Repair of distal finger soft-tissue defects with free fibular great toe neurovascular flaps.

BACKGROUND: This work aimed to investigate the change in fingerprint depth and the recovery rule of fingerprint biological recognition function after repairing finger abdominal defects and rebuilding fingerprint with a free flap. METHOD: From April 2018 to March 2023, we collected a total of 43 cases of repairing finger pulp defects using the free flap of the fibular side of the great toe with the digital nerve. After surgery, irregular follow-up visits were conducted to observe fingerprint clarity, perform the ninhydrin test or detect visible sweating with the naked eye. We recorded fingerprint clarity, nail shape, two-point discrimination, cold perception, warm perception and fingerprint recognition using smartphones. The reconstruction process of the repaired finger was recorded to understand the changes in various observation indicators and their relationship with the depth of the fingerprint. The correlation between fingerprint depth and neural repair was determined, and the process of fingerprint biological recognition function repair was elucidated. RESULT: All flaps survived, and we observed various manifestations in different stages of nerve recovery. The reconstructed fingerprint had a clear fuzzy process, and the depth changes of the fingerprint were consistent with the changes in the biological recognition function curve. CONCLUSION: The free flap with the digital nerve is used to repair finger pulp defects. The reconstructed fingerprint has a biological recognition function, and the depth of the fingerprint is correlated with the process of nerve repair. The fingerprint morphology has a dynamic recovery process, and it can reach a stable state after 6-8 months.

Longitudinal intravital imaging nerve degeneration and sprouting in the toes of spared nerve injured mice.

Neuropathic pain is pain caused by damage to the somatosensory nervous system. Both degenerating injured nerves and neighboring sprouting nerves can contribute to neuropathic pain. However, the mesoscale changes in cutaneous nerve fibers over time after the loss of the parent nerve has not been investigated in detail. In this study, we followed the changes in nerve fibers longitudinally in the toe tips of mice that had undergone spared nerve injury (SNI). Nav1.8-tdTomato, Thy1-GFP and MrgD-GFP mice were used to observe the small and large cutaneous nerve fibers. We found that peripheral nerve plexuses degenerated within 3 days of nerve injury, and free nerve endings in the epidermis degenerated within 2 days. The timing of degeneration paralleled the initiation of mechanical hypersensitivity. We also found that some of the Nav1.8-positive nerve plexuses and free nerve endings in the fifth toe survived, and sprouting occurred mostly from 7 to 28 days. The timing of the sprouting of nerve fibers in the fifth toe paralleled the maintenance phase of mechanical hypersensitivity. Our results support the hypotheses that both injured and intact nerve fibers participate in neuropathic pain, and that, specifically, nerve degeneration is related to the initiation of evoked pain and nerve sprouting is related to the maintenance of evoked pain.

To Be or Not to Be (A Morton's/Interdigital Neuroma): That Is the Question-A Case Series of Lateral Forefoot Pain Localized to the Proper Digital Nerve of the Fifth Toe.

ABSTRACT: We present 2 cases where the initial history and examination were similar to a Morton's/interdigital neuroma. In both cases, however, diagnostic ultrasound revealed symptomatic snapping of the proper digital nerve of the fifth toe. The anatomy of the proper digital nerve of the fifth toe may predispose it to a snapping phenomenon. Clinical awareness of this atypical cause of forefoot pain can help guide the diagnosis and treatment in those patients with persistent and refractory lateral forefoot pain and paresthesias.

Rare Schwannoma Nerve Tumor in a Lesser Toe: A Case Report.

A schwannoma is a solitary benign tumor composed of Schwann cells occurring anywhere in the peripheral nervous system. The diagnosis of a schwannoma is often difficult to make by clinical presentation and advanced imaging modalities. We present a case report of a 61-year-old Hispanic woman with a left-foot, third-digit, soft-tissue mass. The diagnosis of a schwannoma of the proper digital nerve was made postsurgically by means of histopathologic and immunohistochemistry parameters. This is a rare location for a schwannoma, and neurogenic tumor should be included in the differential diagnosis of soft-tissue mass, as there have been prior case reports.

Organized Toe Maps in Extreme Foot Users.

Although the fine-grained features of topographic maps in the somatosensory cortex can be shaped by everyday experience, it is unknown whether behavior can support the expression of somatotopic maps where they do not typically occur. Unlike the fingers, represented in all primates, individuated toe maps have only been found in non-human primates. Using 1-mm resolution fMRI, we identify organized toe maps in two individuals born without either upper limb who use their feet to substitute missing hand function and even support their profession as foot artists. We demonstrate that the ordering and structure of the artists' toe representation mimics typical hand representation. We further reveal "hand-like" features of activity patterns, not only in the foot area but also similarly in the missing hand area. We suggest humans may have an innate capacity for forming additional topographic maps that can be expressed with appropriate experience.

Somatosensory Cortical Neurons Decode Tactile Input Patterns and Location from Both Dominant and Non-dominant Digits.

For neurons of the primary somatosensory cortex, the anatomy of the thalamocortical connections supports a digit-wise specialization, whereas the intracortical connections suggest cross-digit integration. To evaluate the digit-wise specialization in individual somatosensory neurons, we explored the decoding of eight spatiotemporally complex tactile input patterns delivered to two non-adjacent digits in the anaesthetized rat. A striking finding was a good decoding performance for the eight input patterns to the non-dominant digit of the neuron, which in some cases was even better than for the same inputs to the dominant digit. Moreover, individual neurons decoded not only the pattern received but also to which digit it was delivered. These neuronal decoding properties were uniform throughout the cortical layers. Our results indicate that non-trivial tactile inputs to a single digit engage a wide processing circuitry throughout the digit region and suggest a low impact for somatotopy on the organization of the information processing.

Axonal regrowth is impaired during digit tip regeneration in mice.

Mice are intrinsically capable of regenerating the tips of their digits after amputation. Mouse digit tip regeneration is reported to be a peripheral nerve-dependent event. However, it is presently unknown what types of nerves and Schwann cells innervate the digit tip, and to what extent these cells regenerate in association with the regenerative response. Given the necessity of peripheral nerves for mammalian regeneration, we investigated the neuroanatomy of the unamputated, regenerating, and regenerated mouse digit tip. Using immunohistochemistry for ß-III-tubulin (ß3T) or neurofilament H (NFH), substance P (SP), tyrosine hydroxylase (TH), myelin protein zero (P0), and glial fibrillary acidic protein (GFAP), we identified peripheral nerve axons (sensory and sympathetic), and myelinating- and non-myelinating-Schwann cells. Our findings show that the digit tip is innervated by two digital nerves that each bifurcate into a bone marrow (BM) and connective tissue (CT) branch. The BM branches are composed of sympathetic axons that are ensheathed by non-myelinating-Schwann cells whereas the CT branches are composed of sensory and sympathetic axons and are ensheathed by myelinating- and non-myelinating-Schwann cells. The regenerated digit neuroanatomy differs from unamputated digit in several key ways. First, there is 7.5 fold decrease in CT branch axons in the regenerated digit compared to the unampuated digit. Second, there is a 5.6 fold decrease in myelinating-Schwann cells in the regenerated digit compared to the unamputated digit that is consistent with the decrease in CT branch axons. Importantly, we also find that the central portion of the regenerating digit blastema is aneural, with axons and Schwann cells restricted to peripheral and distal blastema regions. Finally, we show that even with impaired innervation, digits maintain the ability to regenerate after re-amputation. Taken together, these data indicate that nerve regeneration is impaired in the context of mouse digit tip regeneration.

The Application of Medical Thermography to Discriminate Neuroischemic Toe Ulceration in the Diabetic Foot.

This study aimed to determine whether thermal imaging can detect temperature differences between healthy feet, nonulcerated neuroischemic feet, and neuroischemic feet with toe ulcers in patients with type 2 diabetes mellitus (T2DM). Participants were prospectively divided into 3 groups: T2DM without foot problems; a healthy, nonulcerated neuroischemic group, and an ulcerated neuroischemic group. Thermal images of the feet were obtained with automated segmentation of regions of interest. Thermographic images from 43 neuroischemic feet, 21 healthy feet, and 12 neuroischemic feet with active ulcer in one of the toes were analyzed. There was a significant difference in toe temperatures between the 3 groups ( P = .001), that is, nonulcerated neuroischemic (n = 181; mean temperature = 27.7°C [±2.16 SD]) versus neuroischemic ulcerated (n = 12; mean temperature = 28.7°C [±3.23 SD]), and healthy T2DM group (n = 104; mean temperature = 24.9°C [±5.04 SD]). A post hoc analysis showed a significant difference in toe temperatures between neuroischemic nonulcerated and healthy T2DM groups ( P = .001), neuroischemic ulcerated and healthy groups ( P = .001). However, no significant differences in toe temperatures were identified between the ulcerated neuroischemic and nonulcerated neuroischemic groups ( P = .626). There were no significant differences between the ulcerated toes (n = 12) and the nonulcerated toes (n = 57) of the same foot in the ulcerated neuroischemic group ( P = .331). Toe temperatures were significantly higher in neuroischemic feet with or without ulceration compared with healthy feet in patients with T2DM. There were no significant differences in temperatures of ulcerated toes and the nonulcerated toes of the same foot, implying that all the toes of the same foot could potentially be at risk of developing complications, which can be potentially detected by infrared thermography.

Thermosensory micromapping of warm and cold sensitivity across glabrous and hairy skin of male and female hands and feet.

The ability of hands and feet to convey skin thermal sensations is an important contributor to our experience of the surrounding world. Surprisingly, the detailed topographical distribution of warm and cold thermosensitivity across hands and feet has not been mapped, although sensitivity maps exist for touch and pain. Using a recently developed quantitative sensory test, we mapped warm and cold thermosensitivity of 103 skin sites over glabrous and hairy skin of hands and feet in male (M; 30.2 ± 5.8 yr) and female (F; 27.7 ± 5.1 yr) adults matched for body surface area (M: 1.77 ± 0.2 m2; F: 1.64 ± 0.1 m2; P = 0.155). Findings indicated that warm and cold thermosensitivity varies by fivefold across glabrous and hairy skin of hands and feet and that hands (warm/cold sensitivity: 1.25/2.14 vote/°C) are twice as sensitive as the feet (warm/cold sensitivity: 0.51/0.99 vote/°C). Opposite to what is known for touch and pain sensitivity, we observed a characteristic distal-to-proximal increase in thermosensitivity over both hairy and glabrous skin (i.e., from fingers and toes to body of hands and feet), and found that hairy skin is more sensitive than glabrous. Finally, we show that body surface area-matched men and women presented small differences in thermosensitivity and that these differences are constrained to glabrous skin only. Our high-density thermosensory micromapping provides the most detailed thermosensitivity maps of hands and feet in young adults available to date. These maps offer a window into peripheral and central mechanisms of thermosensory integration in humans and will help guide future developments in smart skin and sensory neuroprostheses, in wearable, energy-efficient personal comfort systems, and in sport and protective clothing. NEW & NOTEWORTHY We provide the most detailed thermosensitivity maps across glabrous and hairy skin of hands and feet in men and women available to date. Our maps show that thermosensitivity varies by fivefold across hands and feet, distal regions (e.g., fingers, toes) are less sensitive than proximal (e.g., palm, sole), hands are twice as sensitive as feet, and men and women present small thermosensitivity differences. These findings will help guide developments in sensory neuroprostheses, wearable comfort systems, and sport/protective clothing.

Reconstruction of the plantar toe with a distal reverse instep sensory island flap.

BACKGROUND: Plantar toe ulcers are a challenging surgical problem. There are several methods for reconstruction, but no attention has been given to the preservation of sensation. This report proposes a method to provide protective sensation for the reconstructed area. PATIENTS AND METHODS: The ulcers of seven patients ranged from 2 × 3 to 7 × 3 cm with defects of the plantar first toe and distal metatarsus, including four burns, a trauma, a diabetic ulcer, and a neuropathy injury reconstructed with a distal reverse instep sensory island (DRISI) flap. The patients were 21-38 years old. The second metatarsus medial nerve was co-opted using the end-to-side method to the adjacent lateral nerve, then its proximal stump provided the donor nerve for the sensation of the flap. Patients were assessed in terms of protective sensory functions, including touch, pain, dermatomeric somatosensory-evoked potentials (SEP), thermal sensation and Semmes-Weinstein monofilament (SWM) light touch. RESULTS: The flaps ranged from 2 × 3 to 7 × 3 cm. All transferred flaps to the plantar first toe survived. No complications were observed at the donor and flap sites. Patients were followed-up 8-24 months. Except for two cases, all nerves of the donor and flap sites exhibited protective sensation, including positive SEP responses between 44 and 50 ms and positive SWM responses ≤ 3.84. CONCLUSION: The DRISI flap can be used for the reconstruction of various plantar first toe defects with acceptable protective sensation. End-to-side neurorrhaphy provides a sensory nerve end to subsequent end to end co-optation to the flap nerve for protective sensation.

The conventional tuning fork as a quantitative tool for vibration threshold.

INTRODUCTION: This study was undertaken to describe a method for quantifying vibration when using a conventional tuning fork (CTF) in comparison to a Rydel-Seiffer tuning fork (RSTF) and to provide reference values. METHODS: Vibration thresholds at index finger and big toe were obtained in 281 participants. Spearman's correlations were performed. Age, weight, and height were analyzed for their covariate effects on vibration threshold. Reference values at the fifth percentile were obtained by quantile regression. RESULTS: The correlation coefficients between CTF and RSTF values at finger/toe were 0.59/0.64 (P = 0.001 for both). Among covariates, only age had a significant effect on vibration threshold. Reference values for CTF at finger/toe for the age groups 20-39 and 40-60 years were 7.4/4.9 and 5.8/4.6 s, respectively. Reference values for RSTF at finger/toe for the age groups 20-39 and 40-60 years were 6.9/5.5 and 6.2/4.7, respectively. DISCUSSION: CTF provides quantitative values that are as good as those provided by RSTF. Age-stratified reference data are provided. Muscle Nerve 57: 49-53, 2018.

End-to-side neurotization with the phrenic nerve in restoring the function of toe extension: an experimental study in a rat model.

The phrenic nerve being transferred to the posterior division of the lower trunk with end-to-end neurorrhaphy is reported to be effective in restoring the function of digit extension in literature. However, the phrenic nerve is extremely important in respiration. We designed an animal experiment to discover whether the phrenic nerve being transferred to the posterior division of the lower trunk with end-to-side neurotization was feasible and provided the theoretical basis. A sum of 36 Sprague-Dawley rats was randomly assigned to one of two groups. In Group A, the phrenic nerve was transferred to the posterior division of the lower trunk with end-to-side neurotization. In Group B, the posterior division of the lower trunk was directly sutured. The results of behavioral assessment, electrophysiology, histology and nerve fiber count and muscle weight at 12 weeks postoperatively were recorded. In Group A, none of the rats experienced tachypnea. The motion of slight toe extension was observed. The results of electrophysiology, histology and nerve fiber count and muscle weight in Group A were not as well as those of Group B, but gradually improved with time. The phrenic nerve being transferred to the posterior division of lower trunk with end-to-side neurotization can partially restore the function of toe extension in a rat model. Whether the function of digit extension can be restored by the phrenic nerve with end-to-side neurotization in humans still needs more practice in clinic.

Microstimulation of single human motor axons in the toe extensors: force production during long-lasting trains of irregular and regular stimuli.

Human motoneurones are known to discharge with a physiological variability of ~25% during voluntary contractions. Using microstimulation of single human motor axons, we have previously shown that delivering brief trains (10 pulses) of irregular stimuli, which incorporate discharge variability, generates greater contractile responses than trains of regular stimuli with identical mean frequency but zero variability. We tested the hypothesis that longer irregular (physiological) trains would produce greater contractile responses than regular (nonphysiological) trains of the same mean frequency (18 Hz) and duration (45 sec). Tungsten microelectrodes were inserted into the common peroneal nerve of human subjects, and single motor axons supplying the toe extensors (n = 14) were isolated. Irregular trains of stimuli showed greater contractile responses over identical mean frequencies in both fatigue-resistant and fatigable motor units, but because the forces were higher the rate of decline was higher. Nevertheless, forces produced by the irregular trains were significantly higher than those produced by the regular trains. We conclude that discharge irregularity augments force production during long as well as short trains of stimulation.

Toe-Sparing Surgery for Neuropathic Toe Ulcers With Exposed Bone or Joint in an Outpatient Setting: A Retrospective Study.

The purpose of this study was to review the results of aggressive surgical debridement of neuropathic toe ulcers with exposed bone or joint. We identified patients with a single toe ulcer with exposed bone or joint that had been operated on in an outpatient setting. The surgery had included aggressive debridement and was performed using a small curette and rongeur, followed by oral antibiotic treatment at home. Success was defined as complete healing with no recurrence 6 months after full wound closure and epitheliazation was achieved. Twenty-five patients with neuropathic toe ulcers (72% male) had a total of 26 primary operations. Their mean age was 60 ± 12 years. In 22 patients, the neuropathy resulted from diabetes mellitus of 17 ± 9 years' duration. The mean ulcer duration was 6 weeks (range 1-24). The mean number of visits per patient was 6.5 (range 3-20). The ulcers closed in a median of 5 weeks (8 ± 6 weeks, range 3-24 weeks, Q1-Q3 4-10 weeks). At 6 months, 3 (11.5%) patients had needed a toe amputation for infection or necrosis that could not be controlled. None needed a major amputation or hospitalization related to the ulcer. Toe-sparing surgery is feasible and in a select population can have a high success rate (88%), even though it does dictate more dedicated patient care.

Excision With Interpositional Nerve Grafting: An Alternative Technique for the Treatment of Morton Neuroma.

INTRODUCTION: "Morton neuroma" is a common cause of forefoot pain with numbness frequently occurring in the distribution of the third common digital nerve. After the failure of nonoperative measures, decompression with excision of the neuroma is common practice. Residual numbness and recurrent pain has been reported as a consequence of this treatment option. This study describes excision of the neuroma with interpositional nerve grafting as a treatment option for Morton neuroma. This proposed technique has the benefit of reducing pain, reducing recurrent secondary neuromas and restoring postexcision sensory deficits. METHODS: A retrospective chart review of patients who underwent elective primary excision of a Morton neuroma with interpositional nerve grafting was undertaken. Patient demographics, surgical technique, and clinical outcomes, such as pain, neuroma recurrence, 2-point discrimination, numbness, and weight-bearing status at minimum of 1 year postoperation, are reported. RESULTS: Eight patients (9 neuromas) underwent excision of the Morton neuroma with interpositional nerve grafting after failing nonoperative measures. At final follow-up, all patients had improvement of pain and there were no neuroma recurrences. Sensation to the grafted hemi-toe returned in all but 1 case. All patients returned to full weight-bearing status. Although no major complications were reported, wound dehiscence secondary to a hematoma occurred in 1 case. CONCLUSIONS: Excision and interpositional nerve grafting is an effective treatment for Morton neuroma as it alleviates pain, numbness and restores sensation with minimal morbidity and complications.

The combined ALT-groin flap for the mutilated and degloved hand.

BACKGROUND: Degloving and mutilation of the hand is a rare but formidable challenge. When replantation is not possible, we rely on distant pedicled flaps. We present a technique using pedicled anterolateral thigh (ALT) and groin flaps to sandwich and resurface the degloved hand. The purpose of this study is to describe the rationale, indications, methods and outcomes of combined pedicled ALT and groin flap reconstruction of the degloved hand. METHODS: Five injuries were treated at this center between 2011 and 2014. Charts were retrospectively reviewed and outcomes evaluated. Four ALT-groin flaps were performed in a single stage for degloving, crush and combined injuries. In one case, partial necrosis of a tight groin flap necessitated secondary ALT coverage at a second stage. RESULTS: Flaps survived after division at 4 weeks, and venous congestion was not observed at any point. Debulking, syndactyly release and toe transfer followed reconstruction to enhance outcomes. CONCLUSIONS: The combined ALT-groin flap is safe and feasible for the reconstruction of the degloved or mutilated hand when replantation is not an option. It is attractive for familiar donor anatomy, donor-site morbidity and the quantity and composition of the tissue it provides.

Treatment of dystonia in extensor hallucis longus and digitorum muscles with neurotomy of the branches of the deep fibular nerve: Preliminary results.

INTRODUCTION: Dystonia in extensor hallucis and/or digitorum muscles can be observed in pyramidal and extrapyramidal lesions and results in pain in these toes, spontaneous or when walking, problems and discomfort when putting on shoes and socks, and cutaneous lesions on the toes. The objective of this study was to assess the efficacy and safety of deep fibular nerve neurotomy for the extensor hallucis longus (EHL) and/or the extensor digitorum longus (EDL) branches in the treatment of extension dystonia of the hallux and/or other toes. PATIENTS AND METHODS: A deep fibular nerve neurotomy was performed in 20 patients (n=19 for the EHL, n=6 for the EDL). We retrospectively analyzed the treatment's efficacy and safety and assessed the patients' self-reported improvement and overall treatment satisfaction. RESULTS: Dystonia totally disappeared in 15 cases (75%); it persisted at a minimal level in the other patients. The patients reported a decrease in pain (P<0.01) and fewer difficulties putting on shoes and socks (P<0.001) and had a high median level of satisfaction (8.5/10). Adverse effects were rare and transient. The identification of the nerve branches was sometimes difficult. DISCUSSION: Deep fibular nerve neurotomy for the EHL and/or EDL branches seems to be an effective treatment for extension dystonia of the hallux and/or other toes and its consequences for the adult neurological patient. However, these encouraging preliminary results should be confirmed by prospective, longer-term studies.