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Home , Antebrachial fascia, Pronator teres muscle, Pronator teres syndrome

;ry " he tO Copyright1981 by The Journalof Boneand Joint Surgery, Incorporated hy ar- The : ior tal Compressive Neuropathy of the Median * .~nt dl, BY CHARLES R. HARTZ, M.D.’~, RONALD L. LINSCHEID, M.D.’~, R. REED GRAMSE, M.D.’~, AND JASPER R. DAUBE, M.D.J’, ROCHESTER, MINNESOTA ior in From the Departments of Orthopedics, Physical Medicine and Rehabilitation, and , MayoClinic and MayoFoundation, Rochester at- ~re ABSTRACT:Thirty-nine patients with a clinical gically g, an anomalous fibrous band that compressed the the diagnosis of the pronator teres syndrome were seen was identified and cut. Since then, the syn- during a seven-year period. They typically complained drome has been recognized with increasing frequen- FIS, of aching discomfort in the , weakness in the cy2,’,’,9,1e, ¯ it , and numbness in the thumb and index finger. We are reporting a study of thirty-nine patients in as Cyclic stress usually brought on the symptoms. The whomwe diagnosed the pronator teres syndrome and at- the distinctive physical finding was tenderness overthe tempted to identify the factors by which one can differ- ’ tO proximal part of the pronator teres, which was aggra- entiate this disorder from other lesions. SO vated by resisted pronation of the forearm, flexion of To the , and occasionally by resisted contraction of Clinical Material ~al- the flexor superficialis of the long finger..Elec- From 1972 to 1979, thirty-nine patients seen at the der trophysiological testing of the median nerve showed Mayo Clinic were diagnosed as having the pronator teres caft abnormalities in a few patients, but localization of the syndrome. Preoperatively and postoperatively, all of the der abnormality was possible only rarely. Intraoperative patients were examined by one or two of us (C. R. H. and recordings showed some improvement shortly after R. L. L.). Twenty-nine patients were female and ten were release of the median nerve in six of the ten male; their ages ranged from fourteen to seventy-eight that were tested. Surgical exploration of thirty-six years. The criteria for diagnosis were symptoms and signs forearms in thirty-two patients showed intramuscular of a median neuropathy localized to the forearm and hand: tendinous bands in the pronator, indentation of the aching discomfort and easy fatigability of the muscles muscle belly of the pronator teres by the lacertus fi- of tile forearm brought on by cyclic stress, and indentation brosus, or a taut tendinous origin of the flexor super- and tenderness of the . With repeti- ficialis in most forearms. Vascular and muscular tive pronation the patients also had numbness in the dis- abnormalities were seen occasionally. Of the thirty-six tribution of the median nerve in the hand; the nu__mbness operations, twenty-eight gave good or excellent results; seldom was well localized, although it tended to involve five, fair; "and in three patients the symptoms were un- the index finger and thumb and first was noticed after the changed. The cause of failure was either inadequate discomfort became evident. Nocturnal awakening because decompression or misdiagnosis. ~3f pain as well as numbness in the hand in the morning, commonly associated with the syndrome, Compressive neuropathy of the median nerve in the typically was absent. The duration of symptoms averaged and forearm Can be a difficult diagnostic and thera- twenty-three months (range, one to 120 months). The peutic challengeZ’V’a’12~ It must be distinguished from cer- symptoms usually began insidiously, but occasionally vical radiculitis, the , brachial after a specific muscle sprain or episode of activity their plexus neuritis, overuse of the muscles of the forearm, and onset was rapid and dramatic. The symptoms frequently . In 1951, Seyffarth described a began during activities that required repetitive grasping or group of seventeen patients with symptoms that he con- pronation, or both (for example, prolonged hammering, sidered to be caused by compression of the median nerve scraping dishes, ladling food, or practicing tennis serves). in its course through the pronator teres muscle. In the first One of our patients had a rather sudden onset of symptoms patients with pronator teres syndrome to be treated sur- of the pronator teres syndrome in a forearm affected by spastic hemiparesis. Previously he had had a trans- * Read at the Annual Meeting of The American Orthopaedic As- fer from the flexor digkorum superficia~is to the pr~3fundus sociation, San Juan, Puerto Rico, June !8, 1979, and a ieng~hening of the flexor carpi radia!is. It ’,~..’as be- ~" Mayo Clinic. 2!30 First Street S.W., Rochester. Mklnesota 55~05. P!~ase addv~Ss r~r.ri~:t requests ’:o Dr. Hartz, c/o Secti:~ ~f Pub- !ieved ~hat the dorsiflexion of th,~ wris~ ai]o,ve~ by the

VOL. 63-A, NO. 6, JULY1981 885 886 C.R. HARTZ, R. L. LINSCHEID, R. R. GRAMSE, AND J. R. DAUBE der the taut origin of the flexor digitorumsuperficialis. We nerve at the level of the pronator terns, and electromyo- had no patients with po~t-traumatic syndromes in our graphic abnormalities limited to muscles innervated by the series. The lack of specificity of the symptomsand the median nerve, were considered definitive electrophysi- subtlety of the physical findings in-several patients led to ological findings for the pronator terns syndrome. In- suspicion of either functional neurosis or conversion hys- traoperative recordings from the median nerve were made teria. Sevenpatients had had misdiagnoses that had led to in ten forearmsin eight patients in an attempt to identify a carpal tunnel release, and one of them had had an ulnar more localized abnormality than could be detected witti transposition operation without relief of symptoms. The routine recordings, and to record any electrophysiological previous operations were done between three and twenty- changes in the nerve after decompression. Direct in- eight monthsbefore our initial examination. traoperative measurementsof mixed nerve-action poten- The physical findings in the seven patients whowere tials were madefrom the exposed nerve both proximal and not operated on and in the thirty-two whowere operated on distal to the pronator terns before and after surgical release differed only in degree. The outstanding positive finding of compression on the median nerve. Nerve-action poten- was tenderness in the proximal part of the pronator teres tials were stimulated and recorded using hand-held muscle, which was noted in thirty-seven patients. In the silver-hook pairs of electrodes with the nerve elevated other two patients, this symptommay have been present away from surrounding tissue. Stimulation was applied but it was not noted. Wefound tenderness in the median distally in the forearm while recording was done proximal nerve in the antecubital space in thirty-one patients, while to the pronator teres muscle. Recordings were made be- tenderness was noted distally less frequently. Thirty pa- fore, immediatelyafter, and fifteen to twentyminutes after tients experienced paresthesias in the distribution of the surgical decompressionof the nerve. Distances along the median nerve and the hand when the forearm was pronated nerve betweenthe stimulating and the recording electrodes forcibly against resistance. A positive Tinel sign at the were measuredwith a millimeter ruler to allow calculation proximal edge of the pronator teres was elicited in twenty of velocities fromthe latencies of the initial-positive peak. patients. Fourteen patients suffered exacerbation of the Amplitudes were measured from peak to peak. paresthesias whenthe flexors of the long finger were con- tracted against resistance. In seventeen patients, the pro- Treatment nator muscle was observed to be unusually firm compared Seven patients considered that their symptomswere with the contralateral muscle. A depression in the contour not severe enough to justify an operation. Anexplanation of the forearm superficial to the lacertus fibrosus was obvi- of the probable cause for the symptomsand steps that ous in three patients. Mild thenar atrophy was present in could be taken to minimize them, including job only three patients, and the Tinel test was rarely positive at modifications, were given. Surgical exploration was per- the , although nineteen patients had a positive Phalen formedin thirty-two patients (thirty-six forearms). In all sign at the wrist. Hypohidrosis in the distribution of the thirty-two patients, cutaneous sensory of the arm median nerve, which is commonin the carpal tunnel syn- and forearm were identified and protected. Weinspected drome, was not found in any of our patients. the lacertus fibrosus, assessed its thickness, and deter- mined whether it indented the antebrachial -over the Electrical Studies pronator, especially during passive pronation and exten- El.ectromyography was done on forty forearms in sion. Then the course of the median nerve was noted, and thirty-eight patients. One patient had had an electromyo- it wasfreed along the radial border. The relationship of the graphic study at another institution six months before an nerve to the pronator teres was assessed. Intramuscular unsuccessful carpal-tunnel release, and the test was not re- tendinous bands within or under the pronator and fascial peated. All patients had bilateral measurements in the constricting bands betweenthe superficial and deep heads ulnar and median motor and sensory nerves. We measured of the muscle were released from the accompanyingradial the compound muscle and nerve-action potentials , as were vascular leashes or penetrating vessels. (amplitude and latency) from the thenar muscles and index The anterior interosseus nerve was identified and protected, finger during stimulation of the mediannerve at the wrist as was the arch of the flexor digitorum superficialis. If and proximal to the pronator teres muscle. Nine of the there was a tight falciform edge, it was split carefully to thirty-eight patients studied electromyographically had expose the mediannerve as it penetrated deep to the mus- measurementsof segmental conduction velocity across the cle; all motor branches to the musclewere protected.. Pronator muscle by needle-electrode stimulation; in an Postoperative care consisted of immobilization of the additional sixteen studies, the sensory-nerve conduction arm in a paddedplaster splint for two or three weeks, fol- velocity was measuredin the mediannerve of the forearm, lowed by mobilization of the elbow and strengthening of including the segmentthrough the pronator teres. Electro- the muscles with activities added as tolerated. Weadvo- myogramswere made of sew~rai muscles that arc cated avoidance of strenuous work for six weeks. Occa- vated by the mediannerve. A slowing of co~du,.::i,.~c ve- si,onally a patient needed supervised physical thc=:~py be- locity of moreth~ ten meters per secondor ~. ::,! .:.:.: c:~c~seof dif~ct:ityia m,.)bi{izing,,.-,~ >:rcng~b,eni :!: ~;e el- conduction in the motor or sensory fibers in t_~>: bow. THE PRONATOR TERES SYNDROME 887 lyo- Results excellent results werea taut lacertus fibrosus, an intramus- ’ the cular tendinous abnormality about the median nerve, and ~ysi- Evaluation of positive intraoperative findings de- tightness at the arch of the flexor digitorum superficialis. [n- pended On the surgeon’s experience and judgment, and The patients with fair or unchangedratings usually had :tade probably improvedduring the course. Of the study. In sev- fya eral patients more than one abnormality was found¯ Six- less conspicuouslesions, although in all three patients who teen patients (sixteen forearms) had a hypertrophied pro- had unchangedratings at least one anatomical abnormality ¢¢ith nator muscle or a tendinous band in the pronator capable of was identified. Twoof these three patients, however, later ~ical required care for emotional disorders, and in the third an in- constricting the median nerve: fifteen had a thickened undiagnosed neural disease appeared to have developed. ten- lacertus fibrosus that appearedto indent the flexor muscle mass; and twelve patients had a taut fibrous arch of the and Electrodiagnosis .~ase flexor digitorum superficialis. In six patients, the median Amongthe results from forty standard electrical ten- nerve passed posterior to the ulnar head of the pronator. One patient with bilateral symptomshad a large pronator studies, the meanvalues for amplitudes and velocities of add muscle with an extended proximal origin in each forearm, the median motor and sensory nerves in the entire group ated were abnormal (velocities of 58.0 _ 1.1 and 62.1 _+ 1.0 lied as well as tight ligamentous bands extending from the medial intermuscular septum to the pronator fascia. These meters per second, respectively), but only twelve (30 per mal bands simulated the ligament of Struthers and they com- cent) of the forearms showed values outside the normal be- pressed the nerve at the point of entrance to the pronator. range. Of these, only six had evidence of a proximal le- ~fter One patient had a large vascular structure penetrating sion in the median nerve on standard studies. The changes the were elicited primarily by needle-electrode examination. ~des through the nerve and another had a bursa on the insertion Two(22 per cent) of the nine patients whohad mea- tion of the that measured two centimeters in diameter and compressed the nerve. In two patients, no abnor- surements of segmental motor-nerve conduction velocity ink. malities were recognized. showed local slowing or a block at the pronator teres. The seven patients who were not operated on were None had dispersion of evoked responses. Evidence of followed for five to seventy-two months (average. segmental compression of the sensory part of the median twenty-eight months): two improved, four were un- nerve during its course through the pronator teres was lere changed, and one was worse. The improvementin the two sought in twenty-five patients and was elicited in four (16 tion patients was attributed to job modifications that allowed per centl. Four other patients showed other, non- that occasional rest periods and less repetitive use of the . diagnostic abnormalities. job but neither patient was always free of symptoms¯The four A total of nine patients had electromyographic ab- ~er- patients whose condition was unchangedhad adapted their normalities suggestive of damage to the median nerve all jobs or activities to minimizetheir symptoms.At the time proximal to the wrist: five had abnormalities on the trm of writing, the one patient (a dentist) whowas worse was needle-electrode examination of muscles, four had delays :ted " considering undergoing an operation. in sensory conduction (all mild), and two had abnormali- ter- Postoperative follow-up in the thirty-two patients ties on motor conduction studies (Table I). the ranged from three to eighty-eight months and averaged :en- eighteen months. Wedefined an excellent result as no re- TABLE I and sidual pain, paresthesias, or weakness and no hypohi- the drosis, muscle atrophy, or diminished sensibility. A good Electromyographic Patients Not Result(No.) ~lar Findings Operated On Good Fair Poor Total result meant that most symptomswere relieved and the (No.) cial patient could pursue all previously limited activities in ads spite of the fact that a mild weakness, minimumpain, and Totalof forearms* 7 24 6 3 40 :lial Normal 7 12 4 2 25 some paresthesias of a non-disabling degree often were Pronatorteres syndrome 0 1 I 0 2 els. present. A fair result meant that the patient was able to Proximalmedian-nerve :ed, workat least part-time but had residual episodes of dis- damage 0 8 1 0 9 Carpaltunnel syndrome 0 5 I ¯ If ability. 1 7 i to The results were excellent in eight forearms, good in * Somepatients had two types of abnormality. US- twenty, and fair in five~ The condition of three patients was unchanged. One patient whose condition improved Only two patients had definite electrophysiological from fair to good had anomalousmuscles and a small me- evidence of pronator teres syndrome. Seven patients had dian nerve. Postoperatively, she had someweakness of the electromyographic evidence diagnostic of carpal tunnel finger flexors and paresthesias in the hand¯ These gradu- syndrome(Table I). and one of these also had evidence ally resolved during an eight-month period, but some changes in a more proximal part of the nerve. One patient weaknessduring pronation persisted. Another patient had had unusual findings: dense fibrillation potentiai~ in the a good result in the right arm but only a fair result in the pronator teres muscle. left arm. Ten patiems had i>:ra~perafive e!ectrophy:-:i,v!ogical The most commonlesions in the patients with good or studies. On standard electromyographic studies in these

VOL. 63-A, NO. 6. JUI.y 198t 888 C.R. HARTZ, R. L. LINSCHEID, R. R. GRAMSE, AND J. R. DAUBE

patients, five of the recordings were normal, one showed radiculitis, unrelated to the pronator teres syndrome. teres slow sensory conduction velocity, three showed proximal a supi Discussion changes on needle-electrode examination, and four had Ten& evidence of the carpal tunnel syndrome. None showed The pronator teres syndrome can be produced by one hemir clear-cut electrophysiological evidence of neuroi~athy of or more abnormalities that frequently are subtle and re- under the median nerve at the pronator muscle. Conduction ve- quire judgmentsthat are not quantified easily. Constriction our p: locities recorded intraoperatively were within the expected of the nerve is different from that seen in the carpal tunnel I normalrange in nine of the ten patients (fifty-six to sixty- syndrome. Of the thirty-six median nerves that we varia~ eight meters per second), while one patient had slow con- explored, sixteen were constricted by fascia1 or tendinous the r( duction (forty-eight meters per second). Three of the ten structures in the pronator teres. The lacertus fibrosus ap- passe patients showed an improvementof five meters per second peared to be a cause of constriction in fifteen forearms, and per c~ or more after decompression, and seven had conduction the superficialis arch was taut in another thirteen. The in- per c: velocities that were unchanged. cidence of the apparent causes of this syndromein our se- cent, Measurementsof amplitudes of nerve-action poten- ries parallels the experience of Johnsonet al. tials ranged widely, but three increased 50 per cent or Seyffarth described seventeen patients who had medi~ more after decompression, and none decreased by more weaknessof opposition and hyperesthesia of the ulnar bor- Six c than 20 per cent. All ten patients had good to excellent re- der of the thumband radial border of the index finger. This not t: sults after the operation. combination of symptomswas distinctly unusual in our serti: experience. Injections of procaine hydrochloride into the Subsequent Operations pronator teres muscle produced partial or complete relief and Six patients had additional operations after the initial in a numberof his patients at the time of follow-up, seyf- expk so-called index operation for the pronator teres syndrome. farth believed that the "pressure of work" from writing or thou The first patient was essentially symptom-freefor three from the tight gripping and turning of tools resulted in a WaS years, and then the symptomsrecurred. Re-exploration re- hard, painful pronator muscle and caused the syndrome." nerv, vealed that the arch of the flexor digitorum superficialis Hypertrophy of the muscles of the volar part of the the r was markedlytight, a finding that was not observed at the forearm related to workappears to be a factor in the etiol- For first operation forty-four months earlier. Her condition ogy of the pronator teres syndrome. The pronator muscle caus was improved on follow-up examination, six months after maybe overdeveloped during repetitive activity, so that the second operation. The second patient had no sig- the6. lesion represents a dynamic compartment syndrome fore~ nificant relief from the original operation. Re-exploration The muscular induration seen on the symptomatic forearm caus eight monthslater disclosed that the tendon from the ulnar and the indentation of the flexor pronator mass by the head of the pronator ~eres lying beneath the nerve acted as lacertus in someof our patients suggest that there is mus- easy a sharp-edged, compressive structure when the forearm cular hypertrophy within a fascial compartment. A recent tient was pronated. This tendon was released, and the symp- exampleof this in our patients was a school-bus driver who bet~ toms were alleviated. The third patient had two operations had sprained his thumb. The cast that was applied necessi- exaF for carpal tunnel release after the index procedure on the tated his gripping the steering wheelwith only the fingers. pronator teres:. The first release was performedon the left This led to a rather acute pronator teres syndromein a few leas, side six monthsafter the index operation, and the second days, which subsided with rest. Recent work has lent was done on the right side sixteen monthsafter the pronator suggested that the pressures in the proximal muscle com- release. Symptomsof the pronator teres syndrome had partment should be measured to assess the role of in- a pk been relieved by the index operation. The patient and the creased pressures in the etiology of the pronator teres syn- examiner both considered that the symptomsof the carpal drome6. It is possible that fasciotomyin the proximalpart velo tunnel syndrome differed from the earlier symptoms.The of the forearm maybe a significant factor in the favorable have fourth patient underwentexploration of the carpal tunnel response to treatment. sync seventeen monthsafter the release of the pronator teres. Spinner noted acute syndromes in patients who were corn The mediannerve was normalat the wrist, but a functional undergoing renal dialysis and anticoagulant therapy, and anastomosis was found between the flexor pollicis longus others have described patients with the syndromedue to accc and the flexor digitorum profundus tendon of the index trauma4"~, but neither of these causes for the syndrome flew, finger (Linburg’s syndrome). This anastomosis was re- was evident in our patients. Spinner thought that resisted ficia leased and there was subsequent resolution of the symp- flexion and supination of the elbowseemed to significantly toms. In the fifth patient, a symptomaticbilateral ulnar exacerbate symptomscaused by a tight lacertus fibrosus. neuropathy developed six years after she had an excellent Wenoted intraoperatively that the lacertus appears to result from the operation on the pronator teres. She had an- compress the pronator teres during passive pronation, ap- terior transposition of both ulnar nerves ninety-one monihs parently because the tendon of the biceps movesdistally, SCT after the pronator release. Five years after the index oper- drawingthe origin of the iacertus with it. ation the sixth patient, underwentfusion of the sixth and Of ten patients in the series of Bell and Goldner, in seventh cervical vertebrae for symptoms of cervical fo,ar who had cerebral p~sy symptoms of &e pronator

THE JOURNAL OF BONE AND JOINT SURGERY THE PRONATOR TERES SYNDROME 889 teres syndrome developed when the arm was placed in preoperatively, as do a moderate number of patients who a supination cast for pronation contracture of the forearm. are asymptomaticpostoperatively. Tendon-lengthening in another patient with spastic Twoelectromyographic studies of the pronator teres hemiparesis apparently pulled the median nerve, tautly syndromehave been reported. Buchthal et al. found only under the superficialis, a situation similar to that in one of minimumabnormalities in eleven patients. Three patients our patients. had abnormal nerve-conduction studies, while all eleven In 1939, Beaton and Ansondelineated the anatomical had abnormal needle electromyograms. Morris and Peters variations of the pronator teres, with special attention to noted abnormal motor conduction in six of eight involved the route of the median nerve. They found that the nerve in patients whohad significant motor and sensory passed between both heads of the pronator muscle in 82.5 deficits on neurological examination. per cent of 240 arms, below a solitary humeral head in 8.8 The results of electrophysiological testing in our pa- per cent, and below both heads in 6.3 per cent. In 2.5 per tients were similar to those reported by Buchthalet al. The cent of the arms the nerve pierced the humeral head. motor and sensory conduction velocities and amplitudes Spinner discussed the case of one patient in whomthe for the median nerve were significantly although mildly mediannerve ran posterior to both heads of the pronator. reduced, particularly in patients with more severe symp- ~Six of our patients appeared to have this finding. Wedid toms. In most patients, therefore, the nerve was not af- not try to reroute the mediannerve subcutaneouslyby rein- fected severely enoughto result in conduction values out- serting the pronator teres, as suggested by Spinner. side the normal range, and the mildness of the abnormality Solnitzky believed that the variability of symptoms was consistent with the minimumneural deficit. The and physical findings in the pronator teres syndromewas findings were probably due to the intermittent compression explained by changes in patterns of rest and activity. He of the nerve and possibly to a selective involvementof the thought that the variability in the sensory and motor signs small pain fibers. The nerve-conduction findings and the was due to the functional groupings of fibers within the frequency of abnormal studies on needle examination in nerve and the location of the compressingagent relative to this disorder resemble the signs of traumatic neuropathies the nerve. Our experience seems to support this concept. more than those of chronic compressive neuropathies. For example, compression of the median nerve that was Chronic compressive neuropathies typically are charac- caused by a tight lacertus fibrosus in our patients resulted terized by either local slowing of conduction or a conduc- in pain that spread diffusely in the volar aspect of the tion block due to segmental demyelination and axonal nar- forearm, while compression by a tight superficialis arch rowing, while traumatic neuropathies more commonlyre- caused more localized pain. sult in axonal loss with low-amplitude responses. This Diagnosis of the pronator teres .syndrome seldom is type of pathological change also is consistent with our in- easy. This point is illustrated by the cases of the seven pa- ability to localize the damageelectrophysiologically in tients in our group who had had unsuccessful operations most patients. ~ between three and twenty-eight monthsbefore our initial The large number of normal electromyographic examination. findings in our patients indicates that electromyography Five patients required a subsequentoperation after re- cannot exclude the diagnosis of the pronator teres syn- lease of the pronator teres that initially gave goodor excel- drome, nor can it predict the outcome of operation. The lent results. Asidefrom the possibility of error in the orig- entirely normal electromyographicfindings in the patients inal diagnosis or the existence of someuncorrected lesion, whowere not operated on may have influenced this group a plausible reason for the second operation in one patient of patients not to have an operation, and that.fact maybe was that an unrelated ulnar neuropathy might have de- important in the evaluation of electromyogi:aphic tests. veloped. In three patients a carpal tunnel syndromemay However,in patients with suspected pronator teres syn- have coexisted with or developed after the pronator teres drome, electrophysiological testing was of value for two syndrome, perhaps in a nerve rendered more susceptible to specific purposes: (1) it distinguished other peripheral compressionin the carpal tunnel. Inadequate release of the nerve disorders that present with similar symptoms, and compressingstructures at the initial exploration mayhave (2) it showedthat a non-localizable median-nervelesion accounted for the recurrence of symptomsin the fifth pa- was present in 15 to 20 per cent of the patients with the tient. Althougha constricting fascial band and the super- syndrome, and in a smaller percentage it accurately lo- ficialis arch werereported to be divided at the first opera- calized the lesion. tion, at re-exploration the superficialis arch again was Identification and localization were enhanced by all foundto be tight. three types of electrophysiological study -- motor and Lister comparedthe diagnosis of the pronator teres sensory conductions across the pronator and needle elec- syndromewith that of the carpal tunnel syndrome. He de-- scribed features commonto both but noted that the pro- tromyogramsof the forearm and hand muscles. As no one study was superior to the other two, all are neededin test- nator teres syndromewas not associated with a positive Phalrn test. Our experience does not confirm his assertion. ing for the pronator teres syndrome.Precise localization in 51~’ty per cent of our patients had a positive Pha!en test a few patients was ?ossib!e wi~hconduction stuc’ies across short segmentsbut it was not of value unless an abnormal-

VOL. 63-A, NO. 6. JULY 890 C. R. HARTZ, R. L. LINSCHEID, R. R. GRAMSE, AND J. R. DAUBE ity was found on standard studies. The results of the in- ficialis than by the Phalen test. Mostof this small group of traoperative electrophysiological recordings were similar patients had complaints of fatigue and pain in the forearm, to those of preoperative studies: they showedonly mild with paresthesias in the fingers which usually followed the abnormalities that did not identify or localize the damage onset of the pain, Generally, these patients did not have any better than did standard studies. However,after de- nocturnal paresthesias. Three of them had had previous compression of the nerve the change in conduction veloc- carpal-tunnel decompression without relief of their pri- ity and in amplitude of the nerve-action potentials mea- mary symptoms, and two additional patients had not re- sured intraoperatively in somepatients was evidence that spondedto injection of cortisone into the carpal canal. As there was an improvementin nerve function. mentioned, there may be a relationship between the pro- Someof the patients who improved after operation nator teres syndromeand the carpal tunnel syndrome be- had clear-cut electromyographic evidence of other disor- cause of increased susceptibility of the nerve to a com- ders -- carpal tunnel syndromein seven patients and an pression neuropathy when the syndromes coexist. The upper-arm median neuropathy in one other patient. This finding of an increased latency in the conduction time of implies that the pronator teres syndromemay coexist with the median nerve in the carpal tunnel could be explained other median neuropathies or that these other disorders in that way. may improve after decompression of the proximal median It is interesting to speculate whyanterior interosseus- nerve. nerve palsy is not seen with the pronator teres syndrome The fact that increased latencies in conduction in the whenthe sites of the lesions are so near to one another in median nerve were found across the carpal canal in some the area between the ulnar head of the pronator and. the of these patients requires some explanation. The symp- origin of the flexor digitorum superficialis. In the seven- toms in these patients appeared to arise primarily in the year period of this study, only two such patients with the proximal part of the forearm, where tenderness of the pro- Kiloh-Nevinsyndrome were seen in our institution, and in nator and the nerve proximal to the pronator area was evi- them direct pressure of the ulnar head of the pronator teres dent. These symptomscould be worsened more by resisted muscle was seen on the anterior interosseus nerve just pronation and contraction of the flexor digitorum super- belowits origin.

References 1. BE~,TON,L. E., and ANSON,B, J.: The Relation of the Median Nerve to the Pronator Teres Muscle. Anat. Rec., 75: 23-26, 1939. 2. BELL, G. E., JR., and GOLDrqE~,J. L.: Compression Neuropathy of the Median Nerve. Southern Med. J., 49: 966-972, 1956. 3. BUCHTHAL,FRITZ; ROSENFALCK,ANNELISE; and TROJABORG,WERNER: Electrophysiological Findings in Entrapment of the Median Nerve at Wrist and Elbow. J. Neurol., Neurosurg., and Psychiat., 37: 340-360, 1974. 4. FtSHER,D. E., and BR~(~t4, R. S.: Neuropathy from Old Retained Foreign Bodies (Glass) in the Forearm: Report of a Case. Clin. Orthop., 146-148, 1971. 5. GARDNER,R. C.: Impending Volkmann’s Contracture Following Minor Trauma to the Palm of the Hand: A Theory of Pathogenesis. Clin. Orthop., 72: 261-264, 1970. 6. HALP~RN,A. A., and NAVEL,D. A.: CompartmentSyndromes of the Forearm: EarlyRecognition Using Tissue Pressure Measurements. J. Hand Surg., 4: 258-263, 1979. 7. JomqsoN, R. K.; SPINNER,MoRrorq; and SaREWSaURV,M. M.: Median Nerve Entrapment Syndrome in the Proximal Forearm. J. Hand Surg., 4: 48-51, 1979. 8. KO~’ELL,H. P-, and ThONg’SON,W. A. L.: Pronator Syndrome. A Confirmed Case and Its Diagnosis. NewEngland J. Med., 259: 713-715, 1958. -- 9. LISTER,GRAHAM: The Hand: Diagnosis and Indications. Edinburgh, Churchill Livingstone, 1977. I0. MORRIS,H. H., and PETERS,B. H.: Pronator Syndrome:Clinical and Electrophysiological Features in Seven Cases. J. Neurol., Neurosurg., and Psychiat., 39: 461-464, 1976. 11. SEYFFARTn,HZNRI~: Primary Myosesin the M. Pronator Teres as Cause of Lesion of the N. Medianus (The Pronator Syndrome). Acta Psychiat. Neurol. Scandinavica, Supplementum74, pp. 251-254, 1951, . 12. SoLm~z~,OTm, IAR: Pronator Syndrome: Compression Neuropathy of the Median Nerve at Level of Pronator Teres Muscle. Georgetown Med. Bull., 13: 232-238, 1960. 13. Sp~Nrq~R,MORTON: Injuries to the Major Branches of Peripheral Nerves of the Forearm. Ed. 2, pp. 192-198. Philadelphia, W. B. Saunders, 1978.

THE JOURNAl. OF BONF ~,ND IO!\’T qUt~GFRY