Sural-tibial nerve communications in humans

We investigated the occurrence of a communication between the sural and tibial nerves in 49 legs of 28 Japanese cadavers. In front of the calcanean tendon, we found the communication in 7 legs (14.3%) or in 5 cadavers (18.9%). The sural nerve gave rise to a number of medial and lateral branches, including the lateral calcanean branch at the lateral side of the ankle. The communicating branch with the tibial nerve arose from the first medial branch and pierced the deep fascia of the leg. In 4 cases, the U-shaped communication was formed between the sural and tibial nerves, and in 3 cases, the Y-shaped communication. Electrophysiologi-cal evidence of an anomalous motor function of the sural nerve has been reported recently. We consider that the U-shaped communication between the sural and tibial nerves gives a morphological basis to the motor function of the sural nerve.     

Cutaneous innervation of the ankle: An anatomical study showing danger zones for ankle surgery

Three nerves innervate the skin in the foot and ankle region: the saphenous, sural, and superficial peroneal nerves. Because they are close to the medial and lateral malleoli, these nerves are at significant risk during orthopedic interventions. The aims of this study were to investigate the distal courses of the three cutaneous nerves of the ankle and to determine their exact relationships with easily identifiable bony landmarks. Ten freshly frozen and 40 embalmed lower extremities of adults were dissected. The positions of the superficial peroneal, sural, and saphenous nerves were determined using reference lines based on easily palpable osseous landmarks. The frequencies and distributions of all three nerves and their branches were converted into absolute numbers. A danger zone for each nerve was established on the basis of the distribution of crossings between the nerves and the different reference lines. Determination of the exact orientation of the nerves around the ankle should help minimize the nerve injury rate during surgical approaches in this area. Using this easily translatable new grid system, the course and danger zones of each cutaneous nerve around the ankle can be estimated clinically. Clin. Anat. 653–658, 2014. © 2013 Wiley Periodicals, Inc.     

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.     

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.     

带腓肠外侧皮神经及其营养血管筋膜皮瓣的应用解剖

目的 为带腓肠外侧皮神经及其营养血管筋膜皮瓣的临床应用提供解剖学基础.方法 在32例成人下肢标本上,对腓肠外侧皮神经及其营养血管进行解剖观测.结果 腓肠外侧皮神经在腓骨头平面上方 7.1±2.4cm处起于腓总神经,分布于小腿后外侧上半或上2/3的皮肤.其营养动脉主要为:腓肠外侧皮动脉:起自腘动脉,在腓骨头平面上方5.0±1.5cm处浅出,外径为0.9±0.3mm;肌间隔筋膜皮支:起自胫后动脉和腓动脉,分别在腓骨头平面下方9.2±3.8cm和15.8±3.8cm处浅出,外径为0.7±0.3mm和0.9±0.4mm.该营养动脉除在腓肠外侧皮神经周围或其内呈链式吻合外,还发出筋膜皮支与邻位的皮动脉连接.静脉血可沿伴行静脉或小隐静脉及其属支回流至深静脉.结论 以腓肠外侧皮神经及其营养血管为蒂,可设计成顺行或逆行转位筋膜皮瓣,修复邻近部位的软组织缺损.     

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.     

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 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.     

The innervation of the joints of the foot

The nerve supply of the ankle joint and of the joints of the foot was studied in dissections of fetal and adult feet and in serial sections of fetal feet stained with silver. The ankle joint was supplied by the tibial, sural, deep peroneal, and saphenous nerves, and by the accessory deep peroneal nerve when present. The tarsal joints were supplied on their plantar aspects by the medial or lateral plantar nerves, and on their dorsal aspects chiefly by the deep peroneal nerve. The joint between the lateral and intermediate cuneiform received branches from the intermediate dorsal cutaneous nerve also. The lateral dorsal cutaneous nerve and the accessory deep peroneal nerve when present provided additional branches to the subtalar and calcaneocuboid joints. The tarsometatarsal joints were supplied on their plantar aspects by the medial or lateral plantar nerves. Most of them were supplied on their dorsal aspects by the deep peroneal nerve, but the cuboid-metatarsal joints received their supply from the intermediate dorsal cutaneous nerve. The intermetatarsal joints had a similar but sparser supply. The joint between the fourth and fifth metatarsal received branches from the intermediate dorsal cutaneous nerve. The plantar digital nerves provided the main supply to the metatarsophalangeal joints. The dorsal aspect of the first metatarsophalangeal joint was supplied by the deep peroneal and the medial dorsal cutaneous nerves, of the second metatarsophalangeal joint by the deep peroneal nerve, and of the fourth and fifth metatarsophalangeal joints by the lateral dorsal cutaneous nerve. The interphalangeal joints did not receive articular branches from the dorsal digital nerves, except in the case of the interphalangeal joint of the big toe, which was supplied by the deep peroneal and the medial dorsal cutaneous nerves.     

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.     

基于Sihler’s技术的踝和足背皮神经的整体分布模式研究

目的 揭示踝及足背皮神经的整体分布模式,为皮瓣移植感觉重建提供形态学指导。 方法 成年尸体24具,紧贴肌表面摘取含皮下脂肪的踝及足背皮肤,用改良的Sihler’s染色法显示并观察皮神经整体分布模式。 结果 在Sihler’s染色的标本中,肉眼可见隐神经支配踝前区（40.01±7.6）%、踝后区（30±6.7）%、以及部分足背内侧缘。腓浅神经支配踝前区（60.03±6.8）%,其足背内侧皮神经支配足背内侧区、第1、2趾背及第3趾背内侧半;95.83%的足背中间皮神经分布到第3趾背外侧半、第4、5趾背。腓肠神经支配踝后区（70±5.3）%,其足背外侧皮神经支配足背外侧缘皮肤。腓深神经分布到第1、2趾背相对面。初级神经支密度以踝前区最高,次级及以下神经支密度和总的神经支密度均以足背内侧区最高。 结论 在踝或足背的皮瓣移植中,建议把踝前区或足背内侧区设计为利于感觉重建的首选供区或感觉需求较高的受区。     

The consistent presence of the human accessory deep peroneal nerve

Twenty-four human legs were dissected macroscopically to study the morphological details of the accessory deep peroneal nerve. This nerve arose from the superficial peroneal nerve and descended in the lateral compartment of the leg, deep to peroneus longus along the posterior border of peroneus brevis. Approaching the ankle joint, this nerve passed through the peroneal tunnels to wind around the lateral malleolus; it then crossed beneath the peroneus brevis tendon anteriorly to reach the dorsum of the foot. The accessory deep peroneal nerve was found in every case examined and constantly gave off muscular branches to peroneus brevis and sensory branches to the ankle region. In addition, this nerve occasionally had muscular branches to peroneus longus and extensor digitorum brevis, and sensory branches to the fibula and the foot. The anomalous muscles around the lateral malleolus were also innervated by this nerve. Neither cutaneous branches nor communicating branches with other nerves were found. The present study reveals that the accessory deep peroneal nerve is consistently present and possesses a proper motor and sensory distribution in the lateral region of the leg and ankle. It is not an anomalous nerve as has previously been suggested.     

远端蒂腓浅神经营养血管肌皮瓣的解剖与临床应用

目的探讨腓浅神经营养血管为蒂的肌皮瓣修复小腿远端及足踝部皮肤软组织缺损伴骨缺损慢性骨髓炎的解剖学依据及其临床应用效果。方法对30侧成人下肢灌注标本进行解剖,系统观测腓浅神经及其营养血管的来源、走行、分布、吻合及外径;3侧成人新鲜下肢标本墨汁灌注,观测腓浅神经营养血管的墨染范围;在此基础上,自2009年6月以来,应用远端蒂腓浅神经营养血管肌皮瓣修复小腿远端及足踝部皮肤软组织缺损伴骨缺损慢性骨髓炎者12例。结果腓浅神经营养血管发自胫前动脉穿支,其血管在其神经束间及神经旁相互吻合构成丰富的血管网,并借分支与皮下筋膜血管网沟通,并与腓骨长肌、趾长伸肌的肌支有恒定的吻合,营养筋膜皮肤。12例肌皮瓣的肌肉面术中可见渗血活跃,血供良好,皮瓣均成活,术后3~6个月随访12例肌皮瓣均存活,慢性骨髓炎治愈,外形满意。结论腓浅神经营养血管的肌皮瓣转位修复小腿远端及足踝部特殊创面是较佳的选择,该肌皮瓣具有血供可靠,预后良好等优点。     

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.     

Anatomic variation of the spinal origins of lateral and medial pectoral nerves

Lateral and medial pectoral nerves are distributed to the pectoralis major and minor muscles. The purpose of this study was to identify the spinal origins of lateral and medial pectoral nerves and to evaluate the participating amounts of each spinal nerve composing both pectoral nerves. Two types of spinal origins appeared in lateral pectoral nerves. The first type was composed of nerve fibers from C5, C6, and C7 with a frequency of 50.0% and the second type was composed of nerve fibers from C6 and C7 at a frequency of 50.0%. Regarding the average participating diameter to the lateral pectoral nerve, C7 was the thickest with a value of 1.60 +/- 0.35 mm (mean +/- SD), next was C6 at 0.83 +/- 0.18 mm, and C5 was the third at 0.42 +/- 0.24 mm. Three types of spinal origin appeared in the medial pectoral nerve. The first type was comprised of nerve fibers from C8 and T1 in 73.3% of cases. The second type was comprised of C8 only in 23.4% of cases, and the third type was comprised of T1 only in 3.3% of cases. The average participating diameter was 0.71 +/- 0.22 mm from C8 and 0.52 +/- 0.17 mm from T1. These results show that the spinal origins of the both pectoral nerves were various. Participating amounts of the lateral pectoral nerve appeared sequentially in the order of C7, C6, and C5. In the medial pectoral nerve, C8 participated more amounts than T1.     

腓动脉穿支远端蒂保留腓肠神经的筋膜皮瓣临床应用

目的:探讨以腓动脉穿支为蒂的腓肠神经筋膜皮瓣逆行修复足踝部皮肤软组织缺损的临床疗效.方法:临床应用该皮瓣修复足踝部皮肤软组织缺损创面18例,其中保留腓肠神经主干3例,腓肠外侧皮神经l例.结果:18例皮瓣面积9 cm×6cm～18 cm×10 cm.最远修复达足中部皮肤缺损创面.17例随访8个月～27个月.有3例皮瓣远端坏死2.5 cm×2.5 cm～1.7 cm×3 cm游离植皮修复.6例水疱经换药后其余完全成活.足底承重受压后未见异常.10例患者诉外踝及足背外侧皮肤感觉不同程度缺失.结论:腓动脉穿支远端蒂腓肠神经筋膜皮瓣血供可靠,转位更灵活方便是修复足踝部软组织刨面的较好方法.如能实现保留腓肠神经对足背外侧皮肤感觉可有积极意义.     

Lateromedial and dorsoplantar borders among supplying areas of the nerves innervating the intrinsic muscles of the foot

The branching patterns of nerves supplying the intrinsic muscles of the foot were analyzed as a basis to confirm the muscle layer structure. Thirty‐eight feet of 20 Japanese cadavers were examined in detail in this study. The first dorsal interosseus was innervated by a branch from the deep peroneal nerve as well as a branch of the lateral plantar nerve in 92.1%, the second dorsal interosseus in 10.5% and the third dorsal interosseus in 2.6%. In three specimens, branches from the deep peroneal nerve innervated the oblique head of the adductor hallucis or the lateral head the flexor hallucis brevis. In addition, branches from the medial and lateral plantar nerves and the deep peroneal nerve formed communication loops in three specimens. The first dorsal interosseus, the oblique head of the adductor hallucis and the lateral head of the flexor hallucis and their innervating nerve branches are closely related within the first intermetatarsal space. Since the tibial part of the first interosseus muscle primordium is occupied in the space during development, the variations of innervation patterns and formation of the communicating nerve loops may be explained by various combinations of the part and the other muscle primordia. Anat Rec 255:465–470, 1999. © 1999 Wiley‐Liss, 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.     

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.