Automated whole slide morphometry of sural nerve biopsy using machine learning.

AIM: The morphometry of sural nerve biopsies, such as fibre diameter and myelin thickness, helps us understand the underlying mechanism of peripheral neuropathies. However, in current clinical practice, only a portion of the specimen is measured manually because of its labour-intensive nature. In this study, we aimed to develop a machine learning-based application that inputs a whole slide image (WSI) of the biopsied sural nerve and automatically performs morphometric analyses. METHODS: Our application consists of three supervised learning models: (1) nerve fascicle instance segmentation, (2) myelinated fibre detection and (3) myelin sheath segmentation. We fine-tuned these models using 86 toluidine blue-stained slides from various neuropathies and developed an open-source Python library. RESULTS: Performance evaluation showed (1) a mask average precision (AP) of 0.861 for fascicle segmentation, (2) box AP of 0.711 for fibre detection and (3) a mean intersection over union (mIoU) of 0.817 for myelin segmentation. Our software identified 323,298 nerve fibres and 782 fascicles in 70 WSIs. Small and large fibre populations were objectively determined based on clustering analysis. The demyelination group had large fibres with thinner myelin sheaths and higher g-ratios than the vasculitis group. The slope of the regression line from the scatter plots of the diameters and g-ratios was higher in the demyelination group than in the vasculitis group. CONCLUSION: We developed an application that performs whole slide morphometry of human biopsy samples. Our open-source software can be used by clinicians and pathologists without specific machine learning skills, which we expect will facilitate data-driven analysis of sural nerve biopsies for a more detailed understanding of these diseases.

Ultrahigh-frequency ultrasound of fascicles in the common fibular, superficial fibular, and sural nerves.

INTRODUCTION/AIMS: While ultrasound assessment of cross-sectional area and echogenicity has gained popularity as a biomarker for various neuropathies, there is a scarcity of data regarding fascicle count and density in neuropathies or even healthy controls. The aim of this study was to determine whether fascicles within select lower limb nerves (common fibular, superficial fibular, and sural nerves) can be counted in healthy individuals using ultrahigh-frequency ultrasound (UHFUS). METHODS: Twenty healthy volunteers underwent sonographic examination of the common fibular, superficial fibular, and sural nerves on each lower limb using UHFUS with a 48 MHz linear transducer. Fascicle counts and density in each examined nerve were determined by a single rater. RESULTS: The mean fascicle number for each of the measured nerves included the following: common fibular nerve 9.85 (SD 2.29), superficial fibular nerve 5.35 (SD 1.59), and sural nerve 6.73 (SD 1.91). Multivariate linear regression analysis revealed a significant association between cross-sectional area and fascicle count for all three nerves. In addition, there was a significant association seen in the common fibular nerve between fascicle density and height, weight, and body mass index. Age and sex did not predict fascicle count or density (all p > .13). DISCUSSION: UHFUS enabled the identification and counting of fascicles and fascicle density in the common fibular, superficial fibular, and sural nerves. Knowledge about normal values and normal peripheral nerve architecture is needed in order to further understand and identify pathological changes that may occur within each nerve in different disease states.

Initial findings using high-resolution magnetic resonance imaging for visualisation of the sural nerve and surrounding anatomy in healthy volunteers at 7 Tesla.

BACKGROUND AND AIMS: Histopathological diagnosis is the gold standard in many acquired inflammatory, infiltrative and amyloid based peripheral nerve diseases and a sensory nerve biopsy of sural or superficial peroneal nerve is favoured where a biopsy is deemed necessary. The ability to determine nerve pathology by high-resolution imaging techniques resolving anatomy and imaging characteristics might improve diagnosis and obviate the need for biopsy in some. The sural nerve is anatomically variable and occasionally adjacent vessels can be sent for analysis in error. Knowing the exact position and relationships of the nerve prior to surgery could be clinically useful and thus reliably resolving nerve position has some utility. METHODS: 7T images of eight healthy volunteers' (HV) right ankle were acquired in a pilot study using a double-echo in steady-state sequence for high-resolution anatomy images. Magnetic Transfer Ratio images were acquired of the same area. Systematic scoring of the sural, tibial and deep peroneal nerve around the surgical landmark 7 cm from the lateral malleolus was performed (number of fascicles, area in voxels and mm2, diameter and location relative to nearby vessels and muscles). RESULTS: The sural and tibial nerves were visualised in the high-resolution double-echo in steady-state (DESS) image in all HV. The deep peroneal nerve was not always visualised at level of interest. The MTR values were tightly grouped except in the sural nerve where the nerve was not visualised in two HV. The sural nerve location was found to be variable (e.g., lateral or medial to, or crossing behind, or found positioned directly posterior to the saphenous vein). INTERPRETATION: High-resolution high-field images have excellent visualisation of the sural nerve and would give surgeons prior knowledge of the position before surgery. Basic imaging characteristics of the sural nerve can be acquired, but more detailed imaging characteristics are not easily evaluable in the very small sural and further developments and specific studies are required for any diagnostic utility at 7T.

Selective neural inhibition via photobiomodulation alleviates behavioral hypersensitivity associated with small sensory fiber activation.

OBJECTIVE: Photobiomodulation at higher irradiances has great potential as a pain-alleviating method that selectively inhibits small diameter nerve fibers and corresponding sensory experiences, such as nociception and heat sensation. The longevity and magnitude of these effects as a function of laser irradiation parameters at the nerve was explored. METHODS: In a rodent chronic pain model (spared nerve injury-SNI), light was applied directly at the sural nerve with four delivery schemes: two irradiance levels (7.64 and 2.55 W/cm2 ) for two durations each, corresponding to either 4.8 or 14.4 J total energy, and the effect on sensory hypersensitivities was evaluated. RESULTS: At emitter irradiances of 7.64 W/cm2 (for 240 s), 2.55 W/cm2 (for 720 s), and 7.64 W/cm2 (for 80 s) the heat hypersensitivity was relieved the day following photobiomodulation (PBM) treatment by 37 ± 8.1% (statistically significant, p < 0.001), 26% ± 6% (p = 0.072), and 28 ± 6.1% (statistically significant, p = 0.032), respectively, and all three treatments reduced the hypersensitivity over the course of the experiment (13 days) at a statistically significant level (mixed-design analysis of variance, p < 0.05). The increases in tissue temperature (5.3 ± 1.0 and 1.3 ± 0.4°C from 33.3°C for the higher and lower power densities, respectively) at the neural target were well below those typically associated with permanent action potential disruption. CONCLUSIONS: The data from this study support the use of direct PBM on nerves of interest to reduce sensitivities associated with small-diameter fiber activity.

Role of tactile stimulation during the preweaning period on the development of the peripheral sensory sural (SU) nerve in adult artificially reared female rat.

Maternal deprivation, as a result of the artificial rearing (AR) paradigm, disturbs electrophysiological and histological characteristics of the peripheral sensory sural (SU) nerve of infant and adult male rats. Such changes are prevented by providing tactile or social stimulation during isolation. AR also affects the female rat's brain and behavior; however, it is unknown whether this early adverse experience also alters their SU nerve development or if tactile stimulation might prevent these possible developmental effects. To assess these possibilities, the electrophysiological and histological characteristics of the SU nerve from adult diestrus AR female rats that: (i) received no tactile stimulation (AR group), (ii) received tactile stimulation in the anogenital and body area (AR-Tactile group), or (iii) were mother reared (MR group) were determined. We found that the amplitude, but not the area, of the evoked compound action potential response in SU nerves of AR rats was lower than those of SU nerves of MR female rats. Tactile stimulation prevented these effects. Additionally, we found a reduction in the outer diameter and myelin thickness of axons, as well as a large proportion of axons with low myelin thickness in nerves of AR rats compared to the nerves of the MR and AR-Tactile groups of rats; however, tactile stimulation only partially prevented these effects. Our data indicate that maternal deprivation disturbs the development of sensory SU nerves in female rats, whereas tactile stimulation partially prevents the changes generated by AR. Considering that our previous studies have shown more severe effects of AR on male SU nerve development, we suggest that sex-associated factors may be involved in these processes.

Superficial retrocalcaneal bursae and nerves: From anatomy to ultrasound-guided procedures.

The pertinent literature widely describes ultrasound-guided procedures targeting the retrocalcaneal bursa and the tendon tissue to manage insertional Achilles tendinopathy. Synovial bursae and cutaneous nerves of the superficial retrocalcaneal pad are often overlooked pain generators and are poorly considered by clinicians and surgeons. A layer-by-layer dissection of the superficial soft tissues in the retrocalcaneal region of two fresh frozen cadavers was matched with historical anatomical tables of the textbook Traite d'Anatomie Topographique Avec Applications Médico-Chirurgicales (1909 by Testut and Jacob). An accurate and detailed description of the superficial retrocalcaneal pad with its synovial bursae and cutaneous nerves was provided. Cadaveric dissections confirmed the compartmentalized architecture of the superficial retrocalcaneal fat pad and its histological continuum with the superficial lamina of the crural fascia. Superficial synovial tissue islands have been demonstrated on the posterior aspect of the Achilles tendon in one cadaver and on the posterolateral surface of the tendon in the other one. Digitalization of the original anatomical tables of the textbook Traite d'Anatomie Topographique Avec Applications Médico-Chirurgicales (1909 by Testut and Jacob) showed five potential locations of the superficial calcaneal bursa and a superficial retrocalcaneal nerve plexus within the Achilles tendon-fat pad interface. In clinical practice, in addition to the previously described interventions regarding the retrocalcaneal bursa and the tendon tissue, ultrasound-guided procedures targeting the synovial and neural tissues of the superficial retrocalcaneal pad should be considered to optimize the management of insertional Achilles tendinopathy.

Utilization of the Rat Tibial Nerve Transection Model to Evaluate Cellular and Molecular Mechanisms Underpinning Denervation-Mediated Muscle Injury.

Peripheral nerve injury denervates muscle, resulting in muscle paralysis and atrophy. This is reversible if timely muscle reinnervation occurs. With delayed reinnervation, the muscle's reparative ability declines, and muscle-resident fibro-adipogenic progenitor cells (FAPs) proliferate and differentiate, inducing fibro-fatty muscle degradation and thereby physical disability. The mechanisms by which the peripheral nerve regulates FAPs expansion and differentiation are incompletely understood. Using the rat tibial neve transection model, we demonstrated an increased FAPs content and a changing FAPs phenotype, with an increased capacity for adipocyte and fibroblast differentiation, in gastrocnemius muscle post-denervation. The FAPs response was inhibited by immediate tibial nerve repair with muscle reinnervation via neuromuscular junctions (NMJs) and sensory organs (e.g., muscle spindles) or the sensory protection of muscle (where a pure sensory nerve is sutured to the distal tibial nerve stump) with reinnervation by muscle spindles alone. We found that both procedures reduced denervation-mediated increases in glial-cell-line-derived neurotrophic factor (GDNF) in muscle and that GDNF promoted FAPs adipogenic and fibrogenic differentiation in vitro. These results suggest that the peripheral nerve controls FAPs recruitment and differentiation via the modulation of muscle GDNF expression through NMJs and muscle spindles. GDNF can serve as a therapeutic target in the management of denervation-induced muscle injury.

A TRPV4 mutation caused Charcot-Marie-Tooth disease type 2C with scapuloperoneal muscular atrophy overlap syndrome and scapuloperoneal spinal muscular atrophy in one family: a case report and literature review.

BACKGROUND: Charcot-Marie-Tooth disease 2C (CMT2C) and scapuloperoneal spinal muscular atrophy (SPSMA) are different clinical phenotypes of TRPV4 mutation. The mutation of p.R316C has been reported to cause CMT2C and SPSMA separately. CASE PRESENTATION: Here, we reported a Chinese family harboring the same p.R316C variant, but with an overlap syndrome and different clinical manifestations. A 58-year-old man presented with severe scapula muscle atrophy, resulting in sloping shoulders. He also exhibited distinct muscle atrophy in his four limbs, particularly in the lower limbs. The sural nerve biopsy revealed severe loss of myelinated nerve fibers with scattered regenerating clusters and pseudo-onion bulbs. Nerve conduction study showed axon damage in both motor and sensory nerves. Sensory nerve action potentials could not be evoked in bilateral sural or superficial peroneal nerves. He was diagnosed with Charcot-Marie-Tooth disease type 2C and scapuloperoneal muscular atrophy overlap syndrome, whereas his 27-year-old son was born with clubfoot and clinodactyly. Electromyogram examination indicated chronic neurogenic changes and anterior horn cells involvement. Although there was no obvious weakness or sensory symptoms, early SPSMA could be considered for him. CONCLUSIONS: A literature review of the clinical characteristics in CMT2C and SPSMA patients with TRPV4 mutation suggested that our case was distinct due to the overlap syndrome and phenotype variation. Altogether, this case broadened the phenotype spectrum and provided the nerve biopsy pathological details of TRPV4-related neuropathies.

Efficacy of vitamin and antioxidant supplements for treatment of diabetic peripheral neuropathy: systematic review and meta-analysis of randomized controlled trials.

ABSTRACTThe results of treatment effect of vitamin or antioxidant intake on diabetic peripheral neuropathy (DPN) was inconsistent. Therefore, we performed a meta-analysis of randomized controlled trials (RCTs) to examine whether these supplements are effective in DPN treatment. We searched seven databases from inception to October 2021. All RCTs of DPN treatments with vitamin and antioxidant supplements were included. We performed sensitivity and subgroup analysis, and also tested for publication bias by the funnel plot and Egger's test. A total of 14 studies with 1384 patients were included in this systematic review. Three high-quality trials showed that vitamin and antioxidant supplements significantly increased sensory nerve conduction velocity (SNCV) of the sural nerve (MD = 2.66, 95%CI (0.60, 4.72), P < 0.05, I2 = 0%). Seven studies (758 participants) suggested that these supplements might have improvement on motor nerve conduction velocity (MNCV) of the peroneal nerve in DPN patients with the random-effect model (MD = 0.60, 95%CI (0.28, 0.92), P < 0.05, I2 = 65%). In four studies, these supplements could have improved on MNCV of the median nerve with the fixed-effect model (MD = 4.22, 95%CI (2.86, 5.57), P < 0.05, I2 = 0%). However, ten studies (841 participants) have suggested that vitamin and antioxidant supplements have not decreased glycosylated haemoglobin (HbA1c). Vitamin and antioxidant supplements may improve the conduction velocity of nerves, including median, sural and peroneal nerves of patients with DPN. But these supplements have not decreased HbA1c in DPN patients. Several trials with a large sample size are needed to provide evidence support for clinical practice in the future.

Variations in sural nerve formation and course in fetuses.

To investigate variations regarding the formation and course of the sural nerve (SN). We dissected 60 formalin-fixed Brazilian fetuses (n = 120 lower limbs) aged from the 16th to 34th weeks of gestational age. Three incisions were made in the leg to expose the SN, and the gastrocnemius muscle was retracted to investigate the SN course. Statistical analyses regarding laterality and sex were performed using the Chi-square test. Eight SN formation patterns were classified after analysis. Type 4 (in which the SN is formed by the union of the MSCN with the LSCN) was the most common SN formation pattern. Although there was no statistical association between the formation patterns and the lower limb laterality (p = 0.9725), there was as to sex (p = 0.03973), indicating an association between anatomical variation and sex. The site of branch joining was in the distal leg most time (53.75%). In all lower limbs, the SN or its branches crossed from the medial aspect of the leg to the lateral margin of the calcaneal tendon (CT). Most often, the SN is formed by joining the MSCN and the LSCN in the distal leg. The SN or its branches ran close to the saphenous vein, crossed the CT from medial to lateral, and distributed around the lateral malleolus.

Ultrasound evaluation of a new surface reference line to describe sural nerve location and safe zones to consider in posterior leg approaches.

PURPOSE: Several authors have described methods to predict the sural nerve pathway with non-proportional numerical distances, but none have proposed a person-proportional, reproducible method with anatomical references. The aim of this research is to describe ultrasonographically the distance and crossing zone between a surface reference line and the position of the sural nerve. METHODS: Descriptive cross-sectional study, performed between January and April 2022 in patients requiring foot surgery who met inclusion criteria. The sural nerve course in the posterior leg was located and marked using ultrasound. Landmarks were drawn with a straight line from the medial femoral condyle to the tip of the fibula. Four equal zones were established in the leg by subdividing the distal half of the line. This way, areas based on simple anatomical proportions for each patient were studied. The distance between the marking and the ultrasound nerve position was measured in these 4 zones, creating intersection points and safety areas. Location and distances from the sural nerve to the proposed landmarks were assessed. RESULTS: One-hundred and four lower limbs, 52 left and 52 right, assessed in 52 patients were included. The shortest median distance of the nerve passage was 2.9 mm from Point 2. The sural nerve intersection was 60/104 (57.7%) in Zone B, 21/104 (20.1%) in Zone C and 19/104 (18.3%) in Zone A. Safety zones were established. Average 80.5% of coincidence in sural nerve localization was found in the distal half of the leg, in relation to the surface reference line when comparing both legs of each patient. CONCLUSIONS: This study proposes a simple, reproducible, non-invasive and, for the first time, person-proportional method, that describes the distance and location of the main areas of intersection of the sural nerve with points and zones (risk and safe zones) determined by a line guided by superficial anatomical landmarks. Its application when surgeons plan and perform posterior leg approaches will help to avoid iatrogenic nerve injuries. LEVEL OF EVIDENCE: IV.

Minimizing risk of iatrogenic nerve injury during peroneus longus tendon autograft harvest: a cadaveric study at different ankle or knee positions.

PURPOSE: To evaluate the distances using ultrasound between the superficial peroneal nerve (SPN) and sural nerve along the peroneus longus tendon (PLT) autograft harvest path at different ankle or knee positions in order to minimize risk of iatrogenic nerve injury during PLT autograft harvest. METHODS: Twenty-four fresh-frozen human cadaveric lower extremities were used to harvest a full-thickness PLT autograft with a tendon stripper. Four specimens were utilized to validate correct identification of nerves under ultrasound. Sonographically guided perineural injections were performed at the start point and end point of the PLT harvest path using coloured latex, followed by dissection with gross inspection. Using ultrasound, the distance from the peroneus brevis muscle to the sural nerve at different ankle positions (20° dorsiflexion, neutral, and 20° plantarflexion) was measured, and the distance from the end of the tendon stripper to the SPN at different knee positions (full extension and 90° flexion) was also measured. Measurements were performed by two separate observers using ImageJ software. RESULTS: Cadaveric dissection showed the presence of latex around nerves in all four specimens. The average distance from the brevis muscle to the sural nerve increased significantly from dorsiflexion to plantarflexion. The shortest distance from the tenodesis site to the sural nerve was 5.8 ± 1.7 mm. There was no significant difference from the end of the tendon stripper to the SPN between full extension or 90° flexion of the knee. CONCLUSION: When harvesting the PLT, it is recommended to place the ankle at plantarflexion. The knee at full extension or 90° flexion had no effect. Joint positions at the time of graft harvest should be monitored to reduce risks of iatrogenic nerve injury.

Long-Term Donor-Site Morbidity Following Entire Sural Nerve Harvest for Grafting.

PURPOSE: The sural nerve is the autologous nerve used most commonly for grafting. However, recent studies indicate a high rate of complications and complaints after sural nerve removal. In this prospective study, we evaluated donor-site morbidity following full-length sural nerve harvesting on long-term follow-up. METHODS: Fifty-one legs from 43 patients who underwent complete sural nerve harvesting for brachial plexus reconstruction were included in the study. After an average of 5 years, with a minimum postoperative follow-up of 12 months, sensory deficits in the leg and foot were analyzed using 2.0-g monofilaments. Regions of sensory deficit were marked with a skin marker and photographed. Over these regions of decreased sensation, we tested nociception using an eyebrow tweezer. Patients were also asked about pain, cold intolerance, pruritis, difficulties walking, and foot swelling. RESULTS: Regions most affected (84% of patients) were over the calcaneus and cuboid. However, in these regions, nociception was preserved. Regions of decreased sensation extended to the calf region in 11 of 51 legs. In 13 patients, we also observed regions of decreased sensation on the proximal leg. In five feet, the sensation was entirely preserved. No patient had any complaints about pain, cold intolerance, itchiness, difficulties walking, or foot swelling. CONCLUSION: Decreased sensation with nociception preserved was most common along the lateral side of the foot over the calcaneus and cuboid. Removing the entire sural nerve produced no long-term complaints of pain. Sural nerve use appears safe. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic II.

Anatomical patterns of the sural nerve: a meta-analysis with clinical and surgical considerations.

BACKGROUND: The sural nerve (SN) supplies the posterolateral aspect of the leg and the lateral aspects of the ankle and foot and descends through the gastrocnemius muscle along the lower third of leg. Because in-depth knowledge about SN anatomy is essential for clinical and surgical approaches, our study aims to review SN anatomical patterns. METHODS: We searched the PubMed, Lilacs, Web of Science, and SpringerLink databases to find relevant articles for meta-analysis. We assessed the quality of the studies using the Anatomical Quality Assessment tool. We used proportion meta-analysis to analyze the SN morphological variables and simple mean meta-analysis to analyze the SN morphometric variables (nerve length and distance to anatomical landmarks). RESULTS: Thirty-six studies comprised this meta-analysis. Overall, Type 2A (63.68% [95% CI 42.36-82.64]), Type 1A (51.17% [95% CI 33.16-69.04]) and Type 1B (32.19% [95% CI 17.83-48.38]) were the most common SN formation patterns. The lower third of leg (42.40% [95% CI 32.24-52.86]) and middle third of leg (40.00% [95% CI 25.21-53.48]) were the most common SN formation sites. The pooled SN length from nerve formation to the lateral malleolus was 144.54 mm (95% CI 123.23-169.53) in adults, whereas the SN length was 25.10 mm (95% CI 23.20-27.16) in fetuses in the second trimester of gestation and 34.88 mm (95% CI 32.86-37.02) in fetuses in the third trimester of gestation. CONCLUSIONS: The most prevalent SN formation pattern was the union of the medial sural cutaneous nerve with the lateral sural cutaneous nerve. We found differences regarding geographical subgroup and subject age. The most common SN formation sites were the lower and middle thirds of the leg.

Anatomy of the Sural Nerve in the Posterolateral Approach to the Ankle: A Cadaveric Study.

Sural nerve injury may occur during the posterolateral approach to the ankle during fracture fixation. We aimed to map its location in a posterolateral approach in cadaveric specimens. A posterolateral approach was used in 28 cadaver legs with the incision made halfway between the medial border of the fibula and the lateral border of Achilles tendon, extending proximally from the tip of the lateral malleolus. The sural nerve was identified and the distance from the distal tip of the incision to where it crossed the incision proximally was measured. The mean distance was 3.4 ± 1.2 (range 0.5-7.0) cm. In 22 cases (78.5%), the distance from the lowest part of the incision to the inferior part of the nerve was between 2.7 and 4.5 cm. The nerve did not cross the incision in 2 cases. We have demonstrated that the sural nerve crossed the posterolateral incision between 2.7 and 4.5 cm proximal to the tip of the fibula in the majority of cases. However, there remains individual anatomical variation, and we would recommend that care should be taken to look for the nerve closer to the Achilles tendon proximally and nearer the fibula distally. We hope that this information can help surgeons plan their approach and minimize iatrogenic injury to the sural nerve.

Low to moderate risk of nerve damage during peroneus longus tendon autograft harvest.

PURPOSE: This study aims to evaluate the proximity of the tendon stripper to both the peroneal and sural nerves during peroneus longus tendon (PLT) autograft harvesting. METHODS: Ten fresh-frozen human cadaveric lower extremities were used to harvest a full-thickness PLT autograft using a standard closed blunt-ended tendon stripper. The distance to the sural nerve from the PLT (at 0, 1, 2 and 3 cm proximal to lateral malleolus (LM), and the distance to the peroneal nerve and its branches from the end of the tendon stripper were measured by two separate observers using ImageJ software. RESULTS: The average distance from the PLT to the sural nerve increased significantly from 0 to 2 cm proximal to LM. The average distance to the sural nerve at the LM was 4.9 ± 1.5 mm and increased to 10.8 ± 2.4 mm (2 cm proximal to LM). The average distance from the tendon stripper to the deep peroneal nerve was 52.9 ± 11.4 mm. The average distance to the PLT branch of peroneal nerve was 29.3 ± 4.2 mm. The superficial peroneal nerve, which coursed parallel and deep to the tendon stripper, was on average 5.2 ± 0.7 mm from the end of the stripper. No transection injuries of the nerves were observed in any of the ten legs after harvesting. CONCLUSION: This cadaver study found during a full-thickness PLT harvest, the distances between the tendon stripper and the nerves were greater than 5 mm with an initial incision at 2 cm proximal to LM which is recommended.

Relationships of the superficial fibular nerve and sural nerve with respect to the lateral malleolus: implications for ankle surgeons.

PURPOSE: Superficial fibular nerve (SFN) and sural nerve are at risk during osteosynthesis of the lateral malleolus. The aim of this anatomical study was to describe the relationships of the superficial fibular and sural nerves with respect to the lateral malleolus. METHODS: Nine corpses (18 ankles) were dissected, using a direct lateral approach. Measurements were recorded between the fibula and the nerves, and the pattern variations of the SFN were recorded for both right and left side to assess intra-individual variability. RESULTS: Distance between the tip of the lateral malleolus and the piercing of fascia cruris was 111 ± 26 mm for type 1 pattern, and range was 46-161 mm all types included. 78% (14 SFN) were type 1 pattern, 17% (3 SFN) were type 2 pattern, and 5% (1 SFN) were type 3 pattern. 44% (4 specimen) had a type 1 pattern SFN on one ankle and another pattern on the other ankle. The sural nerve was always observed just posterior to the lateral malleolus. CONCLUSION: This study demonstrated a great inter-individual variability especially for the SFN, but also an intra-individual variability with frequent different patterns between right and left leg. It is important to know the anatomical variations of the SFN and sural nerve to decrease the risk of intra operative nerve injury during direct lateral approach of lateral malleolus.

Locating the danger zone to avoid injury to the sural nerve during Achilles calcaneal tendon repair. A systematic review of cadaveric studies with clinical implications.

INTRODUCTION: Although iatrogenic injuries to the sural nerve (SN) are commonly encountered in calcaneal (Achilles) tendon (CaT) repair surgeries, the relationship between both structures have anatomical variations. A quantitative evidence synthesis has not been yet conducted. Our systematic review aims to better define the safe zone where the SN crosses the lateral border of CaT. METHODS: Electronic databases were searched to locate relevant anatomical studies recording details regarding the distance at which SN crosses the CaT. The Checklist for Anatomical Reviews and Meta-Analyses (CARMA) was followed. The primary outcome was the mean distance from CaT insertion to SN crossing site, to locate a safe zone. The secondary outcome was the mean horizontal distance from the SN to the CaT lateral border. RESULTS: Seven studies met the inclusion criteria with a total of 204 cadaveric limbs. The danger zone was located 2 cm distal and proximal to the mean distance of the crossing point. The mean distance from CaT insertion to the SN crossing site was 9.91 ± 0.67 cm. The mean horizontal distance between SN and the CaT lateral border decreased from a mean of 19.8 ± 2.06 mm at the calcaneal tuberosity level to 3.6 ± 0.4 mm at 10 cm proximal to the tuberosity. DISCUSSION: This review demonstrated that 10 cm is the average distance from the CaT insertion onto the calcaneal tuberosity to the point of crossing of the SN. A safe zone would be 2 cm away proximally and distally from the crossing point. We recommend placing the proximal lateral sutures away from this region. This finding should help surgeons avoid SN injuries during open or percutaneous approaches for calcaneal tendon rupture.

Surgical Anatomy of the Endoscopic Gastrocnemius Recession.

The objective of this investigation was to analyze the surgical anatomy of the endoscopic gastrocnemius recession procedure with reference to the curved nature of the aponeurosis. A consecutive series of 34 magnetic resonance imaging scans were evaluated under the direction of a musculoskeletal radiologist. An angular calculation of the effective curvature of the aponeurosis was measured 2 cm distal to the musculotendinous junction based on the maximal posterior excursion and terminal medial and lateral edges. A frequency count was additionally performed of the number of deep intramuscular septa extending from the aponeurosis, as well as a description of the location of the neurovascular bundle in this location. The mean effective curvature was 126.5 degrees (standard deviation [SD] = 6.3 degrees, range 115-143 degrees, 95% confidence interval 124.3-128.7 degrees). We observed an average of 1.2 (SD = 0.5, range = 0-2) deep intramuscular septa extending from the aponeurosis, and that 20.6% of neurovascular bundles were located superficial to the aponeurosis in this location. In conclusion, we found that a straight cannula needs to be navigated around an approximate 125-degree angle during performance of the EGR procedure. We think that this information provides evidence of potentially unrecognized complications of this procedure and leads to future investigations demonstrating anatomic and procedural outcomes.

Bifurcation of the sciatic nerve: A descriptive study on a South African cadaver cohort.

BACKGROUND: The sciatic nerve bifurcates into the tibial and common fibular nerves in six different regions: the pelvic region, gluteal region, proximal, middle, or distal third of the posterior thigh, or in the popliteal fossa. Inadequate knowledge of sciatic nerve anatomy could lead to failed nerve blocks, and damage during intramuscular injections. Limited studies have been done on African population groups and lack a quantifiable method to classify the levels of sciatic nerve bifurcation. AIM: Thus, this descriptive cadaver study aimed to assess the bifurcation level of the sciatic nerve in a South African population group using a quantifiable method. METHODS: Three hundred and thirty-eight formalin-fixed limbs from three universities were dissected between March and August 2018. Type A was classified if the sciatic nerve bifurcated within the pelvic region. A sciatic nerve bifurcation level index (SNBLI) was developed for this study to quantitatively classify the region of sciatic nerve bifurcation into types B to F. RESULTS: Type F bifurcation was most common (79.6%), and types B and C were not observed. In 15 (0.04%) specimens, two separate nerves entered the gluteal region and converged to form the sciatic nerve distal to the piriformis, which could bifurcate either in the distal third of the posterior thigh or popliteal fossa. CONCLUSION: This is the first study to provide information on the sciatic nerve bifurcation in a large South African cadaver cohort. Moreover, we created a quantifiable method that can be used to classify the sciatic nerve bifurcation level. This will be beneficial in ensuring accurate comparison between different population groups in future.