This protocol presents a reproducible rat model using sensory nerves to mimic human neuroma pain and assess surgical treatments, offering a valuable tool for translational neuroma research.
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Method Article
This protocol presents a reproducible rat model using sensory nerves to mimic human neuroma pain and assess surgical treatments, offering a valuable tool for translational neuroma research.
This protocol describes a novel surgical model to study nerve pain and surgical treatment in rats. Traditional neuroma models use mixed nerves, although it is most often the case that sensory nerves give rise to painful neuromas in the clinical setting. By selecting the saphenous nerve, this approach reflects the clinical reality of neuroma formation and provides a relevant platform for evaluating surgical strategies. This method aims to replicate the pathophysiology of human neuroma formation and to evaluate a common surgical intervention for neuroma pain, particularly targeted muscle reinnervation (TMR), a widely used intervention for neuroma-associated pain. The article provides a detailed, step-by-step description of the procedure, beginning with animal preparation and perioperative care. Surgical technique is explained with attention to anatomical landmarks, instrument requirements, and technical considerations that improve accuracy and consistency. Postoperative monitoring and welfare measures are outlined to ensure adherence to ethical standards and reproducibility across laboratories. This model is reproducible, technically accessible, and translationally relevant, as it mimics the clinical reality of sensory neuroma formation. It provides a platform for evaluating surgical strategies and preclinical neuroma research.
Neuromas are painful nerve tumors formed after nerve injury1,2. They represent a significant clinical problem with far-reaching societal consequences and increased medical costs3,4,5,6,7. Treatment options such as pharmacological therapy are often symptomatic, addressing pain but failing to resolve its underlying causes8. Surgical interventions have been shown to have variable success rates (56%-82%), and the mechanisms driving painful neuroma formation remain poorly understood9,10,11.
Pain from neuromas is thought to arise from sensory fascicles in the damaged nerve, underscoring the importance of modeling purely sensory contributions to neuroma-associated pain12. Animal models remain an essential platform for exploring the complex mechanisms underlying neuroma pain and also for developing effective surgical therapies13. However, most available animal models use mixed motor sensory nerves, which limits their translational applicability, since approximately 74% of painful neuromas in the clinical setting originate from purely sensory nerves14,15.
Several animal models have been developed to simulate neuropathic pain and evaluate potential interventions16. Firstly, the chronic constriction injury (CCI) model has been described17. This model induces partial nerve damage through loosely tied ligatures around the sciatic nerve, mimicking neuropathic pain conditions. It provides insight into peripheral sensitization, axonal degeneration, inflammatory responses, and central changes in the spinal cord, and is widely used to evaluate potential analgesic therapies17,18. Secondly, the Spared Nerve Injury (SNI) induces injury to two of the three terminal branches of the sciatic nerve (tibial and common peroneal nerves), leaving the remaining sural nerve intact19. Thirdly, the tibial neuroma transposition (TNT) model, developed by Dorsi et al. The tibial nerve is surgically transected and transposed subcutaneously to facilitate the evaluation of neuroma formation and associated pain16,20. This model allows for primary hypersensitivity assessment by Von Frey stimulation of the skin overlying the transposed neuroma at the pretibial site, and secondary hypersensitivity assessment in the adjacent sural or residual tibial nerve dermatomes. The TNT model was surgically designed to replicate neuroma development, without incorporating any surgical or non-surgical intervention aimed at preventing or treating neuroma-related pain20. As such, it does not allow evaluation of therapeutic strategies, like targeted muscle reinnervation (TMR), in the primary setting (Figure 1).
TMR is a technique that connects a transected (sensory) nerve to an expendable motor branch of a target after resecting the neuroma. This concept uses the principle of give the nerve something to do, whereby the nerve will regenerate into a nerve connected to a muscle target. The philosophy aims to prevent the formation of a neuroma per se by allowing the nerve to regenerate into a denervated muscle11.
In the present study, we describe a rodent model involving the transection of the saphenous nerve. This purely sensory nerve is transected, transposed to the gastrocnemius muscle, and either left untreated (saphenous neuroma transposition, SNT) or coapted to a motor branch (TMR). This model enables investigation of the effects of TMR applied to the saphenous nerve on secondary mechanical hypersensitivity in adjacent dermatomes of anatomically intact nerves, specifically within the tibial territory on the central plantar surface of the hind paw (Figure 1)21,22. This anatomical context also highlights the clinical relevance in patients. Due to its superficial anatomical course, the saphenous nerve is particularly vulnerable to iatrogenic or traumatic injury, especially following knee surgery, often resulting in neuropathic pain; notably, 55.2% of patients report persistent symptoms despite revision surgery such as neurolysis or neurectomy23,24.
This study aims to establish a reproducible rodent model in order to replicate the clinical setting of painful neuroma formation. This model is particularly suited for investigating pure sensory neuroma pathophysiology and the effects of TMR, while its primary outcome measure focuses on secondary mechanical hypersensitivity.
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This protocol aligns with ethical animal research guidelines and emphasizes its translational potential. Project number: AVD1150020198824.
1. Von Frey measurements
2. Preoperative preparation
3. Surgical technique
4. Postoperative care
5. Waste disposal
6. Specimen collection and euthanasia
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Assessment of secondary hypersensitivity (log-transformed 50% withdrawal thresholds) showed group differences in the tibial dermatome (Figure 5A). Transection of the saphenous nerve without treatment (SNT) resulted in the highest sensitivity across the 6-week follow-up. In contrast, animals treated with TMR displayed a consistent trend toward reduced hypersensitivity in the tibial territory. The divergence between groups was most evident at week 2, when the mean 50% withdrawal threshold in t...
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This approach has several strengths. The stepwise description allows reproducibility across laboratories, the procedure can be performed efficiently with microsurgical skills, and the use of a purely sensory nerve enhances its translational relevance. Together, these aspects make the model practical for comparative studies and useful for testing new interventions. Critical steps, such as maintaining aseptic conditions, precise dissection of the saphenous nerve, and careful handling of the vascular structures like the ven...
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Research performed by a PhD student (CB) supported by an Axogen grant (no product relationship). All the other authors have no conflicts of interest to disclose.
The authors gratefully acknowledge Sabine Versteeg for her contribution to behavioral pain assessments. Anja van der Sar and Trudy Oosterveld-Romijn (Common Animal Laboratory, Gemeenschappelijk Dieren Laboratorium) are thanked for their technical support in preparing surgical and microscopy facilities and for their dedicated animal care. The authors also thank Wim van Hecke for his expert evaluation of the collected nerve specimens.
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| Name | Company | Catalog Number | Comments |
|---|---|---|---|
| Carprofen | Local Veterinary Pharmacy | n/a | The local veterinary pharmacy prepares the carprofen dilution |
| Cotton swabs | Nobamed | 974255 | — |
| Electric razor | Aesculap | GT421 | |
| Electrocautery | Fine Science Tools | 18010-00 | — |
| Ethanol 70% | Interchema BV | 400406 | — |
| Ethilon 10.0 | Johnson & Johnson | BV130-3: code 2820G | |
| Ethilon 11.0 | Johnson & Johnson | BV50-3L code 2881G | |
| Ethilon 4.0 | Johnson & Johnson | 1854G: code 1854G | - |
| Ethilon 6.0 | Johnson & Johnson | BV130-5: code 2809G | |
| Ethilon 8.0 | Johnson & Johnson | BV130-5: code 2808G | — |
| Ethilon 9.0 | Johnson & Johnson | BV130-3: code 2819G | |
| Examination gloves nitrile | Sempermed GmbH | 1065920 | |
| Eye protection | 3M™ Health Care | 71512-00001M | |
| Glass Bead Sterilisator | VanPel laboratory equipment | GBS300H | |
| GraphPad Prism | GraphPad Software, San Diego, California USA | version 10 | |
| Heating pad | Conduct Science | CS-HP-2005 | |
| Isoflo (isoflurane) | Zoetis / Dechra Veterinary Products | B506 | — |
| Lidocaine 1% | Henry Schein | 809755 | |
| Mesh bottom cages | Stoelting Co. | 57816, 57824 | — |
| Micro forceps | Fine Science Tools | 11251-35 | — |
| Micro needle holder | Fine Science Tools | 12076-12 | — |
| Micro scissors | Fine Science Tools | 15019-10 | — |
| Micro tweezers | Fine Science Tools | 11254-20 | — |
| NaCl 0.9% | Trademed | H7 1000-FRE | — |
| Needle 25G × 1" | Becton, dickinson & company | 300400 | |
| Needle holder | Fine Science Tools | 12004-16 | — |
| Nerve stimulator | (VARI-STIM Nerve locator) | REF 856200 | |
| RandoMice software | van Eineige et al. Leiden | Version 1.1.7 | |
| Rodent rectal probe | World Precision Instruments | NC9506514 | |
| Scalpel | Fine Science Tools | 10003-12 | — |
| Scissors | Fine Science Tools | 14001-12 | — |
| Sensory evaluator | Linton Instrumentation | 514007–514015 | 0.6 g to 15 g monofilaments |
| Stereo surgical microscope | Leica | A60 F | — |
| Sterile gauze pads | Nobamed | 740113 | |
| Sterile ocular lubricant ointment | Alcon | B00BRLSC8S | |
| Sterile sheet with hole | Evercare / OneMed | 1555-01 | — |
| Surgical blade nr. 15 | Fine Science Tools | 10015-00 | — |
| Surgical face mask | Medline Industries, Inc. | MSK1002 | |
| Syringe luer lock 2 ml | Becton, dickinson & company | 300613 | |
| Tweezers | Fine Science Tools | 11617-12 | — |
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