Vascularized Nerve Grafts for Lower Extremity Nerve Reconstruction

A systematic review of clinical and laboratory studies comparing vascularised versus non-vascularised nerve grafts in peripheral nerve reconstruction

BACKGROUND

Peripheral nerve injuries (PNIs) are common, with complex defects posing a significant reconstructive challenge. Although vascularised (VNGs) and non-vascularised nerve grafts (NVNGs) are established treatment options, there is no comprehensive summary of the evidence supporting their clinical, electrophysiological, and histological outcomes. This review aims to systematically evaluate the clinical and laboratory literature comparing VNGs and NVNGs to inform future clinical practice and research.

METHODS

This review was prospectively registered and reported according to PRISMA guidelines. PubMed, EMBASE, SCOPUS, and the Cochrane Register were systematically searched. Studies comparing VNGs and NVNGs in PNIs were included. Meta-analyses were performed for outcomes reported in ≥3 laboratory studies. Functional outcomes were synthesised by vote-counting based on direction of effect for clinical studies. Risk-of-bias was assessed using RoB2, ROBINS-I, and SYRCLE, and the certainty of evidence was evaluated using GRADE.

RESULTS

Seven clinical and 34 laboratory studies were included. Of the clinical comparisons, 90% and 56% identified an effect on recovery of sensibility (p = 0.01) and motor function (p = 0.05), respectively, that favoured VNGs. Nine (of 13) separate meta-analyses of laboratory studies demonstrated reduced muscular atrophy, superior axonal regeneration, and remyelination in VNGs. VNGs eliminated the 3-day interval of ischaemia otherwise sustained by NVNGs. Overall, the quality of evidence was low.

CONCLUSION

This systematic review indicates that VNGs may offer some advantages over NVNGs in PNI reconstruction. However, due to the low quality of evidence, significant statistical heterogeneity, and clinical diversity of the included studies, these conclusions should be interpreted with caution. Further high-quality clinical trials are necessary to validate these findings.

Surgical management of peroneal nerve injuries

BACKGROUND

Traumatic peroneal nerve injuries are typically associated with high-energy injuries. The aim of this study was to evaluate the demographics and outcomes following surgical management of peroneal nerve injuries.

METHODS

Patients evaluated at a single institution with peroneal nerve injuries between 2001 and 2022 were retrospectively reviewed. Mechanism of injury, time to surgery, pre- and postoperative examinations, and operative reports were recorded. Satisfactory outcome, defined as the ability to achieve anti-gravity dorsiflexion strength or stronger following surgery, was compared between nerve grafting and nerve transfers in patients with at least 9 months of postoperative follow-up.

RESULTS

Thirty-seven patients had follow-up greater than 9 months after surgery, with an average follow-up of 3.8 years. Surgeries included neurolysis (n=5), direct repair (n=2), tibial motor nerve fascicle transfer to the anterior tibialis motor branch (n=18), or interposition nerve grafting using sural nerve autograft (n=12). At last follow-up, 59.5% (n=22) of patients had anti-gravity strength or stronger dorsiflexion. Nineteen (51.4%) patients used an ankle-foot orthosis during all or some activities. In patients that underwent nerve grafting only across the peroneal nerve defect, 44.4% (n=4) were able to achieve anti-gravity strength or stronger dorsiflexion. In patients that had a tibial nerve fascicle transfer to the tibialis anterior motor branch of the peroneal nerve, 42.9% (n=6) were able to achieve anti-gravity strength or stronger dorsiflexion at last follow-up. There was no statistical difference between nerve transfers and nerve grafting in postoperative dorsiflexion strength (p = 0.51).

CONCLUSION

Peroneal nerve injuries frequently occur in the setting of knee dislocations and similar high-energy injuries. Nerve surgery is not universally successful in restoration of ankle dorsiflexion, with one-third of patients requiring an ankle-foot orthosis at mid-term follow-up. Patients should be properly counseled on the treatment challenges and variable outcomes following peroneal nerve injuries.

Restoration of hamstring function following sciatic nerve resection at the greater sciatic foramen with reconstruction involving acellular nerve allograft and vascularized sural nerve autograft: A case report

Segmental loss of the sciatic nerve secondary to oncologic resection or trauma is detrimental to hamstring and leg function. The diameter of this nerve and the length of its axons spanning the lower extremity create significant challenges in reconstruction and optimizing return of sensory or motor function. The purpose of this report is to describe outcomes of a free vascularized sural nerve graft to preserve hamstring function in a large proximal sciatic nerve defect beginning at the greater sciatic foramen. A 44-year-old female underwent neoadjuvant chemotherapy and radiation for treatment of a left sciatic nerve synovial cell sarcoma. The patient underwent R0 resection of the proximal left sciatic nerve resulting in a 15 cm defect. An ipsilateral vascularized sural nerve graft was used to reconstruct the medial aspect of the sciatic nerve, prioritizing the tibial division, in an effort to restore hamstring function and plantar sensation. A 5 cm allograft nerve was added to the cutaneous branches of the sural nerve graft to better span the large defect and reconstruct the lateral aspect of the nerve. The patient's postoperative course was uneventful. At 1-year follow-up, the patient showed MRC grade 4/5 strength with knee flexion and steady gait pattern with a left ankle-foot orthosis. Outcomes support the use of a single vascularized nerve graft alongside acellular nerve allograft to restore motor function in large diameter and large defect mixed nerve injuries.

Traumatic Peroneal Nerve Injuries: A Systematic Review

BACKGROUND

The common peroneal nerve (CPN) is the most commonly injured peripheral nerve of the lower extremity in patients with trauma. Traumatic CPN injuries have historically been associated with relatively poor outcomes and patient satisfaction, although improved surgical technique and novel procedures appear to improve outcomes. Given the variety of underlying injury modalities, treatment options, and prognostic variables, we sought to evaluate and summarize the current literature on traumatic CPN injuries and to provide recommendations from an analysis of the included studies for treatment and future research.

METHODS

A systematic review was performed using PubMed, Embase, and Cochrane databases per the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Search terms consisted of variations of "peroneal nerve" or "fibular nerve" combined with "injury," "laceration," "entrapment," "repair," or "neurolysis." Information with regard to treatment modality, outcomes, and patient demographic characteristics was recorded and analyzed.

RESULTS

The initial search yielded 2,301 articles; 42 met eligibility criteria. Factors associated with better outcomes included a shorter preoperative interval, shorter graft length when an interposed graft was used, nerve continuity, and younger patient age. Gender or sex was not mentioned as a factor affecting outcomes in any study. Motor grades of ≥M3 on the British Medical Research Council (MRC) scale are typically considered successful outcomes. This was achieved in 81.4% of patients who underwent neurolysis, 78.8% of patients who underwent end-to-end suturing, 49.0% of patients who underwent nerve grafting, 62.9% of patients who underwent nerve transfer, 81.5% of patients who underwent isolated posterior tibial tendon transfer (PTTT), and 84.2% of patients who underwent a surgical procedure with concurrent PTTT.

CONCLUSIONS

Studies included in this review were heterogenous, complicating our ability to perform further analysis. It is not possible to uniformly advocate for the best treatment option, given diverse injury modalities and patient presentations and a variety of prognostic factors. Many studies do not show outcomes with respect to injury modality. Future studies should show preoperative muscle strengths and should clearly define outcomes based on the injury modality and surgical treatment option. This would allow for greater analysis of the most appropriate treatment option for a given mechanism of injury. Newer surgical techniques are promising and should be further explored.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Nerve recovery from treatment with a vascularized nerve graft compared to an autologous non-vascularized nerve graft in animal models: A systematic review and meta-analysis

Background

Treatment of nerve injuries proves to be a worldwide clinical challenge. Vascularized nerve grafts are suggested to be a promising alternative for bridging a nerve gap to the current gold standard, an autologous non-vascularized nerve graft. However, there is no adequate clinical evidence for the beneficial effect of vascularized nerve grafts and they are still disputed in clinical practice.

Objective

To systematically review whether vascularized nerve grafts give a superior nerve recovery compared to non-vascularized nerve autografts regarding histological and electrophysiological outcomes in animal models.

Material and methods

PubMed and Embase were systematically searched. The inclusion criteria were as follows: 1) the study was an original full paper which presented unique data; 2) a clear comparison between a vascularized and a non-vascularized autologous nerve transfer was made; 3) the population study were animals of all genders and ages. A standardized mean difference and 95% confidence intervals for each comparison was calculated to estimate the overall effect. Subgroup analyses were conducted on graft length, species and time frames.

Results

Fourteen articles were included in this review and all were included in the meta-analyses. A vascularized nerve graft resulted in a significantly larger diameter, higher nerve conduction velocity and axonal count compared to an autologous non-vascularized nerve graft. However, during sensitivity analysis the effect on axonal count disappeared. No significant difference was observed in muscle weight.

Conclusion

Treating a nerve gap with a vascularized graft results in superior nerve recovery compared to non-vascularized nerve autografts in terms of axon count, diameter and nerve conduction velocity. No difference in muscle weight was seen. However, this conclusion needs to be taken with some caution due to the inherent limitations of this meta-analysis. We recommend future studies to be performed under conditions more closely resembling human circumstances and to use long nerve defects.

Outcomes of Tibial Nerve Repair and Transfer: A Structured Evidence-Based Systematic Review and Meta-Analysis

Although nerve transfer and repair are well-established for treatment of nerve injury in the upper extremity, there are no established parameters for when or which treatment modalities to utilize for tibial nerve injuries. The objective of our study is to conduct a systematic review of the effectiveness of end-to-end repair, neurolysis, nerve grafting, and nerve transfer in improving motor function after tibial nerve injury. PubMed, Cochrane, Medline, and Embase libraries were queried according to the PRISMA guidelines for articles that present functional outcomes after tibial nerve injury in humans treated with nerve transfer or repair. The final selection included Nineteen studies with 677 patients treated with neurolysis (373), grafting (178), end-to-end repair (90), and nerve transfer (30), from 1985 to 2018. The mean age of all patients was 27.0 ± 10.8 years, with a mean preoperative interval of 7.4 ± 10.5 months, and follow-up period of 82.9 ± 25.4 months. The mean graft repair length for nerve transfer and grafting patients was 10.0 ± 5.8 cm, and the most common donor nerve was the sural nerve. The most common mechanism of injury was gunshot wound, and the mean MRC of all patients was 3.7 ± 0.6. Good outcomes were defined as MRC ≥ 3. End-to-end repair treatment had the greatest number of good outcomes, followed by neurolysis. Patients with preoperative intervals less than 7 months were more likely to have good outcomes than those greater than 7 months. Patients with sport injuries had the highest percentage of good outcomes in contrast to patients with transections and who were in MVAs. We found no statistically significant difference in good outcomes between the use of sural and peroneal donor nerve grafts, nor between age, graft length, and MRC score.

Advancements in Reconstructive Surgery Broaden Opportunities for Salvage of the Injured Lower Extremity

Advancements in microsurgery have made lower extremity reconstruction possible even after major soft tissue loss or tibial nerve disruption. There is an ongoing paradigm shift in the indications for amputation versus salvage and in flap selection protocols for different areas of the lower extremity. Initial evaluation, patient selection, triage, and timing of reconstruction are essential factors that can influence functional and aesthetic outcomes. The emergence of perforator flaps and the application of new concepts such as free-style flaps, propeller perforator flaps, thinning of free flaps, and supermicrosurgery have provided reconstructive surgeons with many techniques to decrease donor-site morbidity and improve outcomes. This includes options for reconstruction on extremities with single or no adequate runoff vessels. We present a review of the major advancements in reconstructive surgery for salvage of the traumatic lower extremity.

The role of vascularization in nerve regeneration of nerve graft

Vascularization is an important factor in nerve graft survival and function. The specific molecular regulations and patterns of angiogenesis following peripheral nerve injury are in a broad complex of pathways. This review aims to summarize current knowledge on the role of vascularization in nerve regeneration, including the key regulation molecules, and mechanisms and patterns of revascularization after nerve injury. Angiogenesis, the maturation of pre-existing vessels into new areas, is stimulated through angiogenic factors such as vascular endothelial growth factor and precedes the repair of damaged nerves. Vascular endothelial growth factor administration to nerves has demonstrated to increase revascularization after injury in basic science research. In the clinical setting, vascularized nerve grafts could be used in the reconstruction of large segmental peripheral nerve injuries. Vascularized nerve grafts are postulated to accelerate revascularization and enhance nerve regeneration by providing an optimal nutritional environment, especially in scarred beds, and decrease fibroblast infiltration. This could improve functional recovery after nerve grafting, however, conclusive evidence of the superiority of vascularized nerve grafts is lacking in human studies. A well-designed randomized controlled trial comparing vascularized nerve grafts to non-vascularized nerve grafts involving patients with similar injuries, nerve graft repair and follow-up times is necessary to demonstrate the efficacy of vascularized nerve grafts. Due to technical challenges, composite transfer of a nerve graft along with its adipose tissue has been proposed to provide a healthy tissue bed. Basic science research has shown that a vascularized fascial flap containing adipose tissue and a vascular bundle improves revascularization through excreted angiogenic factors, provided by the stem cells in the adipose tissue as well as by the blood supply and environmental support. While it was previously believed that revascularization occurred from both nerve ends, recent studies propose that revascularization occurs primarily from the proximal nerve coaptation. Fascial flaps or vascularized nerve grafts have limited applicability and future directions could lead towards off-the-shelf alternatives to autografting, such as biodegradable nerve scaffolds which include capillary-like networks to enable vascularization and avoid graft necrosis and ischemia.

Long-Term Outcomes of Digital Nerve Repair Accompanied by Digital Artery Injury in Flexor Zone 2

Objectives  Better healing results of any tissue or area is closely linked with a well-blood supply in reconstructive surgery. Peripheric nerve healing is closely related to blood supply as well. We aimed to assess whether there was any difference between digital nerve healing with and without extrinsic blood supply.

Methods  We assessed 48 patients with unilateral digital nerve injury at zone 2. Twenty-four of them had unrepairable arterial injury and other 24 had no arterial injury. The 24 patients in the “unrepaired artery group” (UA) and 24 patients in the “intact artery group” (IA) were compared.

Results  Mean follow-up time was 17.7 months. The mean two-point discrimination (2PD) was 5.29 mm in IA group and 5.37 mm in UA group. One neuroma in IA group and two neuromas in UA group were determined. We found no statistically significant difference between these groups in terms of neuroma, 2PD, and cold intolerance. The results of British Medical Research Council sensory recovery clinical scale were comparable for these two groups.

Conclusion  Digital nerve healing is related to numerous factors. We hypothesized that blood flow may be one of these factors; however, at this zone digital artery repair is not the foremost determinant for digital nerve healing. Further researches should be done for upper injury levels. Despite this result, we argue not to leave the digital artery without repairment and we propose to repair both artery and nerve to achieve the normal anatomical integrity and to warrant finger blood flow in possible future injuries.

The Surgical Management of Nerve Gaps: Present and Future

Peripheral nerve injuries can result in significant morbidity, including motor and/or sensory loss, which can affect significantly the life of the patient. Nowadays, the gold standard for the treatment of nerve section is end-to-end neurorrhaphy. Unfortunately, in some cases, there is segmental loss of the nerve trunk. Nerve mobilization allows primary repair of the sectioned nerve by end-to-end neurorrhaphy if the gap is less than 1 cm. When the nerve gap exceeds 1 cm, autologous nerve grafting is the gold standard of treatment. To overcome the limited availability and the donor site morbidity, other techniques have been used: vascularized nerve grafts, cellular and acellular allografts, nerve conduits, nerve transfers, and end-to-side neurorrhaphy. The purpose of this review is to present an overview of the literature on the applications of these techniques in peripheral nerve repair. Furthermore, preoperative evaluation, timing of repair, and future perspectives are also discussed.

Use of Vascularized Sural Nerve Grafts for Sciatic Nerve Reconstruction After Malignant Bone and Soft Tissue Tumor Resection in the Lower Legs

BACKGROUND

Vascularized nerve grafting is normally associated with a good outcome, but can be difficult to use for nerve reconstruction in patients with long defects of the sciatic nerve given the graft thickness. We report 3 cases of large defect sciatic nerve reconstruction using the bilateral sural nerves of the lower legs harvested together with the fascia and lesser saphenous vein to form a vascularized flap.

METHODS

The subjects were 3 patients who required the reconstruction of a 10-cm or longer segment of the sciatic nerve. Priority was given to restoring sensation in the plantar region such that reconstruction of the sensory nerves corresponding to the tibial region.

RESULTS

Two patients were followed up for long term. There was some persistent perceptual deficit in the foot, minimal protective sensation had been achieved.

CONCLUSIONS

We were able to selectively reconstruct the sensory nerves to achieve sensation in the soles of the feet by using sural nerve grafts from both legs. As the prognosis for the underlying condition in cases necessitating this procedure is often poor, the costs and benefits of reconstruction should always be weighed carefully for each individual patient.

Combined common peroneal and tibial nerve injury after knee dislocation: one injury or two? An MRI-clinical correlation

OBJECT

Knee dislocations are often accompanied by stretch injuries to the common peroneal nerve (CPN). A small subset of these injuries also affect the tibial nerve. The mechanism of this combined pattern could be a single longitudinal stretch injury of the CPN extending to the sciatic bifurcation (and tibial division) or separate injuries of both the CPN and tibial nerve, either at the level of the tibiofemoral joint or distally at the soleal sling and fibular neck. The authors reviewed cases involving patients with knee dislocations with CPN and tibial nerve injuries to determine the localization of the combined injury and correlation between degree of MRI appearance and clinical severity of nerve injury.

METHODS

Three groups of cases were reviewed. Group 1 consisted of knee dislocations with clinical evidence of nerve injury (n = 28, including 19 cases of complete CPN injury); Group 2 consisted of knee dislocations without clinical evidence of nerve injury (n = 19); and Group 3 consisted of cases of minor knee trauma but without knee dislocation (n = 14). All patients had an MRI study of the knee performed within 3 months of injury. MRI appearance of tibial and common peroneal nerve injury was scored by 2 independent radiologists in 3 zones (Zone I, sciatic bifurcation; Zone II, knee joint; and Zone III, soleal sling and fibular neck) on a severity scale of 1–4. Injury signal was scored as diffuse or focal for each nerve in each of the 3 zones. A clinical score was also calculated based on Medical Research Council scores for strength in the tibial and peroneal nerve distributions, combined with electrophysiological data, when available, and correlated with the MRI injury score.

RESULTS

Nearly all of the nerve segments visualized in Groups 1 and 2 demonstrated some degree of injury on MRI (95%), compared with 12% of nerve segments in Group 3. MRI nerve injury scores were significantly more severe in Group 1 relative to Group 2 (2.06 vs 1.24, p < 0.001) and Group 2 relative to Group 3 (1.24 vs 0.13, p < 0.001). In both groups of patients with knee dislocations (Groups 1 and 2), the MRI nerve injury score was significantly higher for CPN than tibial nerve (2.72 vs 1.40 for Group 1, p < 0.001; 1.39 vs 1.09 for Group 2, p < 0.05). The clinical injury score had a significantly strong correlation with the MRI injury score for the CPN (r = 0.75, p < 0.001), but not for the tibial nerve (r = 0.07, p = 0.83).

CONCLUSIONS

MRI is highly sensitive in detecting subclinical nerve injury. In knee dislocation, clinical tibial nerve injury is always associated with simultaneous CPN injury, but tibial nerve function is never worse than peroneal nerve function. The point of maximum injury can occur in any of 3 zones.

Vascularized sural nerve graft and extracorporeally irradiated osteochondral autograft for oncological reconstruction of wrist sarcoma: case report and review of literature

For tumors that are located beside the main peripheral nerve, combined wide resection of both the tumor and peripheral nerve is mandatory. We here present an interesting case with synovial sarcoma of the wrist. An 8 cm of ulnar nerve defect was reconstructed by vascularized, folded sural nerve graft with the peroneal flap, whereas an 8 cm of distal ulna was reconstructed using extracorporeally irradiated osteochondral autograft. Our case showed excellent nerve regeneration. Extracorporeal irradiated osteochondral graft was a good option for reconstruction of the distal ulna. This procedure should be indicated for the reconstruction of non-weight-bearing joints. These kinds of reconstruction have been addressed in only a few cases of oncological reconstruction.

Use of a bipedicled nerve flap taken from the dorsum of the digit for reconstruction of neurocutaneous defect in the adjacent finger

A digital nerve defect complicated by an associated soft-tissue loss poses a reconstructive challenge. This article reports reconstruction of a similar complex injury using a bipedicled nerve flap including a nerve graft from the dorsal branch of the digital nerve. From July 2008 to May 2010, a retrospective study was conducted with nine consecutive patients who had a combination of soft tissue and digital nerve defects. The injured fingers requiring reconstruction included three index, four middle and two ring fingers. The mean size of the soft-tissue losses was 2.8×2.1 cm. The flap is supplied by the digital artery and the venous drainage is by means of a dorsal vein. The mean flap size was 3.1×2.3 cm. The nerve gaps were bridged with the nerve graft attached with the flap. The average length of the nerve grafts was 3.0 cm. All flaps survived completely, and the defects were reconstructed successfully. Venous congestion was not observed in our series. At a mean follow-up period of 23 months, the average scores of static two-point discrimination (2PD) and Semmes-Weinstein monofilament on the finger pulp of the injured side were 7.5 mm and 3.93, respectively. The donor site morbidity was acceptable. According to the Michigan Hand Outcomes Questionnaire, four patients were strongly satisfied and five were satisfied with functional recovery of the injured finger. The bipedicled nerve flap is a safe and effective option for reconstruction of complex digital injury involving soft tissue and nerve defects. Our technique has been shown to provide sufficient sensory recovery. ClinicalTrials.gov ID: NCT01707654.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

The role of magnetic resonance neurography in the postoperative management of peripheral nerve injuries

Diagnostic limitations exist in the assessment of postoperative nerve regeneration. This article describes the role of available methods, such as clinical assessment, electrophysiologic studies, and magnetic resonance neurography in the postoperative evaluation of peripheral nerve repairs.

Reconstruction of proper digital nerve defects in the thumb using a pedicle nerve graft

BACKGROUND

Traumatic defects of the proper digital nerve in the thumb affect tactile perception of the thumb pulp. This article reports on the treatment of the defect using a pedicle nerve graft taken from the dorsal branch of the proper digital nerve of the index or long finger, or both.

METHODS

From May of 2006 to March of 2010, the pedicle nerve graft was used in 16 thumbs in 16 patients. There were 13 male and three female patients, with an average age of 33 years. Nerve repair was performed on one side in six thumbs and on both sides in 10 thumbs. The average length of the defects was 2.5 cm, between the middle of the distal phalanx and metacarpophalangeal joint. The average length of the nerve grafts was 2.7 cm. For comparison, we also collected a consecutive series of 27 patients with thumb proper digital nerve defects treated using a nonvascularized graft taken from the sural nerve (n = 15) or the medial antebrachial cutaneous nerve (n = 12).

RESULTS

At a mean follow-up of 22 months, the mean static two-point discrimination and Semmes-Weinstein monofilament scores on the thumb pulps were 6.7 mm and 3.62, respectively. The measurements of patients treated using nonvascularized nerve grafts were 9.4 mm and 3.90, respectively. The outcomes of the two groups were significantly different.

CONCLUSIONS

The pedicle nerve graft is useful and reliable for reconstructing proper digital nerve defects in the thumb. Superior sensory recovery was achieved using vascularized instead of unvascularized nerve grafts.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Successful delayed reconstruction of common peroneal neuroma-in-continuity using sural nerve graft

Injuries of the common peroneal nerve (CPN) are frequent and associated with poor motor outcomes. So far, the opinion is held, that nerve reconstruction is reasonable and indicated up to 6 months after injury. We describe successful sural nerve interposition grafting in a patient with neuroma-in-continuity formation of the CPN, presenting with foot drop, 13 months after injury. Due to this positive result, we think nerve grafting in neuroma-in-continuity lesions of the CPN should be contemplated in patients with foot drop even more than one year after injury.

Comparison between neurectomy and botulinum toxin A injection for denervated skeletal muscle

Neurectomy and botulinum toxin A (BoNT-A) injection cause denervated muscle atrophy, but questions remain about their clinical utility. We investigated time-series alterations of rat muscle weight, functional deficits, signaling pathways, and microscopic structures, to gain an understanding of the clinical implications. Between 2008 and 2009, the maximal calf circumference of patients for calf reduction either by neurectomy or BoNT-A injections were recorded for study. A rat skeletal muscle model was established through repeated or dose-adjusted BoNT-A injections and neurectomy. The survival, apoptosis pathways, functional deficits, and microscopic structures were investigated using Western blot, sciatic functional index (SFI), and transmission electron microscopy (TEM), respectively. The rat muscle weight ratio of the BoNT-A group had recovered to 89.3 +/- 3.8% by week 58, but it never recovered in the neurectomy group. Muscle weight reduction by BoNT-A not only depended on the dose, but additive effects were also obtained through repeated injections. Rat SFI demonstrated rapid recovery in both groups. Molecular expressions showed a coherent and biphasic pattern. p-Akt and apoptosis-inducing factor (AIF) were upregulated significantly, with a peak at 8 weeks in the neurectomy group (p < 0.01), but cleaved caspase-9 and caspase-3 showed no significant changes in either group. TEM findings showed irreversible and reversible inner-structure disruption and sarcomere discontinuity in the neurectomy and BoNT-A groups, respectively. We demonstrated that denervation induced lasting muscle weight and structural changes of different degrees. Muscle weight reduction by BoNT-A was related to frequency and dose. AIF-mediated caspase-independent apoptosis was significantly different for neurectomy and BoNT-A injection.