The relative contributions of the medial sural and peroneal communicating nerves to the sural nerve

The medial sural cutaneous nerve (MSCN) and peroneal communicating nerve (PCN) conjoin in the calf area to form the sural nerve (SN). In previous anatomic studies, there was unresolved debate as to the main contributor to the sural nerve, and the relative contributions of MSCN and PCN had not been studied. The purpose of this study is to determine their relative neurophysiologic contributions to the SN by nerve conduction study (NCS). A total of 47 healthy subjects (25 males and 22 females, mean age 29.6 +/- 10.4 yrs, range 20-59 yrs) participated in the study. This study employed the orthodromic nerve conduction technique: stimulation at the ankle and recording at the mid calf (SN); specifically, we preformed stimulation at the mid calf (MSCN, PCN) and recording at 14 cm proximal to the middle of the popliteal fossa (MSCN) and fibular head (PCN). The onset and peak latencies (ms) were SN 2.3 +/- 0.2 and 3.0 +/- 0.2; MSCN 2.1 +/- 0.2 and 2.8 +/- 0.2; and PCN 2.1 +/- 0.2 and 2.8 +/- 0.2. The peak-to-peak amplitudes (microV) and areas (nVsec) of the SN, MSCN, and PCN were 9.7 +/- 3.9, 7.0 +/- 4.7, and 5.0 +/- 3.2; and 7.2 +/- 2.9, 5.7 +/- 3.4, and 4.0 +/- 2.4, respectively. The side-to-side difference was not statistically significant. The main contributor to the SN was found to be the MSCN. The relative contribution ratio of the MSCN to the PCN was 1.37:1 by amplitude and 1.42:1 by area. However, in 32.9% of the subjects, the contribution of the PCN was greater than that of the MSCN.     

Peculiarities of the sural nerve complex morphologic types in human fetuses

The sural nerve is the most frequently used sensory nerve in nerve transplantation. It can be transplanted alone or together with the other elements of the neurovascular stalk within the superficial sural flap. The aim of this study was to define the morphologic types of the sural nerve complex, as well as to describe their specific characteristics. Microdissection was performed on 100 human fetuses (200 calves) after 10% formalin fixation. Five morphologic types of sural nerve complex with different incidence were defined. Two morphologic types dominated: type I (58.5%) in which the sural nerve was formed by merging of a fibular communicating branch and the medial sural cutaneous nerve, and type III (26%) in which the medial sural cutaneous nerve took over the function of the sural nerve. Other morphologic variations were less common.     

Anatomical variations of the human sural nerve and its role in clinical and surgical procedures

The sural nerve is the most commonly nerve used in nerve transplantation, and so the aim of this study was to determine the variations of the sural nerve in the back of the leg, its relations to the calcaneal tendon and lateral malleolus, and determine the patterns of its distribution on the dorsum of the foot. Twenty‐four Egyptian legs and feet were dissected. The results showed that the sural communicating nerve connected with the sural nerve in 87.5%. The predominant site of union between these two nerves was in the lower one‐third of the leg and ankle region (62%). There was only one right leg that the sural nerve passed through the gastrocnemius. The small saphenous vein passed along the medial side of the sural nerve in 100%. The sural nerve crossed the lateral border of the calcaneal tendon in 50%. The distance between the sural nerve and insertion of calcaneal tendon was 16 + 7 mm in 91.7%. There were four types of pattern of innervation of the toes by the sural nerve. The predominant pattern was type I (45.8%), where the lateral side of the little toe was supplied by the sural nerve alone. The second pattern was type IV (29.2%), where the lateral 2 ½ toes were supplied by the sural nerve alone. These findings are important for sural nerve biopsy and grafts, surgical repair of the calcaneal tendon, and regional anesthesia of the foot. Clin. Anat. 24:237–245, 2010. © 2010 Wiley‐Liss, Inc.     

Anatomical and histological morphometry of the sural nerve in human fetuses

Introduction

In our study, the aim was to anatomically and histologically investigate the morphometric structures of the branches involved in the sural nerve and sural nerve formation.

Anatomical variations of the sural nerve

An anatomical study of the formation of the sural nerve (SN) was carried out on 76 Thai cadavers. The results revealed that 67.1% of the SNs were formed by the union of the medial sural cutaneous nerve (MSCN) and the lateral sural cutaneous nerve (LSCN); the MSCN and LSCN are branches of the tibial and the common fibular (peroneal) nerves, respectively. The site of union was variable: 5.9% in the popliteal fossa, 1.9% in the middle third of the leg, 66.7% in the lower third of the leg, and 25.5% at or just below the ankle. One SN (0.7%) was formed by the union of the MSCN and a different branch of the common fibular nerve, running parallel and medial to but not connecting with the LSCN, which joined the MSCN in the lower third of the leg. The remaining 32.2% of the SNs were a direct continuation of the MSCN. The SNs ranged from 6-30 cm (mean = 14.41 cm) in length with a range in diameter of 3.5-3.8 mm (mean = 3.61 mm), and were easily located 1-1.5 cm posterior to the posterior border of the lateral malleolus. The LSCNs were 15-32 cm long (mean = 22.48 cm) with a diameter between 2.7-3.4 mm (mean = 3.22 mm); the MSCNs were 17-31 cm long (mean = 20.42 cm) with a diameter between 2.3-2.5 mm (mean = 2.41 mm). Clinically, the SN is widely used for both diagnostic (biopsy and nerve conduction velocity studies) and therapeutic purposes (nerve grafting) and the LSCN is used for a sensate free flap; thus, a detailed knowledge of the anatomy of the SN and its contributing nerves are important in carrying out these and other procedures.     

Formation and distribution of the sural nerve based on nerve fascicle and nerve fiber analyses

The formation and distribution of the sural nerve are presented on the basis of an investigation of 31 legs of Japanese cadavers using nerve fascicle and fiber analyses. Nerve fibers constituting the medial sural cutaneous nerve were designated as 'T', whereas those constituting the peroneal communicating branch were designated as 'F'. In 74.2% of cases (23/31), the T and F fibers joined each other in the leg, whereas in 9.7% of cases (3/31) they descended separately. In 16.1% of cases (5/31), the sural nerve was formed of only the T fibers. The sural nerve gave off lateral calcaneal branches and medial and lateral branches at the ankle. The lateral calcaneal branches always contained T fibers. The medial branches consisted of only T fibers, whereas most of the lateral branches consisted of only F fibers (71.0%; 22/31). In addition to the T and F fibers, P fibers, which derived from the superficial and deep peroneal nerves, formed the dorsal digital nerves. The P fibers were entirely supplied to the medial four and one-half toes. However, they were gradually replaced by the T and F fibers in the lateral direction. The 10th proper dorsal digital nerve consisted of T fibers only (38.7%; 12/31), of F fibers only (19.4%; 6/31) or of both T and F fibers (38.7%; 12/31). These findings suggest that the T fibers are essential nerve components for the skin and deep structures of the ankle and heel rather than the skin of the lateral side of the fifth toe. The designation of the medial sural cutaneous nerve should be avoided and only the T fibers are appropriate components for naming as the sural nerve.     

Variations in sural nerve formation pattern and distribution on the dorsum of the foot

The sural nerve, a cutaneous nerve, is clinically important because it is frequently for nerve conduction testing, biopsy, and harvesting for nerve grafts. This nerve exhibits a wide variety of variation in formation, distribution on the dorsum of the foot, and so on, depending on the population observed. In this study, we examined the variation in the sural nerve in 110 Korean cadavers. Of these cadavers, 86.1% of the sural nerves corresponded to type A, where tibial and peroneal components were united to form the sural nerve. These two components most frequently united (65.9%) in the third quarter of the calf, and when the union position was expressed as a ratio to calf length, it corresponded to 0.408 in men and 0.346 in women, with a statistically significant difference. Due to this sexual dimorphism in addition to shorter calf length in females, the length of the sural nerve was shorter in females (male average length: 14.5 ± 4.8 cm; female average length: 11.4 ± 2.9 cm). In terms of distribution of the lateral dorsal cutaneous nerve, the distal continuation of the sural nerve on the dorsum of the foot, it showed variation in association with the superficial peroneal nerve. The innervation of the sural nerve extended most frequently up to the lateral two and a half toes, solely or in conjunction with the superficial peroneal nerve. Obtaining further information regarding sural nerve variation will be useful for various clinical procedures and interpretation of sural nerve conduction results. Clin. Anat. 30:525–532, 2017. © 2017 Wiley Periodicals, Inc.     

Origin and make up of the human sural nerve

Abstract The dissection of 37 cadavers has shown that in only a third of cases, the sural nerve comes from the communication between the medial cutaneous nerve, derived from the tibial nerve, and the communicating branch of the lateral cutaneous nerve of the leg which comes from the lateral popliteal nerve. The communication is most often at the junction between the proximal two-thirds and distal third of the leg, on average 2 mm below the transverse crease of the popliteal fossa. The medial cutaneous nerve was absent in only one case. On the other hand, in 11 cases the lateral cutaneous nerve or its communicating branch was missing. In 12 cases without any anastomoses, the route of the sural nerve was followed by the medial cutaneous nerve of the leg in 9 cases and by the lateral cutaneous nerve in 3 cases. The majority of branches to the proximal half of the calf came from the lateral cutaneous nerve. In the lower part of the leg, the sural nerve and/or the medial cutaneous nerve gave numerous branches to the Achilles’ tendon and to the integuments of the lateral aspect of the heel and lateral malleolus.     

腓肠外侧皮神经痛诊治的解剖学基础(系列介绍之十六)

目的 介绍腓肠外侧皮神经痛的诊断与局部注射的治疗方法。方法 选择门诊确诊为腓肠外侧皮神经痛的患者11例，采用强的松龙混悬液加麻药局部注射神经通过胭窝的外下部穿出阔筋膜的局部治疗方法。结果 所有病例皆在注射后短时完全止痛，经1～3次注射后痊愈。结论 对诊断明确的病例，采取强的松龙局部注射法，可以获得满意的疗效。     

Anatomic study of the superficial sural artery and its implication in the neurocutaneous vascularized sural nerve free flap

Combined extended nerve and soft tissue defects of the upper extremity require nerve reconstruction and adequate soft tissue coverage. This study focuses on the reliability of the free vascularized sural nerve graft combined with a fasciocutaneous posterior calf flap within this indication. An anatomical study was performed on 26 cadaveric lower extremities that had been Thiel fixated and color silicone injected. Dissection of the fasciocutaneous posterior calf flap involved the medial sural nerve and superficial sural artery (SSA) with its septocutaneous perforators, extended laterally to include the lateral cutaneous branch of the sural nerve and continued to the popliteal origin of the vascular pedicle and the nerves. The vessel and nerves diameter were measured with an eyepiece reticle at 4.5× magnification. Length and diameter of the nerves and vessels were carefully assessed and reported in the dissection book. A total of 26 flaps were dissected. The SSA originated from the medial sural artery (13 cases), the popliteal artery (12 cases), or the lateral sural artery (one case). The average size of the SSA was 1.4 ± 0.4 mm. The mean pedicle length before the artery joined the sural nerve was 4.5 ± 1.9 cm. A comitant vein was present in 21 cases with an average diameter of 2.0 ± 0.8 mm, in 5 cases a separate vein needed to be dissected with an average diameter of 3.5 ± 0.4 mm. The mean medial vascularized sural nerve length was 21.2 ± 8.9 cm. Because of inclusion of the vascularized part of the lateral branch of the sural nerve (mean length of 16.7 ± 4.8 cm), a total of 35.0 ± 9.6 cm mean length of vascularized nerve could be gained from each extremity. The free vascularized sural nerve graft combined with a fasciocutaneous posterior calf flap pedicled on the SSA offers a reliable solution for complex tissue and nerve defect. Clin. Anat. 26:903–910, 2013. © 2012 Wiley Periodicals, Inc.     

Surgical anatomy of the sural and superficial fibular nerves with an emphasis on the approach to the lateral malleolus

The aim of this study was to investigate the risk and to analyse the significance of laceration of the sural and superficial fibular nerves during the surgical approach to the lateral malleolus. The sural and the superficial fibular nerves, and their branches were dissected under ×3 magnifying lenses in 68 embalmed leg‐ankle‐foot specimens. The specimens were measured, drawn and photographed. In 35% of specimens the superficial fibular nerve branched before piercing the crural fascia, and in all these specimens the medial dorsal cutaneous nerve of the foot was located in the anterior compartment while the intermediate dorsal cutaneous nerve of the foot was located in the lateral compartment. In 35% of specimens the intermediate dorsal cutaneous nerve of the foot was absent or did not innervate any toe. The deep part of the superficial fibular nerve was in contact with the intermuscular septum. Its superficial part was parallel with the lateral malleolus when the nerve pierced the fascia more proximally and oblique to the lateral malleolus when the nerve pierced the fascia distally. In one case the intermediate dorsal cutaneous nerve of the foot was in danger of laceration during a subcutaneous incision to the lateral malleolus. In 7 cases (10%) the sural nerve overlapped or was tangent to the tip of the malleolus. Malleolar nerve branches were identified in 76% of the cases (in 28% from both sources). The sural nerve supplies the lateral 5 dorsal digital nerves in 40% of cases. Our study indicates that during the approach to the lateral malleolus there is a high risk of laceration of malleolar branches from both the sural and the superficial fibular nerves. There is less risk of damage to the main trunk of these nerves, but the 10% chance of laceration of sural nerve at the tip of the malleolus is significant. As the sural nerve supplies the superficial innervation to the lateral half of the foot and toes in 40% of cases, the risk of its laceration is even more important than indicated by the common anatomical teaching.     

腓肠外侧皮神经营养血管岛状筋膜皮瓣的解剖学基础

目的 :为腓肠外侧皮神经营养血管岛状筋膜皮瓣提供解剖学依据。方法 :采用巨微解剖、全身动脉放射显影及电脑图像分析技术 ,解剖观察了腓肠外侧皮神经及其营养血管的起始、走行、分支与分布情况。结果 :腓肠外侧皮神经于腓骨头上方 ( 7.1± 1.3 )cm ,中线外侧 ( 1.8± 0 .6)cm起自腓总神经 ,分支分布于小腿后外侧上 2 /3部 ,末端与腓肠内侧皮神经相吻合。其营养动脉主要为窝外侧皮动脉 ,于腓骨头水平面上方 ( 4 .6± 2 .3 )cm处发自动脉 ,并于腓骨头上 ( 4 .6± 1.2 )cm ,中线外侧 ( 2 .1± 0 .5 )cm处开始伴行腓肠外侧皮神经下降 ,下端主要与腓动脉穿支吻合 ,形成一营养血管链。结论 :以腓肠外侧皮神经及其营养血管链为蒂可以设计近端或远端蒂岛状筋膜皮瓣。     

腓肠神经及其两根的应用解剖学观测

目的观测人腓肠神经的构成类型,长、宽以及构成腓肠神经的两根的位置、长度、宽度,以补充国人腓肠神经的解剖学资料为临床腓肠神经的移植提供依据。方法利用直尺及游标卡尺（精确度0．02mm）对腓肠神经,腓肠内、外侧皮神经的长、宽进行测量,对腓肠内、外侧皮神经位置及腓肠神经的组成型式进行观测统计。结果腓肠神经的构成型式较前人的观察更为复杂,因此本文采用了新的分型方法。腓肠内、外侧皮神经的发出位置多变,腓肠神经起始部、中点及外踝平面宽度不同。结论腓肠神经及其两根型式复杂,临床选择移植体时应充分考虑其型式及长度、宽度,以便更加适应受区特征。     

Formation and location of the sural nerve in the newborn

In this study, the location and formation of the sural nerve were examined in 40 legs of new-born cadavers. The sural nerve was formed by the peroneal communicating branch from the common peroneal nerve joining the medial sural cutaneous nerve in 27 of 40 legs (67.5%). It was formed by the peroneal communicating branch from the lateral sural cutaneous nerve joining the medial sural cutaneous nerve in 4 (10%). It was formed by the peroneal communicating branch from the common peroneal nerve and fibers from the posterior femoral cutaneous nerve joining the medial sural cutaneous nerve in 2 (5%). In 5 of 40 legs (12.5%), the medial sural cutaneous nerve was in the place of the sural nerve without joining any other nerve. In one case (5%), the sural nerve was not formed bilaterally.     

Anatomical variations of the cutaneous innervation patterns of the sural nerve on the dorsum of the foot

The present study attempts to determine the cutaneous pattern of distribution of the sural nerve on the dorsum of the foot to note the predominant pattern present and whether there was any association between the innervation pattern and sex or side. A total of 260 Indian feet (78 adult feet: 60 male, 18 female; 52 fetal feet: 20 male, 32 female) were dissected. The results showed six patterns of innervation of the toes by the sural nerve. In Type I, the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 2nd, 3rd, 4th, and 5th toes by the superficial peroneal nerve alone (35.38%). In Type II the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 4th and 5th toes by the sural nerve along with the superficial peroneal nerve (10%). In Type III the lateral side of the little toe was supplied by the sural nerve alone and the adjacent sides of the 3rd, 4th, and 5th toes by the sural nerve along with the superficial peroneal nerve (21.15%). In Type IV the lateral 1(1/2) toes were supplied by the sural nerve alone and the adjacent sides of the 3rd and 4th toes by the superficial peroneal nerve alone (3.85%). In Type V the lateral 1(1/2) toes were supplied by the sural nerve alone and the adjacent sides of the 3rd and 4th toes were supplied by the sural nerve along with the superficial peroneal nerve (5%). In Type VI the lateral 2(1/2) toes were supplied by the sural nerve alone (24.61%). The predominant patterns were Type I (35.38%), Type VI (24.61%), and Type III (21.15%). There was no association between the innervation pattern of the sural nerve and sex or side. The pattern, which is usually described, was found in only 35.38% of feet. Considering the variation in the pattern of cutaneous distribution of the sural nerve in Indian feet, the function of the sural nerve may be to supply a wider area of skin than is usually described.     

Clinicopathologic study of 43 patients with sural nerve vasculitis

Vasculitis is a relatively uncommon finding in sural nerve biopsy specimens and is associated with significant morbidity. This study retrospectively reviewed the clinicopathologic features of 43 patients (44 sural nerve biopsy specimens) with sural nerve vasculitis, defined as infiltration of vessel walls by inflammatory cells. These biopsy specimens were obtained over a 19-year period, during which 1503 nerve specimens were reviewed. The study group comprised 29 females and 14 males, ranging in age from 19 to 94 years (mean, 72.5 years) at the time of biopsy. The most frequent clinical presentations included paresthesias in 19 patients (61%), pain in 17 patients (57%), weakness in 10 patients (32%), and weight loss in 9 patients (29%). Histologically, 26 of 44 biopsy specimens (59%) demonstrated necrotizing vasculitis. The remaining 18 biopsy specimens demonstrated a nonnecrotizing lymphocytic vasculitis. Eosinophils were identified in 4 biopsy specimens, intravascular thrombi in 10 (22%) specimens, and granulomatous inflammation in 1 specimen. In 39 biopsy specimens (89%), multiple vessels were involved by vasculitis. Epineurial vessels were the most common target of vasculitis, (n = 42; 95%). Evidence of vascular wall scarring, indicative of healed vasculitis, was observed in 13 biopsy specimens (30%). All biopsy specimens showed evidence of axonopathy, with mild axonal loss noted in 14 specimens (32%), moderate loss in 18 specimens (41%), and severe loss in 12 specimens (27%). Concomitant muscle biopsy was performed in 31 patients. Fifteen muscle biopsy specimens demonstrated evidence of vasculitis (48%), which was necrotizing in 11 cases. All muscle biopsy specimens demonstrated features of neurogenic atrophy. Twenty-five out of 32 patients were known to have been treated with steroids and demonstrated some degree of clinical improvement. In conclusion, sural nerve vasculitis is a relatively uncommon pathological finding (prevalence of 2.9% in this study). In most cases, multiple vessels were involved. Concomitant vasculitis was also identified in about half of the muscle biopsy specimens obtained at the time of nerve biopsy. In most patients, the vasculitis appeared to be at least partially responsive to immunosuppressive therapy.     

腓肠神经营养血管蒂岛状皮瓣的应用解剖

目的 :为带腓肠神经营养血管蒂岛状皮瓣的临床应用提供解剖学依据。方法 :在 3 8侧经动脉灌注红色乳胶成人下肢标本上解剖观测腓肠神经及营养血管的起始、走行、分支分布、吻合及外径 ,2侧成人新鲜下肢标本墨汁灌注观察营养血管的墨染范围。结果 :腓肠神经由腓肠内侧皮神经与腓神经交通支汇合而成 ,其汇合点在外踝上 12 .7± 3 .7cm ,腓肠神经沿窝中点至外踝与跟腱中点连线下行 ,外踝上 12 .6± 3 .4cm处穿出深筋膜。其营养血管主要来源于窝中间皮动脉和腓动脉肌间隔穿支 ,上段起始部外径 0 .6± 0 .1mm ,下段距外踝上 6.7± 1.6cm处与腓动脉穿支恒定吻合 ,吻合支外径 0 .6± 0 .1mm ,沿途发出众多筋膜皮支营养小腿后部皮肤。结论 :以腓肠神经及其营养血管为蒂可设计切取顺行或逆行岛状皮瓣。     

腓肠神经临床应用解剖及其临床意义的研究进展

目的 探讨腓肠神经的应用解剖及其在相关手术入路中的损伤风险。方法 以“腓肠神经”“解剖”“手术入路”和“sural nerve”“anatomy”“surgical approaches”为中英文关键词,在中国知网、万方数据、SinoMed、PubMed等中英文数据库检索2000年1月-2019年7月间有关腓肠神经临床应用解剖的文献,检索到文献999篇,剔除内容不符合、无法获取原文、重复性研究或存在设计缺陷的文献,最终纳入34篇。总结腓肠神经应用解剖研究成果,重点阐述踝关节骨折的后外侧入路和跟骨骨折的L型入路、跗骨窦入路,以及第五跖骨基底部骨折入路等4种手术入路与腓肠神经的解剖学关系。结果 研究显示,腓肠神经在解剖学上变异类型众多,其走行区域与踝关节骨折的后外侧入路、跟骨骨折的L型入路和跗骨窦入路、第五跖骨基底部骨折入路4种手术入路的关系十分密切。结论术前正确掌握腓肠神经的解剖特点,对足踝骨折手术入路选择以及减少手术中腓肠神经损伤风险至关重要。     

Anatomical study of the communicating branches between the medial and lateral plantar nerves

The plantar areas of the foot have specific biomechanical characteristics and play a distinct role in balance and standing. For the forefoot surgeon, knowledge of the variations in the anatomy of communicating branches is important for plantar reconstruction, local injection therapy and an excision of interdigital neuroma. The anatomy of the communicating branches of the plantar nerves between the fourth and third common plantar digital nerves in the foot were studied in 50 adult men cadaveric feet. A communicating branch was present between the third and fourth intermetatarsal spaces nerves in all eight left feet and in six right feet (overall, 28%), and absent in 36 (72%). A communicating branch was found in 14 ft. Ten of the 14 communications were from the lateral to the medial plantar nerve. The length of the communicating branch ranged from 8 to 56 mm (average 16.4 mm) and its diameter was 0.2–0.6 times of the fourth common plantar digital nerve. The angle of the communicating branch with the common plantar digital nerve from which it originated was less than 30° in 11 ft, 30–59° in 27 ft, 60–80° in 8 ft, and more than 80° in 4 ft. Classification of the branch is based on the branching pattern of the communicating branch and explains variations in plantar sensory innervations. We think that the perpendicular coursing communicating branch is at higher risk to be severed during surgery.