months, using the sciatic function index (SFI), neurophysiological indices, and histology. The maximum intraoperative elongation was observed in group IV (16-cc volume of tissue expander), at about 23.83%. SFI decreased between the first and seventh postoperative days, but gradually recovered, reaching preoperative values in all groups according to the formulas of De Medinaceli et al. (Exp. Neurol. 77:634-643, 1982) and Bain et al. (Plast. Reconstr. Surg. 83:129-136, 1989). Latency and motor conduction velocity demonstrated deterioration after expansion, which peaked after surgery. Recovery was gradually completed by the end of the experiment. The histological findings indicated minor aberrations immediately after expansion and maximal demyelination with axonal disruption on day 15. The reparative process started by day 30 and continued until day 90, when almost no histological changes were observed. In conclusion, intraoperative nerve expansion successfully elongates the rat sciatic nerve up to 23.83%. But it causes functional and morphological abnormalities, which are of moderate to severe degree, are of short duration, and are reversible. Intraoperative nerve expansion might be a valuable solution in the treatment of short nerve gaps, but its clinical application still needs to be evaluated.

Bridging the neural gap

A major limitation to overall success in peripheral nerve surgery is time for regeneration. Although one can help speed up the regenerative process to some extent, success is hindered by issues such as number of coaptation sites, supply of donor nerves, and the limitations of nerve substitutes. In the case of a large gap, a nerve graft is often used to fill in the deficit. Autogenous nerve grafts are in limited supply, with sural nerve grafts being the primary source. Alternatives to the standard treatment include vein grafts, synthetic nerve conduits, nerve transfers, and nerve transplantation. Schwann cell-lined nerve conduits and tissue-engineered substitutions are still in their infancy and have some limited clinical application.

Pre-degenerated nerve shows enhanced regeneration after incremental elongation in rats

Following nerve degeneration, we investigated effects of linear elongation on subsequent nerve regeneration in a total of 92 Wistar rats (weight 380-430 g). The nerve was ligated at the midthigh and then elongated incrementally by a total of 15 mm by leg lengthening at a rate of 3 or 5 mm/day. Seven days after initiation of nerve elongation, the external fixator was removed and normal leg length was restored with internal fixation. Then a 10 mm nerve segment at the ligature site was excised, and the nerve was repaired with sutures (group D). At 2, 4, 6, and 8 weeks after nerve suturing, we examined transverse semi-thin nerve sections compared with group I (severed and repaired after leg lengthening without a nerve ligature) and control group (severed and repaired without leg lengthening). After lengthening at 3 mm/day, nerve regeneration in group D was enhanced at 4 weeks. After lengthening at 5 mm/day, nerve regeneration in group D also was enhanced at 6 and 8 weeks. Pre-degenerated nerve showed better regeneration after suturing than intact nerve. Elongation holds promise as an alternative to nerve grafting in treatment of nerve injury.

Proximal nerve elongation vs. nerve grafting in repairing segmental nerve defects in rabbits

If segmental nerve defects could be repaired by elongating the proximal or distal segments, nerve grafting might be unnecessary. We elongated a 40-mm proximal segment of an injured median nerve, in the rabbit right forelimb, at a rate of 1 mm/day for 10 days in 10 rabbits and for 15 days in another 10. On the left forelimb of the same rabbits, a 10- for 15-mm segment of the median nerve was removed, and a 10- for 15-mm segment, respectively, of the tibial nerve was grafted in its place. Four months after the initial surgery, nerve conduction velocity (NCV), contractile strength of the flexor digitorum superficialis (FDS), axon count, and axon diameter did not differ significantly between the 10-mm groups but were better in the 15-mm grafted group. Elongating the proximal nerve segment may be an alternative to grafting in repairing segmental defects of less than 10 mm.

Growth and cellular differentiation: a physico-biochemical conundrum? The example of the hand

Currently, the predominant hypothesis explains cellular differentiation as an essentially genetic intracellular process. The goal of this paper is to suggest that cell growth and differentiation may be, simply, the result of physical and chemical constraints. Bone growth occurs at the level of cartilage conjunction (growth plate) in a zone of lesser constrain. It appears that this growth also induces muscle, tendon, nerve and skin elongation. This cartilage growth by itself seems to explain the elongation of the hand. Growth stops at puberty likely because of feed-back from an increasing muscle load. The ossification (that is differentiation of cartilage into bone) appears to result from the shear stress induced. The study of bone age, obtained by X-ray picture of the hand, shows that ossification of epiphyses is very precise both in time and space. Computer modelization suggests that this ossification occurs where shear stress is greatest. The cartilage which does not ossify (joint, nose, larynx, ear, bronchus, etc.) is not exposed to high shear. Shear stress induces the secretion of extracellular matrix and a change of the biochemical environment of the cell. Precipitation of calcium phosphate, as in ossification, seems related to the alkalosis induced by shear stress. To speak in more general terms, loss of cellular differentiation, as occurs with cancer, can result from a change in the physical-chemical environments.

Pathogenesis of the gradually elongated nerve

The rabbits' sciatic nerves were lengthened by 30 mm in increments of 2.0 mm/day (2-mm group) and 4.0 mm/day (4-mm group). In the 2-mm group, the phosphorylated neurofilament (p-NF) immunoreactivity of axons was similar to that of the control group. However, in the 4-mm group, number of p-NF positive axons decreased. The number of p-NF positive cells at the seventh lumbar dorsal root ganglion cells of the 4-mm group was significantly larger than that of the control group. Abnormal p-NF immunoreactivity in the 4-mm group suggested an impairment of the axonal flow. Leakage of Evans blue-albumin into the endoneurial space, which meant destruction of the blood-nerve barrier function, was clearly evident in the 4-mm group, but minor in the 2-mm group. A speed of 2.0 mm/day, therefore, appears to be critical for safe nerve elongation in this model.

Peripheral nerve lengthening by controlled isolated distraction: a new animal model

We have developed a simple and effective animal model to study the distraction neurogenesis utilizing the sciatic nerve-lengthening technique in rats. The model allows macroscopic, physiological, and histological evaluation of the distraction site. Fourteen adult Harlan Sprague Dawley rats (300-350 g) were used in this study. A 10 mm segment of the right sciatic nerve of each animal in the nerve-lengthening group was resected. Gradual nerve lengthening was performed by advancing the proximal nerve stump at a rate of 1 mm/day. The proximal stump neuroma was then resected and a direct nerve anastomosis was performed. On the left side a standard autogenous nerve-grafting procedure was performed with a 10 mm segment of sciatic nerve used as an in situ nerve graft. Three months after the second surgery, the sciatic nerves were exposed and investigated by gross observation and EMG followed by histological processing and tissue analysis. Neomicrovascularization was observed surrounding the sciatic nerve anastomosis in all five specimens of the nerve-lengthening group as compared to the more white-colored scar tissue that was observed in the nerve-grafting group. The EMG results were similar for both groups. Histological studies of the lengthened nerves showed axon morphology equivalent to the grafted nerves. This study demonstrated a clear evidence of the successful nerve regeneration within a segmental nerve gap by nerve lengthening.

Repair of nerve gap with the elongation of Wallerian degenerated nerve by tissue expansion

We have found previously that expansion of the Wallerian degenerated nerve was accompanied by accelerated Schwann cell proliferation. In this study, we investigated the usefulness of the elongation of Wallerian degenerated nerve for the repair of short nerve gap. Male Wistar rats were used. After the left sciatic nerve was transected the rats were divided into 4 groups. In the control group, nerve coaptation was not performed. In group 1, tensionless coaptation was performed immediately. In group 2, delayed tensionless coaptation was performed with the elongation of Wallerian degenerated nerve. In group 3, coaptation was performed immediately with autologous interposition nerve graft. The ideal tensionless nerve repair of group 1 was considered to produce the best result. Rats in group 2 showed functional recovery as good as rats in group 1. On histologic assessment, in group 2, a fibrous capsule that was very rich in vascularity was formed around the tissue expander. After 14 weeks, the capsule was diminished markedly in size, but the vascularity was rich around the sciatic nerve. We think that the excellent functional recovery seen in group 2 can be attributed to the increased activity of Schwann cell proliferation and increased vascularity.

Experimental study of peripheral nerve injury during gradual limb elongation

The purpose of this study was to clarify how fast the peripheral nerve can be elongated gradually without inducing nerve conduction block, and to assess whether the damage to the peripheral nerve is reversible. Rabbit femur was gradually elongated to 30 mm at the rate of 0.8 mm/day, 2.0 mm/day, and 4.0 mm/day to stretch the sciatic nerve. Immediately after and eight weeks after elongation, each group was estimated. Elongation of the Ranvier's node, which was likely the cause of conduction block, was observed and its severity increased with elongation speed. There was no Wallerian degeneration even when conduction block was complete. There was little damage to the sciatic nerve in the group of 0.8 mm/day. Damage in the group of 2.0 mm/day immediately after elongation had a tendency to recover by eight weeks, but there was no such tendency in the group of 4.0 mm/day.

Functional assessment of the rat sciatic nerve following intraoperative expansion: the effect of recovery duration on behavioural, neurophysiological, and morphological measures

The purpose of this study was to investigate the feasibility of rapid intraoperative elongation of the rat sciatic nerve with the use of tissue expander and to assess its functional recovery. Out of 51 rats 43 had their right sciatic nerve expanded with a 5-ml intraoperative expander over 1 hr and 8 were sham-operated controls. The functional recovery of the nerve was assessed at intervals up to 4 months using the Sciatic Functional index (SFI), neurophysiological indices, and histology. Intraoperative expansion elongated the rat sciatic nerve by about 13%. SFI decreased on the first postoperative day and started to recover by Day 7, reaching almost preoperative values by Days 14 and 30 according to De Medinaceli and Bain-Mackinnon-Hunter formulas, respectively. Latency and motor conduction velocity demonstrated a deterioration after expansion which peaked on Day 1. Recovery started by Day 7 and reached preoperative levels by 60 days. The histological findings indicated minor aberrations immediately after expansion and maximal demyelination with minimal axonal disruption on Day 1. The reparative process started by Day 7 and continued till Day 120 when almost no histological changes were observed. In conclusion, intraoperative nerve expansion successfully elongates the rat sciatic nerve. It also causes functional and morphological abnormalities which are of low to moderate degree, have a short duration, and are reversible. Intraoperative nerve expansion might be a valuable solution in the treatment of short nerve gaps, but its clinical application still needs to be evaluated.

Electroneurography during facial nerve expansion

With the use of tissue-expansion techniques, it is possible to elongate the facial nerve without impairing its function. The rate of expansion is limited by ischemic events imposed by stretching of the nerve and by anatomic characteristics of the nerve segment. In this study, we used various electroneurography techniques to determine the first sign of facial dysfunction during expansion. The main objective of the study was to ascertain test-retest variability of electroneurography techniques. Facial nerves were expanded in 16 cats with the use of a tissue expander secured more deeply to the main trunk. We conducted electroneurography measurements with the use of surface electrodes, temporary needle electrodes, and permanently implanted electrodes. Technique-dependent variations encountered with the surface electrodes made this method unreliable. Using implanted electrodes, we noted gradual worsening of the compound-action potential amplitude with increasing expansion. During acute expansion, reduction in compound-action potential amplitude was correlated with clinically observed deterioration of facial-nerve function. In this study, electroneurography with implanted electrodes was found to be the most reliable predictor of the rate of successful facial nerve expansion.

Nerve expansion in nerve regeneration: effect of time on induction of ornithine decarboxylase and Schwann cell proliferation

We studied the effect of initiation time of nerve expansion after nerve transection on the induction of ODC activity and Schwann cell proliferation in nerve tissue under Wallerian degeneration. The levels of ODC activity and Schwann cell proliferation decreased as the initiation time of nerve expansion was delayed after nerve transection, and peak levels of ODC activity following nerve expansion preceded peak levels of Schwann cell proliferation.

Plasticity of the extracranial facial nerve

Although the expansion properties of peripheral nerves have been a matter of considerable study in recent years, investigations of the plasticity of cranial nerves, including the facial nerve, have been lacking. Clinicians, however, have long recognized the tenacity of facial nerve function in patients with slow-growing benign tumors that enormously distort the nerve. An experimental study was designed to assess whether tissue expansion techniques can be applied to the extracranial portion of the facial nerves of cats. In eight cats the frontozygomatic branch of the facial nerve was expanded by stages in seven sessions over a period of 40 days. The length of the nerve increased an average of 95% without significantly impairing nerve function. Pressure changes in the expander averaged 75 mm Hg during each stage of expansion. Electroneurography was performed after each injection of the expander. Statistical analysis of these data did not show consistent evidence of demyelination or denervation, and all but one cat exhibited a normal blink reflex and had normal electromyographic findings at the end of the experiment. Histologic examination of the expanded nerves, however, did show inflammatory changes, intraneural edema, and occasional demyelination.

A case of popliteal pterygium treated along with nerve expansion

The presence of a short sciatic nerve in the free edge of a popliteal pterygium makes this syndrome a surgical challenge. We present a case of popliteal pterygium that was treated by nerve expansion. The range of motion of the patient's knee joint was between 30 and 120 degrees. A 75-cc tissue expander was placed under the sciatic nerve and filled with 5 cc of saline solution weekly. When a total of 60 cc was reached, wound dehiscence was observed, and the procedure had to be stopped. The maximum extension obtained was 160 degrees. Since the expansion process had to be stopped early, the elongation attained by expansion was less than expected. We conclude that the nerve expansion method can be used as a good alternative treatment modality for patients with popliteal pterygium.

Rapid Intraoperative Facial Nerve Expansion

The repair of nerve length defect presents a reconstructive challenge after trauma and oncologic resection. This study examined rapid intraoperative nerve expansion as a method of repairing nerve length defects with the cat facial nerve model. We compared expanded nerves with grafted nerves and intact nerves 1 year after repair using the criteria of gross function (symmetry and blink reflex according to a modified House scale), electromyography thresholds, nerve-conduction velocity, morphology, and axon count. Three of the five expanded nerves regenerated, and all of the grafted nerves regenerated. Functional results were similar for the regenerated expanded and the grafted facial nerves, and both methods achieved an equivalent level of function. The facial nerves of the regenerated expanded group, grafted group, and intact group had mean electromyography thresholds of 132 mV, 98 mV, and 134 mV, respectively, and mean conduction velocities of 48.3 mg/second, 47.9 m/second, and 44.7 m/second, respectively. Morphologic examination of all five expanded nerves immediately after the expansion process revealed an intact fascicular structure. However, 1 year after excision of the expanded segment and repair, only three of the five nerves regenerated. Axon count at 1 year was as follows: 404 for the regenerated expanded nerves, 449 for the grafted nerves, and 403 for the intact nerves. The potential advantages of rapid intraoperative nerve expansion over nerve grafting for the repair of nerve gap defects include a single suture line and absence of donor site morbidity. This pilot study demonstrates that rapid intraoperative nerve expansion and regeneration is possible and can be used to repair a nerve length deficit. The development of a rapid and reliable method of intraoperative nerve expansion deserves further study.

Optic nerve elongation: does it exist?

The length of the optic nerves is a reflection of normal postnatal cranio-orbital development. Unilateral elongation of an optic nerve has been observed in two patients with orbital and skull base neoplasms. In the first case as compared to the patient's opposite, normal optic nerve, an elongated length of the involved optic nerve of 45 mm was present. The involved optic nerve in the second patient was 10 mm longer than the normal opposite optic nerve. The visual and extraocular function was preserved in the second patient. The first patient had only light perception in the affected eye. In this paper, the embryology, anatomy, and physiology of the optic nerve and its mechanisms of stretch and repair are discussed.

A flap for segmental loss of a digital nerve. The Venkataswami flap revisited

The use of a V-Y advancement flap for reconstruction of a volar/lateral soft tissue defect in a digit involving segmental loss of the neurovascular bundle of up to 10 mm at middle phalangeal level is described. This flap allows immediate reconstruction with primary repair of the nerve and gives good functional results. Two cases are presented.

Peripheral nerve elongation by laser Doppler flowmetry controlled expansion: morphological aspects

Peripheral nerve elongation by a tissue expander may offer an alternative to nerve grafting in the management of segmental nerve loss. We investigated the morphological changes in peripheral nerve following slow nerve elongation by laser Doppler flowmetry controlled expansion in a rabbit sciatic nerve model. The animals were randomly assigned to one of four groups, with an expander volume of 0, 5, 10 or 15 cm3, respectively. An elongation of up to 40% was possible with preservation of clinical function. Nerve conduction velocity decreased in relation to elongation. Paranodal widening, followed by remyelination of the node, were early and constant morphological features. Demyelination and remyelination of whole internodes, and axonal degeneration occurred sporadically and did not correlate with elongation, rate of elongation or neurophysiological parameters. The model of laser Doppler flowmetry controlled nerve expansion provides a method for remodelling of myelin sheaths and lengthening of nerve fibers without axonal damage.

Elongation of wallerian degenerating nerve with a tissue expander: a functional, morphometrical, and immunohistochemical study

The purpose of this experimental study was to investigate the usefulness and mechanism of the expansion of wallerian degenerating nerve. The study consisted of two experiments: Experiment I, functional and morphometrical analysis, and Experiment II, immunohistochemical analysis. In Experiment I, the rat nerve crush model was used to assess the effects of mechanical expansion of wallerian degenerating nerves on axonal regeneration. In Experiment II, the rat sciatic nerve cut model was used to investigate the effects of nerve expansion on Schwann cell events in wallerian degenerating nerves. In both experiments, nerve expansion was carried out between days 5 and 9 after nerve injury, using a rubber tissue expander placed beneath the sciatic nerve. In Experiment I, rats were divided into the following three groups according to the volume of saline injected: control group (nerves were crushed, without saline injection); 8-ml injection group; and 11-ml injection group. Functional recovery was assessed using the sciatic functional index until 54 days after nerve injury. Rats in all three groups showed good functional recovery, and the morphometrical analysis revealed no significant differences among the three groups. In Experiment II, anti-S-100 protein polyclonal antibody and anti-proliferating cell nuclear antigen monoclonal antibody were used to identify proliferating Schwann cells. Rats were divided into two groups: control group (nerves were cut, without expansion) and nerve expansion group. In the control group, proliferating Schwann cells were observed only between days 3 and 7. By contrast, these cells continued to be seen in the expanded nerves until day 16. These results suggest that the expansion of wallerian degenerating nerve does not have a deleterious effect on the axon-promoting property of Schwann cell tubes and that the expansion is dependent not only on the viscoelasticity of the nerves but also on enhanced proliferation of Schwann cells.

A comparison of nerve grafting and tissue expansion techniques in the rat

This study compares nerve repair following tissue expansion with nerve repair using an interposed graft in the rat. Group I had expansion conducted over 2 weeks at 40 mmHg. A 4 mm segment was excised from the lengthened nerve and repaired primarily. Group II had a 4 mm segment of nerve excised and then replaced as an interposition graft. Group III was sham-operated controls. Thirteen weeks postoperatively, all animals were evaluated using walking track analysis. Thirty-five rats finished the study: Eleven in group I, 10 in group II, and 14 in group III. The Sciatic Functional Index (SFI) was calculated for each group as follows: group I, -57 +/- 11 (mean +/- standard deviation); group II, -59 +/- 25; group III, -13 +/- 6.5. The control group was significantly better than either experimental group (P < 0.01). The two experimental groups were not statistically different. Nerve repair following expansion allowed only one coaptation to be used. Functional results were the same as with interposition grafting. Repair by the expansion technique would eliminate the need to harvest a nerve graft, and the subsequent donor defect.