Name: an anatomical study of nerves at risk during minimally invasive hallux valgus surgery
Uploaded: 2018-02-17T13:00:00.000+00:00
Duration: 15 min 4 s
Description: Watch this Scientific Journal Video about An Anatomical Study of Nerves at Risk During Minimally Invasive Hallux Valgus Surgery at JoVE.com

We thank the technical staff of the Dissecting Room of the Bellvitge Campus of the University of Barcelona for their skillful assistance. We thank the Audiovisuals department for their work with the video included as part of this publication. We thank the body donors of the Faculty of Medicine of the University of Barcelona.

This study was approved by the institutional Ethical Committee (Comissi&#243; de Bio&#232;tica, UB). The dissection procedures were carried out by an experienced anatomist, specifically trained in plane-by-plane dissection technique. This is an essential prerequisite to ensure a successful outcome of the experiment.
1. Preparation
<ol>
	<li>Select the specimens to be included in the study. Use below-the-knee cadaveric fresh-frozen human feet.
	<ol>
		<li>Exclude the following: any kind of deformities in the leg, ankle or foot (as this could affect the course of the nerves and ultimately affect the results of the study), ulcers, scars or evident signs of previous surgical procedures or any other condition that could difficult the localization of the nerves.</li>
	</ol>
	</li>
	<li>Select ten unpaired feet (five left and five right, amputated at the level of the distal tibia), from Caucasian fresh-frozen not exsanguinated specimens; the specimens included 5 men and 5 women with a median age of 80 (range, 53 - 95) years.</li>
	<li>Defrost the specimens by thawing them in room temperature tap water for 6-8 hours. Do not use hot water as it may alter properties of the specimens.</li>
	<li>Prepare the dissection field. Place the specimen upon a non-sterile surgical drape on the dissection table. Place the specimen in a stable position that permits a comfortable access to the dissection area; preferably, use a support that allows the specimen to be moved as needed.</li>
	<li>Prepare the dissection instruments to be used along with some gauze pads to clean the field during the dissection process.</li>
</ol>
2. Dissection
<ol>
	<li>With a scalpel, incise only the skin to create a window of approximately 20 cm x 5 cm at the medial part of the foot, oriented longitudinally. Start 15 cm proximal to the first metatarso-phalangeal joint, and end 5 cm distal, approximately.
	<ol>
		<li>Dissect the skin without disrupting the subcutaneous tissue and avoiding any displacement of the nervous structures. Use fresh scalpel blades for each plane.</li>
		<li>Perform the incisions with the cutting edge of the scalpel facing out and not facing the specimen. This follows one of the principles of a plane-by-plane anatomical dissection of the skin. Use toothed forceps during this step to tightly hold the skin.</li>
	</ol>
	</li>
	<li>Remove the skin covering the window area. Use gauze to clean the dissecting field if necessary.</li>
	<li>Perform a careful dissection of the subcutaneous tissue to identify the dorsomedial and dorsolateral nerves of the first toe. Use non-toothed forceps and new scalpel blades in order to avoid damage to the structures encountered. Iris scissors and periosteotome are helpful to progress in the dissection of the area where nerves are to be found (but are still not visible), as they allow a less aggressive dissection and prevent damage to the nerves.</li>
	<li>Dissect at the proximal part of the window, to avoid inadvertently cutting the nerves. Identify the nerves without detaching from the inferior part of the subcutaneous tissue to prevent displacement. Once each nerve is identified, dissect through its course until the first metatarso-phalangeal joint.</li>
	<li>Fixate the nerves in its original position with respect to the first metatarso-phalangeal joint, with a needle that will pierce both the nerve and the first metatarsophalangeal joint line.</li>
	<li>Perform manual traction of the first toe so the location of the joint line is made evident between the head of the first metatarsal and the base of the proximal phalanx of the first toe. The needle must puncture the nerve first and then be introduced into the metatarso-phalangeal joint. This step assures that the position of the nerve with respect to the joint will be stable throughout the study.</li>
</ol>
3. Freezing
<ol>
	<li>Protect each specimen with bubble wrap and adhesive tape, to avoid cold burning. Take care during the wrapping process not to move the needles holding the nerves.</li>
	<li>Tag each specimen appropriately.</li>
	<li>Introduce the specimens into the freezer between -17 &#176;C and -20 &#176;C.</li>
	<li>Wait for a minimum of 6 hours (or overnight) for the samples to freeze before performing the next step of the protocol.</li>
</ol>
4. Sawing
<ol>
	<li>Check the sawing equipment. Use a diamond saw with water cooling system.</li>
	<li>Prepare the working field where the specimens will be manipulated after the section.</li>
	<li>Open the water flow and start the bandsaw rotation. Adjust the cutting speed of the saw and the water flow for refrigeration.</li>
	<li>Once frozen, position the specimen on the saw board. Adjust the cutting line 1 cm posterior to the metatarso-phalangeal joint, as this is the point where the relevant surgical incisions are placed. Perform the section immediately after the specimen is removed from the freezer to avoid defrosting.</li>
	<li>Set the water flow to a minimum to protect the specimen from burning due to the friction of the bandsaw, while avoiding thawing the specimen by water and any subsequent alteration of the anatomical structures.</li>
	<li>Once the first section is finished, Discard the anterior block of the specimen (that containing the toes).</li>
	<li>Perform a second section. Make a parallel cut, 1 cm posterior to the first one in order to obtain a 1 cm-thick block. This is the standard thickness, as thinner sections may cause the structures to move from their original path.</li>
	<li>Discard the rest of the specimen or save for further studies. The specimens can be refrozen or fixed by immersion in fixative solutions.</li>
</ol>
5. Measurements
<ol>
	<li>Place the sectioned block flat on the working table and the goniometer flat on the surface of the cut specimen.</li>
	<li>Use a standard goniometer with its center located at the center of the first metatarsal diaphysis. Position one of the axis at the medial border of the extensor digitorum longus tendon, dorsally.</li>
	<li>Measure the location of the dorsomedial and dorsolateral nerves of the first toe by using the second axis of the goniometer.</li>
	<li>Extrapolate the measurements to a clock model, in which the sphere is the contour of the first metatarsal diaphysis.</li>
</ol>

<ol>
	<li>Perera, A. M., Mason, L., Stephens, M. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+pathogenesis+of+hallux+valgus.">The pathogenesis of hallux valgus.</a> J Bone Joint Surg. 93 (17), 1650-1661 (2011).</li><li>Lucas, Y., Hernandez, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Treatment+of+moderate+hallux+valgus+by+percutaneous,+extra-articular+reverse-L+Chevron+(PERC)+osteotomy.">Treatment of moderate hallux valgus by percutaneous, extra-articular reverse-L Chevron (PERC) osteotomy.</a> Bone Joint J. 98B (3), 365-373 (2016).</li><li>Malagelada, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+safety+of+minimally+invasive+hallux+surgery-An+anatomical+study+introducing+the+clock+method.">Increasing the safety of minimally invasive hallux surgery-An anatomical study introducing the clock method.</a> Foot Ankle Surg. , 10-14 (2016).</li><li>Golan&#243;, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+ankle+ligaments:+A+pictorial+essay.">Anatomy of the ankle ligaments: A pictorial essay.</a> Knee Surg Sports Traumatol Arthrosc. 18 (5), 557-569 (2010).</li><li>Dalmau-Pastor, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extensor+apparatus+of+the+lesser+toes:+anatomy+with+clinical+implications--topical+review.">Extensor apparatus of the lesser toes: anatomy with clinical implications--topical review.</a> Foot Ankle Int. 35 (10), 957-969 (2014).</li><li>Dalmau-Pastor, M., Yasui, Y., Calder, J. D., Karlsson, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+inferior+extensor+retinaculum+and+its+role+in+lateral+ankle+ligament+reconstruction+a+pictorial+essay.">Anatomy of the inferior extensor retinaculum and its role in lateral ankle ligament reconstruction a pictorial essay.</a> Knee Surg Sports Traumatol Arthrosc. 24 (4), 957-962 (2016).</li><li>Vesalius, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> De humanis corporis fabrica libris septem. , (1543).</li><li>Dalmau-Pastor, M., Vega, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Letter+Regarding+Cadaveric+Analysis+of+the+Distal+Tibiofibular+Syndesmosis.">Letter Regarding Cadaveric Analysis of the Distal Tibiofibular Syndesmosis.</a> Foot Ankle Int. 38 (3), 343-345 (2017).</li><li>Caraballo, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vascular+Structures+of+the+Lateral+Wall+of+the+Maxillary+Sinus:+A+Vascular+Labeling+Technique.">Vascular Structures of the Lateral Wall of the Maxillary Sinus: A Vascular Labeling Technique.</a> Implant Dent. 26 (1), 153-157 (2017).</li><li>Golan&#243;, P., Vega, J., P&#233;rez-Carro, L., G&#246;tzens, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ankle+Anatomy+for+the+Arthroscopist.+Part+I:+The+Portals.">Ankle Anatomy for the Arthroscopist. Part I: The Portals.</a> Foot Ankle Clin. 11 (2), 253-273 (2006).</li><li>Golan&#243;, P., Vega, J., P&#233;rez-Carro, L., G&#246;tzens, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ankle+Anatomy+for+the+Arthroscopist.+Part+II:+Role+of+the+Ankle+Ligaments+in+Soft+Tissue+Impingement.">Ankle Anatomy for the Arthroscopist. Part II: Role of the Ankle Ligaments in Soft Tissue Impingement.</a> Foot Ankle Clin. 11 (2), 275-296 (2006).</li></ol>

Authors do not have competing financial interests related to or affecting this study.

The basis of the method used in this study is a combination of sectional anatomy and anatomical plane-by-plane dissection, as it has been practiced historically7. This requires not only anatomical knowledge but also specific training for what is a time-demanding technique that greatly relies on the skills of the dissector. Consequently, some anatomical images provided in anatomical textbooks or scientific papers, especially in the field of orthopedic surgery, lack accuracy and are not instructive enough to be useful for the surgeon performing cutting edge techniques, like minimally invasive procedures. For this reason, it has been suggested in the literature that anatomical studies should be carried out with a close collaboration between the experts, surgeons and anatomists8.
The use of fresh-frozen specimens is essential to obtain reliable anatomic results, especially when studying superficial structures as nerves. The use of fixated specimens frequently produces changes in the volume and position of the anatomical structures. Likewise, nervous and vascular structures are susceptible to displacement during its handling at the time of the dissection. For this reason, we have included three critical steps in our technique to ensure that nerves will not be displaced: the dissection performed in the study does not affect the subcutaneous tissue, nerves are fixed with intra-articular needles at the first metatarsophalangeal joint, and specimens are frozen before the sawing process.
Thawing of the samples could lead to the displacement of relevant anatomical structures, thus the need for careful preparation and freezing of the samples. The previous preparation and mounting of the cutting material are important to achieve reliable measures.
One of the possible limitations of this technique arise when the nerve to be studied is not near a joint, which will preclude fixation of the nerve with a needle. The use of a vascular labeling technique could overcome this issue, as vascular structures are in most cases parallel to nerves9.
An increasing number of surgical procedures are nowadays performed by minimally invasive methods, where neurological structures are not directly visualized2,3. In these cases, three-dimensional orientation is paramount for the surgeon. Anatomical references with the clock method provide the surgeon with an easy and reproducible system to locate the nerve position in relation with surgical incisions for Hallux Valgus Minimally Invasive procedures.
This technique, which combines plane-by-plane dissection and sectional anatomy in fresh-frozen specimens has been successfully used to provide anatomical guidance for the newest minimally invasive surgical procedures3,4,10,11.

Hallux valgus is a common pathology affecting the first toe, in which the proximal phalanx is deviated laterally while the first metatarsal is deviated medially1. Percutaneous or minimally-invasive surgical (MIS) techniques for hallux valgus were amongst the first described in this discipline, and numerous studies report their benefits but also their risks2. Hallux Valgus MIS correction involves osteotomies performed through small incisions using specific surgical instruments. Given that open dissections are not performed, the risk of damage to neurovascular structures is higher than when these are identified during open surgery. Also, as in any surgical procedure, the positioning of the patient and the surgeon around the operating table are far from the anatomical position depicted in classic anatomical books or papers.
The neurological structures at risk during Hallux Valgus surgery are the dorsomedial nerve of the big toe, the branch of the superficial peroneal nerve, and the dorsolateral nerve of the big toe, branch of the deep peroneal nerve. The purpose of this study is to describe the position of these nerves with regards to incisions used in hallux surgery and to illustrate it with a new method easily reproducible in surgical conditions. Moreover, a safe portal for the use of percutaneous instruments is described.
A thorough anatomical knowledge is essential in any surgical field, especially during minimally invasive procedures. The development of new surgical and imaging techniques requires a new understanding of both the bi-dimensional and the tri-dimensional location of anatomical landmarks. Previously reported anatomical dissection techniques were developed by our team to overcome the limitations of the classic dissection techniques3,4,5,6 and here are applied to reproduce the skin incisions and instrument entry portals corresponding to the MIS procedures used to treat hallux valgus (HV) and rigidus (HR) pathology. The method is thus applicable to those surgical techniques that evolved from traditional open surgery to MIS3,4,5,6.

<table><tbody><tr><td>Adson Non-Toothed dissection forceps</td><td>Bontempi</td><td>BD-31</td><td></td></tr><tr><td>Adson Toothed dissection forceps</td><td>Bontempi</td><td>BD-30</td><td></td></tr><tr><td>Surgical scalpel handle n&amp;ordm; 4</td><td>Swann-Morton</td><td>4</td><td></td></tr><tr><td>Surgical scalpel blades n&amp;ordm; 24</td><td>Swann-Morton</td><td>24</td><td>&lt;em&gt;Ad libitum&lt;/em&gt;</td></tr><tr><td>Iris scissors- curved</td><td>Bontempi</td><td>FG-2</td><td></td></tr><tr><td>Periostotome P-24</td><td>Bontempi</td><td>718-24G</td><td></td></tr><tr><td>Intramuscular 23G sterile needles</td><td>Totclinic</td><td>23</td><td>&lt;em&gt;Ad libitum&lt;/em&gt;</td></tr><tr><td>Goniometer</td><td></td><td></td><td></td></tr><tr><td>Latex gloves</td><td></td><td></td><td>&lt;em&gt;Ad libitum&lt;/em&gt;</td></tr><tr><td>Gauze pads</td><td></td><td></td><td>&lt;em&gt;Ad libitum&lt;/em&gt;</td></tr><tr><td>Non-Sterile surgical drape</td><td></td><td></td><td></td></tr><tr><td>Saw</td><td>EXAKT Advanced Technologies GmbH</td><td>EXAKT 312 Pathology Saw</td><td></td></tr></tbody></table>

an anatomical study of nerves at risk during minimally invasive hallux valgus surgery

The growing popularity of minimally invasive surgical (MIS) procedures makes it necessary that new anatomical references arise, to aid in tridimensional orientation and localization of structures that are not directly visible to the surgeon. This is especially critical for structures at risk like nerves or blood vessels. Optimization of the handling of cadaveric material and the combination of multiple techniques compensate for the limited availability of adequate specimens. The described protocol combines anatomical plane-by-plane dissection and sectional anatomy of fresh-frozen specimens to help localize relevant structures, such as nerves, arteries, veins and to correctly position the portals during MIS procedures. Depiction of these structures in anatomy textbooks can differ from what is encountered in the surgical field; and for this reason, new anatomical studies with a surgical orientation are needed. However, this is a complex, time-consuming technique requiring specific training. The anatomical references described with the so-called 'clock method' provide the surgeon with an easy and reproducible system to locate the path of the nerves at risk in Hallux Valgus MIS procedures. This model can be extrapolated to many other minimally invasive surgical procedures.

Using the clock method, the dorsomedial and dorsolateral nerves were consistently found between 10 and 2 o&#39;clock (Figure 1). The dorsomedial nerve was found at an average of 26.2&#176; medial to the medial border of the EHL, which corresponds to a zone between 12 and 2 o&#39;clock in a right foot, and between 10 and 12 o&#39;clock in a left foot. The dorsolateral nerve was 32.3&#176; lateral to the medial border of the EHL in average, which corresponds to a zone between 12 and 2 o&#39;clock in a left foot, and between 10 and 12 o&#39;clock in a right foot.
Figure 2 shows the typical distribution of dorsomedial and dorsolateral nerves as revealed by the anatomical plane-by-plane dissection.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/56232/56232fig1.jpg" /> 
Figure 1: Frontal cross section of a right foot showing the position of the dorsomedial nerve (1) and dorsolateral nerve (2). A clock sphere has been superimposed onto the first metatarsal head. Double-headed arrows show the area where nerves have been found to be in this study. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56232/56232fig1large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/56232/56232fig2.jpg" /> 
Figure 2: Anatomical plane-per-plane dissection (dorsal view of a foot) showing the typical distribution of dorsomedial and dorsolateral nerves as has been found in this study. 1. Dorsomedial nerve of the first toe. 2. Dorsolateral nerve of the first toe. 3. Dorsomedial nerve of the second toe. <a href="https://cloudflare-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/56232/56232fig2large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about An Anatomical Study of Nerves at Risk During Minimally Invasive Hallux Valgus Surgery at JoVE.com

An Anatomical Study of Nerves at Risk During Minimally Invasive Hallux Valgus Surgery

Minimally invasive surgical (MIS) procedures rely on anatomical references to localize structures not directly visible to the surgeon. This manuscript describes a combined method of plane-by-plane dissection and sectional anatomy of fresh-frozen specimens to locate the structures at risk during MIS procedures.

The growing popularity of minimally invasive surgical (MIS) procedures makes it necessary that new anatomical references arise, to aid in tridimensional ...

an-anatomical-study-nerves-at-risk-during-minimally-invasive-hallux

Nanyang Technological University

Research

JoVE Journal

Medicine

11.6K Views.  University of Barcelona. Minimaal invasieve procedures voor chirurgische (MIS), is afhankelijk van anatomische verwijzingen naar het lokaliseren van structuren die niet direct zichtbaar naar de chirurg. Dit manuscript beschrijft een gecombineerde methode van vliegtuig-door-plane dissectie en de anatomie van de sectionele van vers bevroren exemplaren te vinden van de structuren in gevaar tijdens de MIS procedures.

Video: An Anatomical Study of Nerves at Risk During Minimally Invasive Hallux Valgus Surgery

The Spared Nerve Injury (SNI) Model of Induced Mechanical Allodynia in Mice

Peripheral neuropathic pain is a severe chronic pain condition which may result from trauma to sensory nerves in the peripheral nervous system. The spared nerve injury (SNI) model induces symptoms of neuropathic pain such as mechanical allodynia i.e. pain due to tactile stimuli that do not normally provoke a painful response [1]. 
The SNI mouse model involves ligation of two of the three branches of the sciatic nerve (the tibial nerve and the common peroneal nerve), while the sural nerve is left intact [2]. The lesion results in marked hypersensitivity in the lateral area of the paw, which is innervated by the spared sural nerve. The non-operated side of the mouse can be used as a control. The advantages of the SNI model are the robustness of the response and that it doesn&#x2019;t require expert microsurgical skills.
The threshold for mechanical pain response is determined by testing with von Frey filaments of increasing bending force, which are repetitively pressed against the lateral area of the paw [3], [4]. A positive pain reaction is defined as sudden paw withdrawal, flinching and/or paw licking induced by the filament. A positive response in three out of five repetitive stimuli is defined as the pain threshold. 
As demonstrated in the video protocol, C57BL/6 mice experience profound allodynia as early as the day following surgery and maintain this for several weeks.

The Spared Nerve Injury SNI Model of Induced Mechanical Allodynia in Mice

The Spared Nerve Injury animal model is described here as a mouse model of peripheral neuropathic pain following partial denervation of the sciatic nerve by lesioning the tibial and common peroneal nerve branches, leaving the remaining sural nerve intact. Behavioral modification resulting from mechanical allodynia is quantified by von Frey filaments.

Peripheral neuropathic pain is a severe chronic pain condition which may result from trauma to sensory nerves in the peripheral nervous system. The spared ...

The Fibular Nerve Injury Method: A Reliable Assay to Identify and Test Factors That Repair Neuromuscular Junctions

The neuromuscular junction (NMJ) undergoes deleterious structural and functional changes as a result of aging, injury and disease. Thus, it is imperative to understand the cellular and molecular changes involved in maintaining and repairing NMJs. For this purpose, we have developed a method to reliably and consistently examine regenerating NMJs in mice. This nerve injury method involves crushing the common fibular nerve as it passes over the lateral head of the gastrocnemius muscle tendon near the knee. Using 70 day old female mice, we demonstrate that motor axons begin to reinnervate previous postsynaptic targets within 7 days post-crush. They completely reoccupy their previous synaptic areas by 12 days. To determine the reliability of this injury method, we compared reinnervation rates between individual 70 day old female mice. We found that the number of reinnervated postsynaptic sites was similar between mice at 7, 9, and 12 days post-crush. To determine if this injury assay can also be used to compare molecular changes in muscles, we examined levels of the gamma-subunit of the muscle nicotinic receptor (gamma-AChR) and the muscle-specific kinase (MuSK). The gamma-AChR subunit and MuSK to are highly upregulated following denervation and return to normal levels following reinnervation of NMJs. We found a close relationship between transcript levels for these genes and innervation status of muscles. We believe that this method will accelerate our understanding of the cellular and molecular changes involved in repairing the NMJ and other synapses.

We have developed a nerve injury method to reliably examine muscle reinnervation, and thus regeneration of neuromuscular junctions in mice. This technique involves injuring the common fibular nerve via a simple and highly reproducible surgery. Muscle reinnervation in then assessed by whole-mounting the extensor digitorum longus muscle.

The neuromuscular junction (NMJ) undergoes deleterious structural and functional changes as a result of aging, injury and disease. Thus, it is imperative ...

Neuroscience

Stromal Vascular Fraction-enriched Fat Grafting for the Treatment of Symptomatic End-neuromata

The purpose of this study was to methodically illustrate and highlight the crucial steps of stromal vascular fraction (SVF)-enriched fat grafting as a novel treatment of symptomatic end-neuromata of peripheral sensory nerves, and in this study, specifically of the superficial branch of the radial nerve (SBRN). Despite a multitude of existing treatments, persistent postoperative pain and common pain relapse are still very common, independent of the procedure assessed. The neuroma is microsurgically excised accordingly to standardized protocol. Instead of the relocation of the regenerating nerve stump in neighboring anatomical structures, such as muscle or bone, a fat graft is applied perifocally and acts as a mechanical barrier. In order to reduce the fat resorption rate and boost the regenerative potential of the graft, the highly concentrated SVF is integrated in the grafting. The SVF is isolated from subcutaneous fat by enzymatic and mechanic separation of the lipoaspirate by a specific commercial isolation system. The SVF-enriched fat graft provides both a mechanical barrier and various biological effects at the cellular level, including improving angiogenesis, inflammation, and fibrosis. Both mechanical and biologic effects help to reduce the disorganized axonal outgrowth of the nerve stump during nerve regeneration and hence prevent the recurrence of painful end-neuromata.

The purpose of the study is to illustrate the technical procedure of stromal vascular fraction (SVF)-enriched fat grafting as a novel treatment of symptomatic end-neuromata. This technique provides advantages of both the mechanical barrier and the biological action at the cellular level by the processed and concentrated SVF.

The purpose of this study was to methodically illustrate and highlight the crucial steps of stromal vascular fraction (SVF)-enriched fat grafting as a ...

Ethanol-Induced Cervical Sympathetic Ganglion Block Applications for Promoting Canine Inferior Alveolar Nerve Regeneration Using an Artificial Nerve

Polyglycolic acid collagen (PGA-C) tubes are bio-absorbable nerve tubes filled with collagen of multi-chamber structure, which consist of thin collagen films. Favorable clinical outcomes have been achieved when using these tubes for the treatment of damaged inferior alveolar nerve (IAN). A critical factor for the successful nerve regeneration using PGA-C tubes is blood supply to the surrounding tissue. Cervical sympathetic ganglion block (CSGB) creates a sympathetic blockade in the head and neck region thus increasing blood flow in the area. To ensure an adequate effect, the blockade must be administered with local anesthetics one to two times a day for several consecutive weeks; this poses a challenge when creating animal models for investigating this technique. To address this limitation, we developed an ethanol-induced CSGB in a canine model of long-term increase in blood flow in the orofacial region. We examined whether IAN regeneration via PGA-C tube implantation can be enhanced by this model. Fourteen Beagles were each implanted with a PGA-C tube across a 10-mm gap in the left IAN. The IAN is located within the mandibular canal surrounded by bone, therefore we chose piezoelectric surgery, consisting of ultrasonic waves, for bone processing, in order to minimize the risk of nerve and vessel injury. A good surgical outcome was obtained with this approach. A week after surgery, seven of these dogs were subjected to left CSGB by injection of ethanol. Ethanol-induced CSGB resulted in improved nerve regeneration, suggesting that the increased blood flow effectively promotes nerve regeneration in IAN defects. This canine model can contribute to further research on the long-term effects of CSGB.

We evaluated the effect of cervical sympathetic ganglion block on nerve repair using artificial nerve conduits. Male beagle dogs were each implanted with an artificial nerve across a 10-mm gap in the left inferior alveolar nerve; left cervical sympathetic ganglion was blocked by injecting 99.5% ethanol via lateral thoracotomy.

Polyglycolic acid collagen (PGA-C) tubes are bio-absorbable nerve tubes filled with collagen of multi-chamber structure, which consist of thin collagen ...

Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different methods of simulating postoperative physiotherapy are presented. Multiple standardized strategies are used to assess motor and sensory recovery using an MN model of peripheral nerve lesion and repair, thus permitting easy comparison of the results. Several options are included for providing a postoperative physiotherapy-like environment to rats that have undergone MN injuries. Finally, the paper provides a method to evaluate the recovery of the MN using several noninvasive tests (i.e., grasping test, pin prick test, ladder rung walking test, rope climbing test, and walking track analysis), and physiological measurements (infrared thermography, electroneuromyography, flexion strength evaluation, and flexor carpi radialis muscle weight determination). Hence, this model seems particularly appropriate to replicate a clinical scenario, facilitating extrapolation of results to the human species.
Although the sciatic nerve is the most studied nerve in peripheral nerve research, analysis of the rat MN presents various advantages. For example, there is a reduced incidence of joint contractures and automutilation of the affected limb in MN lesion studies. Furthermore, the MN is not covered by muscle masses, making its dissection easier than that of the sciatic nerve. In addition, MN recovery is observed sooner, because the MN is shorter than the sciatic nerve. Also, the MN has a parallel path to the ulnar nerve in the arm. Hence, the ulnar nerve can be easily used as the nerve graft for repairing MN injuries. Finally, the MN in rats is located in the forelimb, akin to the human upper limb; in humans, the upper limb is the site of most peripheral nerve lesions.

Presented is a protocol to produce different types of median nerve (MN) lesions and repair in the rat. Additionally, the protocol shows how to evaluate the functional recovery of the nerve using several noninvasive behavioral tests and physiological measurements.

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different ...

Modified Spared Nerve Injury Surgery Model of Neuropathic Pain in Mice

Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular mechanism of neuropathic pain in mice and rats. Currently, there are two types of SNI model, one to cut and ligate the common peroneal and the tibial nerves with intact sural nerve, which is defined as SNIs in this study, and another to cut and ligate the common peroneal and the sural nerves with intact tibial nerve, which is defined as SNIt in this study. Because the sural nerve is purely sensory whereas the tibial nerve contains both motor and sensory fibers, the SNIt model has much less motor deficit than the SNIs model. In the traditional SNIt mouse model, the common peroneal and the sural nerves are cut and ligated separately. Here a modified SNIt surgery method is described to damage both common peroneal and sural nerves with only one ligation and one cut with a shorter procedure time, which is easier to perform and reduces the potential risk of stretching the sciatic or tibial nerves, and produces similar mechanical hypersensitivity as the traditional SNIt model.

The modified surgery is a simplified method for mouse or rat spared nerve injury model that requires only one ligation and one cut to injure both common peroneal and sural nerves.

Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular ...

Traumatic Peripheral Nerve Injury in Mice

Traumatic peripheral nerve injury (TPNI) is a common cause of morbidity following orthopedic trauma. Reproducible and precise methods of injuring nerve and denervating muscle have long been a goal in musculoskeletal research. Many traumatically injured limbs have nerve trauma that defines the long-term patient outcome. Over several years, precise methods of producing microsurgical nerve injuries have been developed, including crush, lacerations, and nerve-gap grafting, allowing for reproducible outcome assessments. Moreover, newer methods are created for calibrated crush injuries that offer clinically relevant correlations with outcomes used to assess human patients. The principles of minimal manipulation to ensure low variability in nerve injury allow for adding still more associated tissue injuries into these models. This includes direct muscle crush and other components of limb injury. Finally, atrophy assessment and precise analysis of behavioral outcomes make these methods a complete package for studying musculoskeletal trauma that realistically incorporates all the elements of human traumatic limb injury.

The present protocol describes traumatic peripheral nerve injuries (TPNIs), including precisely calibrated crush, strictly aligned and misaligned laceration, as well as grafted and non-grafted gaps of the sciatic nerve in mice. Custom-designed sensors are developed to gauge nerve trauma, induced with commonly available tools to ensure reproducible post-TPNI outcomes.

Traumatic peripheral nerve injury (TPNI) is a common cause of morbidity following orthopedic trauma. Reproducible and precise methods of injuring nerve ...

Surgery and Behavioral Testing in the Tibial Neuroma Transposition Model in Rats

The tibial neuroma transposition (TNT) is a rat model in which allodynia at the neuroma site (tibial nerve) can be independently evaluated from allodynia at the plantar surface of the hind paw innervated by the intact sural nerve. This TNT model is suitable to test therapies for neuroma pain, such as the potential superiority of certain surgical therapies that are already used in the clinic, or to evaluate new drugs and their effect on both pain modalities in the same animal. In this model, a distal lesion (neurotmesis) is made in the tibial nerve, and the proximal nerve end is transposed and fixed subcutaneously and pretibially to enable assessments of the neuroma site with a 15 g Von Frey monofilament. To assess allodynia over the sural nerve, Von Frey monofilaments can be used via the up-down method on the plantar lateral region of the hind paw. After cutting the tibial nerve, mechanical hypersensitivity develops at the neuroma site within 1 week after surgery and persists at least until 12 weeks after surgery. Allodynia at the sural innervated plantar surface develops within 3 weeks after surgery compared to the contralateral limb. At 12 weeks, a neuroma forms on the proximal end of the severed tibial nerve, indicated by dispersion and swirling of axons. For the TNT model surgery, multiple critical (micro)surgical steps need to be followed, and some surgery practice under terminal anesthesia is advised. Compared to other neuropathic pain models, such as the spared nerve injury model, allodynia over the neuroma site can be independently tested from sural nerve hypersensitivity in the TNT model. However, the neuroma site can be tested only in rats, not in mice. The tips and directions provided in this protocol can help research groups working on pain successfully implement the TNT model in their facility.

This protocol describes the tibial neuroma transposition model, which entails a lesion of the tibial nerve with subsequent transposition of the proximal nerve end toward a subcutaneous pretibial or lateral position. Behavioral testing of neuroma pain and plantar hyperalgesia is quantified using Von Frey monofilaments.

The tibial neuroma transposition (TNT) is a rat model in which allodynia at the neuroma site (tibial nerve) can be independently evaluated from allodynia ...

Partial Sciatic Nerve Ligation: A Mouse Model of Chronic Neuropathic Pain to Study the Antinociceptive Effect of Novel Therapies

Management of chronic pain remains challenging to this day, and current treatments are associated with adverse effects, including tolerance and addiction. Chronic neuropathic pain results from lesions or diseases in the somatosensory system. To investigate potential therapies with reduced side effects, animal pain models are the gold standard in preclinical studies. Therefore, well-characterized and well-described models are crucial for the development and validation of innovative therapies. 
Partial ligation of the sciatic nerve (pSNL) is a procedure that induces chronic neuropathic pain in mice, characterized by mechanical and thermal hypersensitivity, ongoing pain, and changes in limb temperature, making this model a great fit to study neuropathic pain preclinically. pSNL is an advantageous model to study neuropathic pain as it reproduces many symptoms observed in humans with neuropathic pain. Furthermore, the surgical procedure is relatively fast and straightforward to perform. Unilateral pSNL of one limb allows for comparison between the ipsilateral and contralateral paws, as well as evaluation of central sensitization. 
To induce chronic neuropathic hypersensitivity, a 9-0 non-absorbable nylon thread is used to ligate the dorsal third of the sciatic nerve. This article describes the surgical procedure and characterizes the development of chronic neuropathic pain through multiple commonly used behavioral tests. As a plethora of innovative therapies are now being investigated to treat chronic pain, this article provides crucial concepts for standardization and an accurate description of surgeries required to induce neuropathic pain.

Partial sciatic nerve ligation induces long-lasting chronic neuropathic pain, characterized by exaggerated responses to thermal and mechanical stimuli. This mouse model of neuropathic pain is commonly used to study innovative therapies for pain management. This article describes in detail the surgical procedure to improve standardization and reproducibility.

Management of chronic pain remains challenging to this day, and current treatments are associated with adverse effects, including tolerance and addiction. ...

RPNI Surgery for Treating Postamputation Pain

Regenerative Peripheral Nerve Interface: Surgical Protocol for a Randomized Controlled Trial in Postamputation Pain

Surgical procedures, including nerve reconstruction and end-organ muscle reinnervation, have become more prominent in the prosthetic field over the past decade. Primarily developed to increase the functionality of prosthetic limbs, these surgical procedures have also been found to reduce postamputation neuropathic pain. Today, some of these procedures are performed more frequently for the management and prevention of postamputation pain than for prosthetic fitting, indicating a significant need for effective solutions to postamputation pain. One notable emerging procedure in this context is the Regenerative Peripheral Nerve Interface (RPNI). RPNI surgery involves an operative approach that entails splitting the nerve end longitudinally into its main fascicles and implanting these fascicles within&#160;free denervated and devascularized muscle grafts. The RPNI procedure takes a proactive stance in addressing freshly cut nerve endings, facilitating painful neuroma prevention and treatment by enabling the&#160;nerve to regenerate and innervate an end organ, i.e., the free muscle graft. Retrospective studies have shown RPNI&#39;s effectiveness in alleviating postamputation pain and preventing the formation of painful neuromas. The increasing frequency of utilization of this approach has also given rise to variations in the technique. This article aims to provide a step-by-step description of the RPNI procedure, which will serve as the standardized procedure employed in an international, randomized controlled trial (ClinicalTrials.gov, NCT05009394). In this trial, RPNI is compared to two other surgical procedures for postamputation pain management, specifically, Targeted Muscle Reinnervation (TMR) and neuroma excision coupled with intra-muscular transposition and burying.

Author Spotlight: Regenerative Peripheral Nerve Interface (RPNI) Surgery in Postamputation Pain Management

Here, we describe the surgical procedure to perform Regenerative Peripheral Nerve Interface (RPNI) surgery for treating postamputation neuropathic pain in the context of an international, randomized controlled trial (RCT) (ClinicalTrials.gov, NCT05009394). The RCT compares RPNI with two other surgical techniques, namely, Targeted Muscle Reinnervation (TMR) and neuroma excision combined with intra-muscular transposition.

Surgical procedures, including nerve reconstruction and end-organ muscle reinnervation, have become more prominent in the prosthetic field over the past ...

An Anatomical Study of Nerves at Risk During Minimally Invasive Hallux Valgus Surgery

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