arnalIGF-Ry605602 of THE JOURNAL OF HAND SURGERY Official journal AMERICAN SOCIETY FOR SURGERY OF THE HAND

ORIGINAL COMMUNICATIONS 606 Internal topography of major of the forearm 6O8 and hand: A current view

617 Fresh cadaver nerves were examinedby serial cross-sections and microdissection with the operating microscope. The findings are comparedwith those of previous authors, primarily Sydney Sunderland. Our study cot~rms and amplifies Sunderland’s findings: although it is true that funicular plexus formation and #tterchange takes place in the nerves of the humanforearm, these connections are not of such a degree as to preclude operative procedures such as intraneural neurolysis, fascicular repair, and interfascicular nerve grafting, b~dividual branches and bundles can be identified and traced withht the ma#t nerve trunk for considerable distances without significant trautna to conducting fibers. This 619 arrangementlends itself to the application of modernmicroneurosurgical techniques. Clinical applications of these findings in the repair, lysis, and grafting of the major nerves of the forearm are described. The flossibilit3’ of using such branches as the dorsal cntaneousbranch of the ulnar nerve (if irreparably damaged)as a donor nerve for grafting is noted. 619 Michael E. Jabaley, M.D., F.A.C.S., William H. Wallace, M.D., attd Frederick R. Heckler, M.D., Jackson, Miss. 620

"Honorthose whogo first, even if those whocome later go further." --A fabian proverb* 622

623 The unpredictable quality of functional recovery 624 1945, Sunderland reviewed 40 years of such research which follows nerve repair has stimulated both clinical and described his own work with the internal topog- and basic researchers to continue their investigations of raphy of the radial, median, and ulnar nerves.~-z This the structure and function of peripheral nerves. In well known work is often cited by "other authors to explain their failure to attain a satisfactory level of This paper received the EmanuelKaplan Award,presented by the function following nerve repair and subsequent NewYork Hand Society, for the best paper on an anatomicsubject regeneration. Sunderland pointed out that the cross- at the 1979 meetingof the AmericanSociety for Surgeryof the sectional arrangement of nerve components changes Hand. from level to level and from millimeter to millimeter; Fromthe Departmentof Surgery, Divisionof Plastic Surgery, Uni- histological sections of nerve ends which are examined versity of Mississippi:Medical Center, Jackson, Miss. Receivedfor pubhcat,~[arch 15, 1979. at different levels will appear to be different. This fact Reprint requests: Michael E. Jabaley, M.D., 1417 Lefia Dr., has led some to adopt an attitude of resignation toward Jackson, MS39216 [(601)362-6323]. accurate alignment of fascicles when gaps of more than *Quotedby Sir SydneySunderla:ad. in his Sterling BunnellMemorial a few millimeters exist, Lecture. San Francisco,N,~,. 3, :977. The changing nature of ~he internal arrangement is The Journal of 2 Jabaley, Wallace, Heckler HAND SURGERY

for some dist~ance. Relatively long nerve gaps can sometimes be overcomewith successful restoration of both motor and sensory function either by direct suture or interpositional grafts, suggesting that somemeasure of effective funicular alignment has been accom- plished. Lastly, and most spectacular/y, Manktelow and McKee4 have reported transfer of the gracilis mus- cle to the forearm by microneurovascutar techniques with subsequent recovery of function. Clearly, nerves mayhave a greater potential for functional recovery than is generally assumedprovided circumstances are otherwise favorable. 5 : Definition of terms A peripheral nerve consists of (I) neural elements which are extensions of motor and sensory cells located in the dorsal ganglia and anterior horns of the spinal cord and (2) non-neural connective tissue which sup- ports, separates, nourishes, protects, and maintains the relative position of the various neural elements. The neural elements, called (or fibers), maybe affer- ent, efferent, or sympathetic(sympathetic fibers will be ignored in this discussion). The non-neural elements consist of the , , and en- doneurium. The epineurium can be subdivided into the epineural sheath (which surrounds the whole nerve) and the epineural connective tissue (which lies between funiculi or bundles). Groups of axons enclosed by perineurium are calledfuniculi orfasciculi. They are the smallest clinical units with which surgeons might work using current clinical techniques. Sunderland chose to use the termfuniculus; we have elected to use this term and its synonym,fascicle (orfasciculus), in- terchangably, since both are found frequently in the clinical literature. The term bundleis purely descriptive Fig. 1. Sunderland’s three-dimensional drawing of the and will be used to describe a group of fasciculi which funicular plexus formationin a 3 cmsegment of a specimen appear to be associated topographically within the of th~ musculocutaneousnerve of the arm. (Reproducedby epineurium, either in photomicrographsor upon clinical kind permissionof Churchill-Livingstone,Ltd., Edinburgh, or laboratory dissection. It is a clinical term and does London,and NewYork, and Sir SydneySunderland.) not necessarily imply a functional association. Sir Sydney Sunderland unquestioned. Nevertheless, several clinical observa- tions led us to wonder if other factors knownto be Sunderland’s study of the intraneural topography of involved in peripheral nerve function might not out- the radial, median,and ulnar nerves clarified the diver- weighthe handicapof an evolving cross-sectional rela- gent3 opinions expressedin the literature prior to 1945. tionship in determiningthe quality of a final result. For He later extendedthis investigation to other nerves5 and example, bundles and funiculi of intact nerves can be assembled all his studies in the monumentalpublica- separated (lysed) with no loss of function and some- tion,Nerves and Nerve Injuries. 6 Sunderlandfound "no times even with clinical improvement. Similarly, constant or characteristic funicular pattern for any in ulnar nerve transposition operations, the ," and he stated that "the funicular pattern was branchescan ’.~ safe],,.,’ separatedfrom the m’:.:! ~ ,:~nk continually modified along the entire len_~th of each TheJournal of ID SURGERY Vol. 5, No. I January 1980 Internal topographyof peripheral nerves 3

ve gaps can :estoration of direct suture ome measure ~een accom- Manktelow gracilis mus- tr techniques . early, nerves hal recovery instances are

ral elements cells located 9f the spinal ’ which sup- naintains the -~ments. The aay be affer- ~bers will be ral elements ’~, and en- ided into the e nerve) and ies between .’nclosed by ~i. They are geons might Sunderland ected to use Fig. 2. Theleft mediannerve in upperforearm, looking from proximal to distal. Theradial side is :iculus), in- ently in the on left. A, Discretefascicles can be seen enclosedin perineuriumand separatedby epineurium.B, A line drawingof a nerve..(pt, pronatorteres; t, terminalmotor and sensory fascicles to the hand; ~ descriptive fds, flexor digitorumsuperficialis; fcr, flexor carpi radialis; p, flexor digitorumprofundus: ai, :iculi which anterior interosseous.) Motorbranches to forearmmuscles are situated aboutthe radial and ulnar within the sides; terminalbranches to the handare located in central core. lpon clinical m and does nerve by the repeated division, anastomosis, and mi- terpretation of Sundertand’s work is incomplete and /on. gration of the bundles." The longest section of any unnecessarily pessimistic. nerve with a constant pattern was 15 ram, although At the time of Sunderland’s study, standard nerve individual bundles and bundle groups pursued longer repair was performed by epineurial suture without ~ography of courses without change; the average length of constant magnification. Intraneural topography was of some d the diver- z pattern was only 0.25 to 5.0 ram. Although he dis- academicinterest, but had little clinical importance. ~r to 1945. Since the introduction of magnifyingdevices, sophisti- ~ cussed resection, repair, and regeneration in sutured nerves and nerves, Sunderland made no attempt to correlate his cated instruments, and microsurgical suture, moreand tal publica- findings with function or clinical results. Nevertheless, more surgeons have undertaken interfascicular dissec- ~ found "no his famous three-dimensional reconstruction of the tion for the purposeof neurolysis, interfascicular graft- m for any musculocutaneousnerve (Fig. 1) is frequently associ- ing, and repair. Because of the increasingly frequent pattern was ated with explanations of suboptimal results following use of these techniques, an accurate understanding of ,~th of each nerve repair, r Webelieve that the hand sur~_’een’s in- intrane:~ral architecture has becomemandatory. To bet- TheJournal 4 Jabaley, Wallace, Heckler HAND SURGERy

Ttfenarm.

N NERVE Radialindex

Th~~ enar sensory ~ 2 ndweb space

~ Flexordig. superficialis -""- Ant. interosseous % Pronatorteres Fig. 3. Componentmicmdissection of the mediannerve. Thedark lines diagrammaticallyillustrate the dissection distance for eachbranch. Thering and arrowdepict the anatomicorigin of the nerve branch.The dark line distal to the ring andarrow represents the extraneuraldissection distance; the line proximalrepresents the intraneural dissectiondistance. ter understand the limits and the usefulness of these noted. The entire median nerve and its branches were technical advances, we have undertaken to perform se- removed from the arm, pinned to a board to maintain rial nerve sections in the fashion described by Sunder- correct length and orientation, and fixed in 10%forma~ land and to compare these observations with the lin for 7 days. findings of interfascicular microdissectionsof the major After adequate tissue fixation the mediannerve was nerves of the humanforearm. cut into 44 separate blocks, either 5 or 10 mmin length. The proximal end of each block was labeled and the Method distal 2 mmwas removedas a separate subblock, pro- Weexamined the median~ulnar, and radial nerves of cessed, and embeddedfor microtome slicig’~. The 2 six unfixed humanarms by either serial section (three mmblock was serially cut into 20-micron-thick sec- mediannerves--one sectioned totally, two partially) or tions, which were mountedunstained for examination. microscopic interfascicular dissection (four median, (Initially these sections were stained with hematoxylin four ulnar, and two radial nerves). Serial sections were and eosin, a step later omitted after we learned that we taken between the medial epicondyle of the humerus could see adequate detail on unstained preparations.) and the terminal nerve branches in the palm; the mi- Each microscopic section was projected and traced on crodissections were extended 10 to 12 cm above the thin paper to documentthe relative size and location of medial epicondyle. funiculi, the amount of epineurium present, and the Serial section study. Three median nerves were origin of branches. Brancheswhich could be positively studied, all from adult males. The mediannerve and its identified were followedin retrograde fashion and their branches were exposed throughout the forearm and funicular makeup recorded. Sections were made im- hand and left in place. All branches were identified and mediatelyproximal and distal to all branchesto confirm labeled. The volar (anterior) surface of the nerve was their identity. Additional sections were taken through- marked with a continuous No. 6-0 silk suture placed out each block whennecessary to permit positive iden- within its epineuriumand India ink applied to its sur- tification of bundlesand clarification of their changing face. The length of the nerve and the distance from the pattern. Like Sunderland, we examinedthe nerves in a radial styloid reference point to each branch wa:~ di~tat-~o-proximaldirecti:;~ :o detect change~;:~ num- sured in n-liili.r-:~er.ers arid recorded. Theicca~i~: ber, size, and location of fasciculi. Photograp::; of ap- branches on the perimeter of the main trer~k propriate section:~ were ~ade for permanent ; Journal of 5, No. 1 SURGERy 1980 Internal topography of peripheral nerves 5

~ble I. Mediannerve serial sections

Sunderland Authors

Firsl Total First Total interconnection measurable distance first interconnection measurable distance I Thenar motor branch 56 112 35 70 .Sensory 1st web space 5O 95 2O 55 2nd web space 58 97 25 55 ~S): 3rd web space 66 81 25 55 ~2.~ Palmar cutaneous Distal 74 99 30 70 i ~!.i_ Proximal 37 62 25 65 Fle~er digitorum ::.~icialis Distal 2 4 I8 75 Proximal 16 32 22 22 Anterior interosseous 51 83 59, Flexor carpi radialis 53f 53~ Pronator teres Distal 5 41, 4I? Proximal 95 27~ 27~

*Internal topographyof the mediannerve as measuredin serial sections. All distancesare in millimeters. ~’Siteswhere bundle localization was arbitrarily stoppedat the level of the medialepicondyle, even though more proximal identification waspossible.

-,ve ultimately used a system where one 20-micron- Table II. Mediannerve microdissection distances* thick section out of every five was mountedfor viewing Sunderland [ Authors maintain and the other four were discarded. This was possible b forma- ~i because no significant changein funicular pattern was Thenar motor branch 56 84 ever noted within a 100-micronlength of serially stud- Sensory branches !rve was ied nerve. Ten such sections could be mountedon each 1st web space 50 114 I length. .. Thenar sensory 97 slide so that one slide represented 1,000 micronsor 1.0 Radial side, index finger andthe ’ 97 millimeter of nerve. 2nd web space 58 37 ok, pro- Twofigures are listed for each branch: The first in- 3rd web space 66 37 The 2 terconnection is the level where any connection, re- Palmar cutaneous ick sec- gardless of size, was seen. The total measurable dis- Distal 61 119- ination. tance is the level to whichthe branch could be traced Proximal 24 Flexor digitorumsuperficialis 58 ~toxylin before intermingling with other bundles. Distal 2-4 that we Microscopic dissection was performed with the Zeiss Proximal 22 ations.) OpMi7 operating microscopeat magnifications of 4.,5 Anterior interosseous 51 147, iced on ~"~. to 25 times using standard techniques with jeweler s Pronator teres 1 ation of Distal 5 S-’~!!I:=~:. forceps, scalpel, andscissors. Photographsof represen- Proximal 98? ~nd the ~" tative fields were taken through the microscope with a sitively *Mediannerve microdissecfiondistances, comparingSunderland’s data with ~Yashica FL camera and automatic light meter. The authors’.All distancesare in millimetersand represent the rno~tproximal dis- ad their ~ films were Kodak Ektachrome, ASA 64, and Tungsten tance to whicheach branchcould be isolated withinmain nerve trunk. :de im- *Levelsin the upperarm where branches could still be identifiedbut dissection Ektachrome, ASA160. Three median, ulnar, and m- wasarbitrarily stopped. :on firm s were examinedin fresh autopsy specimens. trough- :In addition, numerous observations were made in the e iden- roomon patients undergoing nerve repair or the palm and traced proximally by incising the anging grafting. These latter observations confirmedour opin- epineurium and separating the branches from the re- es in a ions but were not included in the data drawn from mi- maining nerve trunk for as far as they could be iden- I num- crodissection. tified and easily separatec;. T~i~ ,vas done by gentle of ap- Terminal branches o( the metor and sensory di’d- ,rding. skins of the medianand ulnar nerves were identified in C~nnee:ions between the branches and other bundles The Journal HAND 6 Jabaley, Wallace, Heckler

Fig. 4. A photomicrographof the mediannerve at the distal transverse carpal ligamentlevel. The bundlesand branchesare clearly identifiable and are separated by loose epineurium.They can be easily dissectedfrom each other withoutinjury to the fascicles. [a, two fascicles comprisingthe thenar motorbranch; b, the bundleof sensoryfibers to the thumband the radial side of the index finger; c, bundleof sensoryfibers to secondweb space (index-middle fingers); d. already separate branchto the third webspace (middle-ring fingers).] the five arms examined. All nerves in each arm within the nerve were noted and their size and number not dissected. recorded. The superficial radial and posterior interosse- The motor branch to the thenar muscles. The ous nerves were similarly dissected. branch to the thenar musclesrose as a single The number which is given in the tables for each branch’s microdissection distance is the most proximal all nerves and consisted of two fascicles. In the serial level to which the branch could be readily and posi- sections it joined the maintrunk on its vo 40 mmdistal to the radial styloid (Fig. 4). It could tively separated as a distinct anatomicunit within the main nerve trunk. This is the point where substantial identified and traced proximally in this position about 70 mm(30 mmproximal to the radial styloid). connections with other bundles could be seen and Few interconnecting bundles were seen_in this span. where composition became speculative. Wesaw the first connectionat 35 mmafter it joined the ¯ Results main trunk, a small branch to an adjacent sensory fas. Median nerve. The median nerves provided the cicle. Wethen followed the motor branch for an addi- tional 35 mmbefore it became thoroughly mixed most information since we examined them both his- tologically and by microscopic dissection (Figs. 2 and the sensory bundles from the hand. Thus we could identify and follow the moto.r branch for a total of 70 3). Wecan comparethese observations with each other mmby serial section, considerably less than the 112 as well as with those of Sunderland(Tables I and II). mmmeasured by Sunderland, but still to a level well The distance from the medial epicondyle, where the highest histological sections were taken, to the radial above the transverse carpal ligament. Microdissection of the thenar mofor branch was styloid varied from 26 to 30 cm. The median nerves divided into their terminal motor and sensory branches formedin four mediannerves (Table II). It joined main trunk 31 mmdistal to the radial styloid, and. on the average4 cmdistal to the radial styloid, and all first visible connection appeared 28 mmproximal of the distances described for these branches are re- ferred to their origin. Branches which arose in the this bony landmark. Wecould clearly trace the forearm are described in millimeters proximal to the branch to 59 mmwhere we found large branches to the adjacent Sensory bundles. Since radial styloid. Thedistances cited in the serial sections in.-_e..,:+:~:~nections were nearly as large as the motor are basedo+: :~ .~:,;.;:-,inati,.>n of a single nerve: the figures for (ae microcissec~ions are representative of b~anchitself, we could go no furzher TheJournal 5, No. 1 qD [i January1980 Internal topographyof peripheral ~,erves 7

’he [5? ~ ¯ ~. . . ~’. ~,,~ the g.... ~ "’ ¯

each ~ were

ties. ~e motor ; ’ single branch in ~,es. In the serial~[~ Fig. 5. Serial sections of a 20 mmspan of medianne~e in the lower fore~ viewedfrom proximal volar-radial side to distal ~d showingsep~ation of the palmar cutaneousne~e (PCN)from the maintrunk of the ~. 4). It could be medianne~e. In this patient the PCNconsisted 6f two branches which ~ose 20 and 25 mm :his position for~ ~. proximalto the radial styloid. A, ~e PCNis a sep~atebundle located on the left (radial) side of the ~ mdiMstyloid). ~f mainne~e. It is loosely held by thin epineufum.One l~ge fascicle comprisesthe distal ~unk(D) :en in this span. ~ and two small fascicles formthe proximaltrunk (P). B, Bothne~e branches ~e still present, but after it joined the ~ ¯ cent sensory fas- [~: off and ~e no longer seen. D, ~e l~ge fascicle (D) nowhas dep~edas a second branchof the inch for an ad~- ~; PCN. tghly[i mixed with~[ Thus we could~ e of the nerves exa~ned, the motor branch could ditional 40 mmbefore merging with other sensory for a total of 70"~ isolated for over 80 ~ before fusion with other fascicles. less than the 112:~~undles occu~ed. In the fou~h a connection was seen In the microdissected specimens; this branch ~ose ill to a level well~~tween the motor b~ch and commondigital ne~e to singly at 88 mmand could be easily sep~ated to 190 ~[~e ~kd w ebspace. It was quite small and was the only mmwithout visible connections. At207 mm,consider- ,r branch was rpe ~nnection "~5.p , seen for the first 45 ram. able mixing with adjacent bundles prevented fu~er ’, If). It joinedt -tr, ~-~. e:~ altair cutan,cutaneousnerve. Histological analysis of the dissection. d styloid, andt thermal sectionssections oof the palmar cutaneous branch of both Flexor digitorum superficialis. Wesaw two branches mmproximal d toto~ linens confi:confirmed two separate branches, each con- in the serial sections, the distal one at 102 mmand the ~S~g of a ofsingl, a single moderate-sizefuniculus. Theyentered proximal one at 208 mm.The distal branch entered on ~y trace the motor~ large connectin~~0n the theradial radial sid side 20 and 25 mmproximal to the radial the radial dorsal aspect of the main trunk as a single ~ge~loid and coul, cl be folio.wed proximallyfor 30 and 25 large funiculus. Within 20 mmit had separated into r~dles. Since .. m heft rge as the motor ~ ~could be3re ~een any 5i7. change 5~.in Theyposition could or benumber tracedof funiculian ad- four smaller funiculi. At this level one small funiculus with certain~y. c’:~’~:.:~-,~ wit~ a ~ensor’: bundle, but the other three The Journal of 8 Jabaley, Wallace, Heckler HAND~, SURGERy

Deepmotor branch Ringfinger, ulnar side Littlefinger, radial side

~Flexor d~ Littlefinger, ulnar side ~ Flexorcapri ,,~’~

Dorsalcutaneous

Fig. 6. Componentmicrodissection of the ulnar nerve. The dark lines diagrammatically illustrate the dissection distance for each branch. The ring and arrowdepict the anatomic origin of the nerve branch. The dark line distal to the ring and arrowrepresents the extraneural dissection distance; the line proximalrepresents the intraneural dissection distance.

Table III. Ulnar nerve microdissection distances* they were too small to dissect further. The two more proximal branches were much larger and both origi- Sunderland I Authors nated from the same large bundle within the main Terminal motor 90 81 trunk. The more proximal branch of the two came off Terminalsensory 90 81 196 mmabove the radial styloid, whereas the remain- Individual sensory tier of the bundle proceeded down to 174 mm, where it Hypothenareminence 52 27 exited and traveled parallel to the proximal branch. The Ulnarlittle finger 48 26 4th web space 48 26 common trunk which contained all branches of the Dorsal cutaneous 171 209t flexor digitorum superficialis could be separated for 58 Flexor digitorum 107 mmwithout injury to any large interconnections. profundus Anterior interosseous nerve and flexor carpi radi- Distal 11 Proximal 22 alis. The anterior interosseous nerve is the largest Flexorcarpi ulnaris 7 motor branch of the median nerve in the forearm (Fig. Distal 97 2). In the histological sections it could be seen on the Proximal 74 ulnar-dorsal surface, arising at the same level (208 mm) * Expressedin millimeters. but separate from the proximal branch of the flexor -~Levelsin theupI~"r arm wher e branche~could still beidentified but dissection digitorum superficialis. It contained 14 fascicles and wasarbitrarily stopped. traveled proximally in the same position on the outer perimeter of the remainder of the median nerve. We proceeded proximally for an additional 55 mmwithout still could clearly identify the anterior interosseous further major change. nerve within the main nerve trunk at 267 ram, the level The proximal branch entered as a single large fasci- of the medial epicondyle, and we could see no inter- cle on the ulnar dorsal surface at 208 mm.It was easily connections with other portions of the median nerve traced for 22 mmwithout interconnection. during this 59 mmspan. By microdissection of this nerve in a fresh autopsy By microdissection we located the anterior interos- specimen, we isolated four separate branches to the seous nerve arising on the dorsal surface at 239 mm.It muscle, at 121 mm(radial side), I24 mm(posterior could be easily separated to the level of the medial surface), 185 mm(ulnar side), and 196 mm(ulnar epicondyle (293 ram) and for an additional 93 side). Although the first two branches were little more beyond. Its only attachments to the median nerve than filaments, they wire clearly nerve branches. We epineurial and these were e~.sily divided. The branch to tr-~ced them for 15 mmto substantiate this poin;: tt~.e flexor carpi radiaiis ac~uatly arose from t,~.e anterior anal of Vol. 5, No. 1 GERY January 1980 l mernaltopography of peripheral nerves 9

t~ origi- Fig. 7. Dissectionof the ulnar nervein the lowerthird of forearmand palm. The lower arrow points ~e main to deep motorbranch. The upperarrow points to sensory component.The area to the right of the ame off arrowis the commonsensory bundle. The area to the left of the arrowhas divided into sensory remain- nervesto the ulnar side of the little finger andthe little-ring finger webspace. whereit tch. The interosseous nerve in the histological sections. It en- mm). They were traced proximally for 37 mmto the ; of the tered at 214 millimeters on the dorsal-ulnar aspect. The level of the medial epicondyle, where they joined to d for 58 branch consisted of three medium-sizedfascicles which form a single large funiculus. No sec.tions were made joined as they proceeded proximally to becometwo and proximalto this point. ¯ pi radi- finally one, large fascicle. This single fascicle began24 By microdissection the branch to the flexor digi- ; largest ,mmproximal to the branch point of the flexor carpi torum profundus arose from the anterior interosseous rm (Fig. fadialis from the anterior interosseous nerve. The nerve. Although it was dissected for only 10 mmprox- :n on the branch to the flexor carpi radialis was traced to the imal to its origin, the branch remained separatexrcer 208 ram) medial epicondyle, a distance of 53 mm,without inter- this span. ae flexor connection to other bundles. Pronator teres nerve. The pronator teres nerve was icies and By microdissection we also found the nerve to the the most proximal branch of the median nerve exam- the outer carpi radialis originating as a branchof the an- ined histologically. It arose as two separate branchesat ~rve. We terior interosseous and departing some3 mmdistal to 226 and 240 mmfrom the radial-volar aspect. These ~rosseous nerve’s origin. No significant connections were branches contained two and three f~aniculi, respec- the level seen in the first 20 mmproximal to its branchpoint, and tively, and could be easily identified at the level of the no inter- we madeno attempt to trace it further within the an- medial epicondyle (267 mm). No detectable connec- ian nerve interosseous nerve. tions with other bundles were seen between.the origin Flexor digitorum profundus. The flexor digitorum of these branches and the medial epicondyle, distances ~r interos- was located on histologic section at 230 mm of 41 and 27 mm,respectively. 39 mm.It an independent branch from the radial side of the By microdissection five separate branches to the pro- he medial mediannerve. Anadditional contribution to this muscle nator teres arose from a single large trunk whoseorigin d 93 mm from the anterior interosseous nerve. was wel! proximal to the medial epicondyle (303 ram). ~erve were Twofascicles, one large-and one small, comprised This trunk was 12 mmlong and was easily dissected for branch to the independentprofundus branch at its point of depar- 100 mmwith no evidence of connecting branches to ae anterior ture from the main trunk of the median nerve (230 o~he.r ?.ortions of the mediannerve. TheJournal I0 Jabaley, Wallace, Heckler HAND SURGERy

Fig. 8. Dissectionof the dorsal sensorybranch of ulnar nervein the forearm.This branch(arrow) couldbe isolated fromthe maintrunk, beginningat its normalanatomic origin and goingto a point well abovethe elbowwithout transsecting any interconnections. This distance is approximately 20 cm. Ulnar nerve. We dissected four ulnar nerves into epineural conduit while still retaining their autonomy. their componentbundles with the aid of magnification This arrangement was found in all of the ulnar nerves (4.5 to 25 times) (Fig. 6), but we performed no examined. tological examinations of this nerve (Table liD. Be- Multiple motor branches to the two main forearm ginning in the palm at the terminal branches, the motor muscles, the flexor digitorum profundus and the flexor and sensory components (deep motor branch and carpi ulnaris, were found in all instances. They some- common sensory trunk which became the sensory times arose separately from the main trunk of the ulnar nervesto the ulnar side of the little finger and the fourth nerve and sometimes as branches of a commontrunk, web space) could be separated for a total length of 81 but always in the region of the elbow. Representative mm(Fig. 7). In one nerve these two branches remained levels of origin were 240 to 280 mm;representative ciearly separate to the midforearmlevel. No connec- dissection distances were 74 to 107 mm.These dis- tions were noted before 21 ram; those seen were small tances permitted separation of the flexor digitorum pro- filaments and did not makeup a significant portion of fundus and the flexor carpi ulnaris well into the upper the trunk. Within the sensory componentthe branches arm. to the ulnar side of the little finger and the fourth web Radial nerve. Technically, th~ radial nerve is not a space were separable for 26 mm. forearm nerve, since it terminates at the level of the The level at which the dorsal cutaneous branch medial epicondyle. For this reason, we did not study it joined the main trunk of the ulnar nerve was variable. in detail (Fig. 9). In one specimenit entered as far distal as 48 mmprox- Wedissected the posterior interosseous and super-. imal to the radial styloid; another joined at the 91 mm ficial radial nerves above their origins and found thai: level. It traveled proximally as a separate bundle for we could easily separate them from each other for 90 209 mm,well above the epicondyle, without demon- mmbefore encountering the first interconnection (Table IV). No attempt was madeto separate individual strable connectionsto the maintrunk (Fig. 8). It wasas -: though the dorsal cutaneous nerve and the ulnar nerve motorbranches of either the radial or posterior interos were two separate nerves traveling .within a common seous nerve. " TheJournal of~ 5, No. 1 Internal topographyof peripheral nerves 11 ~ND SURGERY 1980

Posterior interosseous ~,~ ~

Fig. 9. Acomponent microdissection of the radial nerve. Thedark lines diagrammaticallyillustrate the dissection distance for eachbranch. Thering andarrow depict the anatomicorigin of the nerve branch.The dark line distal to the ring and arrowrepresents the extraneuraldissection distance; the line proximalrepresents the intraneural dissectiondistance.

Discussion Table I¥. Radial nerve microdissection distances : Studies conducted by numerous investigators over the oast 70 years have demonstrated that the internal I Sunderland l Auth°r" stru~:ure of peripheral nerves is characterized by nu- Posteriorinterosseous (ram) 72 90 merous intercommunications, position changes, and 72 90 a Superficialradial (mm) ~eir autonomy. :the formation of funicular plexuses, Evenin the early te ulnar nerves 1900s someinvestigators recognized the basic plexi- funiculi contain representative fibers of most if not. form character of the intraneural funicular pattern. The all of the peripheral branches. His compositemodel of main forearm uestion of functional significance was rarely raised, the musculocutaneous.nerveillustrates this point (Fig... and the flexor ~S:. however. Stimulation of exposed nerve by electrical 1). At more distal levels, however, a regrouping of s. They some- ::~~5currents suggestedthat the funcnonacourse of axons is the fibers is gradually effected, whereby individual ~2.a straight one, even ff the fumcular course is not, but nk of the ulnar branches becomeidentifiable as such and come to oc- :ommontrunk, ~2the methods employed made these studies suspect. cupy different funiculi and bundles. He conch.tded that Representative ~:~}~ Nowit has becomeimportant that we try to determine g the purpose of the intraneural plexuses seems to be "to representative :~:~"2~. in ...... what avw_~ and to what de ree internal architecture assemblethe requisite afferent and efferent fibers for tm. These dis- i~mgtters in clinical practice. each branch from the appropriate segmental sources." .Sunderland performed the exhausting task of serial digitorum pro- ~ Hefurther thought that often a plexus is "the product of into the upper ~~l~istological section and examin.ation of the major mesenchymalcondensations which occur during devel- ~!,nerves of the extremities, catalogxng both the arrange opment, regardless of the destina.tion and function of [ nerve is not a of individual fascicles and the distances over the fibers." This is certainly possible, given the capri- they could be identified. Furthermore, he per- ae level of the cious nature and variation of developmental anatomy. did not study it microdissections of the branches and recorded As we come to understand better the complex cir- distances over which they could be isolated from the main trunk of the nerve "without damagingor in- cuitry of the , we gain/in appreciation ~us and super- for the large numberof information interchanges re- and found that with the fiber architecture." Although some quired. The refining process begun at the spinal cord :h other for 90 took note and recognized the significance of level must continue through the larger nerves and their i this latter work, Sunderland’smicrodissections appear interconnection branches until individual fibers can be appropriately have been largely unnoticed by most surgeons. arate individual positioned at their target organs. The sorting probably )sterior interos- .... In his writings Sunderland emphasizedthat in the occurs irrespective of whether the fibers are motor or proximal portion of nerves, the majority of the The Journal 12 Jabaley, Wallace, Heckler HAND SURGER

"remain in the same quadrant over long distances. Moreover,he points out that, "there is no proof that th~ intercommunicationseffect a complete reorientation or! redistribution of fibers or that the intercommunicat erased localization." In fact, he even cautions that" "conclusions~ based on such investigations have given very misleading results." Despite Sunderland’s clear recognition of the plexiform nature of intraneural to- pography, these statements do not imply a constant~ (and hopeless) intermixing of the componentsof ripheral nerve. Rather, they suggest an orderliness and purpose which might be used to advantage in treating: mechanicalailments and injuries if it is recognizedand:: understood. It is noteworthy that subsequent investigations by others have confirmed these points, ~ and we are una-: ware of any contradictory studies. Analysis of our based on serial sections of the median nerve furtheri: documents Sunderland’s interpretation of his mi- croscopic results. In the 33 years which have elapsed since Sundertand’s publication, manysurgeons have!! grasped the fact that funicular plexuses and intercon-~ nections exist but they have failed to appreciate his demonstrationthat fitnctional units (and often discrete branches) remain localized in the same quadrants of nerve trunks for considerable distances and are acces-:i Fig. 10. Thecurrent conceptof the internal topographyof a 3 sible to surgical manipulationand repair. cmsection of the mediannerve in the midportion of the Comparisonof the absolute distances in our forearm.Since this representationis of the moredistal seg- and those of Sunderland show manydiscrepancies and mentsof the nerve, fascicular branching or mixingis in- these distances deserve comment(Tables II, III, and~ frequentlyseen, either in cross-section or longitudinalmi, IV). Dissection distances are not important in and of:~ crodissection.This appearancediffers fromthat seen in Fig. themselves, for they vary from nerve to nerve and per~!! 1, whichrepresents the musculocutaneousnerve at a more son to person. Moreover, landmarks such as bony~ proximallocation. prominencescannot be strictly defined, and-actual mea-~ suring-~ techniques are imprecise. Finally, in fresh spec .sensory. In fact, Terzis8 has referred to her unpublished imens the epineurium is loose and one can vary the work which suggests that even a nerve such as the deep origin of a branch by a few mtlhmeters s~mplyby tug-ff motor branch of the ulnar nerve, heretofore thought to ging on it. For all these reasons, the absolute distances~ be a "pure motor nerve," maycontain as muchas 50% that branches travel are probably unimportant, except~ sensory fibers. Despite these obligatory changesin fiber insofar as they relate to each. other. The point to be~ location, it nowappears that the forearm and hand are made is that, while some internal sectors of a nerve~ characterized by connections within, not between, may be changing, other portions may proceed for con-~ bundles, and that bundles are separable surgically. siderable distances with no major changein position or ~.: Perhaps the most important aspects of Sunderland’s composition and thus may be isolatedsurgically. If one..~ work are these: "Despite the changing plexiform is to perform intraneuml dissections, an understanding~ character of the funicular pattern, fibers from the pe- of the branch patterns and bundlearrangements is of the.~’~ ripheral branches pursue a localized course in the utmost importance. nerve for variable, though often considerable dis- It is impossible, of course, to study the courses o tances." The redistribution of bundles implied in the individual axon fibers by the techniques employed plexus principle "is local and not general." Fibers this study. Sunderland assumedthat constituent fibers~’ "scatter gradually" and, even with intermingling. i:’.termin~!ed wheneverthere wasfusion of f:~’niculi and me 1oumal of Vot. 5, No. I D SURGERY January 1980 lnternal topographyof peripheral nerves 13

~ distances." proof that the 3rientation or mmunication cautions that ~s have given :rland’s clear atraneural to- ly a constant aents of a pe- rderliness and ge in treating ~cognized and

.~stigations by ~ we are una- sis of our data nerve fuaher of his mi- t have elapsed mrgeons have and intercon- appreciate his ’ Qftendiscrete ~ quadrants of "~nd are acces-

s in our study c~pancies and les II, m, and a~t in and of ne~e and per- such as bony and actual mea- ,, in fresh spec- ,e can va~ the ~ simply by tug- solute distances tpo~ant, except "he point to be tors of a ne~e ,roceed for con- ~e in position or ~trgically. If one n understanding gementsis of the Fig. 11. A, A partially dissected mediannerve, seen through the operating microscope.The undissectedportion is at the bottomof the photograph.The upper portion showsseveral parallel the courses o bundles and fasciculi whichwere separated by incising their epineurium.Only an occasional ~es employed in connectionis seen. B, A high powerview of the mixedarea. There are severn1 large parallel :onstituent fibers fasciculi with -no intercoanection.A medium-sized connection is seen in the center of the field anda of funiculi and smallerone is located at the-lowerright. TheJournal of: 14 Jabaley, Wallace, Heckler HAND SURGERY that subsequent separations left representatives of all In our microdissectionsof the fresh autopsymaterial the daughter fibers in each newly formed fascicle. He we were abletto identify large interconnecting branches"i further classified plexuses as (I) those where all the with ease (Fig. 11). There were relatively few such fascicles are derived from one branch and where connections in the distal portion of the forearm. changes are confined to bundles of like origin. (2) though it is possible that smaller branches were present Those where the fascicles of a bundle or branch and could not be seen through the microscope, it is blended with fascicles of a nearby but separate bundle, more likely that microdissection is an effective wayof i.e., one of a different origin. This implies a blending separating bundles and funiculi with very little damage of unlike fibers. (3) Thoseoccurring at the most proxi- to whatever connections exist. It is even possible that mal levels of a nerve, where bundles which already the plane of clinical dissection was between funiculi contain fibers of diverse sources divide and recombine which might have appeared to be associated in a single repeatedly. These three types of union probably occur bundle by histological examination. Since limited dis- in a distal-to-proximal direction and result in progres- sections were performed above the medial epicondyle sively greater fiber, mixing as nerves becomenearer to of the humerus, we cannot say whether such separa- their central origin. Since our study was limited to the tions would also have been possible in the more proxi- forearm and hand, manyof the changes we noted in mal portions of the nerve where considerable inter- funicular pattern were similar to Sunderland’s first mingling of fibers is thought to occur. Sunderland’s type: as two adjacent funiculi movedcloser to each dissections at this level suggest that such separation other, the intraneural epineurium betweenthem thinned would have been less likely. and then disappeared; the position and appearance of An understanding of the character of the non-neural the bundles changed, but there mayhave been no actual connective tissue layers of peripheral nerves suggests a mixingof fibers (Fig. I0). If this supposition is true, possible explanation for the ease of dissection of indi- then bundles which behave in this fashion can probably vidual bundles’-° (Fig. 12). The epineuriuminvests the be separated surgically until a level is reached where entire nerve trunk as well as groups or single funiculi. fibers actually pass from one bundle to another. Such The intraneural epineuriumis loose and areolar, it tears fiber mixing rarely occurs whenbranches and bundles easily, andit possessesrelatively little strength, but it is first fuse, but only at moreproximal levels in the nerve. the stuff whichseparates the bundles. Perineurium, on In our microdissections of the median, ulnar, and the other hand, surrounds each funiculus, has a tight radial nerves, we found that major branches could be lamellar composition, and is quite strong. It is the ma- separated from the main trunk for considerable dis- terial one sews whenmaking an interfascicular stitch, tances by incising the epineural sheath and teasing the and it is the natural plane of dissection upon whichone intraneural epineurium apart (Table II, III, and IV). separates fasciculi. In performinginterfascicular dis- These data are comparable to similar observations by section, the tissue which gives way most easily is Sunderland3 and Seddon.1° Further corroboration can epineural connective tissue. Thus one would expect be found in those clinical studies which describe the that in the relatively distal segments of p-6"ripheral separation of the motor branches for transposition of nerve, the bundles, might be separated into their com- the ulnar nerve at the elbow and separation of the motor ponentfuniculi with little or no loss of function because and sensory branches of the ulnar nerve at its termina- there are relatively few interconnecting fibers. Our tion to permit rerouting and individual repair of the findings suggest that this is indeed the case. branches in the palm. In addition, neurolyses of the It is unclear whya funicutus wouldtravel first with median nerve at the carpal tunnel are performed suc- one bundle and then with another’. Sunderland’s expla- cessfully without functional loss. Morerecently, Mil- nation that it is part of the sorting process whichbegins lesix~ has reported separating the palmarbranches of the with spinal segments and evolves to branches is most median nerve "to the middle or proximal half of the acceptable. Furthermore,his idea of fortuitous conden- forearm"in preparation for specific funicular grafts to sation of mesodermalso maybe true. The impression these branches. These observations all lend credibility we have formed is that fiber and funicular behavior, at to the conclusion that it is possible to perform such least in the moredistal portions of nerves, is rather separations in the clinical setting as well as in the lab- purposeful and that it is the random wandering of oratory. They suggest that manyof the interconnections epineuriumwhich is responsible for muchof the change found below the elbow in the median and ulnar nerves observed. Althoughthis mayseem a subtle distinction may be of less surgical importance, than has been its importancemust be emphasized.It is quite a differ- thought heretofore. ent ma~er’,o suggest that the epineuriumshifts and net e Journalof . :~:;.%, Vol. 5, No.1 Internal topographyof peripheral nerves 15 SURGERY~ January 1980

tg branches t few such rearm. A1- ~ ’ere present ;cope, it is :ire wayof :tie damage 9ssible that

ep.icondyle ach separa- table inter- anderland’s separation non-neural ~ suggests a ion of indi- invests the ~te funiculi. 3lar, it tears ..,th, butit is leurium, on has a tight t is the ma- :ular stitch, ~ which one cicular dis- st easily is 3uld expect ’ peripheral ) their corn- :ion because fibers. Our el first with rod’s expla- Fig. 12. A scanningelectron micmgraphof a dog’s nerve. Aboutthe outer portion, the epine’urium ~hich begins is loosely and randomlyarranged. Thetighter and moreorderly perineuriumencloses the crescent- shapedmass of individual axonfibers. Eachaxon occupies a separate area and is surroundedby :hes is most .In interfascicular dissectionsthe perineuriumis the natural plane of dissection. ous conden- ~ impression appears that the fibers, collected in small funiculi, ’~ehavior,at ~.the fasciculi, but this seemsto be the case over the encountered in our lower forearm dissections. travel in identifiable bundles and can be separated sur- s, is rather gically with little or no damageto the componentparts. ~ndering of Whatis certain and what must be stressed is that the betweenthe cell body in the dorsal or ven- Since most injuries occur in the moredistal portion of a Cthe change nerve, the funicular arrangement and relationship at distinction, ganglia and the end organ, whether sensory or is continuous. Over the distances commonly this level is critical and appears to favor the surgeon. rite a differ- Wehave speculated ~e,:bre that the nervous system rifts andnot encounteredm peripheral nerve repair, lysis, or graft, it The Journal 16 Jabaley, Wallace, Heckler HAND SURGERY~

is blessed with manytimes the numberof sensory fi- fascicular grating seems most appropriate in such in- bers necessary to perform basic functions, provided stances.’6 A technical disadvantage of this approach their central connections are appropriate and undis- the difficulty one encounters in matching seemin torted. 13, 14 Thus a reduction in functioning axons of disparate portions of the proximaland distal ends when some measurable percentage, if it could be accom- a large gap exists. Weshould emphasizethat, despite plished in an orderly fashion, still might permit rela- the disparity in fascicular patterns, fibers remain lo- tively normal sensation which is simply less dis- calized to the samequadrant of a nerve over a distance criminating. This may well happen when one performs of several centimeters, and it is possible to select a neurolysis or separates branches of a nerve. It almost matching motor and sensory components on a quadrant surely occurs in a repair or graft where regenerating basis. Both Sunderland and Millesi lr spoke to this axons are fewer in number and may reach similar but point, and Sunderland observed that in such instances different end organs. Useful function returns, but the the surgeon "must use his best clinical judgement to strength or ability to discern is reduced. This phe- matchgroups of funiculi." Millesi has adopted Sunder- nomenonoccurs naturally in peripheral neuropathies land’s term "’group fascicular matching" and has used and affects both motor components, where it is easily it to describe his technique for choosing bundles to be measured, and sensory components, where it is not. connected by grafts. As used by Millesi, "group fas- cicular matching"means just that: bundles or groups of Clinical applications bundles seen at the cut end of a nerve are selected for Carpal tunnel and other entrapment syndromes. grafting on the basis of size, number, and quadrantic Curtis and Eversman15 suggested, and others have cor- location. It is impossible to matcheach individual fas- roborated, that internal neurolysis, whenindicated, can cicle and it is unnecessaryand probably unwiseto try. be safely carried out in patients with carpal tunnel syn- Sunderland’s initial publication on the topographyof drome and that functional recovery will be more com- the nerves of the upper extremity contains tables which plete than in those patients in whomonly division of the list the componentsof each quadrant of each nerve at transverse carpal ligament is performed. Wenow know several levels and comparesthem with the findings of that axons can be compressed by an epineural sheath other investigators. These tables can be invaluable to which is scarred or thickened, as well as by a tight the surgeon whoundertakes to bridge a large gap by a carpal tunnel, and that only incision of this epineurium nerve graft. will relieve symptomsof intraneural compression. Our Underideal circumstances, it appears that sufficient studies suggest that in such cases, whetherat the elbow numbers of regenerating axons will cross two suture or wrist, the bundlesor individual funiculi can be safely lines, enter the distal stumps, and growto their termi- separated and that little or no functional loss is likely to nations to makenerve grafting a successful procedure. occur. Althoughit is unlikely that any fibers reach their origi- Primary or secondary repair of transseeted nal destination, manymay at least find ttmir way to nerves. In cases wherea nerve is sharply transsected or similar funiculi, so that motor fibers are directed to where the zone of injury is limited, gaps of up to 5 cm motor fasciculi and sensory fibers to sensory fasciculi. may be encountered, and primary or secondary repair, The level of functional recovery in such patients, ~ including excision of neuromaand glioma, can be per- thoughnot ideal, is better than has been possible previ- formed. It is not our purposehere to discuss the role of ously and more than justifies the procedure. tension in the outcomeof such cases, and whether such We can now make some ge.neral statements about gaps should be managedby direct suture or by inter- specific segments of each forearm nerve which maybe positional graft. Weonly wish to emphasizethat it is of some value in accomplishing alignment of bundles possible to recognizd anatomically similar bundles in or quadrants. These commentsare based on both the ~.~ the proximal and distal stumps at these distances and microdissections and analysis of bundl~location in the ~ to connect them correctly by whichever means one serial sections. wishes. In the forearm and wrist, distances of a few In the mediannerve in the upper third of the forearm ~i centimeters have the anatomic potential for recovery the motor branches to the extrinsic muscles lie about ~ of motor and sensory function, other factors notwith- the periphery, primarily on the radial and ulnar sides ~ standing. Interpositional grafts. As the gap between nerve (mF, ig. 2).ruThc~ensorybranches to the hand, the thenar :~ ends increases, there occurs a point ~vhere an interposi- c~OlvO~ "h~ en~era~ ral ~core s, andand thedorsal palmar quadrant. cutaneous Thus, branch if one oc-i~ tional graft becomesnecessary. The technique of inter- v~~shesto bridge a gap at this level by grafting, the real of Vol. 5, No. 1 GERY 1980 Internal topographyof peripheral nerves 17

core of the proximal stump should connect dis- mal to the medialepicondyle. In reality it is a separate with the motor and sensory components of the nerve travehng in the same ep~neural sheath with the i.hand, and the large identifiable forearm motor branches ulnar nerve. The situation is similar to the arrangement ~ould be attached about the periphery of the proximal of the tibial and commonperoneal nerves. It offers end. someintriguing opportunities. In an acute ulnar nerve . In the middle third of the forearm, there are very few injury at the midorearmlevel proximalto the separation !: i branches and no major quadrant changes. Here corre- of the dorsal cutaneous nerve, this branch can be dis- sponding quadrants can be connected directly or with sected out and repaired separately, thereby increasing i:~.~ sections of graft as necessary. If appropriate quadrants the likelihood of accurate alignment of the remaining the likelihood of a correct match-upis good. motor and sensory components. If an injury at this In the distal third of the forearm, the thenar motor, samelevel requires a nerve graft, yet another possibil- ~mbrical, and sensory componentsare well segregated ity exists. In some instances, the dorsal cutaneous. i and each can be isolated for repair. The distal compo- nerve may be considered expendable. Should this be nen:s, of course, can be positively identified by dissec- the case, it might be possible to dissect it for some tic.:~, and attached to proximal bundles chosen on the distance and to use it as a graft. This maneuvercould basis of quadrantic location. Specific bundles can be provide as muchas 25 cm of graft and have three major : identified and expected to conformclosely for about 5 advantages:(I) a graft from the sameoperative site, (2) cm above the wrist. a reduction in the cross-sectional size of ulnar nerve :-~i: In a cooperative patient, one might use the stimula- requiring a graft, and (3), again, a corresponding in- tion technique of Hakstianis to further identify proxi- crease in the accuracy of alignment. :- real elements. Although the cross-sectional appearance Little can be said about the radial nerve, since so of the mediannerve changesin all of these zones, the little of this study pertains to it. It is not primarily a changesare relatively subtle and occur over relatively forearm nerve, but it is clear that its major sensory great, distances. Theyare usually betweenfascicles of branch and the posterior interosseous nerve can be ¯ fi,c ~ameor similar branches; these bundles lend them- separated for several centimeters above the medial selves to connection with reasonable accuracy.. epicondyle without difficulty and that the principles In some respects the ulnar nerve provided the most previously outlined for the median and ulnar nerves <-~ interesting and potentially valuable information of the also apply to the radial nerve. Again, the intriguing entire study. In the elbow region, the ulnar motor possibility exists for using the radial sensory compo- .... branches are well defined and can be separated for long nent for a donor graft in irreparable injuries above the ~distances before encountering interconnections. Such a elbow, by dissecting it out and using it to bridge the separation facilitates anterior transposition of the main motor deficit in the posterior interosseous nerve. Al- trunk, a procedure whichis still indicated at times for though there is a possibility of painful neuromaforma- :relief of compression or entrapment symptoms.In our tion in the superficial radial nerve whenit is injured__ dissections the terminal motor and sensory branches at more distally, the rarity of this problemin the upper .~ Guyon’scanal had only a few fine filamentous connec- armmakes its use as a donornerve at least a possibility. .tions and could be easily separated for a full 8 cm. For This suggestion is speculative and we have not used this reasonan injury in this area offers several treatment this nerve as a graft. Amongthem is a separation of the motor corn- Finally, a word of caution: The study of Rydevik, for somedistance proximally and rerouting it Lundborg, and Nordborgsuggests that intraneural dis- ~ through the carpal tunnel. This maneuvergains length section in animals mayinduce fibrosis witfiin the nerve permits a tension-free juncture of the motor branch and aggravate rather than relieve intraneural constric- having to resort to a graft. If one wishes to tion which has resulted from epineural scarring. ~Inci- direct suturing or to interpose a graft, the ease sion of the epineuriumand interfascicular dissection is of separation and identification of the terminal motor a procedure which should be reserved for the specific branches of the ulnar nerve suits them well situations whereit is likely that epineuriumis constrict- for these procedures. ing the fasciculi and producing symptomswhich cannot The dorsal cutaneous branch of the ulnar nerve is be relieved by external decompressionalone. Our data .unique amongmajor forearm branches. Although it suggest that this procedure, if performedcarefully, can joins the main trunk in .the distal third of the be accomplished without significant injury to the forearm, it progresses independently along-side the perineurium and without further loss of function. Simi- ~:. main nerve trunk tt-~;ough the forearm and well proxi- larly, if intraneural dissection is indicated to facilitate 18 Jabaley, Wallace, Heckler HAND SURGERy

repair, rerouting, or grafting of peripheral nerves, it can tots: Reconstructive microsurgery. Boston, 1977, Little be performed, but one must always weigh the potential Brown g Co. p 387 gain against the risk of further damage. 9. TamuraK: The funicular pattern of Japanese peripheral nerves. Arch Jap Chir 38:35-58, 1969 A project of this magnitude has manycontributors and we 10. Seddon H J: Surgical disorders of the peripheral nerves,~ gratefully acknowledge their contributions: Mr. Thomas Baltimore, 1972, Williams & Wilkins Co, p 267 White, an aspirant medical student, prepared all the mi- 11. Millesi H: Surgical managementof bmchial plexus in- ~.~.’ croscopic sections. Mr. James Goodmancreated the original juries. J HAteDSURG 2:367-79, 1977 art work, and Mr. William DeVeer produced the photo- 12. KuczynskiK: Functional microanatomyof the peripheral :~;-~. graphs. Ms. Cheryl Lyon expertly prepared the manuscript, nerve trunks. Hand 6:1-10, 1974 and Ms. Mary Lou Percy provided the scanning electron mi- 13. Jabaley ME, Bums JA, Orcutt BS, Bryant WM: Com-~ crograph. Dr. Douglas Gorman assisted with the mi- parison of histologic and functional recovery after pe- crodissections. ripheral nerve repair. J HANt~StJRG 1:119-30, 1976 14. Jabaley ME:Recovery of sensation following peripheral REFERENCES nerve repair, in Fredericks S, Brody GS. editors: Sym- 1. Langley JN. Hashimoto M: On the suture of separate posiumon the neurologic aspects of plastic surgery, vol bundles in a nerve trunk and on internal nerve plexuses. J 17. St. Louis. 1978. The CVMosby Co, pp 36-46 Physiol 51:318-45, 1917 15. Curtis RM, Eversman WW:Internal neurolysis as an 2. Lewis D: Principles of peripheral nerve surgery. JAMA adjunct to the treatment of the carpal tunnel syndrome.J 75:73-7, 1920 Bone Joint Surg [Am] 55:733, 1973 3. Sunderland S: The intraneural topography of the radial, 16. Millesi H, Meissl G, Berger A: The interfascicular nerve median, and ulnar nerves. Brain 68:243-98, 1945 grafting of the medianand ulnar nerve. J BoneJoint Surg 4. Manktelow RT. McKeeNH: Free muscle transplantation 54:727-50, 1972 to provide active finger flexion. J H,xrqoSURG 3:416-26. 17. Sunderland S. Millesi H: Nerve repair: its clinical and 1978 experimental basis. A symposiumin honor of Sir Sydney 5. Sunderland S: Factors influencing the course of regener- Sunderland. Nov3-5, 1977, University of California, ation and the quality of the recovery after nerve suture. San Francisco. Calif (to be published) Brain 75:19-54, 1952 18. Hakstian RW:Funicular orientation by direct stimula- 6. Sunderland S: Nerves and nerve injuries, ed 1. Edin- tion: an aid to peripheral nerve repair. J BoneJoint Surg burgh, London, 1968, Churchill-Livingstone, Ltd [Am] 50:1178-86, 1968 7. Sunderland S: Nerves and nerve injuries, ed. 2. Edin- 19. Ryderik B, LundborgG, Nordborg C: Intraneural tissue burgh, London, 1978, Churchill-Livingstone, Ltd, p 32 reactions induced by internal neurolysis. Scand J Plast 8. Terzis JK: Principles, practices, and techniques of pe- Reconstr Surg 10:3-8, 1976 ripheral nerve surgery, in Daniels and Terzis JK, edi2"