Authors:

Nurgu¨ l Arinci I˙ncel, MD H. Genc¸, MD H. R. Erdem, MD Electromyography Z. R. Yorgancioglu, MD

Affiliations:

From the Department of Physical Research Article Medicine and Rehabilitation, Ankara Education and Research Hospital, Ankara, Turkey (HG, HRE, ZRY); Mersin University, Department of Physical Medicine and Rehabilitation, Mersin, Turkey. Muscle Imbalance in Hallux Valgus Correspondence:

All correspondence and requests for An Electromyographic Study reprints should be addressed to Nurgu¨ l Arinci I˙ncel, MD, Mersin University, Department of Physical ABSTRACT Medicine and Rehabilitation, Mersin, Arinci I˙ncel N, Genc¸ H, Erdem HR, Yorgancioglu ZR: Muscle imbal- 33079 Turkey. ance in hallux valgus: An electromyographic study. Am J Phys Med 0894-9115/03/8205-0345/0 Rehabil 2003;82:345–349. American Journal of Physical Medicine & Rehabilitation Objective: Hallux valgus is a very common foot deformity in modern Copyright © 2003 by Lippincott societies. Muscle imbalance in abductor and adductor muscles was Williams & Wilkins cited as a major factor in the production of hallux valgus. Our aim in this

DOI: 10.1097/01.PHM.0000064718.24109.26 study was to evaluate the role of certain muscles in this deformity. Design: Twenty hallux valgus patients and 20 healthy volunteers par- ticipated in the study. After thorough physical, neurologic, and radio- graphic investigations, we performed an electromyographic study to observe the relationship of hallux valgus deformity with the muscles coordinating first metatarsophalangeal joint movements. Voluntary ex- tension, flexion, abduction, and adduction at the hallux with maximum resistance were performed. Firing rates and amplitudes of motor unit potentials of four muscles: musculus abductor hallucis, musculus ad- ductor hallucis, musculus extensor hallucis longus, and musculus flexor hallucis brevis were recorded. Statistical analysis, including Spear- man’s correlation analysis and Mann-Whitney U tests were performed with SPSS 8.0 for Windows. Results: We observed that in the hallux valgus group, abduction activity of musculus abductor hallucis was markedly decreased when compared with adduction of musculus adductor hallucis. Motor unit potential amplitude of abductor activity recorded from musculus abduc- tor hallucis was slightly more than half of the activity in flexion. Conclusion: Muscle imbalance in abductor and adductor muscles is apparent in hallux valgus deformity, and this imbalance may be the reason or the result of joint deformity. Key Words: Hallux Valgus, Foot Deformity, Muscle Imbalance, Electromyography

May 2003 Muscle Imbalance in Hallux Valgus 345 control group were asymptomatic physical examination, and all were Hallux valgus (HV) is a very com- feet with no deformities. Exclusion normal. We used surface electrodes mon deformity of the feet and is char- criteria were the same with the pa- to record the motor unit potentials acterized with medial migration of tient group. All radiologic examina- (MUPs) from four muscles—muscu- the first metatarsus, valgus angula- tions and electromyographic (EMG) lus abductor hallucis, musculus ad- tion of the first metatarsophalangeal studies were performed for both pa- ductor hallucis, musculus extensor joint, and pronation of the proximal tients and the control group. hallucis, and musculus flexor hallu- phalanx.1 Analysis of foot deformities Age, sex, height, and weight of all cis—during maximum muscle con- require an observation including the subjects were recorded. Body mass traction. In general, active electrodes contribution and function of ana- indexes were calculated according to were placed on the most prominent tomic structures and the evolution- weight (in kilograms)/height (square portion of the muscle bulk, and ref- ary state of the foot.2 The evolution- meters) formula. Four muscles erence electrodes were placed ap- ary changes that have affected the known to support the foot arch— proximately 3 cm proximal to the ac- foot allowed the hallux to lose its musculus tibialis anterior, musculus tive electrode. Electrode placements prehensile function, although these tibialis posterior, musculus peroneus for the muscles are given in Table 1.6 changes are not yet complete. The longus, and musculus peroneus bre- An earthing electrode was strapped adductor hallucis is still oriented to vis—were assessed with manual mus- over the lower third of the medial facilitate gripping, and the antagonis- cle testing.4 For radiographic evalua- surface of the tibia. EMG activity was tic abductor hallucis is at a mechan- tion, weight-bearing anteroposterior recorded with a frequency band ex- ical disadvantage. This imbalance is foot radiographs were examined. HV tending from 10 to 5000 Hz, and considered as relevant to the cause of angle was measured as the angle noise was filtered by 60 Hz to sup- HV.3 Our aim in this study was to formed by the intersection of the lon- press the stimulus artifact and stim- evaluate the role of these muscles in gitudinal axes of the proximal pha- ulators causing environmental inter- HV deformity in the light of these lanx and the first metatarsus.5 ference (fluorescence bulbs, wall data. We performed an EMG study to plugs, etc.).7 EMG activity was ac- investigate the relationship of HV de- cepted as absent in a relaxed-feet 8 MATERIAL AND METHODS formity with the muscles coordinat- stance as stated by Duranti et al. in a ing first metatarsophalangeal joint previous study. Voluntary extension, A total of 20 patients (17 female movements. We used the 4 Channel flexion, abduction, and adduction of and three male patients) with com- EMG Navigator version 2.01, Model the hallux against maximum resis- plaints caused by clinically diagnosed 996, Biological Equipment for EMG tance were performed. The primary HV deformity and 20 healthy subjects studies at the same room with tem- function of the muscles were tested (17 female and three male subjects) perature between 20 and 22°C. The before other movements; for exam- were selected for the study. Patients sural nerve sensory latencies were ple, while testing musculus abductor with apparent HV were randomly se- studied to exclude the polyneurop- hallucis, abduction of the hallux was lected from the outpatient clinics of athy cases that might be missed by followed by adduction, extension, and our hospital. History of diabetes mel- litus, HV operation, neuropathy (due to alcohol, vitamin B12 deficiency, TABLE 1 etc.), cerebrovascular problems, po- Active electrode placements for electromyographic studies liomyelitis, cerebral palsy, or inflam- for the muscles observed matory joint disease were exclusion Muscle Electrode Insertion criteria. Thorough neurologic exam- Musculus abductor Approximately 1–2 cm posterior to the navicular ination of the lower limbs, including hallucis tuberosity; this will be just anterior to an muscle testing, were performed. Vas- imaginary line drawn through the anterior cular status of these patients were margin of the medial malleolus evaluated with examination of pe- Musculus adductor For the transverse head, just proximal to the ripheral arteries, venous stasis, and hallucis third metatarsophalangeal joint, the most prominent part of the muscle belly varicose veins. None of these patients Musculus extensor hallucis Three finger widths above the bimalleolar line of had any vascular or neurologic pa- longus the ankle just lateral to the crest of the tibia thologies with physical examination. Musculus flexor hallucis Proximal and medial to the tendon of the flexor Twenty sex-matched control subjects brevis hallucis longus, the most prominent part of the were recruited from the same outpa- muscle tient clinics. Inclusion criteria of the

346 Arinci I˙ncel et al. Am. J. Phys. Med. Rehabil. ● Vol. 82, No. 5 flexion. Amplitude and interference male volunteers, with ages ranging tween patient and control groups patterns of MUPs were recorded. Re- between 26 and 67 yr (mean Ϯ SD, 44 (P Ͻ 0.001 and P Ͻ 0.01, respective- corded MUPs were grouped as full Ϯ 13 yr). There was no statistically ly). The mean MUP amplitude value interference pattern, reduced inter- significant difference for age, sex, of abduction activity recorded at ab- ference pattern, and single-MUP sam- height, weight, and body mass in- ductor hallucis for our control group ples according to their firing frequen- dexes between study groups. Mea- was nearly twice the HV group. For cies. The EMG signal called surements of HV angle revealed sig- the HV group, abduction and flexion interference pattern seems complex, nificant differences between groups. of abductor hallucis longus were ob- contains discharges of several MUPs In the HV group, three patients had served, and MUP amplitudes of ab- that superimpose on one another re- mild HV (HV angle of Ͻ20 degrees), duction activity was slightly more peatedly, and the individual MUPs 16 had moderate HV (HV angle be- than half of the MUPs in flexion. An can no longer be recognized. If the tween 20 and 40 degrees), and one interesting finding was that there was interference pattern contains dis- had serious HV (HV angle of Ͼ40 no significant difference between charges of only a few motor units, it degrees). HV angle ranged between MUP amplitudes of two groups re- is described as reduced or incom- 18 and 55 degrees in HV patients corded during flexion of flexor mus- 9,10 plete. If a reduced interference (mean, 24.85 Ϯ 8.59 degrees) and cles (Fig. 1). pattern is seen on the screen, one ranged between 3 and 11 degrees For all movements and muscles could assume that there is a substan- (mean, 8.05 Ϯ 3.02 degrees) for the examined, amplitude and firing rates tial degree of weakness present.9 control group. of MUPs were well correlated. MUP Statistical analysis were per- The study population all had nor- interference patterns were also com- formed with SPSS 8.0 for Windows mal sural nerve latencies. Mean MUP pared between study groups, and the (SPSS, Chicago, IL). Variables were amplitude values recorded from the abductor hallucis muscle showed a correlated by means of Spearman’s four muscles during four different significant difference for maximum correlation analysis. Results of EMG movements for patient and control voluntary abduction: in the HV analysis of patient and control groups groups are given in Table 2. group, six patients had single-MUP were compared with Mann-Whitney U test. P values of Յ0.05 were con- All amplitude values were higher samples, 13 had a reduced interfer- sidered to be significant. for the control group, compared with ence pattern, and only one patient the patient group. Flexion activity of had a full interference pattern, flexor hallucis had revealed maxi- whereas for the control group, six RESULTS mum amplitude values obtained from reduced interference patterns and 14 The HV group consisted of 17 both groups. There was a statistically full interference patterns were re- female and three male subjects who significant difference (Mann-Whitney corded, with no single-MUP samples. ranged in age from 25 to 70 yr (mean U test) between amplitudes of abduc- MUP patterns recorded from flexion Ϯ SD, 45 Ϯ 12 yr). Our control group tion of abductor hallucis and adduc- movement of abductor hallucis and also included 17 female and three tion of adductor hallucis muscles be- flexor hallucis and adduction of ad-

TABLE 2 Mean values for amplitudes of motor unit potentials recorded during four different movements Muscle Abduction Adduction Flexion Extension Hallux valgus group Musculus abductor hallucis 498 Ϯ 280 45 Ϯ 69 973 Ϯ 349 220 Ϯ 379 Musculus adductor hallucis 5 Ϯ 22 312.5 Ϯ 128 170 Ϯ 113 88 Ϯ 51 Musculus flexor hallucis brevis 315 Ϯ 300 217.5 Ϯ 186 1105 Ϯ 450 50 Ϯ 76 Musculus extensor hallucis longus 185 Ϯ 153 285 Ϯ 221 0 Ϯ 0 828 Ϯ 353 Control group Musculus abductor hallucis 980 Ϯ 456 70 Ϯ 130 773 Ϯ 529 348 Ϯ 570 Musculus adductor hallucis 40 Ϯ 82 435 Ϯ 88 195 Ϯ 119 95 Ϯ 100 Musculus flexor hallucis brevis 490 Ϯ 321 180 Ϯ 217 1148 Ϯ 489 30 Ϯ 73 Musculus extensor hallucis longus 265 Ϯ 146 230 Ϯ 113 40 Ϯ 68 683 Ϯ 262 Values are in microvolts, presented as mean Ϯ SD.

May 2003 Muscle Imbalance in Hallux Valgus 347 hallucis are displayed laterally. As a perform abduction and adduction result, the adductor hallucis and movements at their hallux on de- flexor hallucis brevis are stretched mand. In normal feet, because of the with the adductor losing its force slight obliquity of the metatarsopha- markedly. The tendon of the abductor langeal joints, the toes, including the hallucis moves toward the plantar in hallux, tilt laterally on extension and relation to the metatarsal head, so it medially on flexion.1,13 We observed Figure 1: Comparison of mean mo- completely loses its abductor force that most healthy subjects and HV tor unit potential amplitude values re- instead of gaining flexor force.3 patients cannot perform isolated ab- corded from muscles during activi- Normally at the metatarsopha- duction and adduction movements ties of hallux. E-E, extension of langeal joint, abductor and adductor on a transverse plane. Most of the musculus extensor hallucis longus; forces are balanced. However, in HV, subjects failed abducting the toe away F-F, flexion of musculus flexor hallu- although the adductor force is de- from others. This failure may be re- cis brevis; Ad-Ad, adduction of mus- creased, the abductor force is mostly lated to the decrease in the activity of culus adductor hallucis; Ab-F, flexion lost and the weak adductor force be- the abductor and adductor muscles of musculus abductor hallucis; Ab- comes dominant. These statements or to an altered function of these Ab, abduction of musculus abductor hallucis; HV, hallux valgus. are supported by the observations of muscles resulting from origin and in- Thomson and Coughlin12 for hallux sertion changes. varus treatment. Iıda et al.11 found Generally, intrinsic muscles of ductor hallucis activity did not show that activity of adductor hallucis in the feet and their nerves are relatively significant difference between the HV feet is decreased. In our HV superficial and are subjected to mul- two groups (P Ͼ 0.05). group, MUP amplitudes recorded tiple stresses and pressures from from adductor hallucis were also daily living. This fact may explain 14 DISCUSSION markedly low. The reduced MUP am- some EMG abnormalities. The re- plitudes may be due to muscle fatigue sults of this study indicate that elec- EMG studies helped us to iden- but also can be explained by the deep tromyographic studies can help us tify the role of muscles in HV defor- insertion of adductor hallucis muscle gain an insight about the role of mus- mity, as abductor-adductor muscle recorded by surface electrodes. Fine- cle pathology in HV deformity. We imbalance is cited as a major factor in wire electrodes are superior to sur- noticed that in HV feet, abduction the development of HV deformity.3,11 face electrodes, with the ability to activity of abductor hallucis was In a previous study, Hoffmeyer et al.3 directly reach deep muscles. Surface markedly decreased when compared performed muscle biopsies for 57 HV electrodes do not allow us to detect with adduction of adductor hallucis. patients and reported that in 53 bi- the precise location of the active Abductor hallucis gain flexor activity opsy specimens, the muscles were muscle. We performed our study by with structural deformities. We found to be histologically abnormal. placing surface electrodes to key stated that muscle imbalance and They stated that the surface EMG ac- points accepted in EMG guides and weakness is apparent in HV patients, tivity of the abductor and interosse- by testing all movements of the joint and this may be the result or the ous muscles also were abnormal. for each muscle.6 These electrodes do reason for the deformity. We may ex- These results are in concordance not allow us to detect the precise pect to stop further imbalance, espe- with Iıda et al.11 They also reported location of the active muscle. We pre- cially at the beginning stage, by that in HV patients, abductor and ad- ferred surface electrodes in our pa- terms of exercise and other conven- ductor hallucis muscles have maxi- tients to minimize discomfort. The tional methods, such as splinting and mum activity during flexion.12 In our general advantage of all surface elec- shoe modifications. study, for abductor hallucis muscle, trodes is that they can be secured MUP amplitudes recorded at abduc- simply to the patient’s skin with tape REFERENCES tion were nearly half of the ones re- or in a self retaining manner with corded at flexion. This imbalance may little or no discomfort. A major dis- 1. Jahss MH: Disorders of the hallux and be secondary to some mechanical advantage of surface electrodes is the first ray, in Jahss MH (ed): Disorders of the Foot and Ankle. Philadelphia, WB changes. With malalignment of the that the skin offers a considerable Saunders, 1992, vol 2, pp 943–72 bones, the distance between origin resistant barrier, lessening the bio- 2. Hutton WC, Dhanendran M: The me- and insertion of the muscles is in- logical signal’s ability to reach the chanics of normal and hallux valgus feet: 7 creased, the insertion of the adductor recording electrode. A quantitative study. Clin Orthop 1981; hallucis moves toward the medio- Incidentally, we noticed that it 157:7–13 plantar side, and the tendons of flexor was not easy for the HV patients to 3. Hoffmeyer P, Cox JN, Blanc Y, et al:

348 Arinci I˙ncel et al. Am. J. Phys. Med. Rehabil. ● Vol. 82, No. 5 Muscle in hallux valgus. Clin Orthop mentation, in Johnson EW, Pease WS Practical Electromyography, ed 3. Balti- 1988;232:112–8 (eds): Practical Electromyography,ed3. more, Williams & Wilkins, 1997 Baltimore, Williams & Wilkins, 1997, pp 4. Hislop HJ, Montgomery J: Muscle 11. Iıda M, Basmajıan JV: Electromyo- 63–87 Testing: Technique of Manual Examina- graphy of hallux valgus. Clin Orthop tion. Philadelphia, WB Saunders, 1995, 8. Duranti R, Galletti R, Pantaleo T: Elec- 1974;101:220–4 pp 218–25 tromyographic observations in patients with foot pain syndromes. Am J Phys Med 12. Thompson FM, Coughlin MJ: The 5. Smith RW, Reynolds JC, Stewart MJ: 1985;64:295–304 high price of high-fashion footwear. Hallux valgus assessment: Report of re- J Bone Joint Surg (Am) 1994;76:1586–92 search committee of American Orthopae- 9. Terebush BM, Johnson EW: The elec- trodiagnostic consultation including 13. Saltzman CL, Aper RL, Brown TD: dic Foot and Ankle Society. Foot Ankle Anatomic determinants of first metatar- 1984;5:92–103 EMG examination, in Johnson EW, Pease WS (eds): Practical Electromyography, sophalangeal flexion moments in hallux 6. Delagi E, Perotto A, Iazetti J, et al: ed 3. Baltimore, Williams & Wilkins, 1997 valgus. Clin Orthop 1997;339:261–9 Anatomic Guide for the Electromyogra- 10. Nandedkar SD: Objective EMG: 14. Gatens PF, Saeed MA: Electromyo- pher, ed 2. Springfield, IL, Thomas, 1981, Quantitation and documentation in the graphic findings in the intrinsic muscles pp 120–33 routine needle electromyographic exami- of normal feet. Arch Phys Med Rehabil 7. Dumitru D: Practical aspects of instru- nation, in Johnson EW, Pease WS (eds): 1982;63:317–8

Book Review

Spinal Cord Medicine by Drs. Steven Kirshblum, Denise Campagnolo, and Joel A. Delisa. Published by Lippincott Williams & Wilkins, Baltimore, MD, 2002, 620 pages, $129.00. ISBN: 078172869. Across 39 chapters, this textbook hits the mark in providing a comprehensive overview of the field of spinal cord injury medicine. The author list includes specialists from a wide variety of medical, surgical, and allied health disciplines. The editors’ effort in matching chapter topic to author is stellar; readers will benefit from the contributions of many prominent American clinicians and researchers. This allows the editors to accomplish several important goals. For topics for which peer-review literature is extensive (e.g., neurogenic bladder), expert authors guide the reader by distilling volumes of information into a manageable form, emphasizing only important and clinically useful information. This book passes an even tougher test on topics for which literature support is weak or parochial (e.g., driving assessment). The selection of experienced authors ensures that the information presented is reasonable, comprehensive, and fair. The editor’s topic selection reflects the current science and practice of this subspecialty, heavily weighted toward traumatic spinal cord injury. Other medical conditions producing similar deficits and disabilities receive a level of attention that is generally proportionate to their importance in current clinical practice and to the existing measure of scientific information. As with most large textbooks with multiple editors and authors, chapters vary in level of detail, quality, and readability, but the quality of the literature references is uniformly excellent. I found the chapters on psychological adaptation and vocational aspects of spinal cord injury to be unique, useful, and thought provoking. I will stop there, because it is difficult, and definitely unfair, to single out individual contributions, as there are so many superb chapters. This book will be very useful as a clinical resource for physicians-in- training and practitioners who occasionally treat persons with spinal cord injury and as a reference text for those who treat these patients on a full-time basis. Book Rating: Frederick S. Frost, MD The Cleveland Clinic Foundation Cleveland, OH

April 2003 Muscle Imbalance in Hallux Valgus 349