Edorium Journal of Anatomy and Embryology, Vol. 5; 2018. Edorium J Anat Embryo 2018;5:100025A04AC2018. www.edoriumjournals.com/ej/ae Chernev et al. 1 CLINICAL IMAGE PEER REVIEWED | OPEN ACCESS Supernumerary first dorsal interosseous muscle of the hand Alexandra Chernev, Ivan Chernev CASE REPORT During a routine anatomy module, as part of an educational course, the authors noticed unusual muscle variation of the hand in an upper limb specimen. Details regarding age, gender, race, and cause of death were not available for this specimen. An additional supernumerary first dorsal interosseous (FDI) muscle was observed, which originated from the second metacarpal bone, coursed slightly obliquely and radially, and inserted to the proximal first metacarpal bone. This supernumerary muscle was well defined and completely separate from the other two heads of the main FDI muscle (Figure 1). DISCUSSION The human hand has a complex anatomical structure and includes multiple intrinsic muscles which play a very important role in its function. These muscles of the hand are essential for normal positioning and movement of the fingers. The intrinsic muscles originate distal to the wrist. They are traditionally divided into five groups: thenar, hypothenar, palmar interosseous, dorsal interosseous, and lumbrical muscles. The human hand has four dorsal interosseous muscles. Particularly, the FDI muscle is of marked functional importance to the hand. It is a bipinnate muscle and originates from the medial side of the proximal end of the first metacarpal bone and lateral side of the second metacarpal bone and inserts distally to the radial base of the proximal phalanx of the index finger, Alexandra Chernev 1 , Ivan Chernev 2 Affiliations: 1 Student, Carolinas Hospital System, Florence, SC, USA; 2 Attending Physician, Medical Director, Outpatient Rehabilitation Services, Carolinas Hospital System, Flor- ence, SC, USA. Corresponding Author: Ivan Chernev, MD, 1925 Hoffmey- er Road, Florence, SC, 29501, USA; Email: ivantch- [email protected]Received: 22 September 2018 Accepted: 11 October 2018 Published: 05 November 2018 the palmar plate of the metacarpophalangeal joint, and the dorsal aponeurosis. [1–3]. Typically, it has two heads namely superficial (radial) and deep (ulnar) head. The function of the FDI muscle is to abduct the index finger at the metacarpophalangeal joint, flex proximal phalanx at the metacarpophalangeal joint, adduct the thumb at the first carpometacarpal joint, and act as a stabilizer during various types of apposition of the thumb and index finger [1]. Anatomical variations in the morphology of the dorsal interosseous muscles have been occasionally reported since the 18 th century [4–6]. They are usually presented as variations in the number of heads or locations of insertion. A few cases of supernumerary muscles have been reported as well [5, 6]. However, all of the previously reported cases of supernumerary dorsal interosseous muscles involved the second, third, and fourth dorsal interosseous muscles. To the best of our knowledge, the presence of a supernumerary FDI muscle has not been previously documented and here we present one such case with a very well defined supernumerary FDI muscle completely separate from the main FDI muscle. Figure 1: Dorsoradial view of the hand showing a supernumerary first dorsal interosseous muscle originating from the second metacarpal bone, coursing obliquely and attaching with an individual tendon to the first metacarpal bone.
Transcript
Edorium Journal of Anatomy and Embryology, Vol. 5; 2018.
Supernumerary first dorsal interosseous muscle of the hand
Alexandra Chernev, Ivan Chernev
CASE REPORT
During a routine anatomy module, as part of an educational course, the authors noticed unusual muscle variation of the hand in an upper limb specimen. Details regarding age, gender, race, and cause of death were not available for this specimen. An additional supernumerary first dorsal interosseous (FDI) muscle was observed, which originated from the second metacarpal bone, coursed slightly obliquely and radially, and inserted to the proximal first metacarpal bone. This supernumerary muscle was well defined and completely separate from the other two heads of the main FDI muscle (Figure 1).
DISCUSSION
The human hand has a complex anatomical structure and includes multiple intrinsic muscles which play a very important role in its function. These muscles of the hand are essential for normal positioning and movement of the fingers. The intrinsic muscles originate distal to the wrist. They are traditionally divided into five groups: thenar, hypothenar, palmar interosseous, dorsal interosseous, and lumbrical muscles. The human hand has four dorsal interosseous muscles. Particularly, the FDI muscle is of marked functional importance to the hand. It is a bipinnate muscle and originates from the medial side of the proximal end of the first metacarpal bone and lateral side of the second metacarpal bone and inserts distally to the radial base of the proximal phalanx of the index finger,
Received: 22 September 2018Accepted: 11 October 2018Published: 05 November 2018
the palmar plate of the metacarpophalangeal joint, and the dorsal aponeurosis. [1–3]. Typically, it has two heads namely superficial (radial) and deep (ulnar) head. The function of the FDI muscle is to abduct the index finger at the metacarpophalangeal joint, flex proximal phalanx at the metacarpophalangeal joint, adduct the thumb at the first carpometacarpal joint, and act as a stabilizer during various types of apposition of the thumb and index finger [1].
Anatomical variations in the morphology of the dorsal interosseous muscles have been occasionally reported since the 18th century [4–6]. They are usually presented as variations in the number of heads or locations of insertion. A few cases of supernumerary muscles have been reported as well [5, 6]. However, all of the previously reported cases of supernumerary dorsal interosseous muscles involved the second, third, and fourth dorsal interosseous muscles. To the best of our knowledge, the presence of a supernumerary FDI muscle has not been previously documented and here we present one such case with a very well defined supernumerary FDI muscle completely separate from the main FDI muscle.
Figure 1: Dorsoradial view of the hand showing a supernumerary first dorsal interosseous muscle originating from the second metacarpal bone, coursing obliquely and attaching with an individual tendon to the first metacarpal bone.
Edorium Journal of Anatomy and Embryology, Vol. 5; 2018.
Typically, variations of intrinsic muscles of the hand are asymptomatic. However, they may have implications during movement of the hand, may affect functional capacity of the hand, or may possibly contribute to increased intracompartmental pressures [5, 7]. In addition, they have to be considered when dealing with dislocated fractures of the hand or when muscle transposition flaps are planned [3, 5]. In the case presented above, because of its anatomical position, the supernumerary FDI muscle most likely contributed to the adduction action of the thumb which possibly increased the adduction strength of the thumb as well as the grip strength of the hand.
CONCLUSION
Knowledge about muscular variations of the hand is important and should always be taken into account when assessing hand function and during conservative and surgical treatment of hand conditions.
REFERENCES
1. Masquelet AC, Salama J, Outrequin G, Serrault M, Chevrel JP. Morphology and functional anatomy of the first dorsal interosseous muscle of the hand. Surg Radiol Anat 1986;8(1):19–28.
2. Ikebuchi Y, Murakami T, Ohtsuka A. The interosseous and lumbrical muscles in the human hand, with special reference to the insertions of the interosseous muscles. Acta Med Okayama 1988 Dec;42(6):327–34.
3. Bilbo JT, Stern PJ. The first dorsal interosseous muscle: An anatomic study. J Hand Surg Am 1986 Sep;11(5):748–50.
4. Bharambe VK, Shevde SP, Puranam V, Kanaskar NS. Additional heads of dorsal interosseous muscle in Caucasian cadavers and their clinical significance. Sahel Med J. 2013;16(4):174–7.
5. Natsis K, Tsakotos G, Vlasis K, Koebke J. The cadaver of a Caucasian man with a supernumerary fourth dorsal interosseous muscle in the right hand: A case report. J Med Case Rep 2011 Aug 18;5:393.
6. Nayak VS, Priya A, Bhat N, et al. Cadaveric Study on Morphology of Dorsal Interossei of Hand and its Anatomical Variation. J Clin Diagn Res 2016 Jun;10(6):AC04–6.
7. Chopra R, Hayton M, Dunbar PJ. Exercise induced chronic compartment syndrome of the first dorsal interosseous compartment of the hand: A case report. Hand (N Y) 2009 Dec;4(4):415–7.
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Keywords: First dorsal interosseous muscle, Hand, Su-pernumerary
How to cite this article
Chernev A, Chernev I. Supernumerary first dorsal interosseous muscle of the hand. Edorium J Anat Embryo 2018;5:100025A04AC2018.
Article ID: 100025A04AC2018
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doi:10.5348/100025A04AC2018CL
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AcknowledgementsWe thank Dr. Eric Gomez for his assistance during the literature review process.
Author ContributionsAlexandra Chernev – Substantial contributions to conception and design, Acquisition of data, Analysis and interpretation of data, Drafting the article, Revising it critically for important intellectual content, Final approval of the version to be publishedIvan Chernev – Substantial contributions to conception and design, Acquisition of data, Analysis and interpretation of data, Drafting the article, Revising it critically for important intellectual content, Final approval of the version to be published
Guarantor of SubmissionThe corresponding author is the guarantor of submission.
Source of SupportNone.
Consent StatementThis is an anatomical specimen and no written informed consent was required.
Conflict of InterestAuthors declare no conflict of interest.
Data AvailabilityAll relevant data are within the paper and its Supporting Information files.
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