High-resolution ultrasound demonstrates in vivo effects of wrist movement on the median nerve along the forearm.

INTRODUCTION/AIMS: High-resolution ultrasound (HRUS) is the imaging method of choice to visualize peripheral nerve size, structure, and biomechanical performance. The purpose of this study was to show and quantify the effects of active and passive wrist alignment on median nerve (MN) cross-sectional area (CSA) along the forearm in a healthy population. METHODS: Sixteen healthy volunteers underwent HRUS of their dominant forearm (n = 16, 10 males, 6 females, 18-55 y of age). Median nerve's CSA was assessed at four defined areas on the forearm in relation to active and passive wrist alignment. RESULTS: Changes in wrist alignment were significantly associated with MN CSA (P < .001), regardless if the wrist was moved actively or passively. MN CSA was lowest during passive extension of the wrist joint and highest during passive flexion of the wrist joint (range: 4.5-23.2 mm2 ). DISCUSSION: The elasticity of nerve tissue, the loose connective tissue between the fascicles, and the paraneurium allow peripheral nerves to adapt to longitudinal strain. HRUS enables the demonstration of significant median nerve CSA changes along the forearm during active and passive wrist movement in healthy volunteers.

Hanno Millesi: Pioneer of Plastic Surgery and Nerve Surgery (1927-2017).

Recently, plastic surgery lost one of its most prominent surgeons-Dr. Hanno Millesi. His contributions to the field continue to impact the practice of medicine and surgery. As such, it is appropriate to reflect upon his career and recognize his accomplishments in peripheral nerve surgery, hand surgery, and Dupuytren disease.

Extracorporeal shockwave treatment: A novel tool to improve Schwann cell isolation and culture.

BACKGROUND AIMS: As new approaches for peripheral nerve regeneration are sought, there is an increasing demand for native Schwann cells for in vitro testing and/or reimplantation. Extracorporeal shockwave treatment (ESWT) is an emergent technology in the field of regenerative medicine that has also recently been shown to improve peripheral nerve regeneration. METHODS: In this study, we elucidate the effects of ESWT on Schwann cell isolation and culture. Rat sciatic nerves were dissected and treated with ESWT, and Schwann cells were isolated and cultured for 15 passages. RESULTS: Single treatment of the whole nerve ex vivo led to significantly increased extracellular adenosinetriphosphate as an immediate consequence, and subsequently a number of effects on the culture were observed, starting with a significantly increased Schwann cell yield after isolation. In the ESWT group, the quality of culture, reflected in consistently higher purity (S100b, morphology), proliferation rate (5-bromo-2-deoxyuridine, population doublings per passage) and expression of regenerative phenotype-associated markers (P75, glial fibrillary acidic protein, c-Jun), was significantly improved. In contrast, the control group exhibited progressively senescent behavior, reflected in a decrease of proliferation, loss of specific markers and increase in P16(INK4A) expression. CONCLUSIONS: ESWT has beneficial effects on Schwann cell isolation and culture.

Activated Schwann Cell-Like Cells on Aligned Fibrin-Poly(Lactic-Co-Glycolic Acid) Structures: A Novel Construct for Application in Peripheral Nerve Regeneration.

Tissue engineering approaches in nerve regeneration search for ways to support gold standard therapy (autologous nerve grafts) and to improve results by bridging nerve defects with different kinds of conduits. In this study, we describe electrospinning of aligned fibrin-poly(lactic-co-glycolic acid) (PLGA) fibers in an attempt to create a biomimicking tissue-like material seeded with Schwann cell-like cells (SCLs) in vitro for potential use as an in vivo scaffold. Rat adipose-derived stem cells (rASCs) were differentiated into SCLs and evaluated with flow cytometry concerning their differentiation and activation status [S100b, P75, myelin-associated glycoprotein (MAG), and protein 0 (P0)]. After receiving the proliferation stimulus forskolin, SCLs expressed S100b and P75; comparable to native, activated Schwann cells, while cultured without forskolin, cells switched to a promyelinating phenotype and expressed S100b, MAG, and P0. Human fibrinogen and thrombin, blended with PLGA, were electrospun and the alignment and homogeneity of the fibers were proven by scanning electron microscopy. Electrospun scaffolds were seeded with SCLs and the formation of Büngner-like structures in SCLs was evaluated with phalloidin/propidium iodide staining. Carrier fibrin gels containing rASCs acted as a self-shaping matrix to form a tubular structure. In this study, we could show that rASCs can be differentiated into activated, proliferating SCLs and that these cells react to minimal changes in stimulus, switching to a promyelinating phenotype. Aligned electrospun fibrin-PLGA fibers promoted the formation of Büngner-like structures in SCLs, which also rolled the fibrin-PLGA matrix into a tubular scaffold. These in vitro findings favor further in vivo testing.

Urine toxicology screening in Austrian trauma patients: a prospective study.

INTRODUCTION: The question as to whether the patient consumed drugs prior to the trauma and which drugs were consumed, is of prime importance for the anesthesia required during surgery. However, many patients are unwilling or unable (including those with multiple trauma or impaired consciousness, or unconscious patients) to answer this question. The purpose of our prospective multicenter study was to collect data about drug consumption in Austria to determine whether drugs are identifiable in the urine of recently injured individuals and to establish the types of drugs consumed. MATERIALS AND METHODS: This prospective study included severely and moderately injured patients admitted to the Lorenz Boehler Trauma Hospital (Vienna, Austria), the Trauma Hospital Linz (Linz, Austria) and the Department of Trauma Surgery of the General Hospital Horn (Horn, Austria) during an 18-month period (October 2003-March 2005). All patients were suffering from injuries urgently requiring surgery. Urine samples were gained from all patients immediately after admission. Urinary samples were tested by Immuno-Assay (Triage 8 Immuno-Assay, Biosite, San Diego, USA). Urine samples were screened simultaneously for opiates, methadone, cocaine, barbiturates, amphetamines, cannabinoids, benzodiazepines and tricyclic antidepressants. RESULTS: Our prospective study included a total of 664 patients (320 from Vienna, 193 from the city of Linz, and 151 from Horn). Six hundred and forty-two patients were moderately injured (ISS < 16), suffering mostly from injuries to the extremities (504 patients) and 22 patients were severely injured (ISS > 16). Of the 664 patients, 178 (26.8%) tested positive for one or more drugs. The drugs most commonly detected were benzodiazepines (111 patients, 16.7%), cannabinoides (39 patients, 6%), tricyclic antidepressants (28, 4.2%) and opiates (26, 3.9%). CONCLUSION: Drug use is widespread in patients presenting to urban trauma centers in Austria. Physicians should maintain a high index of suspicion that their patients may be intoxicated and should perform drug testing routinely.

A New Rehabilitative Mechanism in Primary Motor Cortex After Peripheral Trauma.

Homuncular organization, i.e., the neuronal representation of the human body within the primary motor cortex, is one of the most fundamental principles of the human brain. Despite this, in rare peripheral nerve surgery patients, the transformation of a monofunctional (diaphragm activation) into a bifunctional motor area (diaphragm and arm activation is controlled by the same cortical area) has previously been demonstrated. The mechanisms behind this transformation are not fully known. To investigate this transformation of a monofunctional area we investigate functional connectivity changes in a unique and highly instructive pathophysiological patient model. These patients suffer from complete brachial plexus avulsion with arm paralysis and had been treated with reconnection of the end of the musculocutaneous nerve to the side of a fully functional phrenic nerve to regain function. Task-based functional connectivity between the arm representations and the diaphragm (phrenic nerve) representations were examined in six patients and 12 aged matched healthy controls at ultra-high field MRI while they either performed or tried isolated elbow flexion or conducted forced abdominal inspiration. Functional connectivity values are considerably increased between the diseased arm and the bilateral diaphragm areas while trying strong muscle tension in the diseased arm as compared to the healthy arm. This effect was not found as compared to the healthy arm in the patient group. This connectivity was stronger between ipsilateral than between corresponding contralateral brain regions. No corresponding differences were found in healthy subjects. Our data suggests that the increased functional connectivity between the deprived arm area and the diaphragm area drives biceps muscle function. From this findings we infer that this new rehabilitative mechanism in the primary motor cortex may establish new intrahemispheric connections within the brain and the motor cortex in particular to reroute the output of a completely denervated motor area. This study extend current knowledge about neuroplasticity within the motor cortex.

Spatiotemporal Differences in Gene Expression Between Motor and Sensory Autografts and Their Effect on Femoral Nerve Regeneration in the Rat.

To improve the outcome after autologous nerve grafting in the clinic, it is important to understand the limiting variables such as distinct phenotypes of motor and sensory Schwann cells. This study investigated the properties of phenotypically different autografts in a 6 mm femoral nerve defect model in the rat, where the respective femoral branches distally of the inguinal bifurcation served as homotopic, or heterotopic autografts. Axonal regeneration and target reinnervation was analyzed by gait analysis, electrophysiology, and wet muscle mass analysis. We evaluated regeneration-associated gene expression between 5 days and 10 weeks after repair, in the autografts as well as the proximal, and distal segments of the femoral nerve using qRT-PCR. Furthermore we investigated expression patterns of phenotypically pure ventral and dorsal roots. We identified highly significant differences in gene expression of a variety of regeneration-associated genes along the central - peripheral axis in healthy femoral nerves. Phenotypically mismatched grafting resulted in altered spatiotemporal expression of neurotrophic factor BDNF, GDNF receptor GFRα1, cell adhesion molecules Cadm3, Cadm4, L1CAM, and proliferation associated Ki67. Although significantly higher quadriceps muscle mass following homotopic nerve grafting was measured, we did not observe differences in gait analysis, and electrophysiological parameters between treatment paradigms. Our study provides evidence for phenotypic commitment of autologous nerve grafts after injury and gives a conclusive overview of temporal expression of several important regeneration-associated genes after repair with sensory or motor graft.

Nerve fiber transfer by end-to-side coaptation.

To bring some light into the ongoing controversy concerning end-to-side coaptation in brachial plexus surgery, the authors organized a symposium in 2006 titled How To Improve Peripheral Nerve Surgery. The authors sought the participation of experienced surgeons and researchers who had made personal contributions to the field. This article contains information collected at this symposium and presents the authors' clinical results and ideas illustrating the potential of nerve fiber transfer by end-to-side coaptation.

Peripheral Nervous System Reconstruction Reroutes Cortical Motor Output-Brain Reorganization Uncovered by Effective Connectivity.

Cortical reorganization in response to peripheral nervous system damage is only poorly understood. In patients with complete brachial plexus avulsion and subsequent reconnection of the end of the musculocutaneous nerve to the side of a phrenic nerve, reorganization leads to a doubled arm representation in the primary motor cortex. Despite, homuncular organization being one of the most fundamental principles of the human brain, movements of the affected arm now activate 2 loci: the completely denervated arm representation and the diaphragm representation. Here, we investigate the details behind this peripherally triggered reorganization, which happens in healthy brains. fMRI effective connectivity changes within the motor network were compared between a group of patients and age matched healthy controls at 7 Tesla (6 patients and 12 healthy controls). Results show the establishment of a driving input of the denervated arm area to the diaphragm area which is now responsible for arm movements. The findings extend current knowledge about neuroplasticity in primary motor cortex: a denervated motor area may drive an auxilliary area to reroute its motor output.

Hydrogel composition and laser micropatterning to regulate sciatic nerve regeneration.

Treatment of peripheral nerve injuries has evolved over the past several decades to include the use of sophisticated new materials endowed with trophic and topographical cues that are essential for in vivo nerve fibre regeneration. In this research, we explored the use of an advanced design strategy for peripheral nerve repair, using biological and semi-synthetic hydrogels that enable controlled environmental stimuli to regenerate neurons and glial cells in a rat sciatic nerve resection model. The provisional nerve growth conduits were composed of either natural fibrin or adducts of synthetic polyethylene glycol and fibrinogen or gelatin. A photo-patterning technique was further applied to these 3D hydrogel biomaterials, in the form of laser-ablated microchannels, to provide contact guidance for unidirectional growth following sciatic nerve injury. We tested the regeneration capacity of subcritical nerve gap injuries in rats treated with photo-patterned materials and compared these with injuries treated with unpatterned hydrogels, either stiff or compliant. Among the factors tested were shear modulus, biological composition, and micropatterning of the materials. The microchannel guidance patterns, combined with appropriately matched degradation and stiffness properties of the material, proved most essential for the uniform tissue propagation during the nerve regeneration process.

Infusion of increasing doses of endotoxin induces progressive acute lung injury but prevents early pulmonary hypertension in pigs.

Administration of a single bolus of endotoxin is a model of sepsis response in experimental animal studies. Large animal species, such as pigs and sheep, are more sensitive to endotoxin administration due to an initial excessive pulmonary hypertensive response frequently resulting in acute right heart dysfunction. We investigated whether infusion of high-dose endotoxin in pigs but administered in an increasing dose results in inflammatory response without excessive pulmonary hypertension and right heart dysfunction. Piglets of both sexes weighing 25 to 30 kg were anesthetized and mechanically ventilated. After instrumentation and baseline measurements, animals received an infusion of total 500 microg kg(-1) i.v. endotoxin (Escherichia coli LPS) over 2 h in an increasing dose of 0.5 to 12 microg kg(-1) min(-1). Hemodynamic, respiratory, and oxygenation parameters were measured every hour. At 1 and 5 h following endotoxin, plasma levels of inflammatory and organ damage parameters were measured. Endotoxin infusion induced progressive arterial hypoxemia, an increase in peak inspiratory pressure, sustained pulmonary hypertension, and systemic hypotension that persisted throughout the experiment. Endotoxin plasma levels peaked at 1 h following infusion and declined toward baseline values at 5 h thereafter. In contrast, plasma levels of nitrite/nitrate, IL-1ra (as marker of cytokine response), remained markedly increased at 5 h after endotoxin infusion as compared with baseline values. Plasma markers of organ damage were significantly increased. Our data show that the dosing of endotoxin in an increasing manner in pigs produces a reliable model of an experimental sepsis response and organ dysfunction without immediate overwhelming pulmonary hypertension resulting in cardiovascular failure.

Pathophysiological advantages of rinsing-suction-reaming (RSR) in a pig model for intramedullary nailing.

Although reamed intramedullary nailing has been one of the greatest advances in modern fracture care, the concomitant increase in medullary cavity pressure leads to intravasation of bone marrow content into the blood stream, an effect that can evoke serious systemic reactions. A newly developed rinsing-suction-reamer (RSR) was able to substantially reduce the pressure and bone marrow intravasation content during experimental femoral nailing. We investigated the pathophysiological effects using the RSR, testing the hypothesis that by reducing marrow fat embolization, RSR would also reduce the activation of coagulation compared with the universal AO-Reamer (AOR) and comparable to external fixation. Twenty-two pigs were treated with either simulated external fixation or reamed femoral nailing using AOR or RSR. During surgery, the intramedullary pressure was measured and intravasation of medullary material was quantified. After surgery, the pigs were kept anaesthetised and monitored for 6 h. At defined intervals, serological, hematological, and hemodynamic parameters were evaluated. The RSR was significantly superior when compared to AOR with regard to the generation of intramedullary pressure and fat embolization; however, with external fixation the values were even lower. The evaluation of other parameters revealed no clear differences between the two reamers and the external fixator. The pig model showed that RSR led to a significant reduction of the intramedullary increase in pressure and fat intravasation compared to AOR. Although the reduction of fat embolism by RSR is not associated with pathophysiological changes, RSR can have advantages for the treatment of femoral fractures.

Inhibition of calpains fails to improve regeneration through a peripheral nerve conduit.

Intramuscular injection of the calpain inhibitor leupeptin promotes peripheral nerve regeneration in primates (Badalamente et al., 1989 [13]), and direct positive effects of leupeptin on axon outgrowth were observed in vitro (Hausott et al., 2012 [12]). In this study, we applied leupeptin (2mg/ml) directly to collagen-filled nerve conduits in the rat sciatic nerve transection model. Analysis of myelinated axons and retrogradely labeled motoneurons as well as functional 'CatWalk' video analysis did not reveal significant differences between vehicle controls and leupeptin treated animals. Therefore, leupeptin does not improve nerve regeneration via protease inhibition in regrowing axons or in surrounding Schwann cells following a single application to a peripheral nerve conduit suggesting indirect effects on motor endplate integrity if applied systemically.

Improved rate of peripheral nerve regeneration induced by extracorporeal shock wave treatment in the rat.

De-focused low energy extracorporeal shock wave therapy (ESWT) has been widely used in various clinical and experimental models for the treatment of painful conditions such as epicondylitis and plantar fascitis and also bone and wound healing. There is evidence that ESWT improves the metabolic activity of various cell types, e.g. chondrocytes and endothelial cells but little is known about its effects on nervous tissue. The aim of this study was to investigate whether ESWT improves the regeneration of injured nerves in an experimental rat model. Sprague-Dawley rats received an 8mm long homotopic nerve autograft into the right sciatic nerve, fixed with epineurial sutures. Two experimental groups were set up: the group 1 animals received ESWT (300 impulses, 3 Hz) immediately after nerve grafting whereas the group 2 (control) animals received only nerve autografts. Serial CatWalk automated gait analysis, electrophysiological studies and morphological investigations were carried out. The survival time was either 3 weeks or 3 months. At 6 to 8 weeks of survival the ESWT group of animals exhibited a significantly improved functional recovery relative to the controls. Electrophysiological observations at 3 weeks after surgery revealed marked values of amplitude (3.9±0.8 mV, S.E.M.) and compound nerve action potential (CNAP, 5.9±1.4 mV·ms, S.E.M.) in the ESWT group, whereas there were no detectable amplitudes in the control group. This finding was accompanied by significantly greater numbers of myelinated nerve fibres in the middle of the graft (4644±170 [S.E.M., ESWT] vs 877±68 [S.E.M., control]) and in the distal stump (1586±157 [S.E.M., ESWT] vs 308±29 [S.E.M., control]) of ESWT animals relative to the controls 3 weeks after surgery. Three weeks after surgery the nerve grafts of control animals contained great numbers of phagocytes and unmyelinated nerve fibres, while the ESWT nerve grafts were filled with well-myelinated regenerating axons. There was no significant difference between the numbers of endoneural vessels in the ESWT and the control nerves. Three months after surgery, no significant differences were observed in the functional and electrophysiological data. Equally high numbers of myelinated axons distal to the graft could be found in both groups (7693±673 [S.E.M., ESWT] vs 6090±716 [S.E.M., control]). These results suggest that ESWT induces an improved rate of axonal regeneration, this phenomenon probably involving faster Wallerian degeneration, the improved removal of degenerated axons and a greater capacity of the injured axons to regenerate.

An fMRI marker for peripheral nerve regeneration.

Final outcome after surgical repair of peripheral nerve transections varies. Here, we present the first longitudinal functional magnetic resonance imaging (fMRI) observation of cortical somatosensory reorganization patterns after surgery. A 43-year-old man presented with isolated complete transection of the right median nerve and underwent immediate epineural end-to-end coaptation. Applying standardized vibrotactile median nerve stimulation, 3 T brain activation maps were evaluated at 1, 7, 15 weeks and 1 year after surgery. Initially, the affected hemisphere showed no primary activation but increased frontoparietal activity. After 1 year, primary activation had recovered, and frontoparietal activity was decreased relative to the nonaffected hemisphere. Based on these longitudinal fMRI patterns, we propose a new marker for restoration of somatosensory function, which may not be provided by electrophysiological methods.

New type of cortical neuroplasticity after nerve repair in brachial plexus lesions.

BACKGROUND: In brachial plexus avulsion, a recent technique connects the ending of the disrupted musculocutaneous nerve to the side of the intact phrenic nerve to regain elbow flexion. This requires the phrenic nerve to perform a new double function: independent control of breathing and elbow flexion. Neuroplastic changes associated with acquisition of double nerve functions have not yet been investigated. OBJECTIVE: To evaluate neuroplastic changes associated with acquisition of double nerve functions in a monofunctional nerve (phrenic nerve). DESIGN: Clinical and functional magnetic resonance imaging investigations during arm movements, forced inspiration, and motor control tasks. SETTING: Investigations at the Medical University of Vienna, Vienna, Austria. PARTICIPANTS: Three healthy control subjects, 2 patients with phrenic nerve end-to-side coaptation, and 1 control patient with C7 end-to-end coaptation (same clinical presentation but phrenic nerve unchanged). RESULTS: Clinical documentation showed that both patients with phrenic nerve end-to-side coaptation were able to control the diaphragm and the biceps independently via the same phrenic nerve. In contrast to all controls, both patients with phrenic nerve end-to-side coaptation activated the cortical diaphragm areas with flexion of the diseased arm. CONCLUSION: Our functional magnetic resonance imaging data indicate that the patient's cortical diaphragm areas reorganize in such a way that independent control of breathing and elbow flexion is possible with the same neuronal population.

Assessment of bone union/nonunion in an experimental model using microcomputed technology.

BACKGROUND: High-resolution microcomputed tomography (microCT) is one of the most recent technical developments to visualize and quantify primarily cancellous bone. Regarding bone formation, microCT is becoming increasingly important, although its reliability has not yet been evaluated. Our study had two goals: to develop a reproducible nonunion model and to determine the efficacy of microCT for the assessment of bone healing in this model. METHODS: The designed fracture model in the rat simulates secondary fracture healing. After plate fixation to the femur, diaphysis transverse middiaphyseal osteotomy was performed with a reciprocating saw, resulting in a 0.38-mm gap with a defect of bone and periosteum corresponding to the thickness of the blade. Proximally and distally to this gap, the periosteum was preserved. Thus, three separate zones were defined: proximal femur diaphysis with periosteum, gap, and distal femur diaphysis with periosteum. In the nonunion group (NM group), a model of impaired bone healing (nonunion), silicone foil was wrapped around the femur diaphysis to block any influence from surrounding tissue. Coverage of the bone repair site by thigh muscles was designed for a model of bone union (M group). Four weeks postoperatively, callus formation was determined by conventional anterior-posterior and lateral plain radiographs. Ten weeks later, a second x-ray series was done as the clinical standard evaluation method. Afterward, specimens were harvested for microCT examination (two-dimensional and three-dimensional [3D]). Biomechanical testing was carried out to determine fracture healing. RESULTS: Our model is highly reproducible and results in bone nonunion in five out of six cases (83.3%). In determining fracture site, plain radiographs the least reliable method in comparison to the biomechanical testing which is the most accurate reference method. In contrast, microCT (the 3D reconstruction) showed significant correlation (r = 1) to the results assessed by biomechanical testing, whereas microCT was correct in 100%. We found bone healing in five out of six animals in the M group verified by microCT (in accordance to biomechanical data). In the M group, significantly enhanced bone formation (50%) (p = 0.008) was observed within the osteotomy site (i.e. within the gap), but there was no difference in periosteal bone formation between the groups proximally and distally to the gap. Interestingly, we did not find statistically significant differences in mineralization. CONCLUSION: We conclude that microCT with 3D reconstruction is the optimal method diagnostic tool in fracture healing, especially in nonunion. Furthermore, direct coverage of the fracture site by muscle flaps results in a mineralized enhanced bone formation within the osteotomy site (i.e. within the gap). Skeletal muscle coverage hypothetically might have osteogenic augmentation potential, thus being able to prevent pseudoarthrosis.

Bilateral lower leg replantation versus prosthetic replacement: long-term outcome of amputation after an occupational railroad accident.

BACKGROUND: This retrospective study investigated three very similar cases of bilateral lower leg amputation. The aim was to determine which of two therapeutical procedures is associated with better long-term outcome: replantation or primary treatment of the stumps and subsequent prosthetic replacement. METHODS: Evaluation included clinical examination, gait analysis, and a workup of the psychosocial background. Health problems were documented using the Nottingham Health Profile. Follow-up assessments were performed 6, 7, and 18 years after the trauma. RESULTS: One patient underwent successful bilateral lower leg replantation and continued to work for the same employer. Two patients underwent prosthetic replacement. One became a social outcast confined to a wheelchair. The other patient had a good psychosocial background, similar to that of the patient who underwent replantation. He showed a better gait analysis on even ground than the replantation patient, but the findings were vice versa for uneven ground. CONCLUSIONS: The decision between replantation and prosthetic replacement after bilateral lower leg amputation is case related and cannot be generalized. Patients who have undergone these procedures require long-term psychological and physiotherapeutic care to achieve a good long-term surgical outcome.

Alleviated tension at the repair site enhances functional regeneration: the effect of full range of motion mobilization on the regeneration of peripheral nerves--histologic, electrophysiologic, and functional results in a rat model.

BACKGROUND: In the clinical management of combined tendon and nerve injuries, competing treatment strategies are well known. The effect of mobilization on the functional regeneration of peripheral nerves remains controversial. This study sought to determine the effect of full range of motion mobilization on nerve repair by using tubular segmental nerve splinting to block movement, and thereby variable tension, at the nerve repair site. METHODS: In 96 rats, the right sciatic nerve was transected midthigh and coapted immediately microsurgically. The groups used in the study were as follows: group N, epineural nerve repair; group T, segmental tubular nerve splinting with fixed in situ tension at the nerve suture site,allowing segmental movement only; group TN, segmental tubular nerve splinting with alleviated in situ tension at the nerve suture site, allowing segmental movement only; and group TM, segmental tubular nerve splinting without fixed in situ tension at the nerve suture site, allowing movement of the nerve suture site. Full range of motion of the lower limbs was ensured by passive motion of hind limbs once a week after functional testing. Blinded histologic, immunohistochemical, and electrophysiologic assessment and 12 postoperative weekly function tests were carried out. RESULTS: Functional and electrophysiologic results were significantly better in group TN, by segmental tubular nerve splinting with alleviated in situ tension at the nerve repair site, mainly because of less scar formation and enhanced endoneural angiogenesis at the nerve suture segment. CONCLUSION: Full range of motion mobilization may impede functional nerve recovery by significant endoneural collagenization and decreased angiogenesis at the nerve suture segment. Complete alleviation of in situ (pathophysiologic) tension at the nerve suture site seems to improve functional peripheral nerve regeneration.