Extensor digitorum brevis manus: A report on 38 cases and a review of the literature

Extensor digitorum brevis manus: A report on 38 cases and a review of the literature

578 The Journal of HAND SURGERY Wyiock et ai. occur. 2 , 4, 5 In the United States, there were 222 cases between 1955 and 1978 with 10 fatal cases...

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578

The Journal of HAND SURGERY

Wyiock et ai.

occur. 2 , 4, 5 In the United States, there were 222 cases between 1955 and 1978 with 10 fatal cases. 6 REFERENCES 1. Christie AB: Infection diseases. London, 1975, Churchill Livingstone, pp 787-813 2. De Schilder J, De Groef K: Un cas de charbon cutane. Arch Belg Derrnatol Syph 27:211-3,1971 3. Dutz W: Anthrax. In Braude MD, editor: Medical mi-

4. 5. 6. 7.

crobiology and infectious diseases. Philadelphia, 1981, WB Saunders Co, p 1806 Haarman HJ, Sangster D: Anthrax. Ned Tijdschr Geneesk 120:378-81,1976 Heyne D: Le charbon en Belgique. Arch Belg Med Soc 26:401-16, 1968 Brachman PS: In Hoeprich PD, editor: Infectious diseases. Hagerstown, Md., 1982, pp 807-12 McKendrick DRA: Anthrax and its transmission to humans. Cent Afr J Med 26:126-9,1980

Extensor digitorum brevis manus: A report on 38 cases and a review of the literature Three thousand four hundred and four adults were randomly examined and 38 cases of extensor digitorum brevis manus were identified. This short, anomalous muscle located on the dorsum of the hand occurred in 1.1% of the people examined and 19 of the 38 cases required surgery because of pain precluding work. This report reviews the literature and describes the clinical picture of the 38 cases. (J HAND SURG 8:578-82, 1983.)

Christovao Gama, M.D., Sao Paulo, Brazil

One hundred and twenty cases of extensor digitorum brevis manus (EDBM) have been described from 1743 until the present. These reports l - 18 describe the muscle's appearance, origin, insertion, and nerve supply.

Material and methods Three thousand four hundred and four adults between the ages of 23 and 56 years were randomly examined between 1975 and 1981. Two thousand six hundred and seventy five were men and 729 were women. Thirty-eight patients (20 men and 18 women) had an EDBM 25 of which were unilateral and 13 bilateral. Nineteen of the 38 were operated on because of pain that made them unable to work (Table I).

From the Hand Surgery Service, Hospital Dr. Christovao da Gama, SI. Andre, sao Paulo, Brazil. Received for publication May 28, 1982; accepted in revised form Aug. 16, 1982. Reprint requests: Christovao Gama, M.D., Rua Inhambu, 156 Indianopolis, Sao Paulo, Brazil, CEP 04520.

The randomly examined patients were divided into three groups, depending on their symptoms. Group I consisted of 321 adults without clinical manifestations, 214 of which were men and 107 women. In this group the short muscle was found in three women and one man and all were unilateral. None of these patients underwent surgery because they had no clinical complaints. The patients in group II had symptoms localized to the dorsum of the hand and it consisted of 227 patients (183 men and 44 women). Fourteen patients in this group required surgery (eight women and six men). Group III consisted of 2,278 men and 578 women, all examined for a variety of complaints not related to the hand and wrist. The EDBM was found in 20 patients (16 men and four women) five of whom required operations because it prevented them from working.

Clinical picture and diagnosis Constant pain during work occurred in some patients with EDBM and the index and long fingers were the most painful. In every bilateral case the size of the muscle belly was larger on the dominant hand. On clin-

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Fig. 1. The contracted EDBM can be seen on extension against resistance (Case No.8) .

Fig. 2. Sectioned distally, the EDBM on the ulnar side of the third MP joint (Case No . 9).

ical examination the muscle belly was easily identified as a fusifonn mass (Fig. 1), except in those cases in which the muscle was located deep to the extensor digitorum communis and in such cases, the initial diagnosis was frequently incorrect, such as of a ganglion or synovitis . Electromyographic examinations were per-

fonned in seven cases and showed nonnal muscle activity; our results were similar to those obtained by other authors who undertook and reported the same examination. 14 • 15 X-ray films of the hands and wrists in our 38 cases showed carpal bossing in three patients and all laboratory studies were nonnal. Histologic spec-

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Fig. 3. EDBM with the presence of the extensor indicis proprius (Case No.7).

Fig. 4. The EDBM with an intratendinous ganglion (Case No. 17).

imens of the muscles excised showed normal striated muscle tissue, except in two cases in which there was focal atrophy of the muscle fibers.

Results Anatomy. The origin of the EDBM is the wrist capsule beneath the dorsal carpal ligament at the level of

the scaphoid, lunate, capitate, or hamate or occasionally at the level of the distal epiphysis of the radius. The distal insertion was usually found to be on the ulnar side of the extensor mechanism at the level of the metacarpophalangeal (MP) joint. Occasionally the distal insertion was found on the radial side of the long finger and the ring finger MP joint. The shape of the

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Fig. s. A, Bilateral EDBM and ganglion. B, Excised specimen with three muscle bellies and two ganglia (Case No . 14) .

muscle was usually fusiform (Fig. 2) and the length of the muscle ranged from 3 to 7 cm and the tendons from 2 to 4 cm. When the EDBM was present, the extensor indicis proprius was rarely observed (Fig. 3). Innervation and function. Like other authors 10. 19-22. 24. 27 we were able to establish that the posterior interosseous nerve innervated the EDBM. When electrically stimulated, the muscle extended and deviated the finger to the side on which the EDBM was inserted,

relative to the extensor digitorum communis insertion. Treatment. The indication for surgical removal was pain precluding work. In some cases requiring surgery other lesions, such as ganglia, synovitis of the extensor tendons, or carpal bossing, were found and in these cases the lesions were excised at the same time. From one patient requiring surgery a specimen with an intratendinous ganglion as well as an EDBM muscle was obtained (Fig. 4).

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Discussion The EDBM is a well-defined muscle, originating on the extensor surface of the hand and wrist, innervated by the posterior interosseous nerve, and usually between 6 and 9 cm in length. We found this muscle present 38 times in 3,404 adults examined. The breakdown by sex of patient of 20 men and 18 women is somewhat different from the breakdown in the literature (20 men, 11 women, and three cases without reference to sex).23 We feel that the finding in adults, and less frequently in children, is explained by the development of the muscle due to activities and labor. When present the EDBM is located on the ulnar side of the extensor communis of the index finger and the extensor indicis proprius is usually absent. Multiple insertions of the short muscle or a multiplicity of muscle bellies is rarely reported in the literature and occurred in only three of our cases. The EDBM was reported to occur bilaterally in 19 cadaver dissections and has been reported bilaterally eight times in clinical cases. To this number we add 13 new bilateral cases found among our 38 cases (34.2%). Occasionally other lesions have been found in bilateral cases (Fig. 5). When electrically stimulated the EDBM deviates the proximal phalanx to the side on which it is inserted in relation to the extensor digitorum communis. Resistance against finger extension caused pain in some patients and this sign was a reliable indicator of which patients benefited from surgery. Differential diagnoses include ganglia, synovial cyst, synovitis, exostosis, and carpal bossing. In one patient in the literature 13 on which a biopsy was performed and in the 19 cases we operated on, all specimens were examined histologically. Except in three cases, no muscle pathology was seen and two of these showed slight interstitial fibrosis; a third showed focal atrophy of muscle fibers. The EDBM was observed in eight relatives in three cases in our series, which suggests a hereditary influence. The recommended treatment is conservative except in those cases in which pain and weakness of pinch and grip precludes work and, in those cases, surgical excision of the EDBM muscle on the back of the hand is recommended. REFERENCES 1. Albinus BS: Annotationes academicarum, book 4. chap 6, p 28, Table V, Fig. 3, 1734 (cited in ref 2) 2. LeDouble AF: Traite des variations du sisteme musculaire de I 'homme et de leur signification au point de

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vue de I 'anthropologie zoologique, vol II. Paris, 1897, Schleicher, Freres, pp 203-17 de Vilhena H: Mm. Maniosos. Arq Anat Antropol 25/ 26:465-508, 1949 Liaras H, Bourgeon R: Contribution aI 'etude du muscle manieux. Lab Anat Fac Med Alger, pp 46-57, 1941 Smith EB: Some points in the anatomy of the dorsum of the hand, with special reference to the morphology of the extensor brevis digitorum manus. J Anat Physiol 31 :4558, 1897 Wood J: Variations in human myology. Proc Royal Soc London 104:513-4, 1868 Mc Gregor AL: A contribution to the morphology of the thumb. J Anat 60:259-73, 1926 Cunningham DJ: The relation of nerve-supply to muscle-homology. J Anat Physiol 16: 1-9, 1882b Straus WL Jr: The phylogeny of the human forearm extensors. Human BioI 13:203-38, 1941 Buhler A: Beziehungen regressiver und progressiver Vorgange tiefen Fingerstrecker und den Musculi interossei dorsales der menschlichen Hand. Morphol Jahrb 29:563-81, 1902 (cited in ref 9) Macalister A: Cited in ref 5 Meckel: Cited in ref 5 Gama CC da: Musculus extensor digitorum brevis manus. Int J Surg 61:39-40, 1976 Egawa T, Hashimoto K: An anomalous extensor indicis muscle. A case report. Bull Hosp Joint Dis 27: 116-9, 1966 Reef TC, Brestin SG: The extensor digitorum brevis manus and its clinical significance. J Bone Joint Surg [Am] 57:704-6, 1975 Cauldwell EW, Anson BJ, Wright RR: The extensor indicis proprius muscle. A study of 263 consecutive specimens. Quart Bull NW Univ Med School 17:267-79, 1943 Fontes V: Note sur Ie Muscle Manieux. C R Assoc Anat 199:289-94, 1933 Cardia M: In Liaris H, Bourgeon R, editors: Congres luso-espagnol. Section Biologie Medicale, 1921 Bhadkamkar AR, Mysorekar VR: Bilateral extensor digitorum brevis muscle in the hand. J Anat Soc India 9:103-5, 1960 Stith JS, Browne PA: Extensor digitorum brevis manus: A case report and review. Hand 11:217-23,1979 Ross JA, Troy CA: The clinical significance of the extensor digitorum brevis manus. J Bone Joint Surg [Br] 51:473-8, 1969 Varian JPW, Pennington DG: Extensor digitorum brevis manus used to restore function to a ruptured extensor pollicis longus. Br J Plast Surg 30:313-5, 1977 Boyes JH: Bunnell's surgery of the hand, ed. 4. Philadelphia, 1964, JB Lippincott Co, p 29