The Journal of Bone and Joint Surgery

Volume85-B NumberThree (April) 2003

THE JOURNAL OF BONE AND JOINT SURGERY

Editor: Frank Horan

Published in Londonby the British Editorial Society of Bone and Joint Surgery American Volumepublished at 20 Pickering Street, Needham, Massachusetts Reviewarticle

SPONTANEOUS ANTERIOR INTEROSSEOUS NERVE PALSY

Akira Nagano FromHamamatsu University School of Medicine, Hamamatsu,Japan

Palsy of the anterior interosseous nerve (AIN) was first in 61%of 31 cadaver arms and from the deep, posterior described by TinelI in 1918 under the title ’Dissociated aspect in the remainder,l° It runs between the deep and paralysis of the median nerve’. In 1948 Parsonage and superficial heads of pronator teres accompanying the Turner2 noted six examplesof this syndromein a review of mediannerve and passes beneath the arcade of flexor digi- 1.36 patients with neuralgic amyotrophy,and in 1952 Kiloh torum superficialis to lie on the anterior interosseous mem- and Nevin3 reported two cases of the palsy as an isolated brane, terminating in the capsule of the wrist. Proximally, neuritis. In 1955 Lipscomband Burleson4 described the above its branching from the mediannerve, the fasciculus condition in association with a supracondylar fracture and destined to becomethe anterior interosseous nerve runs in 5 the posterior part of the main trunk of the mediannerve. in 1965 Fearn and Goodfellow first observed that an I~ entrapment neuropathy was responsible for someexamples Accordingto Sunderland’s detailed anatomical studies of of the AIN. the mediannerve, fibres destined to becomethe anterior The indications for operative treatment for spontaneous interosseous nerve can be isolated from the main trunk of AINpalsy are controversial. Whenthe cause of the palsy is the mediannerve as far proximalas the brachial plexus, and an entrapment, the nerve should be explored early. If it is clinical experiencehas shownthat the fasciculus can be iso- due to neuralgic amyotrophyor an isolated neuritis, surgery lated proximally for more than 10 cm, with somecommuni- is not generally indicated and conservative treatment is fol- cating fibres to the maintrunk. lowed. However,it is not easyto determine the appropriate Theanterior interosseousnerve supplies flex~.__orpollici.s method of managementbecause there are no clinical find- loq~PL), flexor dig~torum profundus to the index ings or neurophysiological investigations to differentiate (FD.PI_~.)..~doccasionally to the middle finger (FDP2),and these two lesions. Recently, there have been several pronator quadratus__:Sunderland II stated that it wasrare for reports6-8 of cases in which an hourglass-like fascicular FDP’]-~o be innervated other than by the median n~ut constriction was discovered in the main trunk of the median the ’;~pply to the middle finger was variable. In 15%of nerve after interfascicular neurolysis. Theaetiology and the limbs there may be a Marin-Gruber anastomosis between strategy for treating AINpalsy should therefore be reconsid- the ulnar and medianor anterior interosseous nerves. There ered. is no superficial sensorybranch. This reviewdescribes th~ anatomy,cfifiical features, the aetiology and the treatment of an h0urglass-like constriction Clinical features of the fascicles in spontaneouspalsy. The incidence of the palsy is low and accounts for less than Anatomy 1% of all compression syndromes tn the upper lin~.|2 Between 1986 and 1990, we saw only 11 such patients out The anterior interosseous nerve is the largest branch of the of 1011 with peripheral nerve palsy, but the lesion is now mediannerve and arises 5 to 8 cmdistal to the level of the being diagnosed more commonly.I_n the t__~a subsequent lateral epicondyle,9 usually immediatelydistal-to the supe- years, 43 patients werereferred to our clinic with the disor- rior border of the superficial head of pronator teres. It was der ~vhich is four times as manyas in the previous five found to originate from the radial side of the mediannerve years. This change is probably a result of the in~d. awareness of-the condition by ~ns. Occa- sionally7 gila’i-~~l ~ ~-~e" 7e~,,1~-~ and recurrent palsy has been reported. 16 ~7 A. Nagano, MD,Professor Werner summarisedthe clinical features of 69 patients HamamatsuUniversity School of Medicine, 1-21-1 Handayama,Hamamat- reported in the literature before 1985 and included four of su 431-3192,Japan. his own. There were 38 males and 31 females with a mean ©2003British Editorial Society of Boneand Joint Surgery doi. 10.1302/0301-620X.85B3.14147$2.00 age of 37.5 years (9 to 72). Theright side wasaffected in J Bone Joint Surg [Br] 2003;85-B:313-8. and the left in 24. Schantz and Riegels-Nielsenla described

313 VOL.85-B, No. 3, APRIL2003 314 AKIRANAGANO .

I. The aetiology of anterior interosseous ner~’e palsy Traumatic Penetrating injuries Fracture Supracondylar fracture of the humerus Forearmfractures Venepuncture Cast fixation Openreduction and fixation of fractures Spontaneous Entrapment neuropathy Muscular and fibrous abnormalities Gantzer’s muscle Enlarged bicipital bursa Vascular abnormalities Volkmann’sischaemic contracture Neuralgic amyotrophy ’t Isolated neffritis Unknown

Fig. l

Photograph showingthe inability to form an ’O’ with the thumband the index finger ia palsy of the left anterior interos.seous nerve. palsy~ but it.is not a__predictivesign for differentiatin inflammatoryfrom a mechanical origin. Thetypical symptomof the_ pals.y_ is the inabilit~y to an ’O’ with the thumband index finger (Fig. i). Since 21 cases in 20 patients, of whom14 were male and six were and FDPIare paratysed, the patient is not able to fle~ female, with 15 affected on the right.and six the left side. interphalangeal joint of the thumb and the distal i Sood and Burket5 reported 16 patients, nine menand seven phalangeal joint of the index finger. Pronator quadrat~ women,for whomthe age at presentation ranged from 32 to also p~~ its weakness is not noticed by 75 years. The author of this review encountered 43 patients patient, and manualmuscle testing of this muscleis difl between 1992 and 2002. There were 24 males and 19 to judge coffectly, e~ien whencarried out with the elbo females, with the right side affected in 20 and the left in 23. acute.flexio~n. The meanage at onset was 42.7 years (14 to 73). Fromthese The FPLand FDP1are not always pai’alysed simult observations,it i~ clear that there wereno .significant differ- ously. Wemer17 reported that both were paralysed i~ ences in~g_enderor in the side affected and that mostpatients patients, the FPLonly in 25 and the FDP1Only in tel were between 30 and 60.years of age.. Sood and Burke’s report15 of 16 patients, only FPLwas Possible predisposing factors such as an influenza-like alysed in five and FDP1in two; none hadparalysis of Fr illness, venepuncture for m_0dorabdominal surgery, a~y in the author’s series, both FPLand FDP1were paralyse of trauma...____,inoculations, or other manifestationsof musculo- 19 patients, only FPLin 11 and only FDP1in nine. In skeleta_ll or sy,ste~ic diseffses were often recorded immedi- patients both FPL and FDP1were active but weak. E ately prec_~dingth~ onset of paralysis. ~4,15.19. patients had weakness Of FDP2. Sometimes the m Patients usually experienced pain in the region of the branches to pronator teres, flexor carpi radialis and/or elbowbefore the onset of the palsy..Miller-Breslow~Teff’ono marls longusare also involved.23"24In my43 patients, and Mill~nder2° followedten limbs in nine patients;, a..._ll nator teres wasparalysed in 12, flexor carpi radialis in described an acute spontaneouspainful episode lasting for a and palmaris longus in 12. meanof 1 l’~ays. Seror21 reported that pain ,,~as reeord’~ in 85%of the-’fi~TIfcases whichwere collected fromthe liter.a- Aetiology lure and in ten of his 14 13ati~nl~. In the exper~he author, 39 of 43 patients (89%) had-pain at onset; eight The reported causes are listed in Table I and are divided complai....__nedof pain fromthe shouldergirdle to the elbow, two categories, traumatic and non-traumatic/spont~ four_.in the._uupperarm, three in the upper armand fo~rea~m, OUS.25,26 20 in the elbow,_.andfour in the forearm. Rask22 stated that Palsy of the anterior interosseous nerve has b pain maybe the earliest symptomof this entrapment neu- described2’27 in association with neuralgic amyotrophy, rop~thy. However, Wongand D.ellon~9 reported that the lated neuritis, 2 and entrapment neuropathy.4 The nervt impor.tant point in the history for distinguishing a bra_chial susceptible to entraprrient by soft tissue and by vascular neuritis from local compression is pain in the upper arm, bony structures. Accordingto Spinner,28 it is vulnerabk elbow,.and/or foi:~firm often preceding~~hemotor symptoms. injury or compressionby the following: Pain is a comm-~-moneature of anterior interosseous n~rve (i) a tendi~nousorigin of the deephead of p.ro___natof.tere

THE JOURNALOF BONEAND IO[NT SURG[ SPONTANEOUS ANTERIOR INTEROSSEOUS NERVE PALSY 315

(ii) a tendinousorigi~ of flex’or digitorumsubljmis to the most commoncause is a so-called neuritis or neuralgic middlefinger; amyotrophy. (iii) thrombosis of the ulnar collateral vessels which cross it; . Treatment (iv) accessory muscles and tendons from flexor~digito- rumsubli____mis; The recognition of an anatomical cause for the problem (v) an ac~cessoryhead of FPL(Gantzer’s muscle);28 has initiated a debate about the managementof this palsy. (vi) an aberrant radial artery; Theoretically, conservative treatment is recommendedfor (vii) a tendinous.originof palmaris longusor flexor carpi neura|g~ca...____.___~v_9~ophy and isolated neuritis, whereas radialis brevis; and decompressionis advised.for the AINsyndrome. H,~owe~ver, (viii) an enlargedbicipital.bursa. . there are’no c~ical signs and symptomsto differentiate ~ Collins and~eber29 considered entrapment to be by far these~ t~ions. In the specialty literature for orthopaedics, the30 mos~t C0mmoncause and Hill, Ho,~ard and Huffer neurosurg~nd sur.gery and plastic surgery,. 46 of 100.-~ observed it in 24 of ~s of incomplete palsy. Schantz reported cases (46%)were explored surgically, but of those and Riegels-Nielson ~8 found evidence of nerve compression repor~’edin the neurologyjournals, only four of 32 patients in nine of 15 patients. Werner17 reported that fibrous bands (12.5%)underwent surgical exploranon, although the results .within pronator teres were seen in 52 patients, but that an of bo--~ ~ o~eatment were almost the same. ~ ~ indentation in the nerve or neuromatawere found in 14. In Spinne-~r reported that patients whohave spontaneous thet5 eight cases which were studied by Sood and Burke, paralysis of th~-NlNshould initially be treated conserva- there was no demonstrableabnormality in four and a further tively, because manyhave a satisfactory return of function two patients were deemedto have anatomical structures and no recurrence, but if there are no signs_of cli~ or with a potential for causing compressionbut with no evi- electromyographic improvement in six to ei ht~ks, dence of any abnormality of the nerve itself. Between1969 exploration is indicate..__~d...... Nigst and Dick~ recommended and 1985,. the author encountered31 cases of n-on-traumatic operativ~__eetreatment in patients in whomthere was no per- palsy and-performedan exploratory operation in ten.23 The ceptible improvementafter, conservative treatment for eight operative~-’ffffdings showedthat the palsy was due to com- weeks, s~nce surgical decompression reduces the time pression of the nerve by a fibrous bandin one patient, w~_hile neededfor recovery. Hill et al3° recommendedthat e_xplora- in the other nine the nerve was slightly swollen, scarred, tion and external neurolysis be undertakenwhen t__k~re is no hardened, or even normal. Duringthe last ten years, I have clinical and/or ~graphical improvement by 12 explo~ed the nerve in a further 23 patients. Four median weeksa~fter or~.set. nerves showedslight swelling, hardening, or adhesion to the However,several authors advise conservative treatment. surrounding tissue at the elbow, ~0ther 19 were Seror21 concludedthat surgery should not be considered for normal in appearance with no entrapment. F~ear~i and a ~,e--ar because late spontaneousrecovery is sometimesseen Goodfell0w~described a case of entrapment neuropathy after th~"i~ time. Futami et ~at conservative treat- resulting from a crescentic fibrous band. The illustration in ment is advisable in most cases because useful recovery can their paper showed a band which compressed both the be expectedwithin ten monthson average. Sur_r.gical in_ter- median and anterior interossdous nerves. Generally, the vent]0n maybe required only in rare cases which do not latter runs in a posteroradial direction and is located deeper respondto conservativetreatment after moret_.__han tw~ years. than the mediannerve. However,(he patients of Fearn and MillerVB"reslowet al~° treated ten patients and believed the Goodfellow5 had only anterior interosseous nerve palsy condition to be a neuritis. They concluded that surgical without motor and sensory disturbance of the mediannerve, decompression maynot hasten recovery. Tsukahara et a133 which raises the question as to whyit alone was involved. treated 12 hands from 11 patients conservatively. All para- Vichare3~ also found it difficult to explain whya band lysed muscles recovered to more than MRCgrade 3, but it should involve the.anterior interosseous nerve alone, leaving took a long time for adequate recovery when signs of /.._,the adjacent and larger mediannerve unaffected. Fearn and improvement were not detected within six months after Goodfellow5 suggested that it is necessary~o.be wary of onset. Sood and Burke15 explored eight patients and asc~ralysis in the distri~ ~ ~ ~~rve obtaine.__d goo~en and a poor outcome in one. to a hypothetical ’neuritis’ and that the search for a mechan- The..y also treated 11 patients conservatively, with dgoo ical~_caUse maybe rewarding. The converse is also true, results in eight, a_ fair result in one andpoor results in two. A since the cause should not necessarily be attributed to comparison of the results of operative and non:operative ~//entrapmenteven if there is a fibrous band on the nerve since treatment revealed a similar outcomeand thee there_fore an hourglass-like constriction is very often seen in the fasci- concludedthat it is likely that the condition i’esults froma ~/cles de~tined to the anterior ~nterosseous nerve xn the mulfifocal neurit_.ks, which often resolves spontaneously. ~ median" ~ a~-~v~-h~ ~ T~]~ ~ b--~isc--~d ~at~r. Nakanoet a113 described two patients Whopresented with a Overall, we conclude that entrapment neuropathy is one bilateral palsy with separate times of onset for each side. of the causes of this palsy, but its incidenceis low and’ the The first side was treated surgically, and the second con-

VOL. 85-B, No. 3, APRIL 2003 316 AKIRA NAGANO

Fig. 2a Fig. 2b

The centre of the photograph is the elbow flexion crease, and the left side is the arm. The left median nerve was slightly adhered to the surrounding tis- . Two hourglass-like fascicular constrict ons were revealed in one fascic sues, but there was no compression on the nerve. 0 and 20 mmabove the elbow flexion crease after interfascicular rteurob

neurolysis in 23 patients whodid not showany rec.overy ¯ three~ after onset and who agreed to surgical expk tion. There were 12 men and 11 women,with a meanag~ operation of 43.2 years (23 to 64). The mean inter between onsdt and the operation was 5.5 ~3 to 1 No patient showedany clear physical cause such as man work or sports activity. The medianand anterior inter seous nerves were explored from the proximal one-third the forearm to 5 to 10 cmabove the elbow using an ope~ ing microscope. No external compression was found a~ where along the course of,the nerves. By interfascicu neurolysis, an hourglass-like fascicular constriction (Fig and 3) was discoveredin the fascicles of the anterior inl osseous nerve within the mediannerve between2 to 7.5 Fig. 3 above the elbow in 22 patients. The lesion was loca

Photograph showing two hourglass-like fascicular constrictions above the above the elbow, a site whichhad not usually been explo~ elbow in each of two fascicles destined to become the anterior interosseous in"previous cases. This constriction had been reported only five patients in the literature. 7’8’3436However, we found this lesion in almost all cases of palsy whichdid servatively. Noentrapment was found in either patient. All have evidence of external compression. All except four recovered. Opera$~ondid not hasten the return of func- .patient had pain in the elbow, and paralysis was evid, tion, and therefore they concludedthat surgery should not between one and 42 days after the onset of pain. In st necesT"arily be done unless there is compellingevidence of cases, the cause had previously been attributed to isola: an entrapment or a s~ficant iniuryfiuch as a penetrating neuritis whenthere were no findings of entrapment neu wound. pathy at exploration, but our findings suggest that the ba After our experience in managingthe 31 cases of non- abnormalityis this hourglass-like fascicular constriction. traumatic AINpalsy noted above, we felt 23 that the inci- In 21 of 22 patients the lesion was treated onl,Lby int dence of entrapment neuropathy was very low, and therefore fascicular ~ all regained good function. recommen~a policy of ’wait and see’. However.___._e_in1992, ever, we do not know whether this recovery weencounte-’-ffggggffre a patient with tenderness at the distal part_of spontaneous or due to the neuroly~is. We compared the arm~. xploraaon of~he median nerve sh¢zwed it to be results of 15 patients whohad had interfascicular neuroly partial~at the lower part of the arm. Interfascicular and those of i I with Conservative treatment whowere f neurolysis oT-fh--is are~ revealed an hourglass-~--’d-0-~tric- lowed for more than two years. 37 There were no signific~ tion in the~ciculus destined to becomethe anterior inter- differences in age; gender, the affected side, or the peri osseous nerve. Wesuspected that the same lesion mayhave from onset between the two groups. existed in the nine patients whohad no evidence of external had an inteffascicular neurolysis obtained more than M~ compression. Since then, we have performed interfascicular grade 3 powerin flexor pollicis lon_gusand/or flexor digi

THE JOURNAL OF BONE AND JOINT SURGE SPONTANEOUSANTERIOR INTEROSSEOUS NERVE PALSY 317

rumprofundus, but recovery did not o~cur in two patients on those which constitute the main trunk of the median ireated conservatively. The musclepower after interfascicu- nerve, since the traction force is thought to be stronger on lar neurolysis was significantly-better than after c~rva- the shorter segment, causing the fascicles to becomecon- tire treatment at morethan 24 monthsfrom onset, but there stricted. Tazaki et a145 performedan experimentalstudy on were no di-fiVrences in the time fromonset to recovery in the the mediannerve of the rabbit. After the injection of saline two gr..__~p.Egs. It seemsthat nerve regeneration caff be into the fasciculus, the nervewas swollen, lost its flexibility expected without interfascicular neurolysis, but after this and kinked sharply upon passive elbow flexion. Repeated operation morefibres will regenerate. It is therefore recom- saline injection and movementof the elbow caused local mendedthat exploration of the nerve be offered to patients torsion at the kinking point in the fasciculus. They con- whodo not show any s~gns of recovery by three months cluded that the cause of fascicular constrictive neuropathy after onset. External neurolysis alone is not adequate and maybe oedemaand consequentloss of flexibility of the fas- interfascicular ne_~u~plysisshould be performedto detect any ciculus with movementof the elbow. Further study is neces- lesion. However,this is a small retrospective study anffa sary to clarify the pathogenesisof this constriction. prospe~t’~, randomisedinvestigation is required to estab- For treatment Haussmann34 and Nakamura et a135 lish a soundconclusion. resected the constrictibn and performednerve grafting. We Regardless of the cause and managementof the !~alsy, if tiave also carried out nerve grafting in one patient because motor function does not recover, tendon transfers will the constriction was so severe that the fasciculus appeared restore function satisfactorily. The brachioradialis is a good to be completelyruptured. However,recovery after interfas- substitute ort"bT~toring flexion-0f tlae interpha~l joint of cicular neurolysis has generally been good. Therefore, we the th~he transter of the tendon of flexor digitorum recommendonly interfascicular neurolysis, and believe that profundusof the ring or middle finger to that of the index nerve grafting is unnecessary. finger at the wrist can provide satisfactory flexion of the distal phalanx of the index finger. Schantz and Riegels- References Nielson18 recommenddelay in the use of tendon transfer 1. Tinel J. Nerve wounds. NewYork: William Wood,1918:183-5. until one year gfter the onset of palsy. 2.’Parsonage M,I, Turner JWA.Neuralgic amyotrophy: the shouldergirdle syndrome.Lancet 1948; 1:973-8. Hourglass-like’fascicular constriction 3. Kiloh LG,Nevin S. Isolated neuritis of the anterior interosseous nerve. Br MedJ 1952; 1:850-1. 4. Lipscomb PR, Burleson RJ. Vascular and neural complications in This condition was first reported in palsy of the posterior. supracondylar fractures in children. J BoneJoh~t Surg [Am] 1955;37- interosseous nerve.38-41It wasfirst describedin the anterior A:487-92. interosseous nerve by Englert6 in 1976 and again by Hauss- 5. Fearn CBDA,Goodfellow JW. Anterior interosseous nerve palsy. J BoneJoint Sttrg [Br] [ 965;47-B:9I-3. mannand Kendel7 in 1981, Nakamuraet a135 in 1991 and 6. Englert HM. Partial fascicular median-nerve atrophy of unknown Naganoet al8.in 1996. region. Handchirurgie1976;8:61-2. The7’34 aetiology’42 remains unknown.Haussmann et al 7. HaussmannP, Kendel K. O[igofascicular median nerve compression and Nakamuraet a135 have suggested that it maybe the syndrome. Handchirurgie1981; 13:268-71. 8. Nagano A, Shibata K, Tokimura H, YamamotoS, Tajiri Y. Spontane- result of mechanical torsion by rolling of the fascicles ous anterior interosseous nerve palsy with hourglass-like fascicular con- during flexion-extension of the elbowor pronation-supina- striction within the main trunk of the mediannerve. J HandSurg [Am] tion of the forearm.Hosi et a136felt that the constriction did 1996;21-A:266-70. 9. Spinner M. The anterior interosseous nerve syndrome: with special not have a mechanicalorigin, because in their patient one attention to its variations. J BoneJoint Surg [Am]1970;52-A:84-94. lesion was found in each of two fascicles, whichcould not 10. Dellon AL, MackinnonSE. Musculoaponeurotic variations along the be explained by pronation-supination of the forearm. They course of the median nerve in the proximal forearm. J HandSurg [Br] t987;12:359-63. suggested that the lesion maybe due to an inflammatory 11.Sunderland S. The intraneural topography of the radial, median, and response after infection or an autoimmuneresponse. In our ulnar nerves. Brain 1945;68:243-99. series, the constriction was seen in the fascicles of the main 12.Nigst H, Dick W. Syndromesof compressionof the mediannerve in the proximal forearm (pronamr teres syndrome;anterior interosseous nerve trunk of the median nerve and two or more constrictions syndrome). Arch Orthop TraumaSurg 1979;93:307-12. 8 coexisted. Wealso encountereda patient ,,,)-tiff had a con- 13. Nakano KK, Lundergan C, Okihiro MM.Anterior interosseous nerve striction in the anterior interosseous nerve and in other syndromes:diagnostic methodsand alternative treatments. Arch Neurol 1977;34:477-80. motor branches of the median nerve.43 Another had palsies 14.DunneJW, Prentice DA, Stewart-WynneEG. Bilateral anterior inter- of both the anterior and posterior interosseous nerves simul- osseous nerve syndromes associated with cytomegalovirus.infection. taneously44 and both nerves showedthis constriction. Muscle Nerve 1987;10:446-8. 15.Sood MK,Burke FD. Anterior interosseous nerve pal~y: a review of 16 Weconsider that the lesion has a different mechanical cases. J HandSurg [Br] 1997;22-B:64-8. basis and suggest that the initial cause is an inflammationof 16. Brusse CA, Burke FD. Recurrent anterior interosseous nerve palsies the nerve, producing oedemaand consequent adhesions, in related to pregnancy. J HandSurg [Bi’] 1998;23:102-3. the fasciculus. The subsequent traction force producedby 17.Werner CO. The anterior interosseous nerve syndrome, hzt Orthop 1989;13:193-7. flexion and extension of the elbow pulls more strongly on 18.Schantz K, Riegels-Nielsen P. The anterior interosseous nerve syn- the fasciculus formingthe anterior interosseous nerve than drome. J HandSurg [Br] 1992; 17:510-2.

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