Sex-Dependent Reduction in Mechanical Allodynia in the Sural-Sparing Nerve Injury Model in Mice Lacking Merkel Cells.

Innocuous touch sensation is mediated by cutaneous low-threshold mechanoreceptors (LTMRs). Aß slowly adapting type I (SAI) neurons constitute one LTMR subtype that forms synapse-like complexes with associated Merkel cells in the basal skin epidermis. Under healthy conditions, these complexes transduce indentation and pressure stimuli into Aß SAI LTMR action potentials that are transmitted to the CNS, thereby contributing to tactile sensation. However, it remains unknown whether this complex plays a role in the mechanical hypersensitivity caused by peripheral nerve injury. In this study, we characterized the distribution of Merkel cells and associated afferent neurons across four diverse domains of mouse hind paw skin, including a recently described patch of plantar hairy skin. We also showed that in the spared nerve injury (SNI) model of neuropathic pain, Merkel cells are lost from the denervated tibial nerve territory but are relatively preserved in nearby hairy skin innervated by the spared sural nerve. Using a genetic Merkel cell KO mouse model, we subsequently examined the importance of intact Merkel cell-Aß complexes to SNI-associated mechanical hypersensitivity in skin innervated by the spared neurons. We found that, in the absence of Merkel cells, mechanical allodynia was partially reduced in male mice, but not female mice, under sural-sparing SNI conditions. Our results suggest that Merkel cell-Aß afferent complexes partially contribute to mechanical allodynia produced by peripheral nerve injury, and that they do so in a sex-dependent manner.SIGNIFICANCE STATEMENT Merkel discs or Merkel cell-Aß afferent complexes are mechanosensory end organs in mammalian skin. Yet, it remains unknown whether Merkel cells or their associated sensory neurons play a role in the mechanical hypersensitivity caused by peripheral nerve injury. We found that male mice genetically lacking Merkel cell-Aß afferent complexes exhibited a reduction in mechanical allodynia after nerve injury. Interestingly, this behavioral phenotype was not observed in mutant female mice. Our study will facilitate understanding of mechanisms underlying neuropathic pain.

Anatomic relationship of the sural nerve when performing Achilles tendon repair using the percutaneous Achilles repair system, a cadaveric study.

BACKGROUND: Minimally invasive techniques for Achilles tendon repair are increasing due to reports of similar rerupture rates using open and percutaneous techniques with fewer wound complications and quicker recovery with percutaneous methods. The goal of this study was to investigate quantitatively the relationship and risk of injury to the sural nerve during Achilles tendon repair when using the Percutaneous Achilles Repair System (PARS) (Arthrex®, Naples, FL), by recording the distance between the passed needles and the sural nerve as well identifying any direct violation of the nerve with needle passage or nerve entrapment within the suture after the jig was removed. The hypothesis of the study is that the PARS technique can be performed safely and without significant risk of injury to the sural nerve. METHODS: A total of five needles were placed through the PARS jig in each of 10 lower extremity cadaveric specimens using the proximal portion after simulation of a midsubstance Achilles tendon rupture. Careful dissection was performed to measure the distance of the sural nerve in relation to the passed needles. The sutures were then pulled out through the incision as the jig was removed from the proximal portion of the tendon and observation of the suture in relation to the tendon was documented. RESULTS: Of the 10 cadaveric specimens, none had violation of the sural nerve. Zero of the 50 (0%) needles directly punctured the sural nerve. In addition, upon retraction of the jig, all sutures were noted to reside within the tendon sheath with no entrapment of the sural nerve noted. CONCLUSION: This study demonstrated the variable course of the sural nerve and identifies the potential risk for sural nerve injury when using the PARS for Achilles tendon repair. However, this study provides additional evidence of safety from an anatomic standpoint that explains the outcomes demonstrated in the clinical trials. With this information the authors believe surgeons should feel comfortable they can replicate those outcomes while minimizing risk of sural nerve injury when the technique is used correctly.

A network approach to investigating the key microbes and stability of gut microbial communities in a mouse neuropathic pain model.

BACKGROUND: Neuropathic pain is an abnormally increased sensitivity to pain, especially from mechanical or thermal stimuli. To date, the current pharmacological treatments for neuropathic pain are still unsatisfactory. The gut microbiota reportedly plays important roles in inducing neuropathic pain, so probiotics have also been used to treat it. However, the underlying questions around the interactions in and stability of the gut microbiota in a spared nerve injury-induced neuropathic pain model and the key microbes (i.e., the microbes that play critical roles) involved have not been answered. We collected 66 fecal samples over 2 weeks (three mice and 11 time points in spared nerve injury-induced neuropathic pain and Sham groups). The 16S rRNA gene was polymerase chain reaction amplified, sequenced on a MiSeq platform, and analyzed using a MOTHUR- UPARSE pipeline. RESULTS: Here we show that spared nerve injury-induced neuropathic pain alters gut microbial diversity in mice. We successfully constructed reliable microbial interaction networks using the Metagenomic Microbial Interaction Simulator (MetaMIS) and analyzed these networks based on 177,147 simulations. Interestingly, at a higher resolution, our results showed that spared nerve injury-induced neuropathic pain altered both the stability of the microbial community and the key microbes in a gut micro-ecosystem. Oscillospira, which was classified as a low-abundance and core microbe, was identified as the key microbe in the Sham group, whereas Staphylococcus, classified as a rare and non-core microbe, was identified as the key microbe in the spared nerve injury-induced neuropathic pain group. CONCLUSIONS: In summary, our results provide novel experimental evidence that spared nerve injury-induced neuropathic pain reshapes gut microbial diversity, and alters the stability and key microbes in the gut.

The arthroscopic all-inside ankle lateral collateral ligament repair is a safe and reproducible technique.

PURPOSE: Neurovascular structures around the ankle are at risk of injury during arthroscopic all-inside lateral collateral ligament repair for the treatment of chronic ankle instability. This study aimed to evaluate the risk of damage to anatomical structures and reproducibility of the technique amongst surgeons with different levels of expertise in the arthroscopic all-inside ligament repair. METHODS: Twelve fresh-frozen ankle specimens were used for the study. Two foot and ankle surgeons with different level of experience in the technique performed the procedure on 6 specimens each. The repair was performed following a standardized procedure as originally described. Then, an experienced anatomist dissected all the specimens to evaluate the outcome of the ligament repair, any injuries to anatomical structures and the distance between arthroscopic portals and the superficial peroneal nerve (SPN) and sural nerve. RESULTS: Dissections revealed no injury to the nerves assessed. Mean distance from the anterolateral portal and the SPN was of 4.8 (range 0.0-10.4) mm. The mean distance from the accessory anterolateral portal to the SPN and sural nerve was of 14.2 (range 7.1-32.9) mm and 28.1 (range 2.8-39.6) mm, respectively. The difference between the 2 surgeons' groups was non-statistically significant for any measurement (mm). In all specimens both fascicles of the anterior talofibular ligament were reattached onto its original fibular footprint. The calcaneofibular ligament was not penetrated in any specimen. CONCLUSIONS: The all-inside arthroscopic lateral collateral ligament repair is a safe and reproducible technique. The clinical relevance of this study is that this technique provides a safe and anatomic reattachment of the anterior talofibular ligament, with minimal risk of injury to surrounding anatomical structures regardless of the level of experience with the technique.

The distance from the peroneal tendons sheath to the sural nerve at the posterior tip of the fibula decreases from proximal to distal.

PURPOSE: The aim of this study is to compare the distance from the peroneal tendons sheath to the sural nerve in different points proximally and distally to the tip of the fibula. METHODS: Ten fresh-frozen lower extremities were dissected to expose the nerves and tendons. Having the posterior tip of the fibula as a reference, the distance between the tendons sheath and the sural nerve was measured in each point with a tachometer with three independent different observers. Two measures were taken distally at 1.5 and 2 cm from fibula tip and 3 measures were performed proximally at 2, 3, and 5 cm from fibula tip. Data were described using means, standard deviations, medians, and minimum and maximum values. RESULTS: The average distance between distance between the fibula tip and sural nerve is 16.6 ± 4.4 mm. The average distance between peroneal tendons sheath and the sural nerve at 5 cm, 3 cm, and 2 cm from the proximal fibular tip was 29.6 ± 3.2 mm, 24.2 ± 3.6 mm, and 19.7 ± 2.7 mm, respectively. The average distance between the peroneal tendons sheath and the sural nerve at 2 cm and 1.5 cm distal to fibular tip was 9.1 ± 3.5 mm and 7.8 ± 3.3 mm, respectively. CONCLUSION: The distance from the peroneal tendons sheath to the sural nerve decreases from proximal to distal. As the distance between the peroneal tendons sheath and the sural nerve decreases from proximal to distal, performing the tendoscopy portal more distally would increase the risk of nerve iatrogenic injury.

Mechano- and thermosensitivity of injured muscle afferents 20 to 80 days after nerve injury.

Chronic injury of limb nerves leading to neuropathic pain affects deep somatic nerves. Here the functional properties of injured afferent fibers in the lateral gastrocnemius-soleus nerve were investigated 20 and 80 days after suturing the central stump of this muscle nerve to the distal stump of the sural nerve in anesthetized rats. Neurophysiological recordings were made from afferent axons identified in either the sciatic nerve (87 A-, 63 C-fibers) or the dorsal root L4/L5 (52 A-, 26 C-fibers) by electrical stimulation of the injured nerve. About 70% of the functionally identified A-fibers had regenerated into skin by 80 days after nerve suture; the remaining A-fibers could be activated only from the injured nerve. In contrast, 93% of the functionally identified C-fibers could only be activated from the injured sural nerve after 80 days. Nearly half of the injured A- (45%) and C-fibers (44%) exhibited ongoing and/or mechanically or thermally evoked activity. Because ~50% of the A- and C-fibers are somatomotor or sympathetic postganglionic axons, respectively, probably all injured muscle afferent A- and C-fibers developed ectopic activity. Ongoing activity was present in 17% of the A- and 46% of the C-fibers. Mechanosensitivity was present in most injured A- (99%) and C-fibers (85%), whereas thermosensitivity was more common in C-fibers (cold 46%, heat 47%) than in A-fibers (cold 18%, heat 12%). Practically all thermosensitive A-fibers and C-fibers were also mechanosensitive. Thus, unlike cutaneous axons, almost all A- and C-fibers afferents in injured muscle nerves demonstrate ectopic activity, even chronically after nerve injury. NEW & NOTEWORTHY After chronic injury of a muscle nerve, allowing the nerve fibers to regenerate to the target tissue, 1) most afferent A-fibers are mechanosensitive and regenerate to the target tissue; 2) ectopic ongoing activity, cold sensitivity, and heat sensitivity significantly decrease with time after injury in A-afferents; 3) most afferent C-fibers do not regenerate to the target tissue; and 4) injured C-afferents maintain the patterns of ectopic discharge properties they already show soon after nerve injury.

Risk of injury to the sural nerve during posterolateral approach to the distal tibia: An ultrasound simulation study.

When surgeons operate on the foot and ankle, the most common complication that may arise is injury of the cutaneous nerves. The sural nerve (SN) is potentially at risk of being injured when treating fractures involving the distal tibia using the posterolateral approach. The aim of this study was to evaluate how differences in length and position of the surgical treatment of fractures involving the distal tibia can affect the risk of SN injury. The study involved 40 healthy volunteers (n = 80 lower limbs). Ultrasound simulation of each potential surgical incision site was used to locate the SN and to assess the risk of injury. The study showed that the SN predominantly travels more posteriorly at levels more proximal from the tip of the lateral malleolus. At these more proximal points of the SN's course, it was proven that there was an overall increased incidence of iatrogenic injury to the SN in incisions made closer to the Achilles tendon. Based on these results, a quasi 3 dimensional figure was created showing the anatomical structures of this region to identify areas at high risk for SN injury. By revealing how length and position of the surgical incision can influence the risk of SN injury, we hope to provide information to surgeons on the optimal technique to avoid iatrogenic SN injury while operating on the distal tibia via a posterolateral approach. Clin. Anat. 31:870-877, 2018. © 2018 Wiley Periodicals, Inc.

Achillon versus open surgery in acute Achilles tendon repair.

BACKGROUND: Open Achilles tendon repairs (OATR) are associated with high complication rates. Minimally invasive surgery (MIS) techniques like the Achillon Achilles tendon repair (AATR) were developed to reduce this. We performed a systematic review and meta-analysis to compare OATR with AATR. METHODS: We performed an extensive literature search including all studies that compared the two techniques. Outcomes assessed included overall complication rate, re-rupture rate, sural nerve injury, wound length, The American Orthopaedic Foot and Ankle Scores (AOFAS) scores and return to sports. RESULTS: Eight studies were suitable for inclusion totalling 210 patients in the AATR group vs 233 patients in the OATR group. Total complication rates were significantly reduced in the Achillon patients with odd ratio of 0.14 (CI 95%, 0.08-0.27, P<0.00001) in favour. There were no significant differences in re-rupture rate, sural nerve injury, return to sports and AOFAS scores following repair between the two groups. CONCLUSIONS: AATR has fewer overall complications compared with OATR. It should be considered as an alternative to open surgical repair.

Surgical approaches to the calcaneus and the sural nerve: There is no safe zone.

BACKGROUND: Sural nerve related symptoms following the extensile lateral approach to the calcaneus (ELA) and the sinus tarsi approach (STA) are a known postoperative complication despite awareness of the course the sural nerve. While the main trunk of the sural nerve and its location relative to the approaches have been previously described, the nerve gives rise to lateral calcaneal branches (LCBs) and an anastomotic branch (AB) that may be at risk of injury. The purpose of this study was to describe the course of the sural nerve, its LCBs and the AB in relation to the ELA and STA. METHODS: 17 cadaveric foot specimens were dissected, exposing the sural nerve, the LCBs and the AB. A line representing the ELA and STA incision was then created. It was noted if the line crossed the sural nerve trunk, any of the LCBs, and the AB, and at what distance they were crossed using the distal tip of the fibula as a reference. RESULTS: The sural nerve was identified in all specimens, and the main trunk was noted to cross the path of the ELA in no specimens and the path of the STA in 2 (12%) specimens. At least one LCB of the sural nerve was identified in all specimens. The ELA crossed the path of at least one LCB in 15 specimens (88%). An AB was present in 9 specimens (53%). If an AB was present, this was crossed by the STA in every instance. CONCLUSIONS: The ELA and the STA traverses the path of either the main trunk of the sural nerve, the LCBs, or the AB in the majority of specimens, potentially accounting for the presence of sural nerve postoperative symptoms regardless of the approach used.

High resolution real time ultrasonography of the sural nerve after percutaneous repair of the Achilles tendon.

BACKGROUND: Percutaneous Achilles tendon repair has been developed to minimise soft tissue complications following treatment of tendon ruptures. However, there are concerns because of the risk of sural nerve injury. Few studies have investigated the relationship between the Achilles tendon, the sural nerve and its several anatomical course variants. METHODS: We studied 7 cadaveric limbs (7 Achilles tendons) in which a percutaneous repair of the Achilles tendon was performed. On each tendon, high resolution real time ultrasonography examination was performed by an experienced musculoskeletal radiologist before and after the procedure, with the surgeons blind to the results of the scan both before and after surgery. RESULTS: In two instances, high resolution real time ultrasonography examination revealed nerve entrapment at the level of most proximal lateral suture. CONCLUSIONS: Since the sural nerve can be easily visualised using high-frequency high resolution real time ultrasonography, intraoperative ultrasound can be of assistance during percutaneous repair of Achilles tendon rupture. CLINICAL RELEVANCE: The sural nerve can be readily visualised by high-frequency high resolution real time ultrasonography probes. It could be beneficial to use high resolution real time ultrasonography intraoperatively or perioperatively to minimise the risks of sural nerve injury when undertaking percutaneous repair of Achilles tendon tears.

Gastrocnemius recession: A cadaveric study of surgical safety and effectiveness.

Background and purpose - Many methods of gastrocnemius lengthening have been described, with different surgical challenges, outcomes, and risks to the sural nerve. Our aims were (1) to locate the gastrocnemius muscular-tendinous junction in relation to the mid-length of the fibula (from here on designated the mid-fibula), (2) to compare the dorsiflexion achieved with dorsal recession or ventral recession, and (3) to determine the risk of injury to the sural nerve during gastrocnemius recession. Methods - In 10 pairs of fresh-frozen adult cadaveric lower extremities transected above the knee, we measured dorsiflexion, performed dorsal or ventral gastrocnemius recession at the mid-fibula, and then measured the increase in dorsiflexion and fasciotomy gap. We noted the course of the sural nerve and whether the gastrocnemius muscle provided it with enough muscular coverage to protect it during recession. Results - Dorsal and ventral recession produced statistically (p < 0.05) and clinically significant mean increases in dorsiflexion with extended knee from 12° to 19°, but they were not statistically significantly different from each other in this measure or in fasciotomy gap size. At the mid-fibula, the sural nerve coursed superficially between both heads of the gastrocnemius muscle in 14 of 20 specimens. Sufficient gastrocnemius muscle coverage to protect the sural nerve was provided by the medial head in 18 of 20 specimens and by the lateral head in only 5 of 20 specimens. Interpretation - A ventral gastrocnemius recession proximal to the mid-fibula level poses less risk to the sural nerve than a recession at the mid-fibula. This procedure provides adequate lengthening (1-3 cm) and increased dorsiflexion (compared with baseline), with less risk to the sural nerve than is incurred with recession at the mid-fibular reference line.

Severe Functional Debilitations After Complications Associated With Acute Achilles Tendon Rupture With 9 Years of Follow-Up.

The purpose of the present study was to investigate the long-term effect of deep infection, sural nerve injury, and repeat rupture in the treatment of acute Achilles tendon rupture. A total of 324 patients had made a claim to the Danish Patient Insurance Association from 1992 to 2010 for a complication after acute Achilles tendon rupture. Of the 324 patients, 119 (36.7%) (77 [64.7%] males and 42 [35.3%] females) returned the Achilles tendon total rupture score and the 36-item short-form survey questionnaires. Patients with deep infection (n = 10), sural nerve injury (n = 10), and repeat rupture (n = 16) participated in a follow-up investigation. The mean follow-up period was 8.9 (range 3 to 21) years. The mean Achilles tendon total rupture score was 49 ± 27. The summary scores of the physical component and mental components scales of the 36-item Short Form Survey were 43 ± 11 and 52 ± 11, respectively. No significant differences were found among the subpopulations with deep infection, injury to the sural nerve, or repeat rupture. The physical evaluation investigating tendon length and heel rise work revealed a statistically significant difference between the affected and unaffected limb after repeat rupture (p < .01) but not after injury to the sural nerve (p > .05) or deep infection (p > .05). In conclusion, patients with from a complication after acute Achilles tendon rupture had a remarkable reduction of the Achilles tendon total rupture score and physical component scale score at mean follow-up point of 9 years. Patients with repeat rupture had a significant elongation of the tendon and reduction of strength in the affected limb.

Schwann Cell and Axon: An Interlaced Unit-From Action Potential to Phenotype Expression.

Here we propose a model of a peripheral axon with a great deal of autonomy from its cell body-the autonomous axon-but with a substantial dependence on its ensheathing Schwann cell (SC), the axon-SC unit. We review evidence in several fields and show that (i) axons can extend sprouts and grow without the concurrence of the cell body, but regulated by SCs; (ii) axons synthesize their proteins assisted by SCs that supply them with ribosomes and, probably, with mRNAs by way of exosomes; (iii) the molecular organization of the axoplasm, i.e., its phenotype, is regulated by the SC, as illustrated by the axonal microtubular content, which is down-regulated by the SC; and (iv) the axon has a program for self-destruction that is boosted by the SC. The main novelty of this model axon-SC unit is that it breaks with the notion that all proteins of the nerve cell are specified by its own nucleus. The notion of a collaborative specification of the axoplasm by more than one nucleus, which we present here, opens a new dimension in the understanding of the nervous system in health and disease and is also a frame of reference to understand other tissues or cell associations.

Comparative anatomical study of standard percutaneous and modified medialised percutaneous Bunnell type repair for artificial Achilles tendon rupture: positive effect of medialisation of the stitches with lower risk of sural nerve injury.

BACKGROUND: Less invasive percutaneous acute Achilles tendon rupture (AATR) repair techniques gain popularity because of lower risk of surgical wound complications. But these approaches have an increased risk of sural nerve iatrogenic injury as this sensory nerve is usually not visualised during minimally invasive operative procedures. We compared standard percutaneous Bunnell type and our proposed modified-medialised percutaneous technique in a cadaver study to evaluate potential advantages. MATERIALS AND METHODS: Ten pairs of fresh frozen specimens were divided into two groups for comparative anatomical study. Tenotomies of Achilles tendons were made and wounds sutured. Ten standard and 10 modified-medialised repairs were applied for artificially performed ruptures. All sutured tendons were dissected meticulously. We carefully looked at repaired Achilles tendon end-to-end contact and adaptation, distance from Achilles insertion in calcaneal tubercle to place where sural nerve crosses lateral border of the Achilles tendon and possible sural nerve and vein entrapment. Groups were compared using Fisher's exact and Student-T tests. RESULTS: All ends of sharply dissected tendons in both groups were in sufficient contact. No measurable diastasis between tendon ends was found in all cases. No entrapment of sural nerve or vein was found in modified percutaneous Bunnell suture technique group, whereas 7 of 10 sural nerves and 9 small saphenous veins were entrapped when using standard percutaneous Bunnell type technique. Average distance from Achilles tendon insertion in tuber calcanei to sural nerve crossing the lateral border of Achilles was 93 mm. CONCLUSIONS: Medialisation of percutaneous suture in AATR repair shows clear advantages compared to standard non medialised technique ensuring a possible lower incidence of sural nerve entrapment injury. Our modified percutaneous Bunnell type technique allows sufficient adaptation of ruptured Achilles tendon.

Longitudinal FDG microPET imaging of neuropathic pain: does cerebellar activity correlate with neuropathic pain development in a rat model?

BACKGROUND: We used [F-18] FDG microPET imaging as part of a longitudinal study to investigate changes in the brain. METHODS: Glucose metabolism during the development of neuropathic pain after tibial and sural nerve transection (TST) model rats. MicroPET images were obtained 1 week before operation and then weekly for 8 weeks post-operation. RESULTS: The behavioral test was performed immediately after the every FDG administration. After TST modeling, neuropathic pain rats showed increased mechanical sensitivity of the injured hind paw. The withdrawal response to mechanical pain stimulation by von Frey filaments was observed within the first week (3.8 ± 0.73), and it rapidly increased in the third week (7.13 ± 0.82). This response reached a peak in the fourth week after surgery (9.0 ± 0.53), which persisted until the eighth week. In microPET scan imaging, cerebellum, which initially started from the ansiform lobule, was activated gradually to all part from the third week in all image acquisitions through the eighth week. CONCLUSIONS: The longitudinal microPET scan study of brains from neuropathic pain rat models showed sequential cerebellar activity that was in accordance with results from behavioral test responses, thus supporting a role for the cerebellum in the development of neuropathic pain.

Anatomy of the sural nerve with an emphasis on the incision for medial displacement calcaneal osteotomy.

An inappropriately positioned skin incision for medial displacement calcaneal osteotomy can put the sural nerve at risk; however, unanimous agreement has not been reached about the optimal strategy for making this incision. In the present cadaveric study, 20 cadaveric specimens were dissected to describe the anatomic course of the sural nerve within the operative area and to provide a more practical reference for surgeons to make a safe incision. The following points were used in the analyses: point A, the tip of the lateral malleolus; point B, the inferior margin of the calcaneus on the plumb line through point A; point C, the posteroinferior margin of the calcaneus; and point D, the lateral border of the Achilles tendon on the same level (collinear) with point A. With careful dissection, the distances of the sural nerve to points A and B in the vertical direction (lines D1 and D2, respectively), to points A and C in the diagonal direction (lines D3 and D4, respectively), and to points A and D in the horizontal direction (lines D5 and D6, respectively) were measured. The landmarks were identified and the distances measured by 3 independent researchers. The median ratio of D1 to D1+D2, D3 to D3+D4, and D5 to D5+D6 was 0.36 (range 0.20 to 0.47), 0.26 (range 0.19 to 0.32), and 0.43 (range 0.34 to 0.52), respectively. Accordingly, we believe it is relatively safe to make an oblique incision that runs through the point that is no less than one third of the distance from the tip of the lateral malleolus to the posteroinferior margin of the calcaneus.

Single Oblique Posterolateral Approach for Open Reduction and Internal Fixation of Posterior Malleolar Fractures With an Associated Lateral Malleolar Fracture.

The purpose of the present retrospective study was to describe the single oblique posterolateral approach for open reduction and internal fixation of large, displaced, posterior malleolar fractures with an associated lateral malleolar fracture. A single oblique posterolateral approach was used for osteosynthesis of the posterior and lateral malleolus in 50 consecutive patients (23 females [46%], 27 males [54%]; mean age, 47.44 ± 16.13 years; mean follow-up duration, 26.32 ± 5.15 months). The mean interval to surgery was 4.3 ± 1.9 days after the inciting trauma. During the follow-up period, the surgery was complicated by skin necrosis around the incision in 2 (4%) patients and sural nerve damage in 2 (4%) patients. We found that the single oblique posterolateral approach to large, displaced, posterior malleolar fractures with an associated lateral malleolar fracture provided easy exposure of the posterior and lateral malleoli and had the potential to decrease the incidence of sural nerve injury because of the smaller incision size.

Responses of intact and injured sural nerve fibers to cooling and menthol.

Intact and injured cutaneous C-fibers in the rat sural nerve are cold sensitive, heat sensitive, and/or mechanosensitive. Cold-sensitive fibers are either low-threshold type 1 cold sensitive or high-threshold type 2 cold sensitive. The hypothesis was tested, in intact and injured afferent nerve fibers, that low-threshold cold-sensitive afferent nerve fibers are activated by the transient receptor potential melastatin 8 (TRPM8) agonist menthol, whereas high-threshold cold-sensitive C-fibers and cold-insensitive afferent nerve fibers are menthol insensitive. In anesthetized rats, activity was recorded from afferent nerve fibers in strands isolated from the sural nerve, which was either intact or crushed 6-12 days before the experiment distal to the recording site. In all, 77 functionally identified afferent C-fibers (30 intact fibers, 47 injured fibers) and 34 functionally characterized A-fibers (11 intact fibers, 23 injured fibers) were tested for their responses to menthol applied to their receptive fields either in the skin (10 or 20%) or in the nerve (4 or 8 mM). Menthol activated all intact (n = 12) and 90% of injured (n = 20/22) type 1 cold-sensitive C-fibers; it activated no intact type 2 cold-sensitive C-fibers (n = 7) and 1/11 injured type 2 cold-sensitive C-fibers. Neither intact nor injured heat- and/or mechanosensitive cold-insensitive C-fibers (n = 25) and almost no A-fibers (n = 2/34) were activated by menthol. These results strongly argue that cutaneous type 1 cold-sensitive afferent fibers are nonnociceptive cold fibers that use the TRPM8 transduction channel.

An anatomical and cadaveric study examining the risk of sural nerve injury in percutaneous Achilles tendon repair using the Achillon device.

BACKGROUND: Percutaneous Achilles tendon repairs are gaining in popularity. This study aims to quantify the risk of sural nerve injury when using the Achillon device. METHODS: The Achillon device was instrumented into 15 cadaveric specimens and through dissection the rate of sural nerve puncture and the position of the sural nerve in relation to the Achilles tendon was documented. RESULTS: The sural nerve was found lateral to the Achilles tendon insertion point over a range of 14.3mm and crossed the lateral border of the Achilles tendon over a range of 57.7mm. The sural nerve was punctured a total of 6 times and in 4 out of 15 cadaveric specimens (27%). Four out of the 6 punctures occurred when the Achillon device was instrumented distally. CONCLUSIONS: The sural nerve displays a highly variable anatomical course and there is a risk of puncture during percutaneous Achilles tendon repair using the Achillon device.

Posterior ankle and hind foot arthroscopy - how do you responsibly learn this new technique?

Posterior ankle and hind foot arthroscopy has become an important diagnostic and therapeutic tool when dealing with ankle pathology. Although not yet widely adopted it is gaining popularity and there have been various descriptions of the technique [1] and its outcomes [2,3]. With posterior arthroscopy there are well-documented risks of injury to the sural nerve and medial neurovascular bundle in particular [7-9]. These risks need to be carefully considered, particularly by surgeons early in the learning curve of what is undoubtedly a challenging technique. In an ideal world there should be scope for regular simulation to be integrated into a consultant's working week and this would allow them to be prepared for untoward incidences and also learn new techniques such as hind-foot arthroscopy in a safe environment prior to introduction into clinical practice.